i

Novel Ligands based on Imidazole and Triazole:

From Coordination Chemistry to Medicinal Applications and

Material Design

Der Naturwissenschaftlichen Fakultät

der Friedrich-Alexander-Universität Erlangen Nürnberg

zur

Erlangung des Doktorgrades

vorgelegt von

Nina Victoria Fischer

aus Frankfurt

iii

Als Dissertation genehmigt

von der Naturwissenschaftlichen Fakultät der Universität Erlangen-Nürnberg

Tag der mündlichen Prüfung 12.10.2010

Vorsitzender der Prüfungskommission Prof. Dr. R. Fink

Erstberichterstatter Prof. Dr. N. Burzlaff

Zweitberichterstatter Prof. Dr. Dr. h.c. mult. Rudi van Eldik

iv

Die vorliegende Arbeit entstand in der Zeit von November 2007 bis September 2010 im

Department Chemie und Pharmazie (Lehrstuhl für Anorganische und Analytische Chemie) der

Friedrich-Alexander-Universität Erlangen-Nürnberg unter Anleitung von Prof. Dr. Nicolai

Burzlaff.

vi

v

Great ideas need landing gear as well as wings. (Neil Armstrong)

vi

vii

Danksagung

Mein besonderer Dank gilt meinem Doktorvater Prof. Dr. Nicolai Burzlaff für die große

akademische Freiheit bei der Bearbeitung dieses interessanten Themengebiets, die offene

Atmosphäre, die fruchtvollen Diskussionen und nicht zuletzt für die vielen Gelegenheiten zur

Teilnahme an Konferenzen.

Prof. Dr. Lutz Dahlenburg danke ich für die Möglichkeit, meine Arbeiten in seinen

Laboratorien durchzuführen, jegliche fachliche Unterstützung und die vielen interessanten

Diskussionen und Anregungen zu Akademischem, Nützlichem und Alltäglichem.

Vielen Dank an Prof. Dr. Ivana Ivanović-Burmazović, dass ich meine Arbeiten in ihren

Laboratorien zu Ende führen durfte.

Besonderer Dank gilt auch allen Kooperationspartnern hier in Erlangen, aber auch an der

Universität Konstanz: Vielen Dank an insbesondere Prof. Dr. Ulrich Zenneck und Dr. Marat

Khusniyarov für die Einführung in die ESR-Spektroskopie und die Geduld mit meinen vielen

Fragen. Prof. Dr. Paul Müller, Dr. Mohammad Sahabul Alam, Uptal Mitra, Dr. Viacheslav

Dremov, Inshad Jum’h und Michael Stocker für die Durchführung der STM- und AFM-

Messungen, sowie die gute Zusammenarbeit. Prof. Dr. Wilhelm Schwieger und Alexandra Inayat

danke ich für die Thermogravimetrischen Analysen. Schließlich bedanke ich mich bei Dr.

Thomas Huhn und Malin Bein für die Durchführung der vielen Zelltests, sowie insbesondere die

Einladung nach Konstanz und ihr stets offenes Ohr für fachliche Fragen.

Den Angestellten des Instituts für Anorganische Chemie danke ich für die vielseitige

Unterstützung: Dr. Achim Zahl, Dr. Joachim Maigut, Helga Wendler und Jochen Schmidt

(NMR-Spektroskopie), Dr. Frank Heinemann, Susanne Hoffmann und Panagiotis Bakatselos

(Röntgenstrukturanalyse), Christina Wronna (Elementaranalyse), Dr. Jörg Sutter (ESR-

Spektroskopie, Mößbauerspektroskopie und Massenspektrometrie), Martin Bachmüller

viii

(Massenspektrometrie), Ronny Wiefel und Marco Müller (Glasbläser), Ursula Niegratschka

(Sekretariat), dem Team vom Magazin, Christl Hofmann, Manfred Weller, Uwe Reißer, sowie

allen anderen technischen Mitarbeitern. Besonderen Dank an Susanne auch für die

unterhaltsamen Plaudereien.

Danken will ich natürlich auch allen Kollegen aus unserem Arbeitskreis: Danke Dir,

Stefan, für die stete Hilfsbereitschaft und Kameradschaft. Danke aber auch an Gazi, Fatima,

Tom, Andi, Sascha, Eike, Liv, Moni, Astrid und Christina für den Zusammenhalt und die gute

Atmosphäre in der Arbeitsgruppe. Ein besonderes Dankeschön auch an alle „Dahlenburgs“,

„Ivanas“ und „van Eldiks“, insbesondere Harry, Mathias, Katharina, Erika und Steffi für

gemeinschaftliche Ratschrunden und den persönlichen Kontakt.

Schließlich danke ich meiner Familie und meinem Freund Alex, einfach für alles.

ix

Zusammenfassung

Die folgende Arbeit befasst sich mit der Synthese neuer N-heterocyclischer, insbesondere

imidazol- und triazolhaltiger Liganden. Ihre Koordinationseigenschaften in Übergangsmetall-

komplexen werden untersucht und potentielle Anwendungen diskutiert.

Kapitel 1 gibt einen kurzen Überblick über die klassischen Synthesewege für Imidazol-

und Triazolverbindungen sowie über die Forschungsgebiete in denen sie angewendet werden.

Kapitel 2 beschreibt die Synthese und Charakterisierung neuer imidazolbasierter

Liganden. Ihre Koordinationseigenschaften in Übergangsmetallkomplexen werden untersucht

und deren Anwendung als Enzymmodelle diskutiert.

Ausgehend von dem Liganden bmip als „Blueprint“, wurde eine Ligandenbibliothek

neuartiger imidazolbasierter N,N,E-Heteroskorpionatliganden (2,2-bmie, bmidta, rac-1,2-bmie,

bmima, bmimabo und debmimm) entworfen. Hierbei wurden besonders eine Variation der E-

Donorfunktion und die Einführung von Spacer-Einheiten in das Ligandenrückgrad fokussiert. Die

Unterschiedliche Donorstärke der neuen Liganden wurde durch die Koordination der Liganden

an das Re(CO)3- und das RuCl(PPh3)2-Komplexfragment getestet. Während die Liganden 2,2-

bmie, bmidta und rac-1,2-bmie an die Zentralmetalle wie erwartet tripodal in κ3-Bindungsmodus

koordinierten, bevorzugten die Liganden bmima, bmimabo und debmimm eine nur bidentate N,N-

Koordination.

Weiterhin wurde das Bindungsverhalten der Liganden an die biorelevanten Metall Eisen

und Zink untersucht. Dabei erwiesen sich die Liganden 2,2-bmie und rac-1,2-bmie in

deprotonierter Form als relativ empfindlich, so dass die Isolierung definierter Produkte aus

x

basischen Reaktionslösungen sich zuweilen als problematisch erwies. Mit dem Liganden bmidta

konnten Bis(ligand)komplexe dargestellt werden.

Jegliche Versuche zur Synthese von Mn(II)-, Fe(II)-, Co(II)-, Ni(II)-, Cu(II)-, oder Zn(II)-

Komplexen mit den Liganden bmima oder bmimabo in tripodaler κ3-Koordination blieben

erfolglos. Es wurde jedoch die Bildung der Koordinationspolymere [Zn(bmima)Cl]n und

[Zn(bmimabo)Cl]n beobachtet. Daher erschien eine Untersuchung des Koordinationsverhaltens

des Liganden debmimm von Interesse, welcher ein analoges Bindungsmotiv wie bmima und

bmimabo aufweisen sollte. Schließlich konnte eine bidentate N,N-Koordination von debmimm für

die tetraedrischen Komplexe [MCl2(debmimm)] (M = Fe(II), Co(II), Ni(II), Cu(II), und Zn(II))

nachgewiesen werden, deren elektronische sowie elektrochemische Eigenschaften auch durch

ESR, Mößbauer und CV untersucht wurden.

Interessanterweise werden in Komplexen mit debmimm neben der tetraedrischen auch

andere Koordinationssphären angenommen, wie etwa der Oktaeder in [Fe(OTf)2(debmimm)2]

sowie die quadratische Pyramide in [NiCl2(debmimm)]2.

Derartige Wechsel zwischen verschiedenen Koordinationsgeometrien werden auch in

Metalloenzymen beobachtet und stellen eine Schlüsseleigenschaft für funktionelle

Enzymmodelle dar.

Kapitel 3 befasst sich mit der Synthese neuer Metallkomplexe aus

Bis(imidazolyl)liganden für die Krebstherapie.

Es wurden Cu(II)-, Mn(II)- und Pt(II)- Komplexe aus den bis(imidazolyl)basierten

Liganden bmipMe, 2,2-Hbmie, rac-1,2-Hbmie, debmimm, K[bmima], bmiePh, bmiePh3-OMe und

bmiePh4-OMe synthetisiert und mittels Elementaranalyse, IR-Spektroskopie und FAB-

Massenspektrometrie charakterisiert. Zytotoxizitätsstudien, durchgeführt an HeLa S3, zeigten,

dass gerade die arylsubstituierten Liganden bmiePh und bmiePh4-OMe wertvolle Bausteine für

metallbasierte Zytostatika darstellen. Die Mn(II)-Komplexe [MnCl2(bmiePh)]2 und

xi

[MnCl2(bmiePh4-OMe)]2 im Besonderen scheinen erfolgversprechend für weitere Untersuchungen

zu sein. Jedoch besitzt auch der Ligand bmiePh selbst schon zytotoxische Wirkung, so dass durch

folgende Hydrolysestudien seiner Komplexe noch festzustellen ist, ob deren Wirkung tatsächlich

metallbasiert ist, oder doch dem Liganden zugeordnet werden muss.

Interessanterweise zeigt jedoch auch der Ligand 2,2-Hbmie zytotoxische Eigenschaften,

jedoch keiner seiner Komplexe. Dies deutet bereits auf eine ausreichende Hydrolysestabilität der

Komplexe der bis(imidazolyl)methanbasierten Liganden hin.

In Kapitel 4 werden einfache Synthesewege für neue imidazol- und triazolbasierte

Carboxylatliganden entwickelt, sowie ihre Anwendung für die Darstellung von Metal Organic

Frameworks diskutiert. Ihre Bindungseigenschaften werden durch Koordination an

Übergangsmetallionen getestet. Weiterhin erwiesen sich einige der N,N,O-Liganden, welche

bereits in Kapitel 2 behandelt wurden, als wertvolle Bausteine für den Aufbau von

Koordinationspolymeren.

Im Gegensatz zu den Liganden 2,2-bmie, rac-1,2-bmie und bmidta, die κ3-Koordination

zeigen (Kapitel 2), bildeten sich mit den N,N,O-Liganden bmima und bmimabo die

Koordinationspolymere [Zn(bmima)Cl]n und [Zn(bmimabo)Cl]n.

Der N,N-Ligand trans-bis konnte als Nebenprodukt bei der Synthese von bmima isoliert

werden. Mit trans-bis konnte das 2D Koordinationspolymer [Cu2Cl2(trans-bis)3]n dargestellt

werden.

Das Koordinationsverhalten des Liganden btp, welcher bekanntermaßen 1D

Koordinationspolymere mit Zn(II) ausbildet, wurde im Detail untersucht. Die Reaktion von btp

mit Übergangsmetallen der 3d Reihe lieferte isostrukturelle 2D Koordinationspolymere der Form

[M(btp)2]n (M = Mn, Fe, Co, Ni, Cu, Zn).

In ähnlicher Weise wie btp wurden die neuen triazolbasierten N,O-Liganden ta und tzp

synthetisiert. Im Gegensatz zu den isostrukturellen Koordinationspolymeren, die durch die

xii

Reaktion von btp und Übergangsmetallen erhalten wurden, ergaben analoge Reaktionen von ta

und tzp molekulare Strukturen unterschiedlicher Topologien.

Der neue Ligand ta kann mit zwei Carboxylatsauerstoffatomen und zwei

Stickstoffdonoren der Triazolgruppe (in Position 2 und 4 des Heterozyklus), also mit insgesamt

vier Atomen an Metalle binden.

Wenn drei dieser Donoratome Koordinationsbindungen ausbilden, ergeben sich 3D Metal

Organic Frameworks (MOFs), wie durch die Verbindungen [Mn(ta)2]n und [Fe(ta)2]n gezeigt

werden konnte. Ein Koordinationspolymer, bestehend aus ineinandergreifenden

Polymerdoppelsträngen wurde für [Zn(ta)2]n beobachtet. In diesem sind die Hälfte der ta

Liganden über die Carboxylatsauerstoffatome in µ2-ta-κO1:O2 Koordination gebunden.

Eine µ2-ta-κN4:O1 Koordination nimmt der Ligand im Fall des Koordinationspolymers

[Co(ta)2(H2O)2]n ein, in dem zwei Wassermoleküle die trans-Positionen des oktaedrischen

Co(II)-Metallzentrums besetzen. Alle MOFs des Liganden ta, die hier diskutiert werden, weisen

relativ kompakte Strukturen auf. Die Koordinationspolymere [Ni(ta)2(OH2)2]n × 2 H2O,

[Cu(ta)(OH2)2]n und [Ag(ta)]n konnten nur als mikrokristalline Pulver gewonnen werden. Alle

drei scheinen unterschiedliche Strukturen als die hier beschriebenen aufzuweisen, worauf durch

pulverdiffraktometrische Analyse geschlossen wurde.

Der neue Ligand tzp besitzt die gleichen Donorfunktionen wie ta, wobei er aber eine

flexiblere Struktur aufweist. Im 1D Koordinationspolymer [Zn(tzp)2]n × 0.25 H2O zeigt er ein µ2-

tzp-κN4:O1 Bindungsmotiv, welches starke Ähnlichkeit zu dem von btp in [Zn(btp)2]n zeigt.

Jedoch sind die linearen Polymerketten hier nicht über π-π-Wechselwirkung, wie für [Zn(btp)2]n

beobachtet, verbunden. Außerdem kristallisiert [Zn(tzp)2]n mit 0.25 äquiv. H2O pro

Formeleinheit.

In den isostrukturellen Koordinationspolymeren [Co(tzp)2(OH2)2]n × 2 H2O und

[Ni(tzp)2(OH2)2]n × 2 H2O bindet tzp im µ2-tzp-κN4:O1 Modus, ähnlich wie ta in

[Co(ta)2(OH2)2]n.

xiii

Im Allgemeinen werden durch Reaktion von tzp mit Übergangsmetallsalzen offenere

Strukturen geformt, als die Koordinationspolymere mit ta sie aufweisen. Erstere bilden

Hohlräume, die Platz für Gastmoleküle wie H2O bieten.

Das 3D MOF [Ag3(tzp)2(NO3)]n bildet das einzige Beispiel, in dem der Triazolligand tzp

alle seiner potentiellen Bindungsstellen ausnützt, was in einem κ5-N2,N4,O,O,O´ Bindungsmodus

resultiert und zu einer sehr kompakten Kristallstruktur führt, die keine größeren Lücken für

Gastmoleküle lässt.

Die Koordinationspolymere [Mn(tzp)2]n und [Cu(tzp)2(OH2)2]n wurden nur als

mikrokristalline Pulver erhalten. Durch Analyse mittels Pulverdiffraktometrie konnte jedoch eine

Ähnlichkeit der Strukturen [Mn(tzp)2]n und [Mn(ta)2]n abgeleitet werden.

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xv

Abstract

The following work concentrates on the development of novel ligands bearing N-

heterocyclic donor groups, namely imidazole and triazole. Their coordination properties in

transition metal complexes are investigated and possible applications are probed and discussed.

Chapter 1 gives a brief overview of the classic synthetic pathways to imidazole- and

triazole-based compounds and the research fields in which they are applied.

Chapter 2 describes the syntheses and characterization of novel ligands based on

imidazole. Their coordination properties in transition metal complexes were probed and their

importance as enzyme models is discussed.

Taking the ligand bmip as a blueprint, a library of novel imidazole-based N,N,E-

heteroscorpionates, viz. 2,2-bmie, bmidta, rac-1,2-bmie, bmima, bmimabo, and debmimm has

been created. Special attention was turned to the variation of the E-donor functions and the

introduction of spacers into the carbon backbone. The variation of the donor strengths provided

by the new ligands was investigated by coordination towards the complex fragments Re(CO)3

and RuCl(PPh3)2. Whereas 2,2-bmie, bmidta, and rac-1,2-bmie bonded to the central metal in the

expected tripodal κ3-fashion, the ligands bmima, bmimabo, and debmimm favored only N,N-

coordination.

Furthermore, the binding of the ligands by two biorelevant metals, viz. iron and zinc, was

studied. In these studies, the ligands 2,2-bmie and rac-1,2-bmie proved to be rather sensitive

when deprotonated, such that the isolation of defined products formed in basic reaction solution

mixtures remains occasionally a still unresolved problem. With bmidta bis(ligand) complexes

were obtained.

xvi

All attempts to obtain any complexes of Mn(II), Fe(II), Co(II), Ni(II), Cu(II), or Zn(II)

possessing the ligands bmima and bmimabo in tripodal κ3-coordination failed. However, the

formation of the coordination polymers [Zn(bmima)Cl]n und [Zn(bmimabo)Cl]n was observed. In

this respect, it seemed of interest to investigate the coordination behavior of the ligand debmimm,

expected to exhibit bonding properties akin to bmima and bmimabo. Bidentate coordination of

debmimm with formation of tetrahedral complexes [MCl2(debmimm)] (M = Fe(II), Co(II), Ni(II),

Cu(II), and Zn(II)) could be proved. The electronic and electrochemical properties of the

complexes were studied by ESR and Mössbauer spectroscopy, as well as CV. Interestingly, other

coordination geometries of complexes bearing debmimm could be rationalized, e.g. the

octahedral [Fe(OTf)2(debmimm)2] and the square pyramidal [NiCl2(debmimm)]2. Such switches

between different coordination geometries are a key feature for bioinorganic model compounds.

Chapter 3 is concerned with the synthesis of novel metal-based anticancer agents derived

from imidazole-based ligands.

Cu(II), Mn(II) and Pt(II) complexes bearing bis(imidazolyl) ligands, namely bmipMe,

2,2-Hbmie, rac-1,2-Hbmie, debmimm, K[bmima], bmiePh, bmiePh3-OMe, and bmiePh4-OMe were

synthesized and characterized by elemental analysis, IR spectroscopy and FAB mass

spectrometry. Studies regarding their cytotoxicity towards HeLa S3 were conducted and revealed

the aryl-substituted ligands bmiePh and bmiePh4-OMe, in particular, as valuable building

blocks for metal-based cytostatica. The Mn(II) complexes [MnCl2(bmiePh)]2 and

[MnCl2(bmiePh4-OMe)]2 seem to be promising for more detailed investigations. However, the

ligand bmiePh showed to be cytotoxic itself. Hence, hydrolysis studies of its complexes have to

show if the cytotoxicity of [MnCl2(bmiePh)]2 is actually based on the complex or has to be

attributed to the ligand.

xvii

Interestingly, the 2,2-Hbmie ligand proved to be cytotoxic, too, while none of its

complexes did so, which suggests that ligands with an bis(imidazole-2-yl)methane core are

sufficiently stable towards hydrolysis.

In Chapter 4, convenient synthetic routes to novel imidazole and triazole-based

carboxylate ligands are developed and their application as ligands in metal organic framework

syntheses is discussed. The binding properties of the new ligands were probed by the

coordination to transition metal ions. Furthermore, some of the N,N,O-ligands, which have

already been discussed in Chapter 2 proved to be valuable building blocks for coordination

polymer assemblies.

Different from the ligands 2,2-bmie, rac-1,2-bmie, and bmidta discussed in Chapter 2, the

novel N,N,O-ligands bmima and bmimabo were recognized as valuable building blocks for the

syntheses of coordination polymers, such as [Zn(bmima)Cl]n and [Zn(bmimabo)Cl]n. By

serendipity, the N,N-ligand trans-bis was discovered as a side product of the synthesis of bmima

and was found to form the 2D coordination polymer [Cu2Cl2(bie)3]n.

The coordination behavior of the ligand btp, which was already known to form 1D

coordination polymers with Zn(II), was investigated in detail. Reaction of btp with 3d metal salts

yielded the isostructural 2D coordination polymers [M(btp)2]n (M = Mn, Fe, Co, Ni, Cu, Zn).

Following a procedure similar to the synthesis of btp, the novel triazole-based N,O-

ligands ta and tzp were developed. Contrary to the isostructural coordination polymers resulting

from the reaction of btp with transition metals, similar reactions of ta and tzp afforded molecular

structures with varying topologies.

The novel ligand ta offers the two carboxylate O-donors and the two triazole N-donors (in

position 2 and 4 of the heterocycle) as four potential binding sites. If three of these donors take

part in coordination bonds, 3D metal organic frameworks are formed as represented by [Mn(ta)2]n

and [Fe(ta)2]n. A coordination polymer built by interdigitating polymer double strands was

xviii

observed in the case of [Zn(ta)2]n, in which half of the ta ligands are coordinated only through the

carboxylate O-donors in a µ2-ta-κO1:O2 coordination mode. On the other hand µ2-ta-κN4:O1

coordination of the ligand ta was observed in the case of [Co(ta)2(H2O)2]n, in which two water

molecules occupy two trans positions of the octahedral Co(II) center. All MOFs containing the

ligand ta exhibit rather compact structures. The coordination polymers [Ni(ta)2(OH2)2]n × 2 H2O,

[Cu(ta)(OH2)2]n, and [Ag(ta)]n were only obtained as microcrystalline powders. According to

their powder diffraction pattern, all three exhibit structures different from the other ones here

described.

The new ligand tzp offers the same four potential binding sites, while possessing a more

flexible structure. In the 1D coordination polymer [Zn(tzp)2]n × 0.25 H2O tzp is µ2-tzp-κN4:O1

binding. Its structure shows similarities to that observed for [Zn(btp)2]n. However, the linear

chains in [Zn(tzp)2]n × 0.25 H2O are not connected via π-π-bonding. Furthermore, 0.25 equiv.

H2O are contained per formula unit. In the isostructural coordination polymers [Co(tzp)2(OH2)2]n

× 2 H2O and [Ni(tzp)2(OH2)2]n × 2 H2O the ligand binds in a µ2-tzp-κN4:O1 fashion, similar to

the ligand ta in [Co(ta)2(OH2)2]n.

Generally, more open structures are accessible with the ligand tzp, in which H2O

molecules are intercalated. The 3D MOF [Ag3(tzp)2(NO3)]n is the only example, in which the

triazole-based ligand tzp uses all of its binding sites, to bind in a κ5-N2,N4,O,O,O´ mode, by

formation of a compact structure without larger spaces for guest molecules.

Polymers [Mn(tzp)2]n and [Cu(tzp)2(OH2)2]n, were obtained as microcrystalline powders.

From their powder X-ray diffraction patterns, [Mn(tzp)2]n and [Mn(ta)2]n were inferred to possess

related structures.

Isostructural frameworks were observed for the 3D MOFs [Mn(ta)2]n and [Fe(ta)2]n as

well as the 2D coordination polymers [Co(tzp)2(OH2)2]n × 2 H2O and [Ni(tzp)2(OH2)2]n × 2 H2O,

which are structurally closely related to [Co(ta)2(OH2)2]n, but incorporate solvent molecules.

xix

List of abbreviations

ACE Angiotensine Converting Enzyme

AFM atomic force microscopy

Hbdmpza bis(3,5-dimethylpyrazol-1-yl)acetic acid

Hbdmpze bis(3,5-dimethylpyrazol-1-yl)ethanol

trans-bie trans-1,2-bis(N-methylimidazol-2-yl)ethylene

H2bim 2,2´-biimidazole

Hbip bis(imidazol-2-yl)propionic acid

bmic bis(N-methylimidazol-2-yl)carbinol

Hbmidta bis(N-methylimidazol-2-yl)dithioacetic acid

2,2-Hbmie 2,2-bis(N-methylimidazol-2-yl)ethanol

rac-1,2-Hbmie rac-1,2-bis(N-methylimidazol-2-yl)ethanol

bmik bis(N-methylimidazol-2-yl)ketone

bmim bis(N-methylimidazol-2-yl)methane

Hbmima bis(N-methylimidazol-2-ylmethyl)acetic acid

Hbmimabo bis(N-methylbenzo[d]imidazol-2-

ylmethyl)acetic acid

bmiePh 1,1-bis(N-methylimidazol-2-yl)-2-

phenylethane

bmiePh3-OMe 1,1-bis(N-methylimidazol-2-yl)-2-

(3-methoxyphenyl)ethane

bmiePh4-OMe 1,1-bis(N-methylimidazol-2-yl)-2-(4-

methoxyphenyl)ethane

xx

Hbmip bis(N-methylimidazol-2-yl)propionic acid

bmipMe methyl bis(N-methylimidazol-2-yl)propionate

bmipPr n-propyl bis(N-methylimidazol-2-

yl)propionate

Hbpza bis(pyrazol-1-yl)acetic acid

Hbpze bis(pyrazol-1-yl)ethanol

Hbtp bis(1,2,4-triazol-1-yl)propionic acid

Hbtza bis(1,2,4-triazol-1-yl)acetic acid

CITS current imaging tunneling spectroscopy

Cy cyclohexyl

DBU 1,8-diazabicyclo[5.4.0]undec-7-ene

debmimm diethyl 2,2-bis(N-methylimidazol-2-

ylmethyl)malonate

DIMMAL 2-di(imidazolyl)methylmalonate

ESR electron spin resonance

HOPG highly oriented pyrolytic graphite

IC50 50% inhibitory concentration

Hima 2(imidazol-1-yl)acetic acid

INPS Isopenicillin N Synthase

Me2bim N,N´-dimethyl-2,2´-biimidazole

Mes mesityl

MDCK Madin-Darby-Canine-Kidney

MOF metal organic frameworks

MTT 3-(4,5-dimethylthiazol-2-yl)2,5-diphenyl-2H-

tetrazolium bromide

4-NBOH 4-nitrobenzylalcohol

xxi

OTf triflate

PDF peptide deformylase

SOD superoxid dismutase

STM scanning tunneling microscopy

Hta 1,2,4-triazol-1-ylacrylic acid

taa (1,2,4-triazol-1-yl)acetic acid

taMe methyl 1,2,4-triazol-1-ylacrylate

tbz bis(benzo[d]imidazol-2-yl)propane

TDA 1,2,3-triazole-4,5-dicarboxylic acid

TEER transepithelial electric resistance

TGA thermogravimetric analysis

tz 1,2,4-triazolate

Htzp 1,2,4-triazol-1-ylpropionic acid

tzpMe methyl 1,2,4-triazol-1-ylpropionate

ZIF zeolitic imidazolate frameworks

xxii

xxiii

List of compounds

Chapter 2

methylimidazole (1) Hbmimabo × 2 HCl (17)

bmik (2) Hbmima × 2 HCl (18)

bmim (3) debmimm (19)

bmipMe (4) Hbmimabo (20)

2,2-Hbmie (5) K[bmima] (21)

Li[bmidta] (6) [Re(rac-1,2-bmie)(CO)3] (22)

[Re(2,2-bmie)(CO)3] (7) [ReBr(Hbmima)(CO)3] (23)

[Ru(bmidta)Cl(PPh3)2] (8) [Fe(OTf)2(debmimm)2] (24)

[Fe(bmidta)2] (9) [FeCl2(debmimm)] (25)

[Zn(bmidta)2] (10) [MnCl2(debmimm)] (26)

N-methyl-2-imidazolecarboxaldehyde (11) [CoCl2(debmimm)] (27)

rac-1,2-Hbmie (12) [NiCl2(debmimm)] (28)

N-methylimidazol-2-ylmethanole (13) [NiCl2(debmimm)]2 (28b)

N-methylbenzo[d]imidazol-2-ylmethanole (14) [CuCl2(debmimm)] (29)

2-chloromethylimidazole (15) [ZnCl2(debmimm)] (30)

2-chloromethylbenzo[d]imidazole (16)

xxiv

Chapter 3

For clarity reasons, new numbers are introduced in this chapter for the compounds also

mentioned in Chapter 2: bmipMe (1) was designated in Chapter 2 as compound 4; 1,1-Hbmie (2)

was denoted as compound 5 in Chapter 2; 1,2-Hbmie (3) was named compound 12; debmimm (4)

was designated as compound 19; K[bmima] (5) was called compound 21, [CuCl2(debmimm)]

(11) was refered to as compound 29; [MnCl2(debmimm)] (21) was denoted as compound 26.

bmipMe (1) [CuBr2(debmimm)] (17)

2,2-Hbmie (2) [CuBr2(bmiePh)]2 (18)

rac-1,2-Hbmie (3) [CuBr2(bmiePh3-OMe)]2 (19)

debmimm (4) [CuBr2(bmiePh4-OMe)]2 (20)

K[bmima] (5) [MnCl2(debmimm)]2 (21)

bmiePh (6) [MnCl2(bmiePh)]2 (22)

bmiePh3-OMe (7) [MnCl2(bmiePh3-OMe)]2 (23)

bmiePh4-OMe (8) [MnCl2(bmiePh4-OMe)]2 (24)

[CuCl2(bmipMe)]2 (9) [PtCl2(bmipMe)] (25)

[CuCl2(2,2-Hbmie)]2 (10) [PtCl2(2,2-Hbmie)] (26)

[CuCl2(debmimm)] (11) [PtCl2(rac-1,2-Hbmie)] (27)

[CuCl2(bmiePh)]2 (12) [PtCl2(debmimm)] (28)

[CuCl2(bmiePh3-OMe)]2 (13) [PtCl2(Hbmima)] (29)

[CuCl2(bmiePh4-OMe)]2 (14) [PtCl2(bmiePh)] (30)

[CuBr2(bmipMe)]2 (15) [PtCl2(bmiePh3-OMe)] (31)

[CuBr2(2,2-Hbmie)]2 (16) [PtCl2(bmiePh4-OMe)] (32)

xxv

Chapter 4

For clarity reasons, new numbers are introduced in this chapter for the ligands also mentioned in

Chapter 2: compound Hbmima × 2 HCl (1) is depicted as 18 in Chapter 2, compound Hbmimabo

× 2 HCl (2) is referred to as 17 in Chapter 2.

Hbmima × 2 HCl (1) K[tzp] (17)

Hbmimabo × 2 HCl (2) [Mn(ta)2]n (18)

[Zn(bmima)Cl]n (3) [Fe(ta)2]n (19)

[Zn(bmimabo)Cl]n (4) [Co(ta)2(OH2)2]n (20)

[Cu2Cl2(trans-bie)3]n (5) [Ni(ta)(OH2)2]n × 2 n H2O (21)

trans-bie (6) [Cu(ta)2(OH2)2]n (22)

Na[btp] (7) [Zn(ta)2]n (23)

[Zn(btp)2]n (8) [Ag(ta)]n (24)

[Mn(btp)2]n (9) [Mg(H2O)6](ta)2 (25)

[Fe(btp)2]n (10) [Mn(tzp)2]n (26)

[Co(btp)2]n (11) [Co(tzp)2(OH2)2]n× 2 n H2O (27)

[Ni(btp)2]n (12) [Ni(tzp)(OH2)]n × 2 n H2O (28)

[Cu(btp)2]n (13) [Cu(tzp)2(OH2)]n (29)

taMe (14) [Zn(tzp)2]n (30)

K[ta] (15) [Ag3(tzp)2(NO3)]n (31)

tzpMe (16)

xxvi

xxvii

Table of contents

Zusammenfassung ix

Abstract xv

List of abbreviations xix

List of compounds xxiii

1 General introduction 1

1.1 Syntheses and applications of imidazole-based compounds 1

1.2 Syntheses and applications of triazole-based compounds 3

1.3 References and notes 5

2 Transition metal complexes of tripodal, imidazole-based N,N,E ligands (E = O, S):

Structural enzyme mimics 7

2.1 Introduction 7

2.1.1 Bis(imidazole-2-yl)propionic acids 9

2.1.2 Poly(imidazolyl)methanol ligands 10

2.1.3 Bis(imidazolyl)thioethanol ligands 11

2.1.4 Bis(imidazolmethyl)ethers and -thioether ligands 11

2.2 Results 13

2.2.1 Tripodal ligands with bis(imidazole-1-yl)methane cores 13

2.2.1.1 Syntheses of the ligands 13

2.2.1.2 Syntheses of the metal complexes 17

2.2.2 Tripodal ligands without bis(imidazole-1-yl)methane cores 23

xxviii

2.2.2.1 Syntheses of the ligands 24

2.2.2.2 Syntheses of the metal complexes 29

2.3 Conclusion 47

2.4 Experimental section 48

2.4.1 General remarks 48

2.4.2 Syntheses of the ligands 49

2.4.3 Syntheses of the complexes 54

2.4.4 Catalysis protocol 61

2.5 References and Notes 63

3 Pt(II), Cu(II) and Mn(II) complexes bearing imidazole-based N,N-ligands:

Novel anticacer agents 67

3.1 Introduction 67

3.1.1 Pt(II) complexes bearing heterocyclic N,N-ligands 68

3.1.2 Cu(I) and Cu(II) complexes bearing heterocyclic N,N-ligands 71

3.1.3 Mn(II) and Mn(III) complexes bearing N-donor ligands 73

3.2 Results 74

3.2.1 Syntheses of the ligands 75

3.2.2 Syntheses of Cu(II) complexes bearing imidazole-based N,N-ligands 77

3.2.3 Syntheses of Mn(II) complexes bearing imidazole-based N,N-ligands 81

3.2.4 Syntheses of Pt(II) complexes bearing imidazole-based N,N-ligands 84

3.2.5 Cytotoxicity studies 86

3.3 Conclusion 90

3.4 Experimental Section 90

3.4.1 General remarks 90

3.4.2 Syntheses of the ligands 91

xxix

3.4.3 Syntheses of the complexes 94

3.4.3.1 Cu(II) complexes 94

3.4.3.2 Mn(II) complexes 99

3.4.3.3 Pt(II) complexes 100

3.5 References and Notes 104

4 Transition metal coordination polymers bearing imidazole- and triazole-based

N,N,O-, N,N-, and N,O-ligands 108

4.1 Introduction 108

4.1.1 Coordination polymers containing imidazoles 109

4.1.2 Coordination polymers containing 1,2,4-triazoles 111

4.2 Results 114

4.2.1 Imidazole-based N,N,O-ligands suitable for the synthesis of coordination polymers 114

4.2.2 Imidazole-based N,N-ligands suitable for the synthesis of coordination polymers 118

4.2.3 Triazole-based N,N,O-ligands suitable for the synthesis of coordination polymers 124

4.2.4 Triazole-based N,O-ligands suitable for the synthesis of coordination polymers 132

4.2.4.1 Syntheses of the ligands 132

4.2.4.2 Syntheses of the metal complexes and coordination polymers with the ligand ta 134

4.2.4.3 Syntheses of the metal complexes and coordination polymers with the ligand tzp 147

4.3 Conclusion 160

4.4 Experimental section 163

4.4.1 General remarks 163

4.4.2 Syntheses of the ligands 164

4.4.3 Syntheses of the complexes and coordination polymers 166

4.5 References and notes 176

xxx

5 Appendices 180

5.1 Appendices for Chapter 2 180

5.1.1 Additional detail regarding the molecular structures of 23, 26, 27b, 28, and 29 180

5.1.2 Details of X-ray structure determinations 188

5.1.3 Powder X-ray diffraction patterns 195

5.1.4 Additional details of ESR investigations 196

5.1.5 Additional details of CV measurements 197

5.2 Appendices for Chapter 3 204

5.2.2 Details of X-ray structure determinations 204

5.2.3 Biological section 206

5.2.3.1 Materials and methods 206

5.2.3.2 Cell cultivation 206

5.2.3.3 AlamarBlue assay 206

5.3 Appendices for Chapter 4 207

5.3.1 Additional detail regarding the molecular structures of 11, 13, 19, and 28 207

5.3.2 Details of X-ray structure determinations 211

5.3.3 Powder X-ray diffraction patterns 217

5.3.4 Thermogravimetric analysis 220

5.4 References 221

1Chapter 1

1

General introduction

Five-membered N-heterocycles have a long tradition in organic as well as inorganic

chemistry. Imidazoles and triazoles in particular, define a fascinating class of compounds which

have found broad applications in a large variety of fields of research.

1.1 Syntheses and applications of imidazole-based compounds

Imidazoles have been introduced by Radziszewski as early as 1882. In the original three-

component reaction, a diketone, an aldehyde and an excess of ammonia are reacted in a one pot

synthesis to produce the corresponding imidazole derivatives I, (e.g., iophine) as sketched in

Scheme 1.1.1-2 Most of the following approaches to imidazole syntheses are based on this first

report. Drefahl and Herma broadened the synthetic scope of this method showing that one

equivalent of NH3 could be substituted by an amine.3 Recently, also microwave assisted methods

were reported, in which diketones, aldehydes, amines, and ammonium acetate are employed to

produce the imidazole ring.1

Scheme 1.1: Traditional Radziszewski synthesis affording imidazole derivatives I (iophine: R =

Ph); i) NH3 (aqueous solution).

R

OR

OO

RN

HNR

R

Ri)

I

+

2Chapter 1

However, a diversity of different imidazole derivatives are commercially available today,

and especially 2-substituted imidazole derivatives are easily accessible using simple imidazole-

based starting compounds.

Imidazole cores are not only found in biologically active compounds and drugs,4-8 but

were also recognized as valuable organocatalysts, e.g., for asymmetric conjugate addition of

nitroalkanes to aldehydes.9 Furthermore, nitro- and azido-substituted imidazolium salts, when

paired with nitrate or perchlorate form solid energetic salts, such as II, which can be used as

explosives (Figure 1.1).10

Figure 1.1: Some imidazolium-based compounds used as explosives (II; X = NO3−, ClO4

−), ionic

liquids (III), organocatalysts (IV; R = Cy, Mes), and metathesis catalysts (V).

Imidazole functionalities are present as the α-amino acid histidine in the active sites of a

multiplicity of enzymes, especially metalloenzymes, like e.g., the non-heme iron dioxygenases,

the zinc peptidases, or the superoxide dismutases.11-18 In these metalloenzymes the imidazolyl

group is bound to bio-relevant metals, like iron, zinc or copper, forming complexes. Mimicking

these metalloenzymes with small coordination compounds, to understand their mode of operation

and to make their performed catalytic reactions accessible for industrial applications, is an

NNPF6

−

III

N N MesMes

RuCl

Cl

PCy3Ph

V

N N RR

IV

NNX−

NO2

++

II

3Chapter 1

outstanding goal of bioinorganic chemistry. For the development of such model complexes,

ligands based on imidazole and its derivatives, in particular, have been intensively studied.19

Imidazolium ions, on the other hand, were recognized as valuable building blocks for the

synthesis of ionic liquids,10, 20-21 like III, and the famous Arduengo carbenes, such as e.g., IV.22-23

These imidazolium carbenes are potent organocatalysts themselves,24-26 and their ruthenium

complexes, like the “Grubbs-II” catalyst V, bearing an imidazolium-based Arduengo-type

carbene as a ligand represent benchmarks in olefin metathesis catalysis.27-28

Finally, the imidazolate anion and a variety of imidazole derivatives have gained

importance in the field of material science: Coordination polymers and metal organic

frameworks, like the “zeolitic imidazolate frameworks” (ZIFs) were recognized as potent

analogues for zeolite-based materials and kindled much research in this field.29

1.2 Syntheses and applications of triazole-based compounds

In contrast to imidazole and its derivatives, which are ubiquitous in biological systems,

most triazoles known today are of synthetic origin. The triazole family is largely divided into

1,2,3-triazoles (v-triazoles) and 1,2,4-triazoles (s-triazoles).30 In the following, only 1,2,4-

triazoles will be discussed.

The name triazole was first given in 1885 to the five-membered carbon-nitrogen ring

system C2N3H3 by Bladin, who synthesized the 1,2,4-triazole derivative VI by reaction of

dicyanophenylhydrazine (synthesized by reaction of cyanogen and phenylhydrazine) with acetic

anhydride (Scheme 1.2).30-32

Following the early methods of preparation of this parent triazole, a large variety of

synthetic procedures for substituted 1,2,4-triazoles has been developed. The most famous ones

are probably the Einhorn-Brunner reaction, using diacylamine and a substituted hydrazine, for

1,3,5-trisubstituted 1,2,4-triazoles and the Pellizzari reaction for the preparation of mono-, di- and

4Chapter 1

trisubstituted 1,2,4-triazoles, in which an amide and an acid hydrazide are fused at high

temperatures.30

Scheme 1.2: Synthesis of the triazole derivative VI described by Bladin; i) acetic anhydride.

Though, and by analogy to the chemistry of imidazoles, many synthetic routes to complex

1,2,4-triazole target compounds start from simple 1,2,4-triazole-containing building blocks, of

which a bulk is commercially available.

Some characteristic examples of triazole-based compounds, which are used for various

purposes, are given in Figure 1.2.

Figure 1.2: Some triazole-based compounds used as fungicides (VII), ionic liquids (VIII)

metathesis catalysts (IX) and explosives (X).

N

CNHN

CHN

Ph

N

CNN

CN

Ph

Mei)

O

Me

VI

HN N

NNH2

N N

N

(CH2)4SO3H

R

+

VII VIII

NNNPh Ph

Ph

RuCl

Cl

PCy3Ph

X

CF3SO3−

HN N

HN

N3

IX

+

ClO4−

5Chapter 1

Antifungal and antibacterial agents with triazole cores, like amitrol (VII), are used in both

clinical and agricultural applications.33 Recent reports also dealt with 1,3-disubstituted 1,2,4-

triazolium ions, which, similar to their imidazolium analogues, can be used in the synthesis of

ionic liquids (VIII) and Grubbs-type metathesis catalysts (IX).10, 34 By introduction of azido

groups into the triazole unit explosives can be generated (X).10

In the field of metal organic frameworks, triazole and its derivatives were intensively

studied and the resulting triazole-based coordination polymers showed potent applications

regarding luminescence, catalysis, adsorption, nonlinear optics, and magnetism.35

The following work concentrates on the development of novel ligands bearing N-

heterocyclic donor groups, namely imidazole and triazole. Their coordination properties in

transition metal complexes are investigated and possible applications are probed and discussed.

1.3 References and notes

(1) E. Gelens, F. Kanter, R. Schmitz, L. Sliedregt, B. Steen, C. Kruse, R. Leurs, M. Groen, R. Orru, Mol. Diversity 2006, 10, 17-22.

(2) B. Radziszewski, Ber., 15, 1493. (3) G. Drefahl, H. Herma, Chem. Ber. 1960, 93, 486-492. (4) R. Kitbunnadaj, O. P. Zuiderveld, B. Christophe, S. Hulscher, W. M. P. B. Menge, E.

Gelens, E. Snip, R. A. Bakker, S. Celanire, M. Gillard, P. Talaga, H. Timmerman, R. Leurs, J. Med. Chem. 2004, 47, 2414-2417.

(5) J. L. Adams, J. C. Boehm, T. F. Gallagher, S. Kassis, E. F. Webb, R. Hall, M. Sorenson, R. Garigipati, D. E. Griswold, J. C. Lee, Bioorg. Med. Chem. Lett. 2001, 11, 2867-2870.

(6) C. J. Dinsmore, T. M. Williams, T. J. O'Neill, D. Liu, E. Rands, J. C. Culberson, R. B. Lobell, K. S. Koblan, N. E. Kohl, J. B. Gibbs, A. I. Oliff, S. L. Graham, G. D. Hartman, Bioorg. Med. Chem. Lett. 1999, 9, 3301-3306.

(7) I. K. Khanna, R. M. Weier, Y. Yu, X. D. Xu, F. J. Koszyk, P. W. Collins, C. M. Koboldt, A. W. Veenhuizen, W. E. Perkins, J. J. Casler, J. L. Masferrer, Y. Y. Zhang, S. A. Gregory, K. Seibert, P. C. Isakson, J. Med. Chem. 1997, 40, 1634-1647.

(8) K. M. Hindi, M. J. Panzner, C. A. Tessier, C. L. Cannon, W. J. Youngs, Chem. Rev. 2009, 109, 3859-3884.

(9) L. Hojabri, A. Hartikka, F. M. Moghaddam, P. I. Arvidsson, Adv. Synth. Catal. 2007, 349, 740-748.

(10) R. P. Singh, R. D. Verma, D. T. Meshri, J. M. Shreeve, Angew. Chem. 2006, 118, 3664–3682; Angew. Chem., Int. Ed. 2006, 45, 3584-3601.

6Chapter 1

(11) J. M. Leitch, P. J. Yick, V. C. Culotta, J. Biol. Chem. 2009, 284, 24679-24683. (12) P. L. Roach, I. J. Clifton, C. M. H. Hensgens, N. Shibta, C. J. Schofield, J. Hajdu, J. E.

Baldwin, Nature 1997, 387, 827-830. (13) L. Que, Jr., R. Y. N. Ho, Chem. Rev. 1996, 96, 2607-2624. (14) R. Natesh, S. L. U. Schwager, E. D. Sturrock, K. R. Acharya, Nature 2003, 421, 551-554. (15) T. Meinnel, C. Lazennec, S. Blanquet, J. Mol. Biol. 1995, 254, 175-183. (16) A. Serero, C. Giglione, T. Meinnel, J. Mol. Biol. 2001, 314, 695-708. (17) M. K. Chan, W. Gong, P. T. R. Rajagopalan, B. Hao, C. M. Tsai, D. Pei, Biochemistry

1997, 36, 13904-13909. (18) P. T. R. Rajagopalan, X. C. Yu, D. Pei, J. Am. Chem. Soc. 1997, 119, 12418-12419. (19) For more detailed information see Chapter 2.1.(20) H. Xue, J. M. Shreeve, Eur. J. Inorg. Chem. 2005, 2573-2580. (21) P. Wasserscheid, C. Hilgers, Preparation of ionic fluids by treatment of amines,

phosphines, imidazoles, pyridines, triazoles, and pyrazoles with dialkyl sulfates followed by ion exchange EP-A1 1182196, 2002.

(22) A. J. Arduengo, R. L. Harlow, M. Kline, J. Am. Chem. Soc. 1991, 113, 361-363. (23) A. J. Arduengo, G. Bertrand, Chem. Rev. 2009, 109, 3209-3210. (24) J. Raynaud, Y. Gnanou, D. Taton, Macromolecules 2009, 42, 5996-6005. (25) S. Luo, X. Mi, L. Zhang, S. Liu, H. Xu, J.-P. Cheng, Angew. Chem. 2006, 118, 3165–

3169; Angew. Chem., Int. Ed. 2006, 45, 3093-3097. (26) N. Marion, S. Díez-González, S. P. Nolan, Angew. Chem. 2007,119, 3046–3058; Angew.

Chem., Int. Ed. 2007, 46, 2988-3000. (27) H. Clavier, K. Grela, A. Kirschning, M. Mauduit, S. P. Nolan, Angew. Chem., 2007,

119, 6906–6922; Angew. Chem., Int. Ed. 2007, 46, 6786-6801. (28) R. H. Grubbs, Handbook of Metathesis, 1. ed., Wiley-VCH Weinheim, 2003. (29) For more detailed information see Chap 4.1. (30) K. T. Potts, Chem. Rev. 1961, 61, 87-127. (31) J. A. Bladin, Ber. 1885, 18, 1544-1551. (32) J. A. Bladin, Ber. 1887, 19, 2598-2604. (33) Y. Koltin, C. A. Hitchcock, Curr. Opin. Chem. Biol. 1997, 1, 176-182. (34) T. M. Trnka, J. P. Morgan, M. S. Sanford, T. E. Wilhelm, M. Scholl, T.-L. Choi, S. Ding,

M. W. Day, R. H. Grubbs, J. Am. Chem. Soc. 2003, 125, 2546-2558. (35) For more detailed information see Chapter 4.1.

2

Transition metal complexes of tripodal, imidazole-based N,N,E-

ligands (E = O, S): Structural enzyme mimics

2.1 Introduction

Chapter 1 gave an overview of the history of N-heterocyclic compounds and ligands,

and the broad scope of their application. This chapter covers heteroscorpionate ligands, which

have a long tradition in coordination chemistry. In particular, heteroscorpionates with

imidazole moieties will be discussed. Typically, heteroscorpionates are able to bind to a metal

center in a tridentate, tripodal fashion, as sketched in Figure 2.1. This binding motif is

reminiscent of the way a scorpion attacks its prey, grasping it with its two pincers (the two N-

heterocyclic donors), and stabbing it with its sting (E-donor functionality).

Figure 2.1: Schematic representation of the N,N,E-heteroscorpionate - transition metal

interaction.

Since their introduction by Otero,1 particular attention has been drawn to the N,N,O-

heteroscorpionates, because these have been shown to be able to mimic the active site of

enzymes of the group of the non-heme iron dioxygenases and of the zinc peptidases.2-6 These

iron and zinc metalloenzymes feature an N,N,O-motif as their active site: Two histidine and

M

N NX

Chapter 2 8

one carboxylate function of an aspartate or glutamate group coordinate to the metal center,

forming a 2-His-1-Carboxylate Triad (Figure 2.2).7 Residual binding sites of the metal

cofactor can be occupied by solvent (commonly H2O) or substrates and cosubstrates.

Figure 2.2: Schematic picture of the 2-His-1-Carboxylate triad.

To name some outstanding examples of these classes of enzyme, the Isopenicillin N

Synthase (IPNS) and the Angiotensin Converting Enzyme (ACE) can be quoted. The former

plays an important role in the biosynthesis of penicillines and cephalosporines.8-9 ACE is

regulating the blood pressure in the human body.10

N,N,S-heteroscorpionates, on the other hand, can mimic the active site of zinc or iron

containing peptide deformylases (PDFs). These enzymes appear in plants, when they depend

on zinc, as well as in bacteria, here with ferrous cofactors that bind metal ions through two

histidine functions and one cysteine group.11-15

While Otero originally worked with pyrazole-based heteroscorpionates,5-6, 16-17 over

the years more and more research focused on imidazole-based ligands for the development of

enzyme mimics. Imidazolyl substituents can advance the water solubility of the systems and

thus can enable operations close to biological systems. Furthermore, the electronic structure

of the imidazole ring, since it is also part of histidine, is highly favorable for creating

structural enzyme mimics.18

Heteroscorpionates of the N,N,E-type are largely divided into N,N,O-ligands featuring

carboxylate, alcoholate or ether functionalities and N,N,S-ligands bearing the corresponding

M

HisN NHis

OAsp/Glu

Chapter 2 9

thio-donors (thiocarboxylates, thiols, thioethers). In the following, some examples of N,N,O-

and N,N,S-heteroscorpionates possessing imidazolyl groups will be described.

2.1.1 Bis(imidazole-2-yl)propionic acids

Unlike bis(imidazole-2-yl)acetic acids, which are prone to decompose by release of

CO2, bis(imidazole-2-yl)propionic acids are much more stable and, hence, well described in

the literature.18-20 Representative members of this family of compounds are exemplified by

ligands I-V, depicted in Figure 2.3.

Figure 2.3: A Selection of bis(imidazole-2-yl)propionic acids.

Studies of the coordination chemistry of bis(imidazole-2-yl)propionic acid (bip, I),

introduced by Leigh and Swain as early as 1977,21 showed that I frequently coordinates only

through the imidazolyl donors, causing the carboxylate functionality to dangle freely.22-23

Moreover, the formation of coordination polymers was observed.23-25 So far, only scarce

examples of tripodal N,N,O-coordinated complexes bearing I as a ligand are known.26 Hence,

further studies concentrated on the bis(N-methylimidazol-2-yl)propionic acid (bmip, II) and

its derivatives.18-20, 27-30 Sterically highly demanding ligands, such as IV and V, were also

developed19, 29 and recently, bis(imidazole-2-yl)propionic acids suitable for co-

N

N

N

N

CO2HMe Me

N

N

N

N

CO2HR R

R´R´

I R = H, R´ = HII R = Me, R´= H

III R = Vinyl R´ = HIV R = Et, R´ = iPr

V

Chapter 2 10

polymerization, such as III, were reported.20 In particular, ligand II proved to be excellent to

mimic the active site of non-heme iron dioxygenases: Iron-catecholato complexes bearing

bmip showed to react with oxygen resulting in regiospecific cleavage of the catecholato

ligand to the extradiol cleavage products.29 Hence, they mimic the active sites of extradiol-

cleaving catechol dioxygenases, a subset of the non-heme iron oxygenases.7, 31-32. Cationic

iron(II) complexes possessing the propyl ester derivative of II, such as [Fe(bmipPr)2](OTf)2,

were found to be potent catalysts for the epoxidation and dihydroxylation of olefinic

substrates.28 Thus, these complexes can model the Rieske dioxygenases, e.g. the naphthalene

1,2-dioxygenase.7, 33-34.

2.1.2 Poly(imidazolyl)methanol ligands

Many of the tridentate poly(imidazolyl)methanol ligands described in the literature

have one alcohol functionality in addition to two or three imidazolyl donors. Figure 2.4 gives

an overview of current examples.

Figure 2.4: Current examples of poly(imidazolyl)methanol ligands; R = H, Me.

N

NN

NN

N

OH

N

NN

NN N

OH

N

N

OH

N

N

R R

NN

OH

NNR R

NN

NN

NNHO

N

N N

N

R R

R

R

R MeO OH

VIII

R

VI VII

IX X XI

Chapter 2 11

In complexes, the alcohol function frequently remains non-bonded (VI, VII, IX and

X).35-38 Often, unintentional binding is even avoided through protection of the group by

etherification (VIII).39-44 However, in some cases binding tautomerism resulting in binuclear

complexes or metal clusters is observed, e.g. for ligand IX-XI.43, 45-50 Though, scarce

examples of mononuclear N,N,O-complexes with bis(imidazolyl)alcohols are known, such as,

e.g. with the ligands VIII and XI.39, 49

2.1.3 Bis(imidazolyl)thioethanol ligands

Although some zinc and iron complexes with bis(imidazolyl)thioethanol ligands are

known from the literature,51-53 mainly complexes of copper(II) have been investigated in order

to mimic the active sites of copper proteins.40-41, 54-56

Characteristically, the synthetic route results in an additional alcohol functionality at

the bridging carbon atom, which can be protected to avoid binding tautomerism. The S-donor

group can also be alkylated. Figure 2.5 illustrates two bis(imidazolyl)thioethanol ligands, XII

and XIII, both featuring the same carbon backbone structure.

Figure 2.5: Common bis(imidazolyl)thioethanols; R = H, Me; R´ = H, Ph.

2.1.4 Bis(imidazolmethyl)ethers and –thioether ligands

The coordination behavior of bis(imidazolylmethyl)ethers and thioethers, like XIV-

XVII, towards late transition metals has been studied intensively.54 In particular, iron,57

N

N

N

N

NN

NN

SRSRRORO

R´

R´ R´

R´

´R R´XII XIII

Chapter 2 12

zinc,58-59 manganese,60-62 and copper63-65 complexes of these ligands have drawn attention

with regard to their bioinorganic relevance. Because of their easy accessibility,

benzo[d]imidazole derivatives, such as XIV, XV, and XVII have mostly been employed.

Figure 2.6 shows some characteristic representatives of this class of ligands.

Figure 2.6: Examples of bis(imidazolylmethyl)ether and -thioether ligands (XIV-XVI) and a

bis(imidazolylethyl)thioether ligand (XVII); R = H, Me, Et, Pr, Bu; R´= H, Me; R´´ = H,

PhCH2.

The following part deals with the desing of novel N,N,E-heteroscorpionates and the

investigation of their binding properties.

N

NO

N

N

RR

N

NS

N

N

RR

´R

´R

R´

R´

R´

R´´R

´R

NN

S

NN

S

N

NN

N

R´´ R´´

XIV XV

XVI XVII

Chapter 2 13

2.2 Results

As mentioned in the introduction, the ligand bmip has proved to be a potent precursor

for the synthesis of structural and functional enzyme mimics and for oxidation catalysts, as

well.28 Since there exist only rare examples of anionic, tripodal ligands with imidazolyl

substituents, it was a matter of interest to increase the number of such ligands to be screened

as oxidation catalysts.

2.2.1 Tripodal ligands with bis(imidazole-1-yl)methane cores

At the outset, ligands were sought, featuring the same binding geometry as Hbmip,

simultaneously offering different donors.

2.2.1.1 Syntheses of the ligands

The synthesis of 3,3-bis(N-methylimidazol-2-yl)propionic acid (Hbmip, II), described

in the literature, is based on N-methylimidazole (1) (Scheme 2.1).18 Within this procedure, N-

methylimidazole is reacted with n-BuLi and diethyl carbonate to form a bis(N-

methylimidazol-2-yl)ketone (2, bmik). Subsequent Wolff-Kishner reduction results in 3.66

Deprotonation of the methylene linker with n-BuLi, followed by treatment with methyl

bromoacetate yields methyl 3,3-bis(N-methylimidazol-2-yl)propionate (4, bmipMe). Finally,

saponification and acidic workup gives II.18,19

Similar deprotonation of 3 with n-BuLi followed by reaction with electrophiles

seemed to offer a convenient way to ligands varying in the third donor group while

maintaining the binding geometry of the bis(imidazolyl)methane core.

Chapter 2 14

N

N

N

N

N

N

N

N

N

N

N

N

O

CO2Me

N

N

N

N

CO2H

N

N

2 3

4

ii)

iii)

iv)

i)

II

1

Scheme 2.1: Synthesis of Hbmip; i) 1. n-BuLi, THF, –40 °C, 2. CO(OEt)2, –80 °C; ii) KOH,

N2H4, reflux; iii) 1. n-BuLi, THF, –80 °C, 2. BrCH2CO2Me, –40 °C; iv) 1. NaOH (aq.), THF,

reflux, 2. HCl.

Following the concept described above, reaction of 3 and p-formaldehyde afforded the

novel N,N,O-heteroscorpionate ligand 2,2-bis(N-methylimidazol-2-yl)ethanol (2,2-Hbmie, 5)

as depicted in Scheme 2.2. This sequence shows analogies to the synthesis of bis(3,5-

dimethylpyrazol-1-yl)ethanol (Hbdmpze) reported by Hammes and Carrano.67

Scheme 2.2: Synthesis of 5; 1. n-BuLi, THF, –40 °C, 2. p-formaldehyde, –60 °C, 3. H2O.

The formation of the product is clearly indicated by NMR spectroscopy. Due to the Cs

symmetry of the compound in solution, only two signals for the two spectroscopically

equivalent imidazole rings are observed in the 1H NMR spectrum at 6.75 ppm and 7.01 ppm.

N

N

N

N

N

N

N

N

OH

2 5

i)

Chapter 2 15

The ethanol fuctionality gives rise to the two triplet at 4.97 ppm (OH) and 4.48 ppm (bridging

CH group) as well as to a virtual triplet at 4.08 ppm (CH2 group). The 13C{1H}

NMR spectrum exhibits the CH2 group at 38.9 ppm and the bridging CH at 62.7 ppm.

A single crystal X-ray structure analysis of 5 showed the ligand to possess a geometry

similar to the corresponding bis(pyrazol-1-yl)acetic acids or bis(pyrazol-1-yl)ethanols, which

have previously been employed in organometallic chemistry (Figure 2.7).67 As an important

property for comparable applications compound 5 showed sufficient solubility in common

organic solvents such as CH2Cl2 and THF.

Figure 2.7: Molecular structure of 5; thermal ellipsoids are drawn at the 50% probability

level; hydrogen atoms, apart from H10, and co-crystallized solvent molecules have been

omitted for clarity; selected bond lengths (Å) and angles (°): C1-C11 1.505(2), C1-C21

1.501(2), C1-C2 1.535(2), C2-O1 1.4155(2); C11-C1-C21 111.4(1).

The reaction of 3 with n-BuLi and CS2 resulted in lithium bis(N-methylimidazol-2-

yl)dithioacetate (Li[bmidta], 6) (Scheme 2.3). The 1H and 13C{1H} NMR spectra of

Li[bmidta] exhibit one set of signals for the imidazole rings as expeced for a Cs symmetrical

molecule.

Chapter 2 16

Scheme 2.3: Synthesis of 6; i) 1. n-BuLi, THF, –40 °C, 2. CS2.

The CS2 carbon signal is observed at 249.1 ppm in the 13C{1H} NMR spectrum. The

IR bands of this dithioacetate functionality (1030 νas(C=S) and 840 νs(C-S) cm–1) are assigned

according to the values of the analogous bis(3,5-dimethylpyrazol-1-yl)dithioacetate (1081

νas(C=S) and 879 νs(C-S) cm–1) and bis(3,5-diphenylpyrazol-1-yl)dithioacetate (1078 νas(C=S)

and 831 νs(C-S) cm–1) compounds reported by Otero.68 Crystals suitable for X-ray structure

determination were obtained on attempted recrystallization of 6 from hot methanol (Figure

2.8).

Figure 2.8: Molecular structure of 6 × bmim; thermal ellipsoids are drawn at the 50%

probability level; the 15 % occupancy fraction of the disordered molecule is depicted with

dashed bonds; selected bond lengths (Å) and angles (°): C1-C11 1.502(2), C1-C21 1.503(2),

C1-C2 1.579(2), C2-S1 1.675(2), C2-S2 1.687(2), N12-Li 2.063(3), N22-Li 2.022(3), N32-Li

2.037(3), N42-Li 2.090(3); N12-Li-N22 90.67(13), N32-Li-N42 91.06(13).

N

N

N

N

3 6

i)

N

N

N

N

CS2−

Li+

Chapter 2 17

The molecular structure exhibits the composition 6 × bmim in which Li+ coordinates

two imidazole rings of a bmidta anion and two more of a bmim molecule, which was

probably formed by decomposition of 6 in hot methanol. Unfortunately, the structure is

slightly disordered with bmidta and bmim partly sharing common positions (occupancies

85:15). Nevertheless, the molecular structure of 6 × bmim confirms the formation of the novel

imidazole-based N,N,S-heteroscorpionate ligand 6.

2.2.1.2 Syntheses of the metal complexes

To probe of the coordination behavior of the two novel bis(imidazol-2-yl)methane-

based ligands and for comparison, complexes were targeted for which analogous examples

bearing conventional heteroscorpionate ligands – such as bis(pyrazole-1-yl)acetic acid

(Hbdmpza) and bis(imidazol-2-yl)propionic acid (Hbmip, II) – are already known.

Furthermore, the complexes should be diamagnetic to enable investigation by NMR

spectroscopy and – if possible – offer carbonyl ligands as sensitive probes to investigate the

donor properties of the new ligands. Their coordination behavior in these complexes can be

considered as a prototype of their properties.

The coordination motif adopted by the 2,2-bmie anion was tested by the synthesis of

[Re(2,2-bmie)(CO)3] (7). Group VII metal complexes with several bis(pyrazol-1-yl)acetic and

bis(imidazol-2-yl)propionic acids have been reported in the literature.18, 69 Hence, similar to

the synthetic procedure described for [Re(bmip)(CO)3]18, [ReBr(CO)5] was reacted with in

situ synthesized K[2,2-bmie] to give the tricarbonyl rhenium complex [Re(2,2-bmie)(CO)3]

(Scheme 2.4) in moderate yield of 41%, which was purified by repeatedly washing with

CH2Cl2.

Chapter 2 18

Scheme 2.4: Synthesis of 7; i) 1. t-BuOK, THF; 2. [ReBr(CO)5].

The lower yield as compared to that of [Re(bmip)(CO)3]18 probably arises from slow

decomposition of 5 upon prolonged heating in basic solution.

In full agreement with the presence of a Cs symmetric molecule, the IR spectrum of 7

shows the characteristic three A´, A´´ and the A´ signals of a facial tricarbonyl complex at

1997 cm–1, 1892 cm–1, and 1847 cm–1. Compared to the corresponding rhenium complexes of

bmip and especially the bis(pyrazol-1-yl)acetato ligands (Table 2.1), the carbonyl signals are

shifted to lower wavenumbers, which indicates a rather high electron donating character of

the 2,2-bmie system. Unfortunately, no rhenium(I) complexes bearing N,N,O-coordinated

bis(pyrazol-1-yl)ethanolate or related imidazole-based alcoholate ligands, have been reported

so far, such that a direct comparison to alcoholate heteroscorpionates was not possible. Santos

and coworkers did report on the synthesis of some rhenium(I) and technetium(I) complexes

bearing bis- and tris(pyrazol-1-yl)ethanole ethers70 but none of these complexes shows

N,N,O-coordination.

N

N

N

N

Re

C

7

CC OO

O

O

N

N

N

N

OH

i)

5

Chapter 2 19

Table 2.1: Selected IR signals of [ReL(CO)3] (L = 2,2-bmie, rac-1,2-bmie, bmip, bpza,

bdmpza and bmip). a

vas(CO2)

Complex

KBr solution

[Re(2,2-bmie)(CO)3] (7) 1997, 1892, 1847 2017, 1905, 1889b

[Re(rac-1,2-bmie)(CO)3] (22) 2002, 1886, 1845 2007, 1890, 1869c

[Re(bmip)(CO)3] 2018, 1898, 1867 2023, 1914, 1896b

[Re(bdmpza)(CO)3] 2023, 1915, 1903, 1883 2030, 1926, 1908b

[Re(bpza)(CO)3] 2028, 1922, 1906, 1895 2029,1924, 1904d

a All v(CO) values are given in cm–1. b MeOH. c CH2Cl2. d THF

The 13C{1H} NMR spectrum of 7 shows two signals for the carbonyl carbon atoms at

197.7 ppm and 198.9 ppm as well as one signal set for the imidazole rings, which supports the

Cs symmetry of the complex with a κ3-coordinated heteroscorpionate ligand.

Finally, the κ3-coordination of the ligand was unequivocally established by an X-ray

structure determination (Figure 2.9).

Compared to distance d(Re-C4) = 1.896(3) Å, the bond lenghts d(Re-C3) = 1.913(3) Å and

d(Re-C5) = 1.905(3) Å are slightly elongated, which can be attributed to the trans influence

of the imidazolyl donors, exhibiting σ-donor, π-donor and π-acceptor properties.18 For further

comparative studies, the synthesis of additional [Re(L)(CO)3] compounds with L= bpze,

bdmpze and bmidta was targeted. Disappointingly, reactions between K[bpze], K[bdmpze] or

Li[bmidta] and [ReBr(CO)5] did not lead to well defined products – presumably due to

degradation of the ligands under the reaction conditions.

Chapter 2 20

Figure 2.9: Molecular structure of [Re(2,2-bmie)(CO)3] (7); thermal ellipsoids are drawn at

the 50% probability level; hydrogen atoms have been omitted for clarity; selected bond

lengths (Å) and angles (°): Re-C3 1.913(3), Re-C4 1.896(3), Re-C5 1.905(3), Re-N12

2.174(2), Re-N22 2.175(3), Re-O1 2.121(2), C3-O3 1.152(4), C4-O4 1.161(4), C5-O5

1.166(4), C1-C2 1.569(4), C1-C11 1.493(4), C1-C21 1.500(4); O1-Re-N12 82.57(8), O1-Re-

N22 81.80(9), N12-Re-N22 81.26(9), C3-Re-C4 88.62(14), C3-Re-C5 90.12(13), C4-Re-C5

85.82(13), O1-Re-C4 176.38(10).

For investigation of the coordination behaviour of bmidta, [Ru(L)Cl(PPh3)2]-type

complexes were chosen as target compounds. Ruthenium, as the higher homologue of iron, is

frequently used in initial studies modeling analog iron compounds, because its complexes can

more easily be investigated by NMR spectroscopy. Heteroscorpionate containing

Ru(L)Cl(PPh3)2 type complexes are well known in the literature.71-74 Mostly, the chloride

anion and one of the PPh3 molecules can easily be exchanged by various other ligands.

Hence, similar substitution reactions employing [Ru(bmidta)Cl(PPh3)2] (8) as a precursor

seemed promising. As expected, the reaction of Li[bmidta] with [RuCl2(PPh3)3] resulted in

the formation of [Ru(bmidta)Cl(PPh3)2] (Scheme 2.5).

Chapter 2 21

Scheme 2.5: Synthesis of [Ru(bmidta)Cl(PPh3)2]; i) [RuCl2(PPh3)3], THF.

The complex, which crystallized from the reaction mixture as an air-stable compound

in addition with 1 equivivalent of THF, was characterized by elemental analysis, as well as by

IR and 1H, 13C{1H} and 31P{1H} NMR spectroscopy. As expected, the NMR spectra exhibit

sharp signals. Full tridentate coordination of the bmidta ligand is indicated by the position of

the imidazolyl and the methyl proton resonances (6.03 ppm and 5.99 ppm (CHim), and 3.59

ppm (CH3)), which are shifted to higher field compared to those of the free ligand (6.94 ppm

and 6.65 ppm (CHim), and 3.66 ppm (CH3)).

The integration of the PPh3 multiplet signal agrees with the coordination of two

phosphine molecules. The appearance of one singlet signal in the 31P{1H} NMR spectrum (δ

= 36.4 ppm) and of only one sharp set of signals for the imidazole rings in the 1H and 13C{1H}

NMR spectra, further supports Cs symmetry of complex 8 with the phosphines in trans

position to the imidazolyl donors. The dithiocarboxylate group, a soft base, should strongly

coordinate through one sulfur atom. Similar to the complexes reported by Cao and coworkers

this should result in a significant high field shift of the dithiocarboxylate 13C{1H} resonance.75

In fact, the signal of the CS2– carbon atom of the coordinated ligand shows up at 237.6 ppm

that of the uncoordinated ligand at 249.1 ppm.

The IR data support the presence of a tripodal κ3-coordinated bmidta ligand by a

significant shift of the νas(C=S) band from 1030 cm–1 in the free ligand to 1016 cm–1 in the

complex. An assignment of the symmetrical dithiocarboxylate vibration was not possible

because of overlap with several imidazole or phenyl absorptions in the same region.

N

N

N

N

Ru

Cl PPh3Ph3P

Si)S

N

N

N

N

CS2−Li+

6 8

Chapter 2 22

Following these initial studies, complexes of the new heteroscorpionate ligands with

the biorelevant metals iron(II) and zinc(II) were targeted. The low steric demand of the

ligands should lead to octahedral bis(ligand)complexes with N,N,E-binding motif (E = O, S).

Preparations of bis(ligand)complexes bearing 2,2-bmie were attempted by a procedure similar

to that of [Re(2,2-bmie)(CO)3] employing the metal dichlorides MCl2 (M = Fe, Zn) as starting

material. But, as already mentioned above, the alcoholate K[2,2-bmie] turned out to be

instable under the reaction conditions and no defined products were isolated.

In a procedure similar to that described for the synthesis of [Fe(bmip)2],28 Li[bmidta]

was combined with MCl2 (M = Fe, Zn) in MeOH and actually gave [Fe(bmidta)2] (9) as a

blue and [Zn(bmidta)2] (10) as a pale orange complex (Scheme 2.6). Both compounds

precipitate directly from the reaction mixtures, and showed to be insoluble in every common

solvent. The formation of bis(ligand) complexes was established by elemental analysis.

Coordination of the bmidta chelate system akin to that observed for [Ru(bmidta)Cl(PPh3)2]

can therefore be assumed and is also supported by a significant shift of the νas(C=S) band

from 1030 cm–1 to 1014 cm–1 for [Fe(bmidta)2] and 1020 cm–1 for [Zn(bmidta)2], respectively.

Although, the formation of coordination polymers like [Fe(bmidta)2]n or [Zn(bmidta)2]n

cannot be excluded.

Scheme 2.6: Synthesis of the complexes [Fe(bmidta)2] 9 and [Zn(bmidta)2] 10.

N

N

N

N

M

S

i)

S

N

N

N

N

CS2−Li+

6

N

N

N

N

SS

9 (M = Fe)10 (M = Zn)

Chapter 2 23

2.2.2 Tripodal ligands without bis(imidazole-1-yl)methane cores

The ligand bmip has been shown to bind to metal centers with the classic rigid

geometry exhibited by most of the heteroscorpionates.18-19, 27-29, 76 The imidazole rings are

ligated angulately, directly attached through the 2-position to the ligand backbone and the

carboxylate functionality is anti-coordinated (Figure 2.10i). However, this does not exactly

represent the binding motif exhibited by enzymes with a 2-His-1-carboxylate triad, such as by

the Isopenicillin N Synthase and the Extradiol Cleaving Chatechol Dioxygenases 77-78(see

Figure 2.10.). In the active site of these enzymes the carboxylate binds syn towards iron. The

imidazolyl group is attached through the 4-position (ε-position) to the protein backbone, with

a methylene-spacer in between. This results in a twisted arrangement of the imidazolyl donors

around central metal.

Figure 2.10: Cutout of the N,N,O-motif; i) classic heteroscorpionates, exemplified by the

model complex [Mn(bmip)(CO)3]; ii) in enzymes with 2-His-1-Carboxylate triad, exemplified

by the INPS (PDB-Code 1QJE)79.

Chapter 2 24

Against the background of biomimetic catalysis, ligands were developed, which mirror

the binding motif found in these enzymes more closely or which at least exhibit some of the

properties outlined above. Especially ligands with one or two methylene spacers were

targeted. In order to investigate the binding motif of non-carboxylate heteroscorpionates,

ligands with alcoholate functionalities were also of interest. In this context, rac-1,2-bis(N-

methylimidazol-2-yl)ethanol (rac-1,2-Hbmie) and bis(N-methylimidazol-2-ylmethyl)acetic

acid (Hbmima) as well as bis(N-methylbenzo[d]imidazol-2-ylmethyl)acetic acid (Hbmimabo)

appeared to be attractive targets.

2.2.2.1 Syntheses of the ligands

To obtain the ligands rac-1,2-Hbmie, Hbmima and Hbmimabo, synthetic pathways

different from the one established for the methane-core ligands had to be developed.

The ligand rac-1,2-Hbmie was obtained by a two step synthesis. Starting from N-

methyimidazole, which was deprotonated with n-BuLi and further reacted with N,N-

dimethylformamide, N-methyl-2-imidazolecarboxaldehyde (11) was formed (Scheme 2.7).80

Treating 11 with in situ generated lithium[N-methylimidazol-2-ylmethanid] led to rac-1,2-

Hbmie (12), as anticipated. The formation of the compound was indicated by 1H and 13C{1H}

NMR spectroscopy. Due to the C1 symmetry of the molecule, the imidazole rings give rise to

two sets of interfering signals at 6.92 ppm (broad singlet), 6.84 ppm (doublet) and 6.81 ppm

(doublet).

Scheme 2.7: Synthesis of rac-1,2-Hbmie; i) 1. n-BuLi, THF, –40 °C, 2. DMF, –80 °C; ii) 1.

1,2-dimethylimidazole, n-BuLi, THF, –40 °C, 2. X, –80 °C.

N

N

O

N

Ni) ii) N

N OH

N

N

11 12

Chapter 2 25

For the ethanol backbone, 1H signals characteristic of ABX spin systems are observed,

viz. one doublet of doublets at 5.33 ppm (bridging CH, X-part), accompanied by the two

double doublets at 3.29 ppm and 3.44 ppm (bridging CH2, AB-part). The 13C{1H} NMR

spectrum exhibits the CH2 group at 31.2 ppm and the CH bridge at 64.6 ppm. Finally, the

molecular structure of rac-1,2-Hbmie (12) was confirmed by a single crystal X-ray structure

analysis, the result of which is depicted in Figure 2.11.

Figure 2.11: Molecular structure of 12; thermal ellipsoids are drawn at the 50% probability

level; hydrogen atoms apart from H1A and H1B have been omitted for clarity; selected bond

lengths (Å) and angles (°): C7-O1, 1.4303(15), C7-C12 1.5073(16), C7-C8 1.5348(18), C8-

C22 1.4965(17), C12-N13 1.3236(16), C12-N11 1.3662(16), C22-N23 1.3313(17), C22-N21

1.3582(16), N23-O1 2.770(4), O1-C7-C12 108.67(10), O1-C7-C8 109.54(10), N13-C12-N11

111.45(11), N23-C22-N21 110.71(12), O1-H1-N23 179.85(7), N23…H1 1.950(3).

The ligand crystallizes as a racemic mixture of its isomers in space group P1, one of

each filling the triclinic unit cell. The imidazole rings adopt a slightly twisted conformation.

The OH proton is hydrogen bridged to the imidazolyl nitrogen atom N3 of the second ligand.

Chapter 2 26

Two novel N,N,O-ligands with two methylene spacers were likewise synthesized:

Bis(N-methylimidazol-2-ylmethyl)acetate (bmima) as a small ligand of low steric demand,

and bis(N-methylbenzo[d]imidazol-2-ylmethyl)acetate (bmimabo) offering enhanced steric

hindrance. These two ligands were obtained following a general route, which started from

4,5-substituted (imidazol-2-yl)methanol derivatives (see Scheme 2.8). According to published

procedures81-83 N-methylimidazol-2-ylmethanole (13) and N-methylbenzo[d]imidazol-2-

ylmethanole (14) were easily be prepared on a multigram scale and subsequently converted to

the corresponding hydrochlorides of 2-chloromethylimidazole (15) and 2-

chloromethylbenzo[d]imidazole (16).84-85 In the following steps, a procedure similar to that

reported by Sasai and coworkers was employed:86 Reaction of the hydrochlorides 15 and 16

with diethylmalonate and sodium hydride followed by hydrolysis and decarboxylation

resulted in the formation of the dihydrochlorides of the ligands, Hbmimabo × 2 HCl (17) and

Hbmima × 2 HCl (18), respectively. If anhydrous workup, as described by Sasai, was

employed the isolation of debmimm (19) was also possible.86 This compound is an interesting

neutral ligand itself, which might establish an N,N,O-coordination motif. Compound 19 can

be hydrolyzed and decarboxylated to produce K[bmima] (21) as a synthon of bmima

complexes. The acid Hbmimabo (20) precipitated from aqueous solution by neutralization of

Hbmimabo × 2 HCl with KOH. Isolation of the acid Hbmima by neutralization of Hbmima × 2

HCl failed, due to equal solubility of Hbmima and the liberated KCl. The syntheses applied

for the ligands bmima, bmimabo are summarized in Scheme 2.8.

The formation of 18 is clearly indicated by 1H NMR data, revealing a characteristic

ABX spin system of the protons of the carbon backbone with the two diastereotopic protons

of each methylene group at 3.24 ppm and 3.47 ppm, and the methine proton at 3.82 ppm (2JAB

= 15.4 Hz, 3JAX = 6.4 Hz, 3JBX = 8.3 Hz). In solution only two signals for the two

spectroscopically equivalent imidazole rings are observed in the 1H NMR spectrum at 7.58

ppm and 7.63 ppm. The 13C{1H} NMR spectrum exhibits the characteristic signal for the

carboxylate functionality at 172.7 ppm. The IR νas(CO2) band is observed at 1719 cm–1 (KBr).

Chapter 2 27

Scheme 2.8: Synthetic pathways to the ligands bmima and bmimabo; i) 1. glycolic acid, 120

°C, 2. NaH, THF, rt, 3. MeI, rt; ii) p-formaldehyde, 140 °C; iii) SOCl2, CH2Cl2, rt; iv) 1.

diethyl malonate, NaH, THF, 0 °C to rt, 2. NaOH, H2O, reflux, 3. HCl, H2O, rt; v) 1. diethyl

malonate, NaH, THF, 0 °C, anhydrous workup; vi) NaOH (2 eqiv.), H2O; vii) KOH (<1

eqiv.), H2O, reflux.

v)

H+

N

N Cl

Cl−

N

NH+ +HN

N2 Cl−

OHO

iii)

N

N

OH

NH2

NH2

i)

N

Nii)

N

N N

N

OHO

N

NH+ +HN

N2 Cl−

OHOvi)

iv)

N

N N

N

O−O

K+

NN N

N

EtO2C CO2Et

iv)

vii)

13 (imidazole)14 (benzoimidazole)

15 (imidazole)16 (benzoimidazole)

17

20 21

19

18

Chapter 2 28

Finally, the X-ray structure analysis revealed the molecular structure of Hbmima × 2

HCl, as shown in Figure 2.12. The close distance between the protonated imidazolyl nitrogen

atom N12 and the chlorido counter ion Cl1 of 3.047(1) leads one to assume the presence of a

hydrogen bond.

Figure 2.12: Molecular structure of 18; thermal ellipsoids are drawn at the 50% probability

level; hydrogen atoms, apart from H1, H11, and H21 have been omitted for clarity; selected

bond lengths (Å) and angles (°): C1-O21.2085(18), C1-O1 1.3124(17), C1-C4 1.5453(19),

C2-C3 1.5488(18), C3-C11 1.4874(19), C4-C21 1.491(1), C11-N12 1.3314(19), C11-N11

1.3378(18), C12-N12 1.3787(19), C21-N22 1.3348; O2-C1-O1 123.86(14), O2-C1-C2

123.59(13), O1-C1-C4 111.98(11), N12-C11-N11 107.60(12), N22-C21-N21 107.01(13);

H11...Cl1 2.232(20), Cl2...H21 2.905(21), N12…Cl1 3.047(1).

In the 1H NMR spectrum of K[bmima] (21), recorded in D2O, again one set of signals

is observed for the two imidazole rings at 6.83 ppm and 6.93 ppm (CHim) as well as at 3.57

ppm (NCH3). The protons of the methylene and methine groups are superimposed to

unresolved multiplets at 2.76 ppm and 2.99 ppm. In the 13C{1H} NMR spectrum, the

characteristic signal of the carboxylate group appears at 182.4 ppm.

Both Hbmimabo × 2 HCl and Hbmimabo, were fully characterized by 1H NMR and

13C{1H} NMR spectroscopy, mass spectrometry and elemental analysis, all of which clearly

Chapter 2 29

indicated the formation of the target compounds. The IR spectra (KBr) show the characteristic

asymmetric strechtching vibration of the carboxylate group at 1730 cm–1 for Hbmimabo × 2

HCl and at 1715 cm–1 for Hbmimabo. The molecular structure of Hbmimabo was studied by X-

ray structure analysis (Figure 2.13). Unfortunately, the structure turned out to be slightly

disordered with regard to the carboxylate functionality and the carbon backbone, and will

therefore not be discussed in detail.

Figure 2.13: Molecular structure of 20; thermal ellipsoids are drawn at the 50% probability

level; hydrogen atoms, apart from H1 have been omitted for clarity; site occupancy of

backbone carbon atoms C2A and C4A: 70%; Selected bond lengths (Å) and angles (°): C1-O2

1.156(7), C1-O1 1.268(6), C11-N12 1.273(5), C11-N11 1.295(5), C21-N21 1.256(5), C21-

N22 1.363(5); O2-C1-O1 124.0(5), N12-C11-N11 111.4(3), N21-C21-N22 110.4(3).

2.2.2.2 Syntheses of the metal complexes

The binding properties of the ligands were checked by complexation towards the

Re(CO)3 fragment. Reaction of rac-1,2-Hbmie with t-BuOK afforded the complex [Re(rac-

1,2-bmie)(CO)3], as shown in Scheme 2.9. The IR spectrum exhibits the characteristic three

carbonyl signals at 2002 cm–1, 1886 cm–1, 1845 cm–1, arising from ν(CO) carbonyl stretching

Chapter 2 30

Re

C

22a

CC OO

O

i)N

N OH

N

N

N

NO

N

N

N

NO

N

N

Re

C CC OO

O

22b12

vibrations of the Re(CO)3 fragment bearing the κ3-coordinated tripod ligand. They compare

favorably with the absorptions observed for [Re(2,2-bmie)(CO)3] (1997 cm–1, 1892 cm–1,

1847 cm–1, see Table 2.1), which leads one to assume that the donor strengths of the two

alcoholate ligands seem almost equal.

Scheme 2.9: Synthesis of [Re(rac-1,2-bmie)(CO)3] (22); i) 1. t-BuOK, THF, 2. [ReBr(CO)5].

In the 1H NMR spectrum of the complex, the two sets of signals for the imidazolyl

protons are not resolved and give rise to a multiplet at 7.04 ppm. The protons of the ethanol

backbone show up as poorly resolved multiplets at 3.14 (CH2) and 5.64 (CH). Surprisingly, in

the 13C{1H} NMR only two carbonyl resonances are observed at 193.3 ppm and 212.5 ppm,

which may be due to a similar electronical environment of the two carbonyl carbons trans to

the imidazoles. Unfortunately, the anionic rac-1,2-bmie alcoholate seems to be as unstable as

the corresponding 2,2-bmie alcoholate and gave [Re(rac-1,2-bmie)(CO)3] only in poor yields

(36%). Due to decomposition of the ligand in basic solutions, attempted syntheses of the

corresponding iron and zinc complexes failed.

Coordination of the ligand bmima to the Re(CO)3 fragment was attempted by reaction

of in situ generated K[bmima] with [ReBr(CO)5] (Scheme 2.10). The isolated product

displayed only two instead of three ν(CO) infrared bands: One sharp signal at 2019 cm–1

accompanied by a broad band at 1890 cm–1. Although this could be in fair agreement with the

Chapter 2 31

IR characteristics of [Re(bmip)(CO)3] (2018 cm–1, 1898 cm–1 and 1887 cm–1), no elemental

analyses corresponding to the composition [Re(bmima)(CO)3] were obtained.

Scheme 2.10: Attempted Synthesis of [Re(bmima)(CO)3]; i) 1. KOH, THF, 2. [ReBr(CO)5].

Finally, the result of an X-ray structure determination revealed that

[ReBr(Hbmima)(CO)3] (23) instead of [Re(bmima)(CO)3] had been formed (Figure 2.14).

Although, the molecular structure turned out to be severely disordered and could not be

sufficiently refined, it was asserted that bmima is not κ3-coordinated to the Re(CO)3 fragment.

Instead, only N,N-chelation with a dangling protonated carboxylate functionality does occur,

and the sixth coordination site is occupied by a bromide ion.

All attempts to obtain any complexes of Mn(II), Fe(II), Co(II), Ni(II), Cu(II), or Zn(II)

possessing the ligands bmima and bmimabo in tripodal κ3-coordination failed. If procedures

similar to the ones described for [M(bmip)2]19, 28 (M = Fe, Cu) were employed, no defined

NN N

N

Re

C CC OO

O

O

O

N

NH+ +HN

N2 Cl−

OHO

i)

18

NN N

N

Re

C CC OO

O

OHO

i)

Br

23

Chapter 2 32

products whatever could be isolated for Mn(II), Fe(II), Co(II), Ni(II), Cu(II), or Zn(II). In the

reaction of Zn(OAc)2 with Hbmima × HCl × H2O coordination polymers were obtained (for

further details see Chapter 4).

Figure 2.14: Molecular structure of [ReBr(Hbmima)(CO)3] (23);87 thermal ellipsoids are

drawn at the 50% probability level; hydrogen atoms, apart from H1A3 and co-crystallized

solvent molecules have been omitted for clarity; only one enantiomer is shown; selected bond

lengths (Å) and angles (°): ReA-Br1A 2.6156(9), ReA-C31A 1.921(6), ReA-C32A 1.958(7),

ReA-C33A 1.907(6), ReA-N21A 2.234(5), ReA-N11A 2.211(5), C31A-O31A 1.150(7),

C32A-O32A 1.083(7), C33A-O33A 1.153(8), C4A-O2A 1.216(7), C4A-O1A 1.332(6), C2A-

C4A 1.504(7), C31-O31 1.157(7); C33A-ReA-C31A 87.6(3), C33A-ReA-C32A 89.4(3),

C31A-ReA-C32A 89.3(2), N11A-ReA-N21A 94.60(16), C32A-ReA-Br1A 176.19(15),

N11A-ReA-Br1A 84.45(13), N21A-ReA-Br1A 85.83(12);

Chapter 2 33

As noted in the introduction, Klein Gebbink, Bruijnincx, and coworkers reported on

[Fe(bmipPr)2](OTf)2 as a potent catalyst for the epoxidation and cis-dihydroxylation of

olefins.28 For the octahedrally coordinated bis(ligand) complex a catalytic cycle was

suggested, in which the ester functionality is only bound weakly to the metal center and can

be easily replaced by a molecule of the substrate.

In this respect, it seemed of interest to investigate the coordination behavior of the

debmimm chelate ligand to transition metals, particularly towards iron. Furthermore, since

identical coordination motifs had been established for complexes of the ligands bmip and

bmipPr, an emulation of the unrevealed bonding properties of the bmima chelate (see before)

by metal complexes of the structurally related debmimm ligand was feasible.

In a procedure similar to the synthesis of [Fe(bmipPr)2](OTf)2,28 debmimm was

reacted with Fe(OTf)2 × 2 MeCN to form [Fe(OTf)2(debmimm)2] (24). As indicated by FD

mass spectrometry, the expected bis(ligand) complex is produced (Scheme 2.11).

Scheme 2.11: Synthesis of [Fe(OTf)2(debmimm)2]; i) Fe(OTf)2 × 2 MeCN, MeOH, 60 °C.

The NMR spectra of the product showed only broad signals, which might indicate the

formation of a high spin species.

NN N

N

EtO2C CO2Et

i)

19

NN N

N

M OTfOTf

NNN

N

24

EtO2C CO2Et

EtO2C CO2Et

Chapter 2 34

Instead of acting as a tridentate N,N,O-ligand, debmimm is only bonded through the

two imidazolyl donors, the two ester groups are not coordinated to the metal center. As a

consequence, the wavenumber of the νas(CO2) vibration of the complex (1732 cm–1) is only

slightly different from that shown by the free ligand (1726 cm–1) and is furthermore close to

the νas(CO2) band of [Fe(bmipPr)2(MeOH)2](OTf)2 (1732 cm–1), in which the bmipPr chelate

binds in bidentate N,N-fashion.28 In contrast to these findings, the complex

[Fe(bmip)2](OTf)2, featuring bmip in tridentate N,N,O-coordination, displays the νas(CO2)

vibration at 1689 cm–1.28

Finally, an X-ray crystal structure determination gave unequivocal evidence of the

N,N-chelation of debmimm. The four N-donors are positioned cis to each other, analogously

to the complex [Fe(bmip)2(MeOH)2](OTf)2.28 Interestingly, but different from the latter, the

triflates ions rather than the solvent molecules are cis-bonded to the central metal (Figure

2.15). Both the Fe-N distances and the N-Fe-N angles agree nicely with the ones observed for

[Fe(bmipPr)2(MeOH)2](OTf)2.28 However, the more flexible carbon backbone of debmimm

allows a slightly twisted position of the imidazole rings, which is not observed for

[Fe(bmipPr)2(MeOH)2](OTf)2.28

Chapter 2 35

Figure 2.15: Molecular structure of 24; thermal ellipsoids are drawn at the 50% probability

level; hydrogen atoms have been omitted for clarity; selected bond lengths (Å) and angles (°):

Fe1-N41 2.178(7), Fe1-N21 2.181(7), Fe1-N11 2.184(7), Fe-N51 2.196(6), Fe1-O61

2.270(7), Fe1-O71 2.271(7); N21-Fe1-N11 99.9(3), N41-Fe1-N51 98.9(3), N41-Fe1-O61

174.9(2), N21-Fe1-O61 82.8(3), N11-Fe1-O61 90.8(3), N51-Fe1-O61 86.1(2), N11-Fe1-O71

174.9(2), O61-Fe1-O71 87.9(3).

Chapter 2 36

euUsually, free coordination sites are essential for metal complexes with catalytic

activity. For [Fe(OTf)2(debmimm)2] this might be attained by substitution of the weakly

bonded triflate ligands in solution.

However, with the objective of gaining metal complexes with free coordination sites,

monoligand-bis(chlorido) complexes were also targeted. In a first approach, the metal(II)

chlorides were chosen as precursors, because bis(pyrazole) and bis(benzo[d]imidazole)

ligands had been reported to favor tetrahedral coordination in dichlorido compounds of

several 3d metals.88-89 Reactions of debmimm with MCl2 (M = Mn, Fe, Co, Ni, Cu, Zn) were

performed in 1:1 molar stoichiometry (Scheme 2.12) as outlined above for the synthesis of

[Fe(OTf)2(debmimm)2].

Scheme 2.12: Synthesis of the complexes [MCl2(debmimm)] (M = Fe, Co, Ni, Cu, Zn); i)

MCl2, MeOH, 45-50 °C.

The IR spectra (KBr) of all complexes 25-30 show the asymmetric ester stretching

vibration in the region from 1729 cm–1 to 1739 cm–1, which indicates a similar binding motif

of the debmimm ligand as found in its iron triflate complex. Table 2.2 shows an overview of

the characteristic IR signals.

NN N

N

M

ClCl

EtO2C CO2Et

NN N

N

EtO2C CO2Et

i)

19

25 (M = Fe)26 (M = Mn)27 (M = Co)28 (M = Ni)29 (M = Cu)30 (M = Zn)

Chapter 2 37

Table 2.2: Key IR vas(CO2) values of [MCl2(debmimm)] (M = Mn , Fe, Co, Ni, Cu, Zn)

25-30 and [Fe(OTf)2(debmimm)2] (24)a.

vas(CO2)

Complex

KBr solution

[Fe(OTf)2(debmimm)2]

(24) 1732 1735b

[FeCl2(debmimm)]

(25) 1738 1737b

[MnCl2(debmimm)]

(26) 1739 1736b

[CoCl2(debmimm)]

(27) 1730 1736b

[NiCl2(debmimm)]

(28) 1729 1732b

[CuCl2(debmimm)]

(29) 1732 1734c

[ZnCl2(debmimm)]

(30) 1731 1736b

a All vas(CO2) values are given in cm–1. b CH2Cl2. c CHCl3.

Finally, the tetrahedral coordination in all [MCl2(debmimm)] complexes was

established by X-ray structure analysis. As an example, the structure of [FeCl2(debmimm)]

(25) is given in Figure 2.16. Selected bond lengths and angles for the complexes

[MCl2(debmimm)] (with M = Mn, Fe, Co, Ni, Cu, Zn) are presented in Table 2.3.

Transesterification did occur for 27 during recrystallization from MeOH/Et2O solvent

mixtures, such that only crystals of the composition [CoCl2(dmbmimm)] (27b) (with

dmbmimm = dimethyl bis(N-methylimidazol-2-yl)methylmalonate) were obtained.

Chapter 2 38

Nevertheless, the N,N-binding motif of the two ligands dmbmimm and debmimm are barely

different and structural comparison is feasible.90 The Mn(II), Fe(II), Co(II), and Zn(II)

complexes exhibit all slightly distorted tetrahedral coordination spheres, with angles reaching

from 103° (N-M-Cl) to 119° (Cl-M-Cl). In the Ni(II) and Cu(II) complexes 28 and 29 the

distortion is more pronounced. Thus, the Cl-M-Cl angle spreads to ca. 127° for 28 and the N-

M-Cl angles is enlarged up to 133° for 29. Similar trends were also observed by others for

related bis(benzo[d]imidazole) ligands having ethylene or propylene spacers.89, 91

Figure 2.16: Molecular structure of 25; only one f the two molecules of the asymmetric unit

is shown; the thermal ellipsoids are drawn at the 50% probability level; hydrogen atoms have

been omitted for clarity.

Chapter 2 39

Table 2.3: Selected bond lengthsa and anglesb in the complexes 25-30 ([MCl2(debmimm)]

with M = Mn, Fe, Co, Ni, Cu, Zn).

Bond lenghts/Angles [MnCl2(debmimm)] [FeCl2(debmimm)] [CoCl2(dmbmimm)]

M-Cl1 2.3110(10)/2.3381(9) 2.2698(8)/2.2770(8) 2.2554(17)/2.2589(16)

M-Cl2 2.3513(9)/2.3436(9) 2.2798(8)/2.557(8) 2.266(16)/2.2622(17)

M-N11 2.133(2)/2.123(3) 2.065(2)/2.082(2) 2.015(5)/2.016(5)

M-N12 2.149(3)/2.128(3) 2.079(2)/2.089(2) 2.021(4)/2.033(5)

N11-M-N21 106.01(9)/106.77(10) 105.85(8)/105.06(8) 108.82(18)/108.34(19)

N11-M-Cl1 110.53(7)/102.63(7) 104.56(6)/107.64 103.77(14)/112.63(14)

N21-M-Cl1 111.66(8)/114.03(7) 110.26(6)/112.34 114.07(13)/109.46(14)

N11-M-Cl2 107.23(7)/107.79(7) 103.61(6)/109.30(6) 108.28(13)/106.94(13)

N21-M-Cl2 105.74(7)/106.91(7) 112.06(6)/104.20(6) 108.53(13)/106.77(14)

Cl1-M-Cl2 115.14(4)/117.96(4) 119.12(3)/117.59(3) 113.08(7)/112.45(7)

[NiCl2(debmimm)]c [CuCl2(dmbmimm)] [ZnCl2(dmbmimm)]d

M-Cl1 2.2415(6) 2.2398(12) 2.2665(11)

M-Cl2 2.2415(6) 2.2514(13) 2.2443(10)

M-N11 1.9792(15) 1.986(4) 2.008(3)

M-N12 1.9792(15) 1.998(4) 2.014(3)

N11-M-N21 107.99(9) 105.01(15) 108.95(12)

N11-M-Cl1 110.04(5) 130.76(11) 108.60(9)

N21-M-Cl1 100.63(5) 96.84(12) 108.51(9)

N11-M-Cl2 100.63(5) 96.48(11) 112.75(9)

N21-M-Cl2 110.04(5) 133.52(12) 105.01(9)

Cl1-M-Cl2 126.72(4) 99.42(5) 112.85(4)

a All bond lengths are given in Å. b All angles are given in deg. c28 is situated on a C2 axis,

resulting in Cl1 = Cl2, N11 = N21. d Distances an angles refer to Zn1; for more details see

Appendix 5.1.1, Figure 5.6 and Appendix 5.1.2.

Chapter 2 40

In addition to [NiCl2(debmimm)] (28), the dimer [NiCl2(debmimm)]2 (28b) is formed

in solid the state. Thus, along with the blue crystals of [NiCl2(debmimm)] crystals being

composed of [NiCl2(debmimm)]2 × 2 [NiCl2(debmimm)] (28 × 28b) were obtained upon

recrystallization of 28 from MeOH/Et2O. Crystals of 28 × 28b show dichroism, appearing

violet or brown depending on the line of sight. The molecular structure of 28b is shown in

Figure 2.17. Selected bond lengths and angles for 28b and, for comparison, those of the co-

crystalized monomer 28 as well as of the monomer forming the blue crystals 28 are given in

Table 2.4.

Binuclear 28b consists of two [NiCl2(debmimm)] units, which are related by a

crystallographic center of symmetry. The Ni(II) centers are pentacoordinated by two N3-

bonded imidazole rings, one terminal and two bridging chlorido ligands. The Ni-Cl-Ni

bridges are slightly asymmetric. The bond lengths are similar to the those observed for

[NiCl2(tbz)], (with tbz = bis(benzo[d]imidazol-2-yl)propane) possessing a propylene spaced

bis(imidazol) ligand similar to debmimm.92 However, while [NiCl2(tbz)] exhibits a τ value of

0.21, indicating trigonal-bipyramidal coordination of the metal with a distinct distortion

towards square-pyramidal,92 the two largest angles in the coordination polyhedron of the

Ni(II) center in 28b are 159.10(3) (Cl1-Ni-Cl2) and 155.95(5) (N11-Ni-Cl2). This results in

the structural parameter τ = 0.05, i.e. (τ = 0 defines a square-pyramidal coordination, τ = 1

trigonal bipyramidal), and thus corresponds to an almost perfect square-pyramidal

environment of the two nickel atoms.93-94

Chapter 2 41

Figure 2.17: Molecular structure of 28 × 28b; only the [NiCl2(debmimm)]2 (28b) unit is

shown; thermal ellipsoids are drawn at the 50% probability level; hydrogen atoms have been

omitted for clarity.

Table 2.4: Selected bond lengthsa and anglesb of 28 × 28b

Bond lengths/angles 28 28 × 28b, monomer 28 28 × 28b, dimer 28b

Ni-Cl1 2.2415(6) 2.257(6) 2.3025(6)

Ni-Cl2 2.2415(6) 2.2204(6) 2.4004(6), 2.4029(6)

Ni-N11 1.9792(15) 1.9718(18) 2.0503(16)

Ni-N12 1.9792(15) 1.9718(18) 2.0190(18)

Ni-Ni − − 3.591(3)

N11-Ni-N21 107.99(9) 108.26(7) 104.42(7)

N11-Ni-Cl1 110.04(5) 108.24(5) 90.60(5)

N21-Ni-Cl1 100.63(5) 102.48(5) 106.37(6)

N11-Ni-Cl2 100.63(5) 97.73(5) 87.89(5), 155.95(5)c

N21-Ni-Cl2 110.04(5) 109.61(5) 94.18(5), 98.51(5)

Cl1-Ni-Cl2 126.72(4) 130.28(3) 159.10(3),c 89.84(2)

Ni-Cl2-Ni − − 96.76(2)

Cl2-Ni-Cl2 − − 83.24(2)

a All bond lengths are given in Å. b All angles are given in deg. c τ= (159.10−155.95)/60=0.05.

Chapter 2 42

The microcrystalline powder obtained from the reaction mixture exhibits the intense

blue color also observed for monomeric [NiCl2(debmimm)]. Its composition was analyzed by

X-ray powder diffraction. Comparison of the powder pattern of the microcrystalline powder

obtained from the reaction mixture with the powder patterns calculated from the X-ray crystal

structure analyses of the single crystals of 28 and 28 × 28b let assume the main composition

of the powder is [NiCl2(debmimm)] (see Figure 5.7, Appendix 5.1.3). Thus, for the debmimm

derivative a tetrahedral coordination of Ni(II) seem to be favored over the pentacoordinated

dimer [NiCl2(debmimm)]2, which is only observed as a by-product. Quiet a different situation

is met for [NiCl2(tbz)]2, where only the dimeric structure has been reported.92

Nevertheless, the two Ni(II) complexes demonstrate how complexes bearing

debmimm can adopt and change their coordination polyhedra. This is a key feature in

biomimetic catalysis, as enzymes are known to change their coordination geometry during the

catalytic cycle, for example from tetrahedral to square-pyramidal or to trigonal-bipyramidal

geometry.

The electronic properties of the complexes were probed by ESR, NMR and Mößbauer

spectroscopy. The zinc complex 30 was investigated by NMR. In comparison to the

resonances of the free ligand, the 1H NMR signals of the coordinated debmimm are shifted to

low field. The shifts of the imidazole protons are particularly pronounced, appearing at 7.00

ppm and 7.38 ppm in the Zn(II) complex but at 6.74 ppm and 6.91 ppm for the uncoordinated

ligand. For the imidazole rings as well as for the ethyl ester only one set of signals is

observed, as expected for a Cs or a C2 symmetric molecule. In the 13C{1H} NMR spectrum the

signals of the carboxylate carbon atoms are only slightly shifted from 170.0 ppm (free ligand)

to 170.2 ppm (complex), which gives evidence that in solution the carboxylate groups remain

also non-bonded.

The experimental and simulated Mössbauer spectra of [Fe(OTf)2(demimm)2] (24) are

presented in Figure 2.18i. Gradually decomposition of the complex occuring during

Chapter 2 43

measurement with formation of impurities (21%) was detected. At −196 °C, the Mössbauer

spectrum consists of a symmetric doublet. Least-square fit (solid line) to the experimental

points, assuming a Lorentzian line shape, gives an isomer shift of δ = 1.24 mms–1, which is

within the typical range of δ = 1.1-1.3 mms–1 for hexacoordinate high spin iron(II) complexes

bearing N- and O-donors, as is the quadrupol splitting of ∆EQ = 3.09 mms–1 (typical range

2.0-3.2 mms–1).95 The impurity exhibiting an isomer shift δ = 0.51 mms–1 and a quadrupol

splitting of ∆EQ = 0.79 mms–1 can be assumed to be an Fe(III) species. The Mössbauer

spectrum of the tetrahedral coordinated complex [FeCl2(debmimm)] (25) (Figure 2.18ii)

exhibits a clean symmetric doublet with an isomer shift of δ = 0.97 mms–1 and quadrupol

splitting of ∆EQ = 3.47 mms–1, and thus accounts for a high spin iron(II) center in tetrahedral

environment.

Figure 2.18: i) Zero-field Mössbauer spectrum of 24 at −196 °C, δ = 1.24(1) mms–1, ∆EQ =

3.09(1) mms–1, ΓFWHM = 0.43(1) mms–1 (Fe(III) species: δ = 0.51(1) mms–1, ∆EQ = 0.79(1)

mms–1, ΓFWHM = 0.43(1) mms–1); ii) zero-field Mössbauer spectrum of 25 at −196 °C, δ =

0.97(1) mms–1, ∆EQ = 3.47(1) mms–1, ΓFWHM = 0.30(1) mms–1; the solid lines are least-

squares fits to the data.

Chapter 2 44

The ESR spectrum of the Cu(II) complex 29, recorded of solid samples at room

temperature, indicates an approximately axial system (Figure 2.19) with a g┴ = 2.09. The g║

parameter could only approximately be derived as g║ = 2.17, since the observed fine structure

was not clearly resolved.

Figure 2.19: ESR spectrum of 29, recorded at room temperature (solid samples).

However, both values are in good agreement with those observed for tetragonal Cu(II)

centers in similar benzo[d]imidazole complexes (g┴ = 2.08-2.14, g║ = 2.08-2.14) reported by

Reedijk and coworkers.89 This fine structure – incidentally not observed in the

benzo[d]imidazole complexes – can be ascribed to hyperfine coupling to the I = 1.5 nucleus

of the Cu(II) center. However, only two of the required four signals are clearly resolved. Their

distance of 13.4 mT fits in the typical range of A║ values measured for Cu(II) centers.96 Since

the shape of the quartet is dependent on the line width of the signal, broadening of the quartet

could lead to a pseudo doublet shape. Exclusion of the electron-electron interaction present in

the solid state was attempted by recording the spectra of frozen solutions in CHCl3 and of

samples of the complex adsorbed on silica (for graphical details see Figure 5.8, Appendix

5.1.4). Disappointingly, both procedures led to poorly resolved spectra, in which only the g┴

Chapter 2 45

value could be determined. Hence, the fine structure in the solid state spectrum can also be

due to electron-electron interactions between adjacent copper complexes in the crystal lattice.

The ESR spectra of the manganese complex 26 and the cobalt complex 27, recorded in frozen

CHCl3 solutions of the complexes, exhibit isotropic systems with g = 1.98 (26) and g = 2.60

(27) (Figure 2.20). These values fall within the range typically observed for high spin Mn(II)

(g = 2-6) and high spin Co(II) (g = 1.8-6).97 No resolved spectra could be obtained for solid

samples or solutions of the complexes at room temperature.

Figure 2.20: ESR spectra of i) 26 and ii) 27, recorded in frozen CHCl3 solutions at −181 °C.

The redox behavior of the debmimm complexes was studied by cyclic voltammetry

(CV) in 0.002 M CH2Cl2 solutions at room temperature. All complexes showed only

irreversible redox waves. By comparison to the redox inactive complex [ZnCl2(debmimm)]

(30), the redox waves could be assigned to ligand centered oxidations and reductions. Even

though, the specific metal center seems to have an influence on the position of the cathodic

and anodic peak potentials (for more detailed information see Figure 5.9-15, Appendix 5.1.5)

Catalytic reactions employing the complexes bearing debmimm were attempted. First

catalysis tests were performed for [Fe(OTf)2(debmimm)2] (24) and [FeCl2(debmimm)] (25),

Chapter 2 46

employing the catalysis protocol described by Bruijnincx and Klein Gebbink, with

cyclohexene as substrate and H2O2 as oxidation agent.28 However, no conversion of the

substrate into any oxidation products was observed. Not even a stochiometically oxidation of

cyclohexene took place.

Presumably, the complexes underwent oxidative degradation in the presence of the

harsh oxidizing agent H2O2. In future experiments this could be avoided by the use of milder

oxidants, such as, e.g. iodosobenzene, t-BuO2H, and the like.

Chapter 2 47

2.3 Conclusion

Taking the ligand bmip as a blueprint, a library of novel imidazole-based N,N,E-

heteroscorpionates, viz. 2,2-bmie, bmidta, rac-1,2-bmie, bmima, bmimabo, and debmimm has

been created. Special attention was turned to the variation of the E-donor functions and the

introduction of spacers into the carbon backbone. The varied donor strengths provided by the

new ligands were investigated by coordination towards the complex fragments Re(CO)3 and

RuCl(PPh3)2. Whereas 2,2-bmie, bmidta, and rac-1,2-bmie bound to the central metal in the

expected tripodal κ3-fashion, the ligands bmima, bmimabo, and debmimm favored only N,N-

coordination. Furthermore, the binding of the ligands by two biorelevant metal ions iron(II)

and zinc(II), was studied. The ligands 2,2-bmie and rac-1,2-bmie proved to be rather sensitive

when deprotonated, so that the isolation of defined products formed in basic reaction solution

mixtures remains still unresolved problem. With bmidta, most likely the bis(ligand)

complexes were obtained.

All attempts to obtain any complexes of Mn(II), Fe(II), Co(II), Ni(II), Cu(II), or Zn(II)

possessing the ligands bmima and bmimabo in tripodal κ3-coordination failed. In this respect,

it seemed of interest to investigate the coordination behavior of the ligand debmimm,

expected to exhibit bonding properties akin to bmima and bmimabo. Bidentate coordination of

debmimm with formation of tetrahedral complexes [MCl2(debmimm)] (M = Fe(II), Co(II),

Ni(II), Cu(II), and Zn(II)) was proven. The electronic and electrochemical properties of the

complexes were studied by ESR and Mössbauer spectroscopy, as well as CV. Interestingly,

other coordination geometries of complexes bearing debmimm could be rationalized, e.g. an

octahedral geometry for [Fe(OTf)2(debmimm)2] and the square pyramidal geometry in

[NiCl2(debmimm)]2. Such changes between different coordination geometries are a key

feature for bioinorganic model compounds. In future work, a detailed analysis of the catalytic

properties of the iron and zinc complexes possessing the chelate systems bmima, bmimabo and

debmimm has to show their potential in biomimetic catalysis.

Chapter 2 48

2.4 Experimental section

2.4.1 General remarks

All experiments were carried out under nitrogen atmosphere using standard Schlenk

techniques, unless noted otherwise. All solvents (analytical-grade purity) were degassed and

stored under nitrogen atmosphere. Reported yields refer to analytically pure substances and

were not optimized. 1H, 13C{1H} and 31P{1H} NMR spectra: Bruker DPX 300 AVANCE, δ

values relative to the residual solvent signal (1H: CHCl3, 7.26 ppm; dmso-d5, 2.50 ppm;

CHD2OD, 3.31 ppm; HDO, 4.79 ppm; 13C{1H}: CHCl3, 77.2 ppm; dmso-d5, 39.5 ppm;

CHD2OD, 49.0 ppm; 31P{1H}: H3PO4 (sealed capillary, 85%), 0.0 ppm). IR spectra: Varian

Excalibur FTS-3500 FT-IR spectrometer, CaF2 cuvett (d = 0.2 mm) or KBr matrix. UV/Vis

spectroscopy: Varian Carry-50 spectrometer, quartz cuvette (d = 1 cm). Mass spectra: Jeol

JMS-700 using FD technique or FAB technique with 4-NBOH as matrix. Elemental analysis:

Elemental Analyser Euro EA 3000 Euro Vector instrument. Melting points: Electrothermal

digital melting point apparatus (capillary). X-ray structure determination: A Bruker Nonius

Kappa CCD or a Smart APEX II diffractometer (graphite monochromator, Mo-Kα radiation,

λ = 0.71073 Å). Powder XRD analysis: Philips X’Pert powder diffractometer with Cu Kα

radiation (40 kV, 40 mA). EPR spectra: JEOL continuous wave spectrometer JES-FA200

equipped with an X-band Gunn oscillator bridge, a cylindrical mode cavity and a Helium

cryostat. 57Fe Mößbauer spectroscopy: WissEl Mößbauer spectrometer (MRG-500) at 77 K in

constant acceleration mode. 57Co/Rh was employed as the radiation source. WinNormos was

used for Igor Pro software was used for the quantitative evaluation of the spectral parameters

(leasts quares fitting to Lorentzian peaks). The minimum experimental line widths were 0.23

mms−1. The temperature of the samples was controlled by an MBBC-HE0106 MÖSSBAUER

He/N2 cryostat within an accuracy of ±0.3 K. Isomer shifts were determined relative to α-iron

at 298 K. Cyclic voltammetry: Autolab instrument with PGSTAT 30 potentiostat. A

Chapter 2 49

conventional three electrode arrangement was employed consisting of a gold working disk

electrode (Metrohm, geometric area: 0.07 cm2), a platinum wire (Metrohm) as the auxiliary

electrode and Ag wire as pseudo reference electrode. During the measurements a nitrogen

atmosphere was kept. Bis(N-methylimidazol-2-yl)keton (bik) (1),66 bis(N-methylimidazol-2-

yl)methane (bmim) (2),66 N-methyl-2-imidazolecarboxaldehyde (11),80 debmimm (20),86 (N-

methylimidazol-2-yl)methanol (14),81 2-chlormethyl-N-methylimidazole hydrochloride

(16),84 (N-methylbenzo[d]imidazol-2-yl)methanol (15),82 2-chlormethyl-N-

methylbenzo[d]imidazole hydrochloride (17),85 [ReBr(CO)5],98 [RuCl2(PPh3)3],

99 and

Fe(OTf)2 × 2 MeCN100, were prepared according to published procedures. All other chemicals

were used as purchased.

2.4.2 Syntheses of the ligands

2,2-Hbmie (5): A Schlenk flask was charged with bmik (2) (6.00 g, 34.0 mmol) and

THF (300 mL), and cooled to –40 °C (EtOH/liquid nitrogen bath). After 15 min, n-BuLi

(21.3 mL, 1.6 M/hexane, 34.1 mmol) was added with stirring. After 1 h, the mixture was

cooled to –60 °C and p-formaldehyde (2.04 g, 68.0 mmol) was added. The reaction mixture

was allowed to warm slowly to room temperature and stirred for 2 d. All volatiles were

removed in an oil pump vacuum and CHCl3 (400 mL) and water (5 mL) were added.101 The

mixture was dried (Na2SO4), filtered and all volatiles were removed by rotary evaporation.

The residue was triturated with cold CH2Cl2 (5 × 5 mL) and dried in an oil pump vacuum to

give a colorless powder (4.30 g , 20.8 mmol, 61%). M. p. 170 °C (dec.); C10H14N4O

(206.24 g mol–1): calcd. C 58.24, H 6.84, N 27.17; found C 58.23, H 6.86, N 27.20%.

1H NMR (DMSO-d6): δ = 3.43 (s, 6H, CH3), 4.08 (vt, 3JH,H = 5.8 Hz, 3JH,H = 6.7 Hz,

2H, CH2), 4.48 (t, 3JH,H = 7.1 Hz, 1H, CHbridge), 4.97 (t, 3JH,H = 5.6 Hz, 1H, OH), 6.75 (d, 3JH,H

= 0.5 Hz, 2 H, CHim), 7.01 (br s, 2 H, CHim) ppm; 13C{1H} NMR (DMSO-d6): δ = 32.2 (CH3),

38.9 (CH2), 62.7 (CHbrigde), 121.6 (CHim), 126.1 (CHim), 145.5 (Cim) ppm.

Chapter 2 50

FD MS (MeOH): m/z (%) = 207 (100) [MH]+, 177 (65) [bmimH]+; IR (CH2Cl2):

ν~ = 3315 (w), 3200 (w), 3117 (w), 3047 (m), 2955 (m), 1493 (s), 1281 (s), 1056 (s) cm–1. IR

(KBr): ν~ = 3315 (s), 3215 (s), 2949 (sh), 1494 (s), 1285 (m), 1136 (m), 1072 (s), 1998 (m),

774 (s) cm–1.

Li[bmidta] (6): A Schlenk flask was charged with 2 (5.00 g, 28.4 mmol) and THF

(200 mL), and cooled to –40 °C (EtOH/liquid nitrogen bath). After 15 min, n-BuLi (17.7 mL,

1.6 M in n-hexane, 28.3 mmol) was added with stirring. After 1 h, CS2 (2.06 mL, 2.60 g,

34.1 mmol) was added dropwise by syringe. The mixture was allowed to warm slowly to

room temperature over night. All volatiles were removed in an oil pump vacuum. The residue

was triturated with THF (3 × 20 mL) and dried in an oil pump vacuum, to yield an orange

powder (6.48 g, 25.1 mmol, 89%). M. p. 203 °C (dec.); C10H11LiN4S2 (258.29 g mol–1): calcd.

C 46.50, H 4.29, N 21.69, S 24.83; found C 46.51, H 4.31, N 21.41, S 24.08%.

1H NMR (DMSO-d6): δ = 3.66 (s, 6H, CH3), 5.66 (s, 1H, CHbridge), 6.65 (br s, 2 H,

CHim), 6.94 (br s, 2 H, CHim) ppm; 13C{1H} NMR (DMSO-d6): δ = 33.4 (CH3), 62.7 (Cbrigde),

120.9 (Cim), 125.4 (Cim), 146.9 (Cim), 249.1 (CS2) ppm.

IR (KBr): ν~ = 3420 (w), 3127 (w), 1526 (w), 1501 (s), 1471 (w), 1282 (m), 1256 (m),

1177 (m), 1155 (m), 1131 (m), 1086 (w), 1030 (s), 1017 (m), 994 (s), 944 (m), 840 (m), 776

(m), 751 (m), 660 (w), 473 (w) cm–1.

rac-1,2-Hbmie [12]: A Schlenk flask was charged with 1,2-dimethylimidazole

(15 mL, 16.26 g, 169 mmol) and THF (600 mL), and cooled to −40 °C. After 15 min, n-BuLi

(68 mL, 170 mmol, 2.5 M/hexenes) was added dropwise with stirring. After 2 h the mixture

was cooled to −80 °C and N-methyl-2-imidazolecarboxaldehyde (18.62 g, 170 mmol) in THF

(500 mL) was added dropwise over a period of 1 h. The reaction mixture was allowed to

warm slowly to room temperature with stirring.101 After 48 h, water was added (50 mL) and

all volatiles were removed by rotary evaporation. The residue was suspended in CH2Cl2 and

Chapter 2 51

the mixture was dried (Na2SO4). The organic extracts were combined and the solvent

removed by rotary evaporation. The resulting brown residue was recrystallized from toluene

to give an offwhite powder (4.65 g, 22.6 mmol, 13%). M. p. 134°C (dec.); C10H14N4O

(206.24 g mol–1): calcd. C 58.24, H 6.84, N 27.17; found C 58.25, H 6.97, N 27.22%.

1H NMR (CDCl3): δ = 3.44, 3.29 (ABX-system, 2JAB = 16.1 Hz, 3JH,H = 3.4 Hz, 3JH,H

= 9.4 Hz, 2H, CH2), 3.58 (s, 3H, CH3), 3.73 (s, 3H, CH3), 5.33 (dd, 3JH,H = 3.4 Hz, 3JH,H =

9.4 Hz), 5.40 (s, 1H, OH), 6.81 (d, 1H, 3JH,H = 1.1 Hz, CHim), 6.84 (d, 1H, 3JH,H = 1.0 Hz,

CHim), 6.92 (s, 2H, CHim) ppm; 13C{1H} NMR (CDCl3): δ = 31.2 (CH2), 32.8 (CH3), 33.2

(CH3), 64.6 (CHOH), 120.7 (CHim), 122.1 (CHim), 126.6 (CHim), 126.9 (CHim), 146.6 (Cim),

147.8 (Cim) ppm.

FAB MS (4-NBOH): m/z (%) = 207 (100) [MH]+; IR (CH2Cl2): ν~ = 3048 (w), 2955

(w), 1492 (w), 1414 (w), 1279 (s), 1135 (w) cm–1. IR (KBr): ν~ = 3107 (s), 2837 (m), 1532

(w), 1490 (s), 1415 (w), 1316 (w), 1281 (m), 1148 (w), 1120 (m), 1081 (w), 1054 (m), 1025

(m), 933 (w), 915 (w), 777 (w), 738 (s), 714 (m), 662 (w), 522 (w) cm–1.

Hbmimabo

× 2 HCl × 0.5 H2O (17): A Schlenk flask was charged with NaH (3.79 g,

94.7 mmol, 60% in mineral oil) and THF (200 ml), and cooled to 0°C (ice bath). After

15 min, diethylmalonate (3.69 mL, 3.89 g, 24.3 mmol) was added dropwise with stirring. The

ice bath was removed. After 30 min, the mixture was again cooled to 0°C and 2-

chloromethylbenzo[d]imidazole (16) (10.0 g, 46.1 mmol) was added with stirring. The

mixture was allowed to warm slowly to room temperature.101 After 48 h H2O (40 mL), EtOH

(150 mL) and NaOH (3.79 g, 94.7 mmol) were added and the mixture was heated under

reflux. After 1 h, the mixture was cooled to room temperature and HCl (20 mL, 37% solution

in H2O) was added, and all volatiles were removed by rotary evaporation. The residue was

triturated with CH2Cl2 (3 × 150 mL) and extracted with EtOH (300 mL). The extracts were

dried by rotary evaporation and the residue recrystallized from water-acetone to yield a

Chapter 2 52

offwhite powder (5.26 g, 12.2 mmol, 51 %). M. p. 216 °C (dec.); C20H22Cl2N4O2 × 0.5 H2O

(430.33 g mol–1): C 55.82, H 5.39, N 13.02; found: C 55.61, H 4.98, N 13.29.

1H NMR (DMSO-d6, 300 MHz): δ = 3.61, 3.80 (ABX-system, 2JAB = 15.5 Hz, 3JH,H =

6.5 Hz, 3JH,H = 8.2 Hz, 4H, CH2,bridge), 4.08 (s, 6H, NCH3), 4.11 (m, 1H, CHCO2H), 7.54 (m,

4H, Hboim), 7.72 (m, 2H, Hboim), 7.94 ppm (m, 2H, Hboim); 13C{1H NMR (DMSO-d6, 75 MHz):

δ = 26.8 (CH2), 31.4 (NCH3), 40.5 (CHbridge), 112.6 (CHboim), 114.1 (CHboim), 125.2 (Cboim),

125.7 (CHboim), 130.7 (Cboim), 132.6 (Cboim), 151.7 (C2-boim), 172.6 (CO2H) ppm.

FD MS (MeOH): m/z (%) = 305 (10) [(H2bmimabo) – CO2]+, 350 (100) [H2bmimabo]+;

IR (KBr): ν~ = 3388 (s), 2868 (s), 2813 (m), 2641 (m), 2564 (m), 1730 (s), 1562 (m), 1535

(m), 1489 (w), 1466 (m), 1407 (w), 1235 (w), 1189 (m), 1162 (w), 1105 (w), 908 (w), 800

(w), 764 (s), 579 (w), 432 (w) cm–1.

Hbmima × 2 HCl × H2O (18): A Schlenk flask was charged with NaH (0.960 g,

24.0 mmol, 60% in mineral oil) and dry THF (30 ml), and cooled to 0 °C (ice bath). After

15 min, diethylmalonate (0.911 mL, 0.961 g, 6.00 mmol) was added dropwise with stirring.

The ice bath was removed. After 30 min the mixture was cooled to 0°C again and 2-

chloromethylimidazole (15) (2.00 g, 12.0 mmol) was added. The mixture was allowed to

warm slowly to room temperature over the course of 48 h,101 treated with a mixture of H2O

(10 mL), EtOH (50 mL), NaOH (0.960 g, 24.0 mmol), and heated under reflux. After 1 h the

mixture was cooled to room temperature, HCl (4.00 mL, 47.9 mmol, 37% solution in H2O)

was added, and all volatiles were removed by rotary evaporation. The residue was extracted

with EtOH. The extracts were dried by rotary evaporation and the residue recrystallized from

EtOH/MeCN (0.823 g, 2.43 mmol, 40%). M. p. 148 °C; C12H18Cl2N4O2 × H2O (339.22 g

mol–1): C 42.49, H 5.94, N 16.52; found C 42.81, H 5.96, N 16.70.

1H NMR (DMSO-d6, 300 MHz): δ = 3.24, 3.47 (ABX-system, 2JAB = 15.4 Hz, 3JH,H =

6.4 Hz, 3JH,H = 8.3 Hz, 4H, CH2), 3.82 (m, 1H, CHCO2H), 3.86 (s, 6H, NCH3), 7.58 (d, 3JH,H

= 1.9 Hz, 2H, CHim), 7.63 (d, 3JH,H = 1.9 Hz, 2H, CHim) ppm; 13C{1H} NMR (DMSO-d6, 75

Chapter 2 53

MHz): δ = 25.6 (CH2), 34.3 (NCH3), 40.5 (CHCO2H), 118.1 (Cim), 123.3 (Cim), 144.4 (Cim),

172.7 (CO2H) ppm.

FAB MS (4-NBOH): m/z (%) = 249 (100) [Hbmima]+; IR (MeOH): ν~ = 1728 (m),

1612 (m), 1531 (w) cm–1; IR (KBr): ν~ = 1719 (m) , 1602 (w), 1529 (w), 1247 (w) cm–1.

Selected data for debmimm (19):86 1H NMR (CDCl3, 300 MHz): δ = 1.18 (t, 3JH,H =

7.1 Hz, 6H, CH2CH3), 3.48 (s, 6H, CH2), 3.59 (s, 4H, NCH3), 4.22 (q, 3JH,H = 7.2 Hz, 4H,

OCH2), 6.74 (d, 3JH,H = 0.8 Hz, 2H, CHimid), 6.91 (d, 3JH,H = 0.9 Hz, 2H, CHimid) ppm;

13C{1H} NMR (CDCl3, 75 MHz): δ = 13.90 (CH2CH3), 28.2 (CH2), 32.7 (NCH3), 56.4

(OCH2), 61.9 (C(CO2Et)2), 120.45 (CHimid), 126.8 (CHimid), 144.2 (Cimid), 170.0 (CO2Et) ppm.

IR (KBr): ν~ = 3142 (w), 3116 (w), 2986 (w), 1726 (s), 1714 (s), 1492 (w), 1434 (w),

1415 (m), 1325 (m), 1282 (m), 1236 (s), 1184 (m), 1141 (m), 1134 (m), 1040 (w), 753 (s),

654 (w), 531 (w) cm–1.

Hbmimabo

(20):101 A flask was charged 17 (1.50 g, 3.49 mmol), water (20 ml), and

KOH (0.384, 6.85 mmol). The mixture was heated under reflux with stirring. After 5 min, the

mixture was cooled to room temperature and stored at 4 °C (refrigerator) over night. The

colorless precipitate was filtered off, triturated with water (2 × 10 ml) and dried in an oil

pump vacuum to yield a colorless powder (0.732 g, 2.10 mmol, 61%). M. p. 262 °C (dec.);

C20H20N4O2 (348.40 g mol–1): C 68.95, H 5.79, N 16.08; found: C 69.61, H 5.82, N 16.33

cm–1.

1H NMR (DMSO-d6, 300 MHz): δ = 3.28, 3.34 (ABX-system, 2JAB = 16.0 Hz, 3JH,H =

6.9 Hz, 3JH,H = 7.0 Hz, 4H, CH2,bridge), 3.73 (m, 1 H, CHCO2H), 3.75 (s, 6H, NCH3), 7.16 (m,

4H, CHboim), 7.48 (m, 2H, CHboim), 7.54 (m, 2H, CHboim) ppm; 13C{1H} NMR (DMSO-d6, 75

MHz): δ = 28.3 (CH2), 29.5 (NCH3), 40.9 (CHbridge), 109.8 (CHboim), 118.3 (Cboim), 121.2

(CHboim), 121.6 (Cboim), 135.8 (Cboim), 142.0 (Cboim), 153.2 (Cboim), 175.0 (CO2H) ppm.

Chapter 2 54

FD MS (MeOH): m/z (%) = 305 (15) [(H2bmimabo) – CO2]+, 350 (100) [H2bmimabo]+;

IR (KBr): ν~ = 2944 (w), 2439 (w), 1715 (m), 1507 (w), 1478 (s), 1448 (m), 1403 (w), 1361

(w), 1335 (w), 1288 (w), 1239 (w), 1195 (w), 756 (m), 738 (s) cm–1.

K[bmima] (21):101 A flask was charged with 20 (1.00 g, 2.87 mmol), KOH (0.145 g,

2.59 mmol), and water (50 mL). The mixture was refluxed for 16 h and all volatiles were then

removed by rotary evaporation. The residue was triturated with CH2Cl2 and dried in an oil

pump vacuum to give a colorless powder (0.489 g, 1.71 mmol, 66%). M. p. 268 °C (dec.);

C12H15KN4O2 (286.37 g mol–1): calcd. C 50.33, H 5.28, N 19.56; found C 49.94, H 5.25, N

19.53%.

1H NMR (D2O): δ = 2.76, 2.99 (m, 5H, CH2, CHCO2H), 3.57 (s, 6H, NCH3), 6.83 (d,

3JH,H = 1.2 Hz, 2H, CHim), 6.93 (d, 3JH,H = 1.1 Hz, 2H, CHim) ppm; 13C{1H} NMR

(D2O/MeOD-d4 10%): δ = 29.6 (CH2), 33.4 (NCH3), 47.6 (CHCO2H), 122.8 (Cim), 126.5

(Cim), 147.9 (Cim), 182.4 (CO2H) ppm.

IR (KBr): ν~ = 3411 (s), 1653 (w), 1580 (s), 1497 (m), 1415 (m), 1398 (s), 1283 (m),

1140 (w), 1086 (w), 1028 (w), 934 (w), 748 (m) cm–1.

2.4.3 Syntheses of the complexes

[Re(2,2-bmie)(CO)3] (7): A Schlenk flask was charged with 2,2-Hbmie (5) (0.100 g,

0.485 mmol) and THF (15 mL), and t-BuOK (0.050 g, 0.446 mmol) was added with stirring.

After 1 h, [ReBr(CO)5] (0.160 g, 0.394 mmol) was added and the mixture was heated under

reflux. After 16 h, the mixture was cooled to room temperature, the solvent was removed in

an oil pump vacuum and the residue was triturated with degassed water (20 mL) and CH2Cl2

(3 × 2 mL). Drying in an oil pump vacuum yielded an offwhite powder (0.076 g, 0.160 mmol,

41%). M. p. 270 °C (dec.); C13H13N4O4Re × H2O (475.47 g mol–1): calcd. C 31.64, H 3.06, N

11.35; found C 31.78, H 2.89, N 11.06%.

Chapter 2 55

1H NMR (MeOH-d4): δ = 3.58 (d, 3JH,H = 2.0 Hz, 2H, CH2), 3.85 (s, 6H, CH3), 5.02 (t,

3JH,H = 1.9 Hz, 1H, CHbridge), 7.14 (d, 3JH,H = 1.5 Hz, 2 H, CHim), 7.23 (d, 3JH,H = 1.6 Hz, 2 H,

CHim) ppm; 13C{1H} NMR (methanol-d4): δ = 34.1 (CH3), 37.1 (CH2), 60.2 (CHbrigde), 123.4

(CHim), 130.9 (CHim), 145.8 (Cim), 197.7 (CO), 198.9 (CO) ppm.

FD MS (MeOH): m/z (%) = 891 (45) [2 × M–2 CO]+, 477 (100) [MH]+, 447 (60)

[(MH–CO)]+; IR (methanol): ν~ = 2017 (s), 1905 (s), 1889 (s), 1513 (w) cm–1. IR (KBr):

ν~ = 3445 (m), 1997 (s), 1892 (s), 1847 (s), 1633 (w), 1511 (m), 1290 (w), 1180 (w), 1062 (w)

cm–1.

[Ru(bmidta)Cl(PPh3)2] (8): A Schlenk flask was charged with Li[bmidta] (6)

(0.259 g, 1.00 mmol) and THF (5 mL), and [RuCl2(PPh3)3] (0.959 g, 1.00 mmol) was added

with stirring. The orange precipitate, which deposited, was separated by filtration and dried in

an oil pump vacuum to yield a bright orange powder (0.282 g, 0.286 mmol, 29%). M. p. 123

°C (dec.); C46H41ClN4P2RuS2 × THF (984.55 g mol–1): calcd. C 61.00, H 5.02, N 5.69, S 6.51;

found C 60.71, H 5.07, N 5.59, S 6.23%.

1H NMR (CDCl3): δ = 1.79 (m, 4 H, THF), 3.59 (s, 6H, CH3), 3.67 (m, 4 H, THF),

5.99 (br s, 2 H, CHim), 6.03 (br s, 3 H, CHim, CHbridge), 6.93–7.29 (m, 30 H, PPh3) ppm;

13C{1H} NMR (CDCl3): δ = 25.7 (THF), 33.7 (CH3), 61.0 (CHbrigde), 68.1 (THF), 119.1 (Cim),

127.3 (vt, 3JC,P = 4.2 Hz, m-PPh3), 128.9 (p-PPh3), 131.4 (Cim), 135.0 (vt, 3JC,P = 4.5 Hz, o-

PPh3), 135.3, 135.8 (d, 3JC,P = 38.4 Hz, i-PPh3), 141.6 (Cim), 237.6 (CS2–) ppm; 31P NMR

(CDCl3): δ = 36.4 ppm.

IR (KBr): ν~ = 3430 (w), 3142 (w), 3053 (w), 1507 (s), 1481 (w), 1433 (m), 1282 (m),

1261 (m), 1286 (w), 1261 (w), 1086 (m), 1016 (s), 846 (w), 743 (m), 696 (s), 522 (s), 416 (w)

cm–1.

[Fe(bmidta)]2 [9]: A Schlenk flask was charged with FeCl2 (0.269 g, 0.967 mmol)

and MeOH (10 mL), and a solution of 6 (0.500 g, 1.94 mmol) in MeOH (10 mL) was added

Chapter 2 56

with stirring. After 1 h, the product was formed as a blue precipitate, which was separated by

filtration and dried in an oil pump vacuum to give a blue powder (0.347 g, 0.621 mmol, 64%).

M. p (capillary).: 231 °C (dec.); C20H22FeN8S4 (558.55 g mol–1): calcd. C 43.01, H 3.97, N

20.06 S 22.96; found C 42.82, H 4.00, N 20.08, S 22.21%.

FAB-MS (4-NBOH): m/z (%) = 559 (10) [Fe(bmidta)2]+, 407 (100) [Fe(bmim)2]

+; IR

(KBr): ν~ = 3104 (w), 2939 (w), 1534 (w), 1507 (m), 1417 (w), 1285 (m), 1241 (m), 1183

(m), 1140 (m), 1085 (w), 1014 (s), 962 (w), 771 (w), 739 (w), 661 (w), 531 (w), 410 (w)

cm–1.

[Zn(bmidta)]2 [10]:101 A flask was charged with ZnCl2 (0.136 g, 0.967 mmol) and

MeOH (10 mL), and a solution of 6 (0.500 g, 1.94 mmol) in MeOH (10 mL) was added, with

stirring. After 1 h the pale orange precipitate, which separated from solution, was collected by

filtration and dried in an oil pump vacuum to give a pale orange powder (0.455 g,

0.800 mmol, 82%). M. p. 149 °C (dec.); C20H22ZnN8S4 (568.11 g mol–1): calcd. C 42.28, H

3.90, N 19.72 S 22.58; found C 42.31, H 3.92, N 19.87, S 22.18%.

FAB MS (4-NBOH): m/z (%) = 567 (60) [Zn(bmidta)2]+, 491 (100) [Zn(bmim)2]

+; IR

(KBr): ν~ = 3436 (br), 3117 (w), 1539 (w), 1506 (s), 1414 (w), 1287 (m), 1240 (w), 1139 (m),

1020 (s), 957 (m), 841 (m), 774 (m), 755 (m), 658 (w) cm–1.

[Re(rac-1,2-bmie)(CO)3] (22): A Schlenk flask was charged with 12 (0.100 g, 0.492

mmol) and THF (15 mL), and t-BuOK (0.050 g, 0.446 mmol) was added with stirring. After

1 h, [ReBr(CO)5] (0.160 g, 0.394 mmol) was added and the mixture was heated to reflux.

After 16 h the mixture was cooled to ambient conditions and the solvent was removed in an

oil pump vacuum. The residue was triturated with degassed water (20 mL) and CH2Cl2 (3 ×

2 mL) and dried in an oil pump vacuum to yield an offwhite powder (0.067 g, 0.141 mmol,

36%). M. p. 209 °C (dec.); C13H13N4O4Re × H2O (475.47 g mol–1): calcd. C 31.64, H 3.06, N

11.35; found C 31.41, H 2.72, N 11.06%.

Chapter 2 57

1H NMR (CDCl3): δ = 3.04, 3.26 (m, 2H, CH2), 3.54 (s, 3H, CH3), 3.75 (s, 3H, CH3),

5.64 (dd, 3JH,H = 1.6 Hz, 3JH,H = 5.5 Hz, 1H, CH), 7.02 (m, 4H, CHIm) ppm; 13C{1H} NMR

(CDCl3): δ = 31.7 (CH2), 32.6 (CH3), 34.7 (CH3), 69.0 (CHOH), 122.8 (CHIm), 123.7 (CHIm),

128.3 (CHIm), 131.3 (CHIm), 145.0 (CIm), 158.3 (CIm), 193.3 (CO), 212.5 (CO) ppm.

FAB MS (4-NBOH): m/z (%) = 476 (100) [MH]+, 449 (38) [Re(rac-1,2-bmie)(CO)2]+,

420 (11) [Re(rac-1,2-bmie)(CO)]+, 390 (18) [Re(rac-1,2-bmie)]+ ; IR (CH2Cl2): ν~ = 2007 (s),

1890 (s), 1869 (s), 1506 (w), 1415 (w) cm–1. IR (KBr): ν~ = 3432 (w), 2002 (s), 1886 (s), 1845

(s), 1503 (w), 1080 (w) cm–1.

[ReBr(Hbmima)(CO)3] (23): A Schlenk flask was charged with 18 (0.198 g, 0.617

mmol) and THF (20mL), and KOH (0.066 g, 1.18 mmol) was added with stirring. After 1 h

[ReBr(CO)5] (0.198 g, 0.514 mmol) was added and the mixture was heated to reflux. After

20 h all volatiles were removed in an oil pump vacuum. The residue was triturated with water

(10 mL), hexanes (20 mL), and dried in an oil pump vacuum to give a colorless powder

(0.221 g, 0.369 mmol, 72 %). C15H16BrN4O5Re (598.42 g/mol): ber.: C 30.11, H 2.69, N 9.36;

gef.: C 32.07, H 2.88, N 9.29.

1H NMR (DMSO-d6): δ = 2.86 (m, 5H, CH2 and CHbridge), 3.65 (brs, 6 H, NCH3), 7.30

(m, 4H, CHim) ppm; 13C{1H} NMR (DMSO d6): δ = 23.9 (CH2), 33.6 (NCH3), 42.0 (CHbridge),

123.1 (Cim), 132.5 (Cim), 148.2 (Cim), 173.8 (CO2), 192.4 (CO), 196.2 (CO) ppm.

FAB-MS (4-NBOH): m/z (%) = 519 (100) [M]+, 249 (42) [bmimaH2]+; IR (THF):

ν~ = 2017 (s), 1903 (s), 1882 (s), 1732 (w), 1501 (w), 1287 (w) cm–1. IR (KBr): ν~ = 2019 (s),

1890 (s), 1696 (w), 1507 (w), 1287 (w) cm–1.

[Fe(OTf)2(debmimm)2] (24): A Schlenk flask was charged with Fe(OTf)2 × 2 MeCN

(0.476 g, 1.09 mmol) and MeOH (10 mL), and 19 (0.761 g, 2.18 mmol) and the mixture was

heated at 60 °C with stirring. After 1 h, the mixture was cooled to room temperature and the

solvent was removed in an oil pump vacuum. The residue was recrystallized from CH2Cl2/n-

Chapter 2 58

Pentane at –20 °C and dried in an oil pump vacuum to give a colorless powder (0.401 g,

0.382 mmol, 35%). M. p. 91 °C (dec.); C36H48F6FeN8O14S2 (1050.78 g mol–1): calcd. C 41.15,

H 4.60, N 10.66, S 6.10; found C 40.52, H 4.52, N 10.39, S 5.96%.

FD MS (MeCN): m/z (%) = 1256 (41) [Fe2(OTf)3(debmimm)2]+, 1051 (4)

[Fe(OTf)2(debmimm)2]+, 902 (100) [Fe(OTf)2(debmimm)2]

+, 703 (22)

[Fe(OTf)2(debmimm)]2+, 554 (30) [Fe(OTf)(debmimm)]+, 350 (24) [Hdebmimm]+; IR

(CH2Cl2): ν~ = 3140 (w), 3063 (w), 2992 (w), 1735 (s), 1495 (m), 1225 (s), 1154 (m), 1031 (s)

cm–1. IR (KBr): ν~ = 3428 (br), 3136 (w), 2988 (w), 1732 (s), 1547 (w), 1496 (m), 1446 (w),

1415 (w), 1370 (w), 1291 (s), 1256 (s), 1225 (s), 1191 (m), 1147 (s), 1095 (w), 1031 (s), 1010

(w), 949 (w), 861 (w), 758 (w), 713 (w), 639 (s), 573 (w), 518 (w), 440 (w) cm–1.

[FeCl2(debmimm)] (25): A Schlenk flask was charged with FeCl2 (0.400 g,

3.16 mmol) and MeOH (10 mL), and 19 (1.10 g, 3.16 mmol), and the mixture was heated at

45 °C with stirring. After 1 h the mixture was cooled to room temperature and the colorless

precipitate that was formed, was separated by filtration and dried oil pump vacuum to give a

colorless powder (0.985 g, 2.07 mmol, 66%). M. p. 213 °C (dec.); C17H24Cl2FeN4O4 (475.15

g mol–1): calcd. C 42.97, H 5.09, N 11.75; found C 42.77, H 5.07, N 11.31%.

FD MS (MeCN): m/z (%) = 788 (19) [FeCl(debmimm)2]+, 475 (52)

[FeCl2(debmimm)]+, 377 (100) [Fe(debmimm)2]2+, 350 (6) [Hdebmimm]+; IR (CH2Cl2): ν~ =

3132 (w), 3049 (w), 2985 (w), 1737 (s), 1497 (s), 1291 (m), 1225 (s), 1193 (m), 1149 (m),

1091 (w), 1010 (w) cm–1; IR (KBr): ν~ = 3128 (w), 2983 (w), 1738 (s), 1727 (s), 1545 (w),

1497 (s), 1448 (w), 1415 (w), 1368 (w), 1291 (m), 1253 (w), 1223 (s), 1191 (m), 1144 (s),

1091 (w), 1061 (w), 1010 (w), 859 (w), 774 (w), 708 (w), 483 (w) cm–1.

[MnCl2(debmimm)] (26):101 A Schlenk flask was charged with MnCl2 × 2 H2O

(0.232 g, 1.44 mmol) and MeOH (10 mL), and 19 (0.500 g, 1.44 mmol), and the mixture was

heated at 50 °C with stirring. After 3 h the mixture was cooled to room temperature and Et2O

Chapter 2 59

(15 mL) was added. The offwhite solid that separated from the solution, was collected by

filtration and recrystallized from MeOH/Et2O (0.303 g, 0.639 mmol, 45%). M. p. 197 °C

(dec.); C17H24Cl2MnN4O4 (474.24 g mol–1): calcd. C 43.05, H 5.10, N 11.81; found C 43.07,

H 5.14, N 11.75%.

FAB MS (4-NBOH): m/z (%) = 913 (4) [Mn2Cl3(debmimm)2]+, 438 (100)

[MnCl(debmimm)]+, 349 (40) [debmimm]+; IR (CH2Cl2): ν~ = 3156 (w), 3131 (w), 2984 (w),

1736 (s), 1544 (w), 1497 (s), 1446 (w), 1413 (w), 1370 (w), 1292 (m), 1225 (m), 1193 (m),

1148 (s), 1092 (w), 1011 (w), 956 (w) cm–1; IR (KBr): ν~ = 3476 (br), 3128 (w), 2984 (w),

1739 (s), 1546 (w), 1498 (s), 1444 (w), 1418 (w), 1370 (w), 1296 (m), 1253 (w), 1224 (s),

1192 (m), 1143 (s), 1092 (w), 1062 (w), 1011 (w), 956 (w), 860 (w), 776 (m), 759 (w), 707

(w), 648 (w), 571 (w), 483 (w), 441 (w) cm–1.

[CoCl2(debmimm)] (27):101 A Schlenk flask was charged with CoCl2 × 6 H2O

(0.238 g, 1.44 mmol), MeOH (10 mL), and 19 (0.500 g, 1.44 mmol), and the mixture was

heated at 50 °C with stirring. After 2 h the mixture was cooled to room temperature and Et2O

(15 mL) was added. The blue solid that was deposited, was separated by filtration and dried in

an oil pump vacuum to give a blue powder (524 g, 1.10 mmol, 77%). M. p. 207 °C (dec.);

C17H24Cl2CoN4O4 (478.24 g mol–1): calcd. C 42.69, H 5.60, N 11.72; found C 42.44, H 5.09,

N 11.58%.

UV/Vis (CH2Cl2) λmax (log ε) = 575.4 (1.53), 608.4 (1.72), 633.7 (1.71) nm; FAB MS

(4-NBOH): m/z (%) = 921 (15) [Co2Cl3(debmimm)2]+, 442 (100) [CoCl(debmimm)]+; IR

(CH2Cl2): ν~ = 3158 (w), 3134 (w), 2985 (w), 1736 (s), 1546 (w), 1500 (s), 1446 (w), 1414

(w), 1369 (w), 1291 (m), 1225 (s), 1194 (m), 1152 (s), 1092 (w), 1057 (w), 1011 (w) cm–1; IR

(KBr): ν~ = 3459 (br), 3125 (w), 2984 (w), 1730 (s), 1547 (w), 1499 (s), 1448 (w), 1416 (w),

1369 (w), 1291 (m), 1224 (s), 1193 (m), 1147 (s), 1091 (w), 1062 (w), 1010 (w), 859 (w), 776

(w), 708 (w), 482 (w) cm–1.

Chapter 2 60

[NiCl2(debmimm)] (28):101 A Schlenk flask was charged with NiCl2 × 6 H2O

(0.238 g, 1.44 mmol), MeOH (10 mL), and 19 (0.500 g, 1.44 mmol), and the mixture was

heated at 50 °C. After 2 h the mixture was cooled to room temperature and Et2O (15 mL) was

added. The blue solid that was formed, was separated by filtration and dried in an oil pump

vacuum to give a blue powder (0.378 g, 0.791 mmol, 55%). M. p. 239 °C (dec);

C17H24Cl2NiN4O4 (478.00 g mol–1): calcd. C 42.72, H 5.06, N 11.72; found C 42.68, H 5.04,

N 11.55%.

UV/Vis (CH2Cl2): λmax (log ε) = 523.4 (1.07), 566.0 (1.17) nm; FAB MS (4-NBOH):

m/z (%) = 919 (15) [Ni2Cl3(debmimm)2]+, 441 (100) [NiCl(debmimm)]+, 349 (17)

[debmimm]+; IR (CH2Cl2): ν~ = 3158 (w), 3136 (w), 2984 (w), 1736 (s), 1548 (w), 1503 (s),

1446 (w), 1414 (w), 1369 (w), 1291 (m), 1226 (s), 1195 (m), 1153 (s), 1092 (w), 1058 (w),

1011 (w) cm–1; IR (KBr): ν~ = 3381 (br), 2984 (w), 1729 (s), 1546 (w), 1501 (s), 1448 (w),

1369 (w), 1299 (m), 1255 (w), 1228 (s), 1193 (m), 1147 (s), 1094 (w), 1059 (w), 1010 (m),

860 (w), 760 (w), 490 (w) cm–1.

[CuCl2(debmimm)] (29):101 A Schlenk flask was charged with CuCl2 × 2 H2O

(0.170 g, 1.44 mmol), MeOH (10 mL), and 19 (0.500 g, 1.44 mmol), and the mixture was

heated at 50 °C. After 2 h the mixture was cooled to room temperature and Et2O (10 mL) was

added. The orange solid that was formed, was separated by filtration and dried in an oil pump

vacuum to give an orange powder that was recrystallized from MeOH/Et2O (0.512 g,

0.955 mmol, 66%). M. p. 187 °C (dec); C17H24Cl2CuN4O × 0.5 MeOH × 0.5 Et2O (535.93 g

mol–1) calcd. C 43.70 H 5.83 N 10.45; found C 43.38, H 5.52, N 10.83%.

UV/Vis (CH2Cl2): λmax (log ε) = 281.7 (2.33), 364 (1.84), 420 (1.59) nm; FAB MS (4-

NBOH): m/z (%) = 894 (3) [Cu2Cl3(debmimm)2]+, 459 (1) [Cu(debmimm)2]

+, 411 (100)

[CuCl(debmimm)]+, 349 (55) [debmimm]+; IR (CHCl3): ν~ = 2988 (m), 1734 (s), 1491 (s),

1491 (s), 1286 (m), 1180 (m), 1146 (m), 1010 (w) cm–1; IR (KBr): ν~ = 3463 (br), 3130 (w),

Chapter 2 61

2984 (w), 1732 (s), 1549 (w), 1496 (s), 1444 (w), 1414 (w), 1368 (w), 1290 (m), 1224 (s),

1192 (m), 1145 (s), 1059 (w), 1010 (w), 857 (w), 786 (w), 450 (w) cm–1.

[ZnCl2(debmimm)] (30):101 A Schlenk flask was charged with ZnCl2 (0.196 g,

1.44 mmol), MeOH (10 mL), and 19 (0.500 g, 1.44 mmol), and the mixture was heated at

50 °C. After 2 h the mixture was cooled to room temperature and Et2O (10 mL) was added.

The colorless solid that was deposited, was separated by filtration and dried in an oil pump

vacuum to give a colorless powder (0.607 g, 1.25 mmol, 87%). M. p. 239 °C (dec);

C17H24Cl2CuN4O4 (482.85 g mol–1): calcd. C 42.72, H 5.06, N 11.72; found C 42.68, H 5.04,

N 11.55%.

1H NMR (CDCl3, 300 MHz): δ = 1.25 (t, 3JH,H = 7.1 Hz, 6 H, CH2CH3), 3.48 (s, 4H,

CH2), 3.64 (s, 6 H, NCH3), 4.21 (q, 3JH,H = 7.1 Hz, 4H, OCH2), 7.00 (d, 3JH,H = 1.2 Hz, 2H,

CHimid), 7.38 (d, 3JH,H = 1.1 Hz, 2H, CHimid) ppm; 13C{1H} NMR (CDCl3, 75 MHz): δ = 14.0

(CH2CH3), 28.3 (CH2), 32.9 (NCH3), 56.6 (OCH2), 62.1 (C(CO2Et)2), 120.6 (CHimid), 127.0

(CHimid), 144.3 (Cimid), 170.2 (CO2Et) ppm.

FAB MS (4-NBOH): m/z (%) = 933 (9) [Zn2Cl3(debmimm)2]+, 447 (100)

[ZnCl(debmimm)]+, 349 (6) [debmimm]+; IR (CH2Cl2): ν~ = 3158 (w), 3134 (w), 3049 (w),

2985 (w), 1736 (s), 1548 (w), 1502 (s), 1446 (w), 1414 (w), 1369 (w), 1292 (m), 1226 (s),

1195 (m), 1154 (s), 1092 (w), 1058 (w), 1011 (w), 960 (w), cm–1; IR (KBr): ν~ = 3186 (br),

3127 (w), 2986 (w), 1731 (s), 1548 (w), 1501 (s), 1446 (m), 1417 (w), 1369 (w), 1292 (m),

1224 (s), 1193 (m), 1149 (s), 1091 (w), 1062 (w), 1010 (w), 961 (w), 859 (w), 778 (w), 757

(w), 648 (w), 573 (w), 482 (w), 445 (w) cm–1.

2.4.4 Catalysis protocol28

A Schlenk flask was charged with cyclohexene (0.304 mL, 3000 µmol, 1000 equiv) and

acetonitrile (2.196 mL), and a solution of catalyst (3 µmol) in acetonitrile (2.000 mL) was

Chapter 2 62

added with stirring. After 5 min, the oxidant solution (0.500 mL, 30 µmol, 10 equiv, 60 mM

solution in acetonitrile diluted from 35% aqueous H2O2) was added dropwise. After 1 h (from

the start of oxidant addition), bromobenzene (0.010 mL, 0.1 µmol) as internal standard was

added.101 An aliquot of the reaction mixture was filtered over a short silica plug (0.5 × 2 cm).

The short column was flushed diethyl ether (2 × 5 mL). The combined organic fractions were

concentrated in a stream of nitrogen and analyzed by GC. The products were identified and

quantified by comparison with authentic compounds.

Chapter 2 63

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D. P. Goldberg, Chem. Commun. 2002, 2772-2773. (53) L. Bénisvy, J.-C. Chottard, J. Marrot, Y. Li, Eur. J. Inorg. Chem. 2005, 999-1002. (54) E. Bouwman, W. L. Driessen, J. Reedijk, Coord. Chem. Rev. 1990, 104, 143-172. (55) L. Zhou, D. Powell, K. M. Nicholas, Inorg. Chem. 2006, 45, 3840-3842. (56) J. M. Downes, J. Whelan, B. Bosnich, Inorg. Chem. 1981, 20, 1081-1086. (57) G. Batra, P. Mathur, Polyhedron 1993, 12, 2635-2643.

Chapter 2 65

(58) C. J. Matthews, W. Clegg, S. L. Heath, N. C. Martin, M. N. S. Hill, J. C. Lockhart, Inorg. Chem. 1998, 37, 199-207.

(59) R. Gregorzik, H. Vahrenkamp, Ber. 1994, 127, 1857-1863. (60) G. Batra, P. Mathur, Transition Met. Chem. 1994, 19, 160-164. (61) Y. Nishida, N. Tanaka, A. Yamazaki, T. Tokii, N. Hashimoto, K. Ide, K. Iwasawa,

Inorg. Chem. 1995, 34, 3616-3620. (62) Rajesh, S. K. Das, P. Mathur, Polyhedron 1997, 16, 3511-3517. (63) J. V. Dagdigian, V. McKee, C. A. Reed, Inorg. Chem. 1982, 21, 1332-1342. (64) C. J. Matthews, T. A. Leese, W. Clegg, M. R. J. Elsegood, L. Horsburgh, J. C.

Lockhart, Inorg. Chem. 1996, 35, 7563-7571. (65) J. Liu, Z. Song, L. Wang, J. Zhuang, X. You, X. Huang, Transition Met. Chem. 1999,

24, 499-502. (66) N. Braussaud, T. Ruther, K. J. Cavell, B. W. Skelton, A. H. White, Synthesis 2001,

626-632. (67) B. S. Hammes, B. S. Chohan, J. T. Hoffman, S. Einwaechter, C. J. Carrano, Inorg.

Chem. 2004, 43, 7800-7806. (68) A. Otero, J. Fernández-Baeza, A. Antiñolo, F. Carrillo-Hermosilla, J. Tejeda, A. Lara-

Sánchez, L. F. Sánchez-Barba, M. Fernández-López, A. M. Rodríguez, I. López-Solera, Inorg. Chem. 2002, 41, 5193-5202.

(69) N. Burzlaff, I. Hegelmann, B. Weibert, J. Organomet. Chem. 2001, 626, 16-23. (70) L. Maria, S. Cunha, M. Videira, L. Gano, A. Paulo, I. C. Santos, I. Santos, Dalton

Trans. 2007, 3010-3019. (71) S. Tampier, R. Müller, A. Thorn, E. Hübner, N. Burzlaff, Inorg. Chem. 2008, 47,

9624-9641. (72) R. Müller, E. Hübner, N. Burzlaff, Eur. J. Inorg. Chem. 2004, 2151-2159. (73) H. Kopf, C. Pietraszuk, E. Hübner, N. Burzlaff, Organometallics 2006, 25, 2533-

2546. (74) H. Kopf, B. Holzberger, C. Pietraszuk, E. Hübner, N. Burzlaff, Organometallics 2008,

27, 5894-5905. (75) M. Ortiz, A. Penabad, A. Díaz, R. Cao, A. Otero, A. Antiñolo, A. Lara, Eur. J. Inorg.

Chem. 2005, 3135-3140. (76) P. C. A. Bruijnincx, G. van Koten, R. J. M. Klein Gebbink, Chem. Soc. Rev. 2008, 37,

2716-2744. (77) L. Que, Jr., Nat. Struct. Mol. Biol. 2000, 7, 182-184. (78) N. I. Burzlaff, P. J. Rutledge, L. J. Clifton, C. M. H. Hensgens, M. Pickford, R. M.

Adlington, P. L. Roach, J. E. Baldwin, Nature 1999, 401, 721-724. (79) N. I. Burzlaff, P. J. Rutledge, Nature 1999, 401, 721. (80) H. Carlsson, M. Haukka, A. Bousseksou, J.-M. Latour, E. Nordlander, Inorg. Chem.

2004, 43, 8252-8262. (81) C. B. Reese, P. Z. Zhang, J. Chem. Soc., Perkin Trans. 1 1993, 2291-2301. (82) A. Bistrzycki, G. Przeworski, Ber. Dtsch. Chem. Ges. 1913, 45, 3483-3495. (83) O. Algul, N. Duran, G. Gulbol, Asian J. Chem. 2007, 19, 3085-3092. (84) E. Alcalde, M. Alemany, M. Gisbert, Tetrahedron 1996, 52, 15171-15188. (85) A.-S. Bessis, C. Bolea, B. Bonnet, M. Epping-Jordan, N. Poirier, S.-M. Poli, J.-P.

Rocher, Y. Thollon, Preparation of heterocycle-containing alkynyl derivatives as modulators of metabotropic glutamate receptors WO-A2 2005123703, 2005.

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Chapter 2 66

(87) This is only a preliminary result of the X-ray structure analysis. The molecular structure of 23 was largely disordered and could not be sufficiently refined. See also Appendix 5.1.2.

(88) B. Kozlev, ccaron, ar, T. Pregelj, A. Pevec, N. Kitanovski, J. S. Costa, G. v. Albada, P. Gamez, J. Reedijk, Eur. J. Inorg. Chem. 2008, 4977-4982.

(89) I. Riggio, G. A. van Albada, D. D. Ellis, I. Mutikainen, A. L. Spek, U. Turpeinen, J. Reedijk, Polyhedron 2001, 20, 2659-2666.

(90) The identity of 27 is backed by elemental analysis as well as mass spectrometry, hence transesterification has to be occurred during the recrystallization process.

(91) V. Broughton, G. Bernardinelli, A. F. Williams, Inorg. Chim. Acta 1998, 275-276, 279-288.

(92) G. A. v. Albada, J. J. A. Kolnaar, W. J. J. Smeets, A. L. Spek, J. Reedijk, Eur. J. Inorg. Chem. 1998, 1337-1341.

(93) A. W. Addison, T. N. Rao, J. Reedijk, J. Van Rijn, G. C. Verschoor, Dalton Trans. 1984, 1349-1356.

(94) D. S. Marlin, M. M. Olmstead, P. K. Mascharak, Inorg. Chem. 2001, 40, 7003-7008. (95) E. Münck, in Physical Methods in Bioinorganic Chemistry: Spectroscopy and

Magnetism (Ed.: L. Que, Jr.), University Science Books, Sausalito, 2000, p. 291. (96) E. Hübner, G. Türkoglu, M. Wolf, U. Zenneck, N. Burzlaff, Eur. J. Inorg. Chem.

2008, 1226-1235. (97) G. Palmer, in Physical Methods in Bioinorganic Chemistry: Spectroscopy and

Magnetism (Ed.: L. Que, Jr.), University Science Books, Sausalito, 2000, p. 123. (98) E. W. Abel, G. Wilkinson, J. Chem. Soc. 1959, 1501-1505. (99) P. S. Hallman, T. A. Stephenson, G. Wilkinson, Inorg. Syn. 1970, 12, 237-240. (100) K. S. Hagen, Inorg. Chem. 2000, 39, 5867-5869. (101) All following procedures were performed under airobic conditions.

67Chapter 3

3

Pt(II), Cu(II) and Mn(II) complexes bearing imidazole-based N,N-

ligands: Novel anticancer agents

3.1 Introduction

First reports on cytostatic compounds appeared about 1950 in the literature and they

were recognized as promising candidates for the treatment of cancer.1-3 Whereas these first

examples of cytostatica were generally organic molecules, Rosenberg shortly after discovered

the value of metal-based compounds in this matter. In 1965 he found – more by serendipity

than by targeted research – Pt(II) and Pt(IV) complexes to inhibit the cell division in Gram-

negative rods.4-5 One of the described compounds was cis-[Pt(NH3)2Cl2], commonly also

known as CISPLATIN, which is nowadays one of “the blockbusters” in anticancer drugs with

sales of US $ 400 Mio in the year 2004 ( see Figure 3.1).

Figure 3.1: Best-selling anticancer drugs worldwide; CISPLATIN (I), CARBOPLATIN (II),

OXALIPLATIN (III).

H3N NH3

ClCl

OO

O O

H2N NH2

OO

OOI II III

NH3 NH3

Pt

Pt

Pt

68Chapter 3

This was only topped by Pt(II) drugs of the second generation, like CARBOPLATIN,

which developed sales up to US $ 800 Mio, and by Pt(II) drugs of the third generation, like

OXALIPLATIN, which showed a profit of US $ 1500 Mio.6

But not only Pt(II) was focused for the development of metal-based cytostatica. Over

the years enormous research efforts have been ventured and complexes based on a large

variety of main group elements, such as Sn, Ge, and Ga, as well as transition metals, such as

Ru, Rh, Pd, Cu, Fe, Mn, Ti, V, Au, and Co, featuring manifold ligands were tested.7-12

However, only scarce examples of these complexes have ever entered clinical trials. An

overview of the approaches in that field was recently given by Ott and Gust.8

Hence, the demand for novel anticancer agents – Pt(II)-based and others – is still high,

with the hope of finding compounds overcoming the disadvantages of the classical Pt(II)

drugs regarding toxicities and resistance. To explore new classes of compounds and to expand

the therapeutic scope of these metalladrugs is still an outstanding goal in medicinal chemistry.

In the following, some approaches in this matter focusing Pt(II) and Cu(II) complexes,

which feature bis(heterocyclic) N,N-donor ligands will be discussed.

3.1.1 Pt(II) complexes bearing heterocyclic N,N-ligands

In addition to bis(pyridine)-based13-18 and bis(pyrazolyl)-based ligands,19-24

bis(imidazolyl)-based ligands have been intensively investigated for the synthesis of Pt(II)-

based cytostatica. All these complexes have the same basic structure, which mimics the

structure of CISPLATIN (Figure 3.2).

Usually, the two N-heterocyclic donor groups are bonded cis to the square planar

coordinated Pt(II) center, often with two chlorido ligands occupying the residual coordination

sites. The imidazole rings can be directly fused25-26 or connected through a spacer X.27-29 The

substituents R, as well as the spacer unit X can contain additional groups, influencing the

DNA-binding properties of the compounds and thereby the cytotoxicity.

69Chapter 3

Figure 3.2: Basic structure of platinum complexes with cytostatic properties bearing ligands

based on N-heterocycles, exemplified by the binding motif of a bis(imidazol-2-yl)-based

ligand.

However, examples of cytotoxic compounds are also known, in which the two

imidazole rings are unconnected.22, 30-34 Then, an even higher cytotoxicity of the trans isomer

compared to the cis isomer is observed.35-36

The relationship of the cytostatic activity on the structure of the ligand can be

rationalized by the example of the bis(imidazole) complexes given in Figure 3.3.

Figure 3.3: The structure-activity-relationship (SAR) exemplified by [PtCl2(Me2bim)] (IV),

[PtCl2(H2bim)] (V), and [PtCl2(bmic)] (VI), [PtCl4(Me2bim)] (VII).

The Pt(II) complex bearing the dimethylated N,N´-dimethyl-2,2´-biimidazole

(Me2bim) IV shows no antitumor activity.25 On the other hand, the non-alkylated derivative

N NPt

ClCl

N NXR R

N NPt

ClCl

N N

IV V

VI VII

N NPt

ClCl

N N

N NPt

ClCl

HN

HN

OH

N NPt

ClCl

N N

Cl

Cl

70Chapter 3

of H2bim (2,2´-biimidazole) V showed significant cytostatic activity towards HeLa-299 cell

lines (IC50 = 25).26 The structurally related complex [PtCl2(bmic)] (VI) is also active, leading

to an increased life span of 56% for mice with P388 mice leukemia.25 However, Pt(IV)

complexes with Me2bim, such as VII were reported to exhibit cytotoxicity towards A2780

and A2780cis cell lines.29

By the introduction of aryl-linkers into the spacer unit of the bis(N-methylimidazol-2-

yl)methane ligands Pt(II) complexes were obtained, which showed good cytotoxicity, while

exhibiting low epithelial toxicity. The complexes used in that study are summarized in Figure

3.4.27-28

Figure 3.4: Pt(II) complexes bearing bis(N-methylimidazole-2-yl)methane ligands with aryl-

linkers.27-28

N NPt

ClCl

N N

VIII

OH

N NPt

ClCl

N N

XI

OH

OMe

MeO

N NPt

ClCl

N N

XII

OH

OMe

XIII

X

N NPt

ClCl

N N

OH

OMe

MeO OMe

N NPt

ClCl

N N

OH

NH2

IX

N NPt

ClCl

N N

OH

Cl

71Chapter 3

The cytotoxicity of VIII-XIII towards HeLa cells was quantified by an 3-(4,5-

dimethylthiazol-2-yl)2,5-diphenyl-2H-tetrazolium bromide (MTT) assay, revealing

cytotoxicities of X, XII and XIII similar to OXALIPLATIN and of XI similar to CARBOPLATIN.

The epithelial toxicity was tested by transepithelial electric resistance (TEER) measurements,

using the C7-clone of Madin-Darby-Canine-Kidney (MDCK) cells. The complexes X and XII

showed no epithelial toxicity at all, while complexes XI and XIII exhibited low epithelial

toxicity, compared to CISPLATIN and OXALIPLATIN. Hence, Pt(II) complexes bearing aryl-

substituted bis(imidazole-2-yl)methane ligands can be regarded as promising candidates for

novel anticancer agents with improved pharmacological properties.27-28

3.1.2 Cu(I) and Cu(II) complexes bearing heterocyclic N,N-ligands

Besides the large variety of Pt(II) complexes bearing ligands based on N-heterocycles,

also complexes with Cu(I) and Cu(II) centers were reported to show cytotoxic activity. Some

ligands used in this field are depicted in Figure 3.5.

Lately, Marzano, Santini and coworkers reported on the syntheses and in vitro

antitumor activity of Cu(I) complexes bearing the bis(triazole-1-yl)-based ligands XIV and

XV in addition to mono and bidentate phosphines.37-38

As early as 1983 Saha suggested an antitumor activity of Cu(II) complexes bearing the

mixed pyrazole/pyrimidine ligand XVII. Recently, Budzisz and Lorenz investigated the

cytotoxic activity of Cu(II) complexes derived from the mixed pyrazole/pyridine ligand

XVI.39

Few examples of Cu(II) complexes with cytostatic properties, which have two cis

bonded imidazole moieties are noted in literature: In 1987, Tamura and coworkers reported

on antitumor activity of the octahedrally coordinated [Cu(OAc)2(Him)2] bearing two

imidazoles (Him, XVIII) as ligands.40-41 The complex was comparable to CISPLATIN in its

cytotoxicity regarding the mouse cancer cell line B16 melanoma. Lukevics and coworkers

72Chapter 3

investigated the in vitro and in vivo cytotoxic activity of Cu(II) complexes derived from

substituted benzo[d]imidazole derivatives XIX.42 Silicon-containing alkyl groups, in

particular introduced in the N1 position of the imidazole ring led to an enhanced cytotoxicity

towards all tested cell lines.

Figure 3.5: Common imidazole-derived ligands used in cytotoxicity studies dealing with

Cu(I) and Cu(II) complexes (R = alkyl).

Cu(II) complexes with benzo[d]imidazole-derived chelating ligands exhibited potent

SOD activity. Cytotoxic studies with seven different human tumor cell lines in vitro revealed

the Cu(II) complexes derived from 2-imidazole-2-ylbenzo[d]imidazole (XX) to be most

promising.43

N N

NN NN

B

N

N

XIV

HH

N N

NN NN

CO2H

O2N NO2

NN

N

MeO2C

HO

NN

N

N

R

N

HN

N

HN

N

HN

XV

XVI XVII

XVIII XIX XX

O2N

73Chapter 3

3.1.3 Mn(II) and Mn(III) complexes bearing N-donor ligands

Within the last decade a few Mn(II) and Mn(III) complexes derived from ligands with

N-donor groups were also reported to possess antitumor activity. In particular, salene

derivatives XXI,44-45 as well as tridentate hydrazide derivatives such as N-salicyloyl-N´-o-

hydroxythiobenzhydrazide (XXII) and N´-[(2-hydroxyphenyl)carbonothioyl] pyridine-2-

carbohydrazide (XXIII)46 were used as ligands in these studies. Figure 3.6 gives some

relevant examples. However, so far no cytotoxicity studies have been reported for Mn(II)

complexes bearing bis(imidazolyl)-based ligands.

Figure 3.6: Ligands used in cytotoxicity studies dealing with Mn(II) and Mn(III) complexes

(Z = (CH2)n with n = 2-4; R3, R3´, R4, R4´; R5, R5´ are indepently H, OH, Me).

In the following the syntheses and characterisation of novel Pt(II), Cu(II) and Mn(II)

complexes with ligands derived from N-methylimidazole are described. Furthermore, the

complexes are investigated regarding their antitumor properties.

OH

NH

SHN

O

N

OH

NH

SHN

O

HO

NZ

N

OH HO

R3

R4

R5

R3´

R4´

R5´

XXI

XXII XXIII

74Chapter 3

3.2 Results

As pointed out in the introduction, Pt(II) and Cu(II) complexes bearing bis(imidazolyl)

ligands were recognized as valuable cytostatica. Hence, it was a matter of interest to

synthesize novel Pt(II) and Cu(II) complexes with some of the bis(imidazolyl) ligands

described in Chapter 2 and to probe their cytotoxicity. Namely these ligands are bmipMe

(1),47 2,2-Hbmie (2), rac-1,2-Hbmie(3), debmimm (4),48 and K[bmima] (5) (see Figure 3.7).49

Furthermore, analogous Mn(II) complexes should be synthesized and tested.

Figure 3.7: Ligands used in this study; bmipMe (1), 2,2-Hbmie (2), rac-1,2-Hbmie (3),

debmimm (4), K[bmima] (5), bmiePh (6), bmiePh3-OMe (7), and bmiePh4-OMe (8).49

N

N

N

N

OH

2

N

N OH

N

N

3

NN N

N

EtO2C CO2Et

4

N

N N

N

O−O

K+

5

N

N

N

N

N

N

N

N

N

N

N

N

OMe

OMe

6 7 8

N

N

N

N

CO2Me

1

75Chapter 3

The hydroxyl and carboxylate groups of ligands 2, 3, and 5 were expected not to

coordinate to the metal center, thus allowing N,N-coordination. For ligand 4 the successful

N,N-coordination towards Cu(II) has already been discussed in Chapter 2. All the ligands

provide additional donor groups, which can selectively influence the DNA binding properties

of the corresponding complexes. On the other hand the diversity of the groups can be used for

a precise adjustment of the reactivity and the properties of the complexes. Finally, the

methylene spacers in 3, 4, and 5 provide a different coordination motif, in which the aromatic

imidazole rings exhibit a twisted conformation. The influence of this feature on the antitumor

properties of the complexes should be investigated.

Since bis(N-methylimidazol-2-yl)methane ligands with additional aromatic groups

already proved to form cytostatic Pt(II) complexes,27-28 similar ligands, which seemed to be

easily accessible by the general synthetic route to N,N-ligands possessing a bis(imidazole-2-

yl)methane core, were also targeted. In this context, the novel N,N-ligands bmiePh (6),

bmiePh3-OMe (7), and bmiePh4-OMe (8) were developed (see Figure 3.7). Their coordination

properties were studied using Pt(II), Cu(II), and Mn(II) complexes.

3.2.1 Syntheses of the ligands

The aryl-substituted 1,1-bis(N-methylimidazol-2-yl)ethane ligands were synthesized

by deprotonation of bis(N-methylimidazol-2-yl)methane (bmim),47 followed by the addition

of the corresponding aryl chlorides (Scheme 3.1). After aqueous workup the products were

obtained as viscous pale yellow oils. While 8 could easily be purified by recrystallization

from EtOH at –20 °C, the isolation of 6 and 7 in pure state turned out to be difficult. Ligand 7

could be obtained up to 85 % purity without further purification. Ligand 6 was obtained as

pale yellow solid of ca 80% purity after distillation and recrystallization from CH2Cl2/Pentane

at – 20°C. However, in both syntheses the absence of residual bmim,47 which can act as

bidentate N,N-ligand itself, was ensured by 1H NMR spectroscopy.

76Chapter 3

Scheme 3.1: General synthetic route to the aryl-substituted 1,1-bis(N-methylimidazol-2-

yl)ethane ligands 6 (R = R´ = H), 7 (R = OMe, R´= H), and 8 (R = H, R´ = OMe): i) 1. n-

BuLi, THF, –40 °C, 2. ArCH2Cl, –60 to –80 °C.

The formation of the three ligands was clearly indicated by 1H NMR and 13C{1H}

NMR spectroscopy and backed by mass spectrometry. Table 3.1 gives an overview of the

proton NMR signals of the ligands 6, 7, and 8. Due to the Cs symmetry of the compounds in

solution, only one set of signals is observed for the imidazole rings in the proton and 13C {1H}

NMR spectrum.

Table 3.1:1H NMR signals of the aryl-substituted 1,1-bis(N-methylimidazol-2-yl)ethane

ligands.a

Ligand Proton resonances

for 6 7 8

Methyl 3.36 3.38 3.40

Methoxy – 3.69 3.75

Methylene 3.64 3.62 3.58

Methine 4.63 4.64 4.64

Imidzole 6.71, 6.93 6.73, 6.95 6.76, 6.98

Aryl 7.04-7.18 6.58-6.97 6.73-7.01

aAt 300 MHz with CDCl3 as solvent, δ given in ppm.

N

N

N

NN

N

N

N

R´

Ri)

bmim 6-8

77Chapter 3

In the 1H NMR spectrum, the bridging CH group appears as a triplet, the methylene

moiety as a doublet. The protons of the aryl substituents give rise to a multiplet, which is

superimposed by the imidazole signals of 7 and 8. Selected 13C {1H} NMR data of the aryl-

substituted 1,1-bis(N-methylimidazol-2-yl)ethane ligands are given in Table 3.2. As

anticipated, the 13C {1H} NMR spectra exhibit only one set of signals for the two imidazole

rings for all three ligands.

Table 3.2: Selected 13C {1H} NMR signals of the aryl-substituted 1,1-bis(N-methylimidazol-

2-yl)ethane ligands.a

Ligand 13C {

1H} resonances

for 6 7 8

Methyl 32.9 33.2 33.0

Methoxy – 55.3 55.3

Methylene 38.3 38.4 37.4

Methine 40.2 39.6 40.3

Imidzole 121.7, 127.1, 146.1 121.1, 126.6, 145.9 121.8, 127.0, 146.2

aAt 75 MHz with CDCl3 as solvent, δ given in ppm.

3.2.2 Syntheses of Cu(II) complexes bearing imidazole-based N,N-ligands

The syntheses of all Cu(II) complexes were conducted following the same general

procedure: The halides CuCl2 or CuBr2 were reacted with the respective ligand in warm

MeOH (60 °C) as sketched in Scheme 3.2. The analytically pure complexes were then

precipitated by the addition of Et2O and obtained in moderate to good yields of 45-91%. Only

with ligand 3 no defined products could be isolated.50 Table 3.3 gives an overview of the

synthesized complexes and yields.

78Chapter 3

Scheme 3.2: Overview of the synthesized Cu(II) complexes 9-20; i) MeOH, 60 °C.

Table 3.3: Yields of the Cu(II) complexes 9-20 synthesized for this study.

Ligand [CuCl2(L)] Isolated

yieldb

[CuBr2(L)] Isolated

yieldb

1[CuCl2(bmipMe)]2

(9) 78

[CuBr2(bmipMe)]2

(15) 83

2[CuCl2(2,2-Hbmie)]2

(10) 78

[CuBr2(2,2-Hbmie)]2

(16) 78

4[CuCl2(debmimm)]

(11)4966

[CuBr2(debmimm)]

(17) 45

6[CuCl2(bmiePh)]2

(12) 59

[CuBr2(bmiePh)]2

(18) 91

7[CuCl2(bmiePh3-OMe)]2

(13) 74

[CuBr2(bmiePh3-OMe)]2

(19) 82

8[CuCl2(bmiePh4-OMe)]2

(14) 84

[CuBr2(bmiePh4-OMe)]2

(20) 79

b Yields given in %.

+ CuX2 i)

N

NCu

X

X N

NCu

X

X

9, 10, 12-16, 18-20

N N

N N

Cu

ClCl

11, 17

1, 2, 4, 6-8

79Chapter 3

The complexes were characterized by IR spectroscopy, FAB MS (4-NBOH) and

elemental analysis. Elemental analysis values revealed all complexes to possess the

composition [CuX2(L)]. Fragments containing two copper(II) centers were detected by mass

spectrometric investigation of the complexes 9, 10, 12-16, and 18-20, which points to the

formation of binuclear complexes in these cases.

Characteristic IR vibrations are summarized in Table 3.4. For comparison, the

characteristic IR data of the corresponding ligands are also included. Only one ν(C=N)

vibration is exhibited – not only in the ligand spectra but also in the complexes. Hence, both

imidazole rings seem to be coordinated to the metal. The signals are shifted to higher

frequencies, typical for bis(imidazolyl)-derived ligands coordinated to Cu(II).51-52 The ∆

ν(C=N) values vary from 2 cm–1 to 20 cm–1, depending on the ligand structure.

Table 3.4: Characteristic IR vibrations of the ligands 1-8 and complexes 9-20.a

Ligand ν(C=N)b Compound ν(C=N)

b Compound ν(C=N)

b

1 1501479 1512 15 1511

2 1493 10 1512 16 1510

4 1492 11 1496 17 1494

6 1495 12 1510 18 1511

7 1492 13 1509 19 1508

8 1493 14 1513 20 1512

a All ν(C=N) values are given in cm–1; b KBr.

Compounds 9, 10, and 12-20 could not be characterized by single crystal X-ray

structure analysis. But, as discussed in Chapter 2, compound 11 was shown to form a

mononuclear complex with a tetrahedrally coordinated metal center49 and the structure of 17

is most likely analogous to that of 11.

80Chapter 3

For the bis(imidazol-2-yl)methane complexes 9, 10, 12-16, and 18-20, a common

structure as sketched in Figure 3.8 is proposed. In a close to trigonal bipyramidal or square

pyramidal coordination geometry, two chlorido ligands bridge the Cu(II) centers, with one

terminal chloride and two imidazole units occupying the remaining coordination sites.

Figure 3.8: General structure proposed for complexes 10, 12-16 and 18-20; R = alkyl, aryl,

X = Cl, Br.

An explanation for the fact that complexes with varying coordination geometries and

nuclearities are formed with the bis(imidazol-2-yl)methane-based ligands (1, 2, 6-8), on the

one hand, and the debmimm ligand (4), on the other hand, can be given by the different bite

angles of these two chelate-types. Ligand 4 bearing the methylene-spacer units “bites” to

transition metal ions with N-M-N angles from ranging from 105.06(8)° to 108.95(12)° (see

Chapter 2, Table 2.3). Hence, the tetrahedral geometry is favored in complexes with

debmimm. For bis(imidazol-2-yl)methane-based ligands bite angles from 83.8° to 94.0° were

reported.53-59 To saturate the metal center in complexes bearing these ligands, a trigonal

bipyramidal or square pyramidal coordination geometry might be preferred. Presumably due

to the low sterical demand of the here described bmim-based chelates the formation of

binuclear complexes seems to be favored in complexes 9, 10, 12-16, and 18-20.

Structurally related Cu(II) complexes with bis- and tris(pyrazol-1-yl)methane

derivatives having a distorted trigonal bipyramidal or a square pyramidal geometry were

recently reported.60-61 Furthermore, binuclear pentacoordinated Cu(II) complexes with halide

ligands and two imidazolyl groups are common in the literature.62-63 As mentioned above, the

NN

NN

CuX

X NN

NN

CuR R

X

X

81Chapter 3

assumption of dimeric structures for 9, 10, 12-16, and 18-20 is also backed by mass

spectrometry.

3.2.3 Syntheses of Mn(II) complexes bearing imidazole-based N,N-ligands

The Mn(II) complexes were prepared analogously to the corresponding Cu(II)

compounds. Generally, these complexes are less soluble in MeOH and frequently began to

precipitate from the reaction mixtures. Reactions of the ligands 4 and 6-8 with MnCl2

afforded the complexes [MnCl2(debmimm)]2 (21),49 [MnCl2(bmiePh)]2 (22), [MnCl2(bmiePh3-

OMe)]2 (23), and [MnCl2(bmiePh4-OMe)]2 (24) in moderate to good yields of 42-81%. With

ligands 1-3 and 5, on the other hand, no defined products could be isolated. An overview of

the synthesized complexes is given in Scheme 3.3. Elemental analysis revealed complexes 22-

24 to have the composition [MnCl2(L)]. Complex 22 crystallized with one equivalent of

solvent and was obtained as compounds [MnCl2(bmiePh)]2 × MeOH (22a) or

[MnCl2(bmiePh)]2 × EtOH (22b), depending on the solvent employed.50 The complexes were

furthermore analyzed by IR spectroscopy and FAB MS (4-NBOH). An overview of the

synthesized manganese(II) complexes is given in Table 3.5.

The IR vibrations of the coordinated ligands are shifted to higher wavenumbers, as observed

for the corresponding Cu(II) complexes. This is particularly pronounced for the characteristic

ν(C=N) band, exhibiting shift values of ∆ ν(C=N) = 6-19 cm–1. Table 3.6 gives an overview

of the key IR signals of the complexes prepared and the ligands employed. Complex

[MnCl2(debmimm)] (21),49 which is explicitly discussed in Chapter 2, is included for

comparison.

During mass spectrometric investigation of compounds 22-24 fragments of binuclear

species were observed. Hence, these complexes were supposed to possess dimeric structures,

similar to the Cu(II) complexes described above.

82Chapter 3

Scheme 3.3: Overview of the synthesized Mn(II) complexes 21-24; i) MeOH or EtOH, 60 °C.

Table 3.5: Yields of the Mn(II) complexes 21-24 synthesized for this study.

Ligand L [MnCl2(L)] Isolated yieldb

4 [MnCl2(debmimm)]2 (21) 35

6 [MnCl2(bmiePh)]2 × MeOH (22a) 49

6 [MnCl2(bmiePh)]2 × EtOH (22b) 91

7 [MnCl2(bmiePh3-OMe)]2 (23) 42

8 [MnCl2(bmiePh4-OMe)]2 (24) 45

b yields given in %.

Table 3.6: Key IR vibrations of the ligands 4,6-8 and the complexes 21-24.a

Ligand ν(C=N)b Compound ν(C=N)

b

4 1492 [MnCl2(debmimm)]2 (21) 1498

6 1495 [MnCl2(bmiePh)]2 (22) 1504

7 1492 [MnCl2(bmiePh3-OMe)]2 (23) 1504

8 1493 [MnCl2(bmiePh4-OMe)]2 (24) 1512

a All ν(C=N) values are given in cm–1; b KBr.

+ MnX2 i)

N

NMn

X

X N

NMn

X

X

22-24

N N

N N

Mn

ClCl

21

4, 6-8

83Chapter 3

Since the three ligands only differ in the substitution patterns of the aryl linkers, it can

be assumed that they form isostructural molecules. Hence, complex 24 was subjected to an

exemplary X-ray structure analysis. The result of the structure determination actually revealed

the binuclear character of the complex (see Figure 3.9).

Figure 3.9: Molecular structure of 24; thermal ellipsoids are drawn at the 50% probability

level; hydrogen atoms have been omitted for clarity; selected bond lengths (Å) and angles (°):

Mn1-Mn1 3.824(6), Mn1-N21 2.2021(11), Mn1-N11 2.2118(10), Mn1-Cl1 2.3541(4), Mn1-

Cl2 2.5264(4), Mn1-Cl2 2.5464(4); N21-Mn1-N11 83.39(4), N21-Mn1-Cl1 104.29(3), N11-

Mn1-Cl1 106.66(3), N21-Mn1-Cl2 148.37(3), N11-Mn1-Cl2 88.50(3), Cl1-Mn1-Cl2

107.322(15), N21-Mn1-Cl2 87.42(3), N11-Mn1-Cl2 145.50(3), Cl1-Mn1-Cl2 107.822(14),

Cl2-Mn1-Cl2 82.145(13), Mn1-Cl2-Mn1 97.855(13).

Both metal centers are pentacoordinated by two imidazole rings, one terminal and two

bridging chlorido ligands. The Mn-Cl-Mn bridges are slightly asymmetric, with bond lengths

of d(Mn1-Cl2) = 2.5264(4) and 2.5464(4). The complex consists of two MnCl2(bmiePh4-OMe)

units, which are connected by a crystallographic center of symmetry. As the τ value was

determined as τ = 0.68, the coordination sphere of 22 can best be described as a trigonal

bipyramidal coordination slightly distorted to square pyramidal.64 Interestingly, no bis(ligand)

84Chapter 3

complexes were formed during coordination experiments employing ligands 6-8. For the

reaction of the structurally related ligand bis(N-methylimidazol-2-yl)ketone (bmik) with

MnCl2 only mononuclear bis(ligand) Mn(II) complexes have been reported so far.65 However,

some complexes [MnCl2(L)]2, where L = (–)pine[5,6]bipyridine or 2,2-biquinoline, show

structural similarity to 22.66-67 The Mn-Mn distance of 22 (3.824(6) Å) falls within the range

of 3.7-3.9 Å, observed for these latter compounds, the coordination geometry of which is

somewhat closer to square pyramid than in 22 (τ = 0.28-0.44). Trigonal bipyramidal

pentacoordination was observed for two trinuclear Mn(II) complexes [Mn3(OAc)6(L)2]

bearing the ligands bis(N-methylimidazol-2-yl)keton (bmik) and bis(N-methylimidazol-2-

yl)phenylmethoxymethane (biphme),68-69 for which shorter metal-to-metal distances of 3.64 Å

were reported.

3.2.4 Syntheses of Pt(II) complexes bearing imidazole-based N,N-ligands

Reactions of ligands 1-8 with K2[PtCl4] in H2O or EtOH/H2O mixtures resulted in the

formation of complexes 25-32 having the composition [PtCl2(L)]. An overview of the

synthesized compounds is sketched in Scheme 3.4.

The neutral complexes precipitated from the reaction mixtures, either immediately, or

after storing in a refrigerator for several days and were obtained in moderate yields of 21-

59%. Table 3.7 gives an overview of the synthesized Pt(II) complexes and corresponding

yields. The complexes were characterized by IR, FAB MS (4-NBOH), and elemental analysis.

The fragmentation patterns observed for the mass spectra of the complexes account for a

mononuclear composition of the complexes.

85Chapter 3

Scheme 3.4: Overview of the synthesized Pt(II) complexes 25-32; i) H2O or H2O/EtOH, 50-

60 °C.

Table 3.7: Yields of the Pt(II) complexes 25-32 synthesized for this study.

Ligand L [PtCl2(L)] Isolated yieldb

1 [PtCl2(bmipMe)] (25) 35

2 [PtCl2(2,2-Hbmie)] (26) 52

3 [PtCl2(rac-1,2-Hbmie)] (27) 32

4 [PtCl2(debmimm)] (28) 28

5 [PtCl2(Hbmima)] (29) 21

6 [PtCl2(bmiePh)] (30) 66

7 [PtCl2(bmiePh3-OMe)] (31) 29

8 [PtCl2(bmiePh4-OMe)] (32) 59

b yields given in %.

Table 3.8 contrasts the key IR vibrations of ligands 1-8 with those of their complexes

25-32. The vibrations of the ligands are shifted to higher wavenumbers when coordinated to

Pt(II), as already observed for the Cu(II) complexes 9-20 as well as for the Mn(II) complexes

21-24. The ∆ ν(C=N) values are dependent on the ligand ranging from 9 cm–1 to 22 cm–1.

Similar ∆ ν(C=N) shifts were measured for the analogous Cu(II) complexes 9-20 and Mn(II)

compounds 22-24 derived from the corresponding ligands. Hence, similar N,N-coordination

of the ligands as in the Cu(II) and Mn(II) complexes is assumed. However, as already noted in

N N

ClCl

Pt+ CuX2

i)N N

1-8 25-32

86Chapter 3

the introduction, Pt(II) complexes prefer square planar coordination geometries. Thus, square

planar geometries have to be assumed for the complexes 25-32 as well.

Table 3.8: Key IR vibrations of the ligands 1-8 and the complexes 25-32.a

Ligand ν(C=N)b Compound ν(C=N)

b

1 150147 [PtCl2(bmipMe)] (25) 1513

2 1493 [PtCl2(2,2-Hbmie)] (26) 1514

3 1490 [PtCl2(rac-1,2-Hbmie)] (27) 1512

4 1492 [PtCl2(debmimm)] (28) 1509

5 1497 [PtCl2(Hbmima)] (29) 1506

6 1495 [PtCl2(bmiePh)] (30) 1513

7 1492 [PtCl2(bmiePh3-OMe)] (31) 1513

8 1493 [PtCl2(bmiePh4-OMe)] (32) 1512

a All ν(C=N) values are given in cm–1; b KBr.

3.2.5 Cytotoxicity studies70

The cytotoxicity of selected complexes was probed using an AlmarBlue assay in the

human cervix carcinoma cell line HeLa S3.71 The AlmarBlue assay was reported to be highly

reproducible and more sensitive than the MTT assay.72 Cells were incubated for 48 h with

different concentrations [c] of the complexes. AlmarBlue was added and converted by living

cells to the red fluorescent dye resorufin.71 Measuring the fluorescence and comparing it to a

negative control gave the relative number of cells that survived the treatment.73 Plotting the

dose applied to the cells (log[c]/M) versus the viability (%) results in the dose-response curve.

The IC50 (inhibitory concentration) value describes the concentration at which 50% of cells

remain viable, with respect to controls.74

87Chapter 3

Figure 3.10 summarizes the relevant dose-response curves. Table 3.9 gives an

overview of the tested complexes and the observed IC50 values. Interestingly, apart from

complex [PtCl2(bmiePh)] (30), which exhibits a IC50 value 49 µM, the Pt(II) complexes did

not possess any detectable cytotoxicity. However, the ligand bmiePh (6) exhibits similar

cytotoxicity itself (IC50 = 33). Hence future hydrolysis studies have to show if the cytotoxic

impact of 30 can actually be attributed to the Pt(II) complex or if it is only a result of partial

hydrolysis of [PtCl2(bmiePh)] and generation of the free ligand.

For complex [PtCl2(bmiePh4-OMe)] (32) no cytotoxicity was detectable, which is

similar to the trends observed for the related aryl-substituted complexes reported by Krebs.27-

28 For complex XII, bearing the para-methoxy-substituted phenyl-linker, an IC50 value of 248

was observed, revealing low toxicity. However, the IC50 of [PtCl2(bmiePh)] 30 (IC50 = 49)

was considerably better than that of the corresponding complex VIII with the unsubstituted

phenyl-linker (IC50 >300). Forthcoming tests must show if complexes 30 and 32 will

comparably exhibit low epithelial toxicity.

Interestingly, while the ligand 2,2-Hbmie (2) exhibited an IC50 value of 85, none of the

tested complexes bearing this ligand displayed any cytotoxicity, which is a first indication of

good hydrolysis stability of the ligands with an bis(imidazole-2-yl)methane core.

The tested Cu(II) complexes proved to be nontoxic. Though, the IC50 is highly

dependent on the concerning cell line. Enhanced values might be observed in human acute

leukemia HL-60 and NALM-6 or melanoma WM-115 cell lines, for which IC50 values up to

6-8 µM were reported for structurally related Cu(II) complexes bearing ligand XVI.39

Further tests using the aryl-substituted Mn(II) complexes 22 and 24, which exhibited

IC50 values of 41 and 36, respectively, could be promising. Though these cytotoxicities are

low compared to CISPLATIN (IC50 = 1.2),71 they are in the range of CARBOPLATIN (IC50 =

16).27 Unfortunately, direct comparison with similar Mn(II) complexes was not possible, since

there are no studies in the literature concerning these complexes and HeLa cells so far.

88Chapter 3

Figure 3.10: Dose-response curves: i) the ligand 2,2-Hbmie (2), ii) the ligand bmiePh (6), iii)

the complex [MnCl2(bmiePh)]2 × EtOH (22b), iv) the complex [MnCl2(bmiePh4-OMe)]2 (24),

and v) the complex [PtCl2(bmiePh)] (30); loss of viability (HeLa S3) as a function of

treatment with varying complex concentrations.

89Chapter 3

IC5

0a

n.t.b

n.t.b

n.t.b

−

−

49

−

n.t.b

[PtC

l 2(L

)]

25

26

27

28

c

29

c

30

31

c

32

IC5

0a

−

−

−

n.t.b

−

41

−

36

[Mn

Cl 2

(L)]

2

−

−

−

21

−

22

b

23

c

24

IC5

0a

n.t.b

n.t.b

−

n.t.b

−

n.t.b

−

n.t.b

[Cu

Br 2

(L)]

2

15

16

−

17

−

18

19

c

20

IC5

0a

n.t.b

n.t.b

−

−

−

n.t.b

n.t.b

n.t.b

[Cu

Cl 2

(L)]

2

9

10

−

11

c

−

12

13

14

IC5

0a

n.t.b

85

n.t.b

n.t.b

n.t.b

33

−− −− n.t.b

Ta

ble

3.9

: IC

50 v

alue

s of

the

test

ed C

u(II

) co

mpl

exes

mea

sure

d in

HeL

a S

3.

L

1

2

3

4

5

6

7

8

a All

IC

50 v

alue

s gi

ven

in µ

M. b n

.t. =

non

toxi

c. c n

ot te

sted

.

90Chapter 3

3.3 Conclusion

Cu(II), Mn(II) and Pt(II) complexes derived from bis(imidazolyl)-based ligands,

namely bmipMe, 2,2-Hbmie, rac-1,2-Hbmie, debmimm, K[bmima], bmiePh, bmiePh3-OMe,

and bmiePh4-OMe were synthesized and characterized by elemental analysis, IR spectroscopy

and FAB mass spectrometry. Studies regarding their cytotoxicity towards HeLa S3 were

conducted and revealed the aryl-substituted ligands bmiePh and bmiePh3-OMe, in particular, as

valuable building blocks for metal-based cytostatica. The Mn(II) complexes

[MnCl2(bmiePh)]2 and [MnCl2(bmiePh4-OMe)]2 seem to be promising for more detailed

investigations. However, the ligand bmiePh showed to be cytotoxic itself. Hence, hydrolysis

studies of its complexes have to show if the cytotoxicity of [MnCl2(bmiePh)]2 is actually

based on the complex or has to be attributed to the ligand.

Interestingly, the 2,2-Hbmie ligand proved to be cytotoxic, too, while none of its

complexes did so, which suggests that ligands with an bis(imidazole-2-yl)methane core are

sufficiently stable towards hydrolysis.

3.4 Experimental section

3.4.1 General remarks

Experiments were carried out under nitrogen atmosphere using standard Schlenk

techniques only if noted. Solvents used in these syntheses (analytical-grade purity) were

degassed and stored under nitrogen atmosphere. Reported yields refer to analytically pure

substances and were not optimized. 1H and 13C{1H} NMR spectra: Bruker DPX 300

AVANCE, δ values relative to the residual solvent signal. IR spectra: Varian Excalibur FTS-

3500 FT-IR spectrometer, CaF2 cuvett (d = 0.2 mm) or KBr matrix. UV/Vis spectroscopy:

Varian Carry-50 spectrometer, quartz cuvette (d = 1 cm). Mass spectra: Jeol JMS-700 using

91Chapter 3

FD technique or FAB technique with 4-NBOH as matrix. Elemental analysis: Elemental

Analyser Euro EA 3000 Euro Vector instrument. Melting points: Electrothermal digital

melting point apparatus (capillary). X-ray structure determination: Bruker Nonius Kappa

CCD (graphite monochromator, Mo-Kα radiation, λ = 0.71073 Å). Bis(N-methylimidazol-2-

yl)keton (bik) and bis(N-methylimidazol-2-yl)methane (bmim) were prepared according to

published procedures.75 The compounds bmipMe (1), 2,2-Hbmie (2), rac-1,2-Hbmie(3),

debmimm (4), and K[bmima] (5) were synthesized as described in Chapter 2.49 All other

chemicals were used as purchased.

3.4.2 Syntheses of the ligands

Selected data for bmipMe (1):47, 76 IR (KBr): ν~ = 3121 (m), 3007 (w), 2923 (w),

2854 (w), 1732 (s), 1505 (s), 1439 (m), 1424 (m), 1384 (m), 1213 (m), 1279 (m), 1226 (m),

1200 (m), 1172 (w), 1133 (s), 1016 (m), 1000 (m), 975 (m), 910 (w), 869 (w), 816 (w), 735

(w), 699 (w), 675 (s), 544 (w) cm–1.

bmiePh (6): A Schlenk flask was charged with bmim (5.00 g, 28.4 mmol) and THF

(200 mL), and the mixture was cooled to –40 °C. To the mixture n-BuLi (14.0 mL, 2.5

M/hexane, 35.0 mmol) was added with stirring. After 1 h, the mixture was cooled to –60 °C.

Benzyl chloride (4.25 mL, 4.68 g, 37.0 mmol) was added with stirring. The mixture was

allowed to warm slowly to room temperature overnight, followed by the addition of water

(100 mL).77 The organic phase was separated and the aqueous layer was extracted with

EtOAc (4 × 100 mL). The combined organic extracts were dried (Na2SO4) and all volatiles

were removed by rotary evaporation. The residue was purified by distillation (210 °C, 0.03

mbar) to give a pale yellow oil, which was recrystallized from CH2Cl2/n-Pentane at –20 °C.

The pale yellow solid that formed was separated by filtration and dried in oil pump vacuum to

92Chapter 3

give pale yellow powder (2.06 g, 6.19 mmol, 22 %) of ca 80 % purity.78 C16H18N4 (266.34 g

mol–1).

1H NMR (CDCl3): δ = 3.36 (s, 6H, CH3), 3.64 (d, 3JH,H = 7.9 Hz, 2H, CH2), 4.63 (t,

3JH,H = 7.8 Hz, 1H, CH), 6.71 (d, 3JH,H = 0.9 Hz, 2H, CHIm), 6.93 (d, 3JH,H = 0.9 Hz, 2H,

CHIm), 7.04-7.18 (m, 5H, CHAr) ppm; 13C{1H} NMR (CDCl3): δ = 32.9 (CH3), 38.3 (CH2),

40.2 (CH), 121.7 (CHIm), 126.6 (CHp-Ar), 127.1 (CHIm), 128.4 (CHm-Ar), 129.2 (CHo-Ar), 139.2

(Ci-Ar), 146.1 (CIm) ppm.

FD MS (MeOH): m/z (%) = 267 (80) [M]+; IR (CH2Cl2): ν~ = 3046 (w), 2972 (w),

1521 (w), 1495 (s, νas(C=N)), 1454 (m), 1410 (w), 1281 (s), 1133 (w), 1084 (w), 919 (w) cm–

1; IR (KBr): ν~ = 3543 (w), 3106 (w), 3027 (w), 2943 (w), 1521 (w), 1495 (s), 1453 (m), 1409

(w), 1282 (s), 1128 (w), 1079 (w), 755 (m), 744 (s), 706 (s), 694 (m), 694 (m), 672 (w) 542

(m) cm–1.

bmiePh3-OMe

(7): A Schlenk flask was charged with bmim (5.63 g, 31.9 mmol) and

THF (300 mL), and cooled to –40 °C. To the mixture n-BuLi (12.8 mL, 2.5 M/hexanes, 31.9

mmol) was added with stirring. After 1 h, the mixture was cooled to –80 °C and a solution of

3-methoxybenzyl chloride (4.64 mL, 5.00 g, 31.9 mmol) in 20 mL THF was added by

syringe. The reaction mixture was allowed to warm slowly to room temperature overnight,

followed by addition of water (100 mL).77 The organic phase was separated and extracted

with H2O (2 × 50 mL). The aqueous layer was extracted with CH2Cl2 (4 × 60 mL). The

combined organic extracts were dried (Na2SO4). All volatiles were removed by rotary

evaporation. The resulting residue was washed with n-pentane and dried in vacuum to give a

yellow oil (9.30 g, 26.7 mmol, 84%) of ca 85 % purity.78 C17H20N4O (296.37 g mol–1)

1H NMR (CDCl3): δ = 3.38 (s, 6H, CH3), 3.62 (d, 3JH,H = 7.9 Hz, 2H, CH2), 3.69 (s,

3H, OCH3), 4.64 (t, 3JH,H = 7.8 Hz, 1H, CH), 6.58-6.97 (m, 3H, CHAr), 6.73 (d, 3JH,H= 0.9 Hz,

2H, CHIm), 6.95 (d, 3JH,H= 0.9 Hz, 2H, CHIm), 7.11 (t, 3JH,H= 7.9 Hz, CHAr, 1H) ppm; 13C{1H}

NMR (CDCl3): δ = 33.2 (NCH3), 38.4 (CH2), 39.6 (CH), 55.3 (OCH3), 112.8 (CHo-Ar), 114.1

93Chapter 3

(CHp-Ar), 121.1 (CHIm), 121.8 (CHo-Ar), 126.6 (CHIm), 129.3 (CHm-Ar), 140.4 (Ci-Ar), 145.9

(CIm), 159.7 (COm-Ar) ppm;

FD MS (MeOH): m/z (%) = 297 (100) [MH]+; IR (CH2Cl2): ν~ = 3310 (br), 3045 (w),

2961 (m), 2838 (w), 1602 (m), 1586 (m), 1521 (w), 1492 (s), 1467 (m), 1456 (m), 1438 (w),

1411 (w), 1314 (w), 1277 (s), 1168 (w), 1155 (m), 1133 (w), 1084 (w), 1050 w), 1041 (m)

cm–1. IR (KBr): ν~ = 3406 (br), 3005 (m), 2939 (m), 2836 (w), 2629 (w), 1620 (s), 1585 (m),

1522 (m), 1492 (s), 1466 (m), 1456 (m), 1437 (m), 1320 (w), 1265 (s), 1170 (m), 1156 (m),

1084 (w), 1037 (m), 873 (w), 775 (m), 736 (m), 700 (m), 564 (w), 501 (w), 446 (w) cm–1.

bmiePh4-OMe

(8): A Schlenk flask was charged with bmim (4.83 g, 27.4 mmol) and

THF (150 mL), and cooled to –40 °C. To the mixture n-BuLi (11.0 mL, 2.5 M/hexane, 27.5

mmol) was added with stirring. After 1 h, the mixture was cooled to –60 °C and 4-

methoxybenzyl chloride (3.72 mL, 4.30 g, 27.5 mmol) was added by syringe. The reaction

mixture was allowed to warm slowly to room temperature overnight, followed by addition of

water (100 mL).77 The organic phase was separated and the aqueous layer was extracted with

EtOAc (4 × 100 mL). The combined organic extracts were washed with brine (1 × 100 mL)

and dried (Na2SO4). All volatiles were removed by rotary evaporation. The resulting residue

was recrystallized from EtOH at –20 °C to give an offwhite powder (5.37 g, 18.12 mmol,

66%). M. p.: 92 °C; C17H20N4O (296.37 g mol–1): calcd. C 68.89, H 6.80, N 18.90; found C

68.76, H 6.90, N 18.81 %.

1H NMR (CDCl3): δ = 3.40 (s, 6H, CH3), 3.58 (d, 3JH,H = 7.7 Hz, 2H, CH2), 3.75 (s,

1H, OCH3), 4.64 (t, 3JH,H = 7.8 Hz, 1H, CH), 6.73-7.01 (m, 4H, CHAr), 6.76 (s, 2H, CHIm),

6.98 (s, 2H, CHIm) ppm; 13C{1H} NMR (CDCl3): δ = 33.0 (NCH3), 37.4 (CH2), 40.3 (CH),

55.3 (OCH3), 113.9 (CHm-Ar), 121.8 (CHIm), 127.0 (CHIm), 130.2 (CHo-Ar), 131.2 (Ci-Ar), 146.2

(CIm), 158.4 (COp-Ar) ppm;

FD MS (MeOH): m/z (%) = 297 (100) [MH]+; IR (CH2Cl2): ν~ = 3045 (w), 3007 (w),

2961 (w), 2914 (w), 2838 (w), 1612 (w), 1584 (w), 1513 (s), 1493 (m), 1466 (m), 1411 (w),

94Chapter 3

1301 (w), 1280 (m), 1247 (s), 1179 (m), 1131 (w), 1106 (w), 1085 (w), 1035 (m) cm–1. IR

(KBr): ν~ = 3203 (br), 3134 (w), 3110 (w), 3067 (w), 3036 (w), 3004 (w), 2960 (w), 2936 (w),

2834 (w), 1613 (m), 1512 (s), 1455 (m), 1406 (w), 1297 (w), 1282 (m), 1243 (s), 1172 (m),

1134 (w), 1103 (w), 1028 (m), 958 (w), 933 (w), 914 (w), 828 (m), 764 (w), 738 (s), 694 (w),

668 (w), 613 (w), 553 (w), 540 (w) cm–1.

3.4.3 Syntheses of the complexes

3.4.3.1 Cu(II) complexes

General Procedure A: A flask was charged with the metal salt (1.00 equiv.) and

MeOH (5 mL), and the ligand (0.80-1.00 equiv.) was added with stirring. The mixture was

heated to 60 °C. After 1 h, the mixture was cooled to room temperature and Et2O (15 mL) was

added. The solid that formed was separated by filtration and dried in oil pump vacuum. All

Cu(II) complexes were synthesized under aerobic conditions, whereas all Mn(II) complexes

were prepared under nitrogen atmosphere.

[CuCl2(bmipMe)]2 (9): Following general procedure A, reaction of CuCl2 × 2 H2O (0.106 g,

0.623 mmol) and bmipMe (1) (0.155 g, 0.623 mmol) resulted in a green solid (0.185 g, 0.242

mmol, 78%). M. p.: 211 °C (dec.); C24H32Cl4Cu2N8O4 (765.47 g mol–1): calcd. C 37.66, H

4.21, N 14.64; found C 37.63, H 4.26, N 14.23%.

FAB MS (4-NBOH): m/z (%) = 729 (3) [Cu2Cl3(bmipMe)2]+, 559 (2)

[Cu(bmipMe)2]+, 346 (100) [CuCl(bmipMe)]+; IR (KBr): ν~ = 3453 (br), 3142 (m), 2951 (w),

2923 (w), 1735 (s), 1512 (s), 1441 (m), 1347 (m), 1272 (m), 1200 (m), 1159 (m), 1139 (m),

1019 (m), 782 (w), 754 (m), 470 (w) cm–1.

95Chapter 3

[CuCl2(2,2-Hbmie)]2 (10): Following general procedure A, reaction of CuCl2 × 2

H2O (0.106 g, 0.623 mmol) and 2,2-Hbmie (2) (0.129 g, 0.623 mmol) yielded a green solid

(0.165 g, 0.242 mmol, 78%). M. p.: 215 °C (dec.); C20H28Cl4Cu2N8O2 (681.39 g mol–1): calcd.

C 35.25, H 4.14, N 16.44; found C 35.45, H 4.20, N 16.24%.

FAB MS (4-NBOH): m/z (%) = 307 (100) [CuCl(bmieH)]+, 289 (52)

[Cu2Cl(bmieH)2]2+; IR (KBr): ν~ = 3419 (s), 3137 (m), 3119 (m), 2937 (m), 2872 (w), 1550

(m), 1512 (s), 1458 (w), 1425 (w), 1382 (w), 1283 (m), 1177 (w9, 1141 (m), 1069 (s), 1000

(m), 973 (m), 949 (w), 855 (m), 781 (s), 759 (s), 727 (s), 709 (m), 679 (w), 606 (m), 500 (m),

449 (w) cm–1.

[CuCl2(bmiePh)]2 (12): Following general procedure A, reaction of CuCl2 × 2 H2O

(0.192 g, 1.13 mmol) and bmiePh (6) (0.300 g, 0.904 mmol) yielded a green solid (0.213 g,

0.266 mmol, 59%). M. p.: 184 °C (dec.); C35H36Cl4Cu2N8 (801.59 g mol–1): calcd. C 47.95, H

4.53, N 13.98; found C 47.90, H 4.53, N 13.72 %.

UV/Vis(CH2Cl2): λmax(log ε): 370 (3.9), 685 (3.1) nm; FAB MS (4-NBOH): m/z (%) =

765 (20) [Cu2Cl3(bmiePh)2]+, 364 (100) [CuCl(bmiePh)]+; IR (KBr): ν~ = 3134 (w), 3105 (w),

3025 (w), 2932 (w), 1548 (w), 1510 (s), 1456 (m), 1282 (w), 1145 (m), 1078 (w), 975 (m),

945 (w), 869 (w), 765 (m), 749 (m), 725 (m), 700 (m), 525 (m) cm–1; IR (CH2Cl2): ν~ = 2960

(w), 1514 (s), 1363 (w), 1250 (m), 1143 (w), 1028 (w) cm–1.

[CuCl2(bmiePh3-OMe

)]2 (13): Following general procedure A but omitting the addition

of Et2O, reaction of CuCl2 × 2 H2O (0.106 g, 0.623 mmol) and bmiePh3-OMe (7) (0.185 g,

0.530 mmol) yielded a green solid (0.170 g, 0.197 mmol, 74%). M. p.: 247 °C (dec.);

C34H40Cl4Cu2N8O2 (861.64 g mol–1): calcd. C 47.39, H 4.68, N 13.00; found C 47.69, H 4.78,

N 12.92%.

FAB MS (4-NBOH): m/z (%) = 825 (13) [Cu2Cl3(bmiePh3-OMe)2]+, 690 (2)

[CuCl(bmiePh3-OMe)2]+, 655 (3) [Cu(bmiePh3-OMe)2]

+, 394 (100) [CuCl(bmiePh3-OMe)]+, 359

96Chapter 3

(52) [Cu(bmiePh3-OMe)]+; IR (KBr): ν~ = 3456 (br), 3131 (w), 3111 (w), 3064 (w), 3002 (w),

2958 (w), 2923 (w), 2836 (w), 1603 (s), 1595 (m), 1550 (w), 1509 (s), 1491 (m), 1466 (m),

1279 (m), 1266 (s), 1175 (s), 1144 (m), 1086 (w), 1045 (m), 983 (m), 929 (w), 881 (w), 779

(s), 765 (s), 741 (m), 722 (m), 700 (m), 675 (w), 494 (w) cm–1.

[CuCl2(bmiePh4-OMe

)]2 (14): Following general procedure A, reaction of CuCl2 × 2

H2O (0.173 g, 1.01 mmol) and bmiePh4-OMe (8) (0.300 g, 1.01 mmol) resulted in a green solid

(0.364 g, 0.431 mmol, 84%). M. p.: 234 °C (dec.); C34H40Cl4Cu2N8O2 (861.64 g mol–1): calcd.

C 47.39, H 4.68, N 13.00; found C 47.38, H 4.71, N 12.75 %.

UV/Vis(CH2Cl2): λmax(log ε): 371 (3.9) 703 (3.1) nm; FAB MS (4-NBOH): m/z (%) =

823 (15) [Cu2Cl3(bmiePh4-OMe)2]+, 394 (100) [CuCl(bmiePh4-OMe)]+; IR (KBr): ν~ = 3134 (w),

3115 (m), 3081 (w), 3031 (w), 3003 (w), 2963 (w), 2952 (w), 2939 (w), 2923 (w), 2835 (w),

1635 (w), 1610 (m), 1583 (w), 1548 (w), 1513 (s), 1462 (w), 1332 (w), 1295 (w), 1284 (w),

1249 (s), 1213 (w), 1182 (m), 1148 (m), 1110 (w), 1093 (w), 1029 (m), 972 (w), 877 (w), 838

(w), 821 (w), 810 (w), 780 (m), 764 (m), 749 (w), 727 (w), 701 (w), 678 (w), 645 (w), 555

(w), 528 (w), 493 (w), 443 (w) cm–1; IR (CH2Cl2): ν~ = 3141 (w), 2960 (w), 1712 (m), 1611

(w), 1514 (s), 1363 (w), 1223 (w), 1179 (w) cm–1.

[CuBr2(bmipMe)]2 (15): Following general procedure A, reaction of CuBr2 (0.139 g,

0.623 mmol) and bmipMe (1) (0.155 g, 0.623 mmol) resulted in a green solid (0.243 g, 0.258

mmol, 83%). M. p.: 204 °C (dec.); C24H32Cl4Cu2N8O2 (943.27 g mol–1): calcd. C 30.56, H

3.42, N 11.88; found C 30.63, H 3.45, N 11.67%.

FAB MS (4-NBOH): m/z (%) = 640 (3) [CuBr(bmipMe)2]+, 559 (10) [Cu(bmipMe)2]

+,

311 (100) [Cu(bmipMe)]+; IR (KBr): ν~ = 3444 (br), 3136 (m), 2951 (w), 1732 (s), 1551 (w),

1511 (s), 1429 (m), 1354 (m), 1291 (m), 1220 (m), 1198 (m), 1161 (m), 1145 (m), 1088 (w),

974 (m), 900 (w), 778 (w), 759 (m), 735 (m) cm–1.

97Chapter 3

[CuBr2(2,2-Hbmie)]2 (16): Following general procedure A, reaction of CuBr2 (0.139

g, 0.623 mmol) and 2,2-Hbmie (2) (0.129 g, 0.623 mmol) yielded a green solid (0.208 g,

0.242 mmol, 78%). M. p.: 201 °C (dec.); C20H28Br4Cu2N8O2 (859.20 g mol–1): calcd. C 27.96,

H 3.28, N 13.04; found C 28.27, H 3.08, N 12.71%.

FAB MS (4-NBOH): m/z (%) = 698 (5) [Cu2Br2(2,2-Hbmie)2]+, 556 (1) [CuBr(2,2-

Hbmie)2]+, 350 (100) [CuBr(2,2-Hbmie)]+; IR (KBr): ν~ = 3423 (s), 3137 (w), 3116 (w), 2935

(w), 2871 (w), 1549 (m), 1510 (s), 1453 (m), 1423 (w), 1382 (w), 1283 (m), 1155 (m), 1142

(m), 1065 (s), 999 (m), 971 (w), 948 (w), 855 (m), 780 (s), 758 (s), 726 (m), 708 (w), 679 (w),

646 (w), 572 (w), 499 (w) cm–1.

[CuBr2(debmimm)] (17): Following general procedure A, reaction of CuBr2 (0.139 g,

0.623 mmol) and debmimm (4) (0.217 g, 0.623 mmol) resulted in a green solid (0.162 g,

0.283 mmol, 45%). M. p.: 211 °C (dec.); C17H24Br2CuN4O4 (571.75 g mol–1): calcd. C 35.71,

H 4.23, N 9.80; found C 35.26, H 4.06, N 10.21%.

UV/Vis(CH2Cl2): λmax (logε): 433 (4.20), 530 (3.80) nm; FAB MS (4-NBOH): m/z

(%) = 307 (13) [CuBr(debmimm)]+, 411 (100) [Cu(debmimm)]+, 349 (60) [debmimm]+; IR

(KBr): ν~ = 3480 (br), 3127 (m), 2984 (w), 1737 (s), 1553 (w), 1494 (m), 1447 (w), 1414 (w),

1286 (m), 1220 (s), 1188 (s), 1147 (s), 1013 (w), 861 (w), 774 (m), 647 (w) cm–1.

[CuBr2(bmiePh)]2 (18): Following general procedure A, reaction of CuBr2 (0.139 g,

0.623 mmol) and bmiePh (6) (0.187 g, 0.561 mmol) resulted in a green solid (0.249 g, 0.254

mmol, 91%). M. p.: 256 °C (dec.); CH14Cl2CuN4O (979.39 g mol–1): calcd. C 39.24, H 3.70,

N 11.44; found C 39.53, H 3.57, N 11.09%.

FAB MS (4-NBOH): m/z (%) = 899 (1) [Cu2Br3(bmiePh)2]+, 820 (1)

[Cu2Br2(bmiePh)2]+, 676 (6) [CuBr(bmiePh)2]

+, 595 (6) [Cu(bmiePh)2]+, 410 (100)

[CuBr(bmiePh)]+, 329 (42) [Cu(bmiePh)]+; UV/Vis(CH2Cl2): λmax (log ε): 381 (4.2), 483

(3.8), 737 (3.4) nm; IR (KBr): ν~ = 3444 (br), 3141 (w), 3134 (m), 3122 (w), 3027 (w), 2948

98Chapter 3

(w), 1603 (w), 1548 (w), 1511 (s), 1456 (m), 1422 (m), 1289 (w), 1144 (m), 1076 (w), 977

(w), 764 (m), 748 (m), 724 (w), 706 (m), 527 (m) cm–1.

[CuBr2(bmiePh3-OMe

)]2 (19): Following general procedure A but omitting the

addition of Et2O, reaction of CuBr2 (0.139 g, 0.623 mmol) and bmiePh3-OMe (7) (0.185 g,

0.530 mmol) yielded a green solid (0.226 g, 0.217 mmol, 82%). M. p.: 238 °C (dec.);

C34H40Br4Cu2N8O2 (1039.44 g mol–1): calcd. C 39.29, H 3.88, N 10.78; found C 39.58, H

3.83, N 10.46%.

FAB MS (4-NBOH): m/z (%) = 503 (2) [Cu2Br(bmiePh3-OMe)]+, 440 (95)

[CuBr(bmiePh3-OMe)]+, 359 (100) [Cu(bmiePh3-OMe)]+; IR (KBr): ν~ = 3443 (br), 3128 (w),

3109 (w), 3057 (w), 2997 (w), 2921 (w), 2835 (w), 1603 (s), 1549 (w), 1508 (s), 1490 (m),

1466 (m), 1453 (w), 1278 (m), 1264 (s), 1175 (m), 1144 (m), 1085 (w), 1041 (m), 983 (m),

777 (s), 763 (s), 741 (m), 699 (m), 493 (w) cm–1.

[CuBr2(bmiePh4-OMe

)]2 (20): Following general procedure A, reaction of CuBr2

(0.139 g, 0.623 mmol) and bmiePh4-OMe (8) (0.185 g, 0.623 mmol) gave a green solid (0.257

g, 0.247 mmol, 79%). M. p.: 240 °C (dec.); C34H40Cl4Cu2N8O2 (1039.44 g mol–1): calcd. C

39.29, H 3.88, N 10.78; found C 39.44, H 3.93, N 10.55%.

UV/Vis(CH2Cl2): λmax (logε): 381 (4.2), 482 (3.8), 737 (3.4) nm; FAB MS (4-NBOH):

m/z (%) = 959 (2) [Cu2Br3(bmiePh4-OMe)2]+, 880 (2) [Cu2Br2(bmiePh4-OMe)2]

+, 736 (2)

[CuBr(bmiePh4-OMe)2]+, 655 (5) [Cu(bmiePh4-OMe)2]

+, 440 (100) [CuBr(bmiePh4-OMe)]+, 359

(73) [Cu(bmiePh4-OMe)]+; IR (KBr): ν~ = 3113 (m), 3000 (w), 2932 (w), 2835 (w), 1612 (m),

1548 (w), 1512 (s), 1460 (m), 1327 (w), 1280 (w), 1246 (s), 1177 (m), 1141 (m), 1106 (m),

1032 (m), 968 (w), 839 (w), 823 (w), 806 (w), 768 (w), 745 (m), 646 (w), 555 (w), 529 (w)

cm–1.

99Chapter 3

3.4.2.2 Mn(II) complexes

[MnCl2(bmiePh)]2 × MeOH (22a): Following general procedure A, reaction of

MnCl2 × 2 H2O (0.101 g, 0.623 mmol) and bmiePh (6) (0.166 g, 0.498 mmol) yielded a

colorless solid (0.100 g, 0.123 mmol, 49%). C32H36Cl4Mn2N8O2 × MeOH (816.41 g mol–1):

calcd. C 48.55, H 4.94, N 13.73; found C 48.86, H 5.05, N 13.40%.

[MnCl2(bmiePh)]2 × EtOH (22b): Following general procedure A but employing

EtOH as solvent, reaction of MnCl2 × 2 H2O (0.101 g, 0.623 mmol) and bmiePh (6) (0.166 g,

0.498 mmol) gave a colorless solid (0.188 g, 0.226 mmol, 91%). M. p.: 211 °C (dec.);

C32H36Cl4Mn2N8O2 × EtOH (830.44 g mol–1): calcd. C 49.17, H 5.10, N 13.49; found C

49.24, H 5.34, N 13.31%.

FAB MS (4-NBOH): m/z (%) = 749 (12) [Mn2Cl3(bmiePh)2]+, 473 (21)

[Mn2Cl(bmiePh)3]2+, 356 (100) [MnCl(bmiePh)]+; IR (KBr): ν~ = 3467 (br), 3124 (w), 2967

(w), 1604 (w), 1541 (m), 1504 (s), 1456 (m), 1418 (w), 1282 /m), 1137 (w), 1078 (w), 1048

(m), 962 (s), 772 (m), 749 (s), 705 (s), 529 (m) cm–1.

[MnCl2(bmiePh3-OMe

)]2 (23): Following general procedure A but omitting the

addition of Et2O, reaction of MnCl2 × 2 H2O (0.101 g, 0.623 mmol) and bmiePh3-OMe (7)

(0.185 g, 0.530 mmol) yielded a colorless solid (0.095 g, 0.113 mmol, 42%). M. p.: 332 °C

(dec.); C34H40Cl4Mn2N8O2 (844.42 g mol–1): calcd. C 48.36, H 4.77, N 13.27; found C 48.66,

H 4.85, N 13.37%.

FAB MS (4-NBOH): m/z (%) = 809 (2) [Mn2Cl3(bmiePh3-OMe)2]+, 682 (11)

[MnCl(bmiePh3-OMe)2]+, 386 (100) [MnCl(bmiePh3-OMe)]+; IR (KBr): ν~ = 3448 (br), 3120 (m),

3014 (w), 2963 (w), 2940 (w), 2832 (w), 1609 (m), 1585 (m), 1504 (s), 1486 (m), 1452 (m),

100Chapter 3

1433 (w), 1276 (s), 1255 (m), 1173 (w), 1155 (s), 1146 (s), 1132 (s), 1048 (s), 961 (m), 880

(w), 777 (s), 768 (s), 742 (m), 724 (w), 699 (s), 676 (w), 491 (w) cm–1.

[MnCl2(bmiePh4-OMe

)]2 (24): Following general procedure A, reaction of MnCl2 × 2

H2O (0.101 g, 0.623 mmol) and bmiePh4-OMe (8) (0.185 g, 0.623 mmol) yielded a colorless

solid (0.178 g, 0.211 mmol, 68%). M. p.: 316 °C (dec.); C34H40Cl4Mn2N8O2 (844.42 g mol–1):

calcd. C 48.36, H 4.77, N 13.27; found C 48.09, H 4.81, N 12.98%.

FAB MS (4-NBOH): m/z (%) = 809 (2) [Mn2Cl3(bmiePh4-OMe)2]+, 682 (30)

[MnCl(bmiePh4-OMe)2]+, 386 (100) [MnCl(bmiePh4-OMe)]+; IR (KBr): ν~ = 3470 (br), 3120 (w),

3011 (w), 2936 (w), 1610 (m), 1542 (w), 1512 (s), 1462 (w), 1284 (w), 1249 (s), 1180 (m),

1133 (m), 1108 (w), 1029 (m), 960 (m), 835 (w), 767 (m), 752 (w), 556 (w), 524 (w), 442 (w)

cm–1.

3.4.2.3 Pt(II) complexes

General Procedure B: Under nitrogen atmosphere a flask was charged with K2PtCl4

and water (40 mL), and the ligand was added with stirring. The mixture was warmed to 40 °C.

After 1 h, the mixture was filtered. The filtrate was stored at 0 °C for 7-28 d. The solid that

formed was separated by filtration, washed with water (4 × 5 mL), EtOH (2 × 5 mL), and

Et2O (5 × 2 mL), and dried in oil pump vacuum to yield an offwhite powder.

[PtCl2(bmipMe)] (25): Following general procedure B, reaction of K2PtCl4 (0.262 g,

0.623 mmol) and bmipMe (1) (0.155 g, 0.623 mmol) resulted in an offwhite powder after 7 d

(0.112 g, 0.237 mmol, 35%). M. p.: 267 °C (dec.); C12H16Cl2N4OPt (514.27 g mol–1): calcd. C

28.03, H 3.14, N 10.89; found C 27.71, H 3.11, N 10.51 %.

101Chapter 3

FAB MS (4-NBOH): m/z (%) = 514 (17) [M]+, 479 (100) [M–Cl]+; IR (KBr): ν~ =

3491 (br), 3127 (w), 2951 (w), 1732 (s), 1625 (w), 1554 (w), 1513 (s), 1438 (m), 1358 (w),

1286 (m), 1203 (m), 1159 (m), 1091 (w), 998 (w), 909 (w), 760 (w), 734 (w) cm–1.

[PtCl2(2,2-Hbmie)] (26): A flask was charged with 2,2-Hbmie (2) (0.200 g, 0.968

mmol) and water (20 mL), and a solution of K2PtCl4 (0.402 g, 0.968 mmol) in water (20 mL)

was added with stirring. The mixture was heated to 50 °C. After 2 h, the mixture was cooled

to 0°C. The offwhite solid that formed was separated by filtration and washed with water (2 ×

10 mL) and EtOH (2 × 10 mL) and dried in oil pump vacuum to yield an offwhite powder

(0.236 g, 0.500 mmol, 52%). M. p.: 232 °C (dec.); C10H14Cl2N4OPt (472.23 g mol–1): calcd. C

25.43, H 2.99, N 11.86; found C 24.99, H 2.90, N 11.42 %.

FAB MS (4-NBOH): m/z (%) = 472 (30) [M]+, 437 (100) [M–Cl]+; IR (KBr): ν~ =

3456 (s), 3134 (km), 1559 (m), 1514 (s), 1456 (m), 1285 (m), 1154 (m), 1061 (s), 1003 (w),

856 (w), 748 (m) 718 (w) cm–1.

[PtCl2(rac-1,2-Hbmie)] (27): Following general procedure B, reaction of K2PtCl4

(0.262 g, 0.623 mmol) and rac-1,2-Hbmie (3) (0.129 g, 0.623 mmol) yielded an offwhite

powder after 9 d (0.093 g, 0.197 mmol, 32%). M. p.: 254 °C (dec.); C10H14Cl2N4OPt (472.23

g mol–1): calcd. C 25.43, H 2.99, N 11.89; found C 25.16, H 3.02, N 11.44 %.

FAB MS (4-NBOH): m/z (%) = 472 (43) [M]+, 437 (71) [M–Cl]+, 399 (100) [Pt(rac-

1,2-Hbmie)]+, 206 (43) [rac-1,2-Hbmie]+; IR (KBr): ν~ = 3463 (s), 3120 (s), 2953 (w), 1617

(w), 1554 (w), 1512 (s), 1492 (s), 1454 (m), 1415 (m), 1288 (s), 1228 (w), 1172 (s), 1160 (s),

1056 (s), 836 (w), 764 (s), 734 (s), 602 (w) cm–1.

[PtCl2(debmimm)] (28): A flask was charged with debmimm (4) (0.200 g, 0.574

mmol) and EtOH (20 mL), and a solution of K2PtCl4 (0.238 g, 0.574 mmol) in water (20 mL)

was added with stirring. The mixture was heated to 40 °C. After 2 h, the mixture was cooled

102Chapter 3

to 0 °C (ice bath). After 10 d, the solid that formed was separated by filtration, washed with

water (2 × 10 mL) and EtOH (2 × 10 mL), and dried in oil pump vacuum to yield an offwhite

powder (0.097 g, 0.158 mmol, 28%). M. p.: 209 °C (dec.); C17H24Cl2N4O4Pt (614.38 g mol–1):

calcd. C 33.23, H 3.94, N 9.12; found C 32.40, H 3.89, N 8.69 %.

FAB MS (4-NBOH): m/z (%) = 615 (52) [M]+, 578 (81) [M–Cl]+, 542 (100) [M–

CO2Et)]+; IR (KBr): ν~ = 3162 (br), 3119 (w), 2983 (w), 2940 (w), 2904 (w), 1741 (s), 1722

(s), 1633 (w), 1552 (w), 1509 (m), 1466 (w), 1445 (w), 1412 (w), 1395 (w), 1368 (w), 1292

(m), 1231 (s), 1170 (m), 1114 (w), 1092 (w), 1068 (w), 1048 (w), 1011 (w), 863 (w), 741 (w),

716 (w), 688 (w), 569 (w), 495 (w), 451 (w) cm–1.

[PtCl2(Hbmima)] (29): A flask was charged with K2[PtCl4] (0.457 g, 1.10 mmol) and

water (30 mL), and K[bmima] (5) (0.317 g, 1.11 mmol) was added with stirring. The mixture

was heated to 40°C. After 2 h, the mixture was cooled to 0°C. After 2 d, the solid that formed

was separated by filtration, washed with water (5 × 10 mL) and Et2O (1 × 10 mL), and dried

in oil pump vacuum to yield an offwhite powder (0.119 g, 0.231 mmol, 21%). M. p.: 202 °C

(dec.); C12H16Cl2N4O2Pt (514.27 g mol–1): calcd. C 28.03, H 3.14, N 10.89; found C 28.38, H

3.36, N 10.93 %.

FAB MS (4-NBOH): m/z (%) = 515 (100) [M]+; IR (KBr): ν~ = 3443 (s br), 3130 (m),

2951 (m), 1718 (m), 1624 (s), 1506 (s), 1415 (m), 1384 (s), 1290 (s), 1206 (m), 1162 (s),

1092 (m), 1035 (w), 861 (w), 750 (m) cm–1.

[PtCl2(bmiePh)] (30): A flask was charged with bmiePh (6) (0.247 g, 0.742 mmol)

and EtOH (10 mL), and a solution of K2PtCl4 (0.385 g, 0.927 mmol) in water (10 mL) was

added with stirring. The mixture was heated to 50 °C. After 2 h, the mixture was cooled to

0°C. After 1 h, the solid that formed was separated by filtration, washed with water (2 × 10

mL) and EtOH (2 × 10 mL), and dried in oil pump vacuum to yield an offwhite powder

103Chapter 3

(0.261 g, 0.490 mmol, 66%). M. p.: 214 °C (dec.); C16H18Cl2N4Pt (532.32 g mol–1): calcd. C

36.10, H 3.41, N 10.52; found C 36.10, H 3.85, N 10.09 %.

FAB MS (4-NBOH): m/z (%) = 532 (20) [M]+, 498 (100) [M–Cl]+; IR (KBr): ν~ =

3487 (m), 3126 (m), 2950 (w), 1603 (w), 1554 (m), 1513 (s), 1495 (m), 1454 (w), 1422 (w),

1287 (w), 1180 (w), 1161 (w), 1078 (w), 995 (w), 871 (w), 748 (s), 720 (m), 704 (s), 531 (m)

cm–1.

[PtCl2(bmiePh3-OMe

)] (31): Following general procedure B, reaction of K2PtCl4

(0.262 g, 0.623 mmol) and bmiePh3-OMe (7) (0.185 g, 0.530 mmol) yielded an offwhite

powder after 7 d (0.087 g, 0.155 mmol, 29%). M. p.: 214 °C (dec.); C17H20Cl2N4OPt (562.35

g mol–1): calcd. C 36.31, H 3.58, N 9.96; found C 36.10, H 3.67, N 9.18 %.

FAB MS (4-NBOH): m/z (%) = 562 (13) [M]+, 527 (100) [M–Cl]+; IR (KBr): ν~ =

3480 (m), 3125 (m), 3006 (w), 2943 (w), 2835 (w), 1601 (s), 1585 (s), 1555 (m), 1513 (s),

1491 (s), 1454 (m), 1437 (m), 1289 (m), 1260 (s), 1156 (m), 1091 (w), 1037 (m), 870 (w),

756 (m), 699 (m), 501 (w), 461 (w) cm–1.

[PtCl2(bmiePh4-OMe

)] (32): Following general procedure B, reaction of K2PtCl4

(0.262 g, 0.623 mmol) and bmiePh4-OMe (8) (0.185 g, 0.623 mmol) gave an offwhite powder

after 28 d (0.205 g, 0.365 mmol, 59%). M. p.: 217 °C (dec.); C17H20Cl2N4OPt (562.36 g mol–

1): calcd. C 36.31, H 3.58, N 9.96; found C 36.19, H 3.63, N 9.68 %.

FAB MS (4-NBOH): m/z (%) = 561 (24) [M]+, 527 (100) [M–Cl]+; IR (KBr): ν~ =

3479 (br), 3126 (w), 3026 (w), 3001 (w), 2951 (w), 2935 (w), 2835 (w), 1611 (m), 1583 (w),

1556 (w), 1512 (s), 1457 (m), 1423 (w), 1289 (w), 1248 (s), 1179 (m), 1161 (w), 1108 (w),

1091 (w), 1029 (w), 997 (w), 876 (w), 825 (w), 745 (m), 726 (w), 699 (w), 681 (w), 647 (w),

556 (w), 530 (w), 501 (w), 443 (w), 421 (w) cm–1.

104Chapter 3

3.5 References and notes

(1) F. Windisch, W. Heumann, Naturwissenschaften 1954, 41, 481. (2) S. Petersen, W. Gauss, E. Urbschat, Angew. Chem. 1955, 67, 217-231. (3) L. Heilmeyer, J. Mol. Med. 1948, 26, 97-101. (4) B. Rosenberg, L. Van Camp, T. Krigas, Nature 1965, 205, 698-699. (5) B. Rosenberg, L. Van Camp, E. B. Grimley, A. J. Thomson, J. Biol. Chem. 1967, 242,

1347-1352. (6) N. Summa, Doctoral Thesis, University of Erlangen-Nürnberg 2006. (7) P. Köpf-Maier, Naturwissenschaften 1987, 74, 374-382. (8) I. Ott, R. Gust, Arch. Pharm. 2007, 340, 117-126. (9) S. Agrawal, N. K. Singh, R. C. Aggarwal, A. Sodhi, P. Tandon, J. Med. Chem. 1986,

29, 199-202. (10) R. Basosi, L. Trabalzini, R. Pogni, W. E. Antholine, J. Chem. Soc., Faraday Trans. 1

1987, 83, 151-159. (11) P. Lay, T. Hambley, L. S. F. Casbolt, Sunscreen and cosmetic compositions for

prophylaxis or treatment of skin cancers WO-A1 2007026240, 2007. (12) N. Saha, D. Mukherjee, Polyhedron 1983, 2, 47-51. (13) V. Vo, Z. G. Kabuloglu-Karayusuf, S. W. Carper, B. L. Bennett, C. Evilia, Bioorg.

Med. Chem. 2010, 18, 1163-1170. (14) S. Rubino, P. Portanova, A. Girasolo, G. Calvaruso, S. Orecchio, G. C. Stocco, Eur. J.

Med. Chem. 2009, 44, 1041-1048. (15) S. A. D. Pascali, D. Migoni, P. Papadia, A. Romano, S. Marsigliante, A. Pellissier, S.

Chardon-Noblat, A. Ciccarese, F. P. Fanizzi, Dalton Trans. 2008, 5911-5921. (16) H.-L. Chan, D.-L. Ma, M. Yang, C.-M. Che, ChemBioChem 2003, 4, 62-68. (17) A. K. Paul, H. Mansuri-Torshizi, T. S. Srivastava, S. J. Chavan, M. P. Chitnis, J.

Inorg. Biochem. 1993, 50, 9-20. (18) L. K. Webster, G. B. Deacon, D. P. Buxton, B. L. Hillcoat, A. M. James, I. A. G.

Roos, R. J. Thomson, L. P. G. Wakelin, T. L. Williams, J. Med. Chem. 1992, 35, 3349-3353.

(19) N. J. Wheate, A. I. Day, R. J. Blanch, A. P. Arnold, C. Cullinane, J. G. Collins, Chem. Commun. 2004, 1424-1425.

(20) N. J. Wheate, B. J. Evison, A. J. Herlt, D. R. Phillips, J. G. Collins, Dalton Trans. 2003, 3486-3492.

(21) F. Keter, S. Kanyanda, S. Lyantagaye, J. Darkwa, D. Rees, M. Meyer, Cancer Chemother. Pharmacol. 2008, 63, 127-138.

(22) D. W. Gilmour, P. J. Sadler, Metal complexes of nitro-substituted pyrazoles, imidazoles and isothiazoles GB-A 2122194, 1984.

(23) J. A. Broomhead, M. J. Lynch, Inorg. Chim. Acta 1995, 240, 13-17. (24) K. Sakai, Y. Tomita, T. Ue, K. Goshima, M. Ohminato, T. Tsubomura, K. Matsumoto,

K. Ohmura, K. Kawakami, Inorg. Chim. Acta 2000, 297, 64-71. (25) M. J. Bloemink, H. Engelking, S. Karentzopoulos, B. Krebs, J. Reedijk, Inorg. Chem.

1996, 35, 619-627. (26) Y. Parajó, J. L. Arolas, V. Moreno, Á. Sánchez-González, J. Sordo, R. de Llorens, F.

X. Avilés, J. Lorenzo, Inorg. Chim. Acta 2009, 362, 946-952.

105Chapter 3

(27) T. Ludwig, S. Fakih, H. Bertram, B. Krebs, H. Oberleithner, Cell Biochem. Biophys. 2006, 45, 31-41.

(28) T. Ludwig, S. Fakih, B. Krebs, H. Oberleithner, K. Rohmann, H. Bertram, Platinum complex compounds, production thereof, and use for the treatment of cancer WO-A1 2005058927, 2005.

(29) J. S. Casas, A. Castiñeiras, Y. Parajó, A. Sánchez, Á. Sánchez-González, J. Sordo, Polyhedron 2005, 24, 1196-1202.

(30) G. Ponticelli, M. Biddau, I. A. Zakharova, L. V. Tatjanenko, J. Inorg. Biochem. 1987, 29, 101-109.

(31) G. van Kralingen, J. Reedijk, Inorg. Chim. Acta 1978, 30, 171-177. (32) F. Gümüş, Ö. Algül, G. Eren, H. Eroglu, N. Diril, S. Gür, A. Özkul, Eur. J. Med.

Chem. 2003, 38, 473-480. (33) O. Algül, B. Özçelik, U. Abbasoglu, F. Gümüş, Turk. J. Chem. 2005, 29, 607-615. (34) F. Gümüş, G. Eren, L. Acik, A. Celebi, F. Ozturk, S. Yilmaz, R. I. Sagkan, S. Gur, A.

Ozkul, A. Elmali, Y. Elerman, J. Med. Chem. 2009, 52, 1345-1357. (35) M. Van Beusichem, N. Farrell, Inorg. Chem. 1992, 31, 634-639. (36) L. Szucová, Z. Trávnícek, M. Zatloukal, I. Popa, Bioorg. Med. Chem. 2006, 14, 479-

491. (37) C. Marzano, M. Pellei, D. Colavito, S. Alidori, G. G. Lobbia, V. Gandin, F. Tisato, C.

Santini, J. Med. Chem. 2006, 49, 7317-7324. (38) C. Marzano, M. Pellei, S. Alidori, A. Brossa, G. G. Lobbia, F. Tisato, C. Santini, J.

Inorg. Biochem. 2006, 100, 299-304. (39) E. Budzisz, M. Miernicka, I.-P. Lorenz, P. Mayer, U. Krajewska, M. Rozalski,

Polyhedron 2009, 28, 637-645. (40) H. A. Henriksson, Acta Crystallogr., Sect. B 1977, 33, 1947-1950. (41) H. Tamura, H. Imai, J. Kuwahara, Y. Sugiura, J. Am. Chem. Soc. 1987, 109, 6870-

6871. (42) E. Lukevics, P. Arsenyan, I. Shestakova, I. Domracheva, A. Nesterova, O. Pudova,

Eur. J. Med. Chem. 2001, 36, 507-515. (43) F. Saczewski, E. Dziemidowicz-Borys, P. J. Bednarski, R. Grünert, M. Gdaniec, P.

Tabin, J. Inorg. Biochem. 2006, 100, 1389-1398. (44) S. S. Mandal, K. I. Ansari, J. D. Grant, III, Apoptotic and antitumor activities of

metallo-salens US-A1 2009326061, 2009. (45) K. I. Ansari, S. Kasiri, J. D. Grant, S. S. Mandal, Dalton Trans. 2009, 8525-8531. (46) A. Shrivastav, N. K. Singh, S. M. Singh, BioMetals 2003, 16, 311-320. (47) L. Peters, E. Hübner, N. Burzlaff, J. Organomet. Chem. 2005, 690, 2009-2016. (48) M. L. Patil, C. V. L. Rao, K. Yonezawa, S. Takizawa, K. Onitsuka, H. Sasai, Org.

Lett. 2006, 8, 227-230. (49) For clarity reasons, new numbers are introduced in this chapter for the compounds

also mentioned in Chapter 2: bmipMe (1) was designated in Chapter 2 as compound 4; 1,1-Hbmie (2) was denoted as compound 5 in Chapter 2; 1,2-Hbmie (3) was named compound 12; debmimm (4) was designated as compound 19; K[bmima] (5) was called compound 21, [CuCl2(debmimm)] (11) was refered to as compound 29;

[MnCl2(debmimm)] (21) was refered to as compound 26. (50) No complexation experiments were conducted employing ligand 5 and CuCl2, CuBr2,

and MnCl2. (51) L. S. Baugh, J. A. Sissano, S. Kacker, E. Berluche, R. T. Stibrany, D. N. Schulz, S. P.

Rucker, J. Polym. Sci., Part A: Polym. Chem. 2006, 44, 1817-1840.

106Chapter 3

(52) V. Broughton, G. Bernardinelli, A. F. Williams, Inorg. Chim. Acta 1998, 275-276, 279-288.

(53) D. F. Kennedy, B. A. Messerle, M. K. Smith, Eur. J. Inorg. Chem. 2007, 80-89. (54) S. Abuskhuna, M. McCann, J. Briody, M. Devereux, V. McKee, Polyhedron 2004, 23,

1731-1737. (55) E. Bulak, O. Sarper, A. Dogan, F. Lissner, T. Schleid, W. Kaim, Polyhedron 2006, 25,

2577-2582. (56) R. T. Stibrany, D. N. Schulz, S. Kacker, A. O. Patil, L. S. Baugh, S. P. Rucker, S.

Zushma, E. Berluche, J. A. Sissano, Macromolecules 2003, 36, 8584-8586. (57) P. Bruijnincx, M. Viciano-Chumillas, M. Lutz, A. Spek, J. Reedijk, G. van Koten, R.

Klein Gebbink, Chem. – Eur. J. 2008, 14, 5567-5576. (58) S. L. Dabb, J. H. H. Ho, R. Hodgson, B. A. Messerle, J. Wagler, Dalton Trans. 2009,

634-642. (59) G. J. A. A. Koolhaas, P. M. van Berkel, S. C. van der Slot, G. Mendoza-Diaz, W. L.

Driessen, J. Reedijk, H. Kooijman, N. Veldman, A. L. Spek, Inorg. Chem. 1996, 35, 3525-3532.

(60) E. Lider, O. Krivenko, E. Peresypkina, A. Smolentsev, Y. Shvedenkov, S. Vasilevskii, L. Lavrenova, Koord. Khim. 2007, 33, 896-907.

(61) T. F. S. Silva, G. S. Mishra, M. F. G. d. Silva, R. Wanke, L. M. D. R. S. Martins, A. J. L. Pombeiro, Dalton Trans. 2009, 9207-9215.

(62) D. H. Jeong, W. J. Park, J. H. Jeong, D. G. Churchill, H. Lee, Inorg. Chem. Commun. 2008, 11, 1170-1173.

(63) L. Dobrzanska, D. J. Kleinhans, L. J. Barbour, New J. Chem. 2008, 32, 813-819. (64) For details of the calculation and interpretation of τ see 2.2.2.2. (65) L. Peters, M.-F. Tepedino, T. Haas, E. Hübner, U. Zenneck, N. Burzlaff, Inorg. Chim.

Acta 2009, 362, 2678-2685. (66) E. Sinn, J. Chem. Soc., Dalton Trans. 1976, 162-165. (67) J. Rich, M. Rodriguez, I. Romero, L. Vaquer, X. Sala, A. Llobet, M. Corbella, M.-N.

Collomb, X. Fontrodona, Dalton Trans. 2009, 8117-8126. (68) R. L. Rardin, A. Bino, P. Poganiuch, W. B. Tolman, S. Liu, S. J. Lippard, Angew.

Chem. 1990, 102, 842-844; Angew. Chem. Int. Ed. 1990, 29, 812.(69) M. Kloskowski, D. Pursche, R.-D. Hoffmann, R. Pöttgen, M. Läge, A.

Hammerschmidt, T. Glaser, B. Krebs, Z. Anorg. Allg. Chem. 2007, 633, 106-112. (70) These data were obtained with the cooperation of Dr. Thomas Huhn, Fachbereich

Chemie der Universität Konstanz. (71) T. A. Immel, M. Debiak, U. Groth, A. Bürkle, T. Huhn, ChemMedChem 2009, 4, 738-

741. (72) R. Hamid, Y. Rotshteyn, L. Rabadi, R. Parikh, P. Bullock, Toxicol. in Vitro 2004, 18,

703-710. (73) R. D. Fries, M. Mitsuhashi, J. Clin. Lab. Anal. 1995, 9, 89-95. (74) Further details concerning materials and methods, cell cultivation, and the AlmarBlue

assay are given in Appendix 5.2.3. (75) N. Braussaud, T. Ruther, K. J. Cavell, B. W. Skelton, A. H. White, Synthesis 2001,

626-632. (76) L. Peters, Doctoral Thesis, Universität Konstanz 2009. (77) All following procedures were performed under airobic conditions.

107Chapter 3

(78) Purity was determined by 1H NMR spectroscopy. The impurities were mainly composed of benzyl chloride and CH2Cl2 (for ligand 6) or 3-methoxybenzyl chloride (for ligand 7).

108Chapter 4

4

Transition metal coordination polymers bearing imidazole- and

triazole-based N,N,O-, N,N-, and N,O-ligands

4.1 Introduction

Coordination polymers or metal organic frameworks (MOFs) – as they are often

designated – are metal-ligand compounds that extend “infinitely” in one, two or three

dimensions. The metal centers are solely bridged by one or several organic ligands in at least

one dimension. The donating groups of the bridging ligands should be separated by at least

one carbon atom.1-2 An accurate classification of hybrid framework structures is given by

Cheetham, Rao and Feller.3

The history of coordination polymers goes back to the last mid-century, when the first

compounds were reported in which an organic ligand acts as a bridging ligand between metal

centers, forming polymeric structures.4-9 A pioneering report on that topic was published by

K. A. Jensen, who suggested that nickel mercaptides ([Ni(SR)2]n) form polymeric structures.4

The first use of the term “coordination polymers” can be traced back to J. C. Bailar.1, 9-10

However, the Golden Age of coordination polymers was heralded with the

introduction of bi- and trivalent aromatic carboxylic acids. As early as 1965, Tomic reported

on materials derived from these ligands with high thermal stability which nowadays would be

refered to as metal organic frameworks.11 In 1999, the group of O. M. Yaghi published the

structure of “MOF-5” and coordination polymers with aromatic carboxylic acids were

recognized as valuable materials for gas storage, such as hydrogen.12-13 Enormous research

efforts have been ventured to optimize the hydrogen uptake by metal organic frameworks, and

109Chapter 4

storage data up to 7.5 wt% (32 g/L) have been reported for “MOF-177” at 9 MPa and −196

°C.14-15 Despite these promising results, hydrogen storage at ambient conditions is still

challenging.16-17

In addition to hydrogen storage,16-20 a broad variety of other applications for

coordination polymers, viz. luminescence,21 catalysis,22 gas adsorption and separation,23

conductivity,1, 24 and magnetism,25 are known in the literature. Apart from the carboxylic acid

derivatives, also aromatic N-heterocyclic ligands are commonly used in MOF synthesis.

Popular donor groups include pyridines, pyrazoles, triazoles and imidazoles.

In the following, coordination polymers containing triazoles and imidazoles will be

discussed in detail.

4.1.1 Coordination polymers containing imidazoles

The imidazolate ligand itself is an angular, twofold connected building block with two

nitrogen donors oriented at an angle of ca. 145 ° (see Figure 4.1).26 It was recently recognized

that this angle is coincident with the Si-O-Si angle observed in zeolites. Hence, it should be

possible to develop “zeolitic imidazolate frameworks” (ZIFs). This idea stimulated the field

of imidazol-based coordination polymers over the last five years and led to over 90 new ZIF

structures with unique properties, such as CO2 capture.27

Figure 4.1: Analogy of the bridging angle of imidazolate in ZIFs and the Si-O-Si angle

preferred of zeolites.

NNM M

OSiSi

145° 145°

110Chapter 4

Bis(imidazole)-type ligands are used in MOF synthesis, too. Mostly, the imidazole

rings are connected through the N1 position of the imidazole ring. The spacers range from

short and longer alkyl chains (I, II) to aromatic (III-V) groups.28-31 Figure 4.2 gives some

examples for common bis(imidazole) ligands, which are applicable for the formation of

coordination polymers.

Figure 4.2: Common bis(imidazol) ligands used in MOF synthesis.28-31

Furthermore, within the last few years some examples of MOFs have been reported in

which imidazole-based ligands are combined with carboxylate units. Generally, mixtures of

the classic MOF carboxylate building blocks, such as bi-, tri- and tetravalent aromatic

carboxylic acids or squaric acid, and imidazole-containing ligands are used.32-36

Scarce examples of imidazole-based ligands are noted in the literature in which

carboxylate functions and imidazole groups are united in one ligand (Figure 4.3), like

bis(imidazole-2-yl)propionic acid (Hbip, VI) and its derivatives (e.g. Hbmip, VII), which

have found applications in MOF syntheses. The two imidazole rings commonly bind

chelating to the same metal, while the carboxylate functionalities acts as the bridging unit to a

second metal ion.37-39 Thus, linear zinc coordination polymers bearing the ligand bmip have

NNNN

N

NN

N

NNN

N

N

NN

N

NN N

N

I II

III IV

V

111Chapter 4

been reported.40 Two other examples of imidazole-based carboxylates used for generation of

MOFs are the 2-di(imidazolyl)methylmalonate (DIMMAL, VIII)41 and 2(imidazol-1-

yl)acetate (ima, IX) ligand.42

Figure 4.3: Carboxylate ligands containing imidazoles used in MOF synthesis.37-42

4.1.2 Coordination polymers containing 1,2,4-triazoles

The simplest ligand that can be imagined to form 1,2,4-triazole-based coordination

polymers is the 1,2,4-triazole itself. Following deprotonation, the anionic triazolate has three

possible donor sites (Figure 4.4).26

Figure 4.4: The possible binding sites present at the 1,2,4-triazolate ligand.

The 1,2,4-triazolate and related ligands have been studied intensively. Cu(I) and Ag(I)

MOFs in particular give rise to a large diversity of structures, often only depending on the

N

N

CO2H

VI

N

HN

N

HN

CO2H

N

N

N

N

CO2H

VII

N

HN

N

HN

CO2HHO2C

VIII IX

N

N N

112Chapter 4

reaction conditions.26 Thus, in Cu(I) coordination polymers the 3,5-disubstituted 1,2,4-

triazolates are commonly generated in situ, by oxidative cycloaddition between alkyl nitriles

and ammonia, in which Cu(II) serves as oxidant and is converted to Cu(I) in the final

products.43-46 Despite the pronounced variety of univalent 1,2,4-triazolate coordination

polymers, only rare examples of binary divalent metal 1,2,4-triazolates, such as [Cu(tz)2]n, are

noted in the literature.26

Moreover, bis(1,2,4-triazole) ligands, such as those depicted in Figure 4.5, are popular

for the development of transition metal organic framework structures. These ligands can be

largely divided into N1,N1-bridged (X-XIV) and N4,N4-bridged ligands (XV-XVII).

Figure 4.5: Common examples of bis(triazol) ligands.47-59

A large variety of spacers have been used to bridge the two triazole units, ranging

from simple alkyl chains (X-XII, XVI, XVII)47-52 to homocyclic (XIV)53-54 and heterocyclic

arenes (XIII)55 which can contain further donating groups.56-57 But ligands are known as well,

in which the triazole rings are directly connected (XV).58-59

N

NN

NN

NN

N

NNNN

N

N

NNN

N

N

NN N

N

N

X XI

XII

XIV

XV

N

N

NNNN

NNNN

NN N

N

NN

NN

N

NN

NN N

N

XIII

XVI

XVIII

N1,N1-bridged N4,N4-bridged

113Chapter 4

Despite the large variety of triazole-based ligands described in the literature, there are

only a few examples of coordination polymers incorporating both triazole and carboxylate

units. Some mixed-ligand frameworks constructed by carboxylates and triazole-based ligands

have been reported.60-64 Even fewer coordination polymers are known, which bear ligands

with both triazole and carboxylate functionalities. Y.-T. Fan and coworkers investigated the

coordination chemistry of (1,2,4-triazol-1-yl)acetate (taa, XIX) towards copper(II).65 The

tridentate ligand bis(1,2,4-triazol-1-yl)acetate (btza, XX) bearing two triazole units and one

carboxylate functionality and its coordination behavior towards transition metals were

recently studied by S. R. Batten.66 The ligand 1,2,3-triazole-4,5-dicarboxylic acid (TDA,

XXI) was used by W. Shi et. al. for the synthesis of some rare earth metal coordination

polymers.67 Figure 4.6 summarizes the ligands used in these studies.

Figure 4.6: Carboxylate ligands containing triazole units used in MOF synthesis.60-67

This chapter deals with the development of convenient synthetic routes to novel

imidazole and triazole-based carboxylate ligands and their application as ligands in metal

organic framework syntheses. Their binding properties are probed by the coordination to

transition metal ions. Furthermore, some of the N,N,O-ligands, which have already been

discussed in Chapter 2 proved to be valuable building blocks for coordination polymer

assemblies.

CO2HN

N

NHN

N NXXI

NNNN

NN

XIX XX

CO2H CO2H

CO2H

114Chapter 4

4.2 Results

As mentioned in the introduction, examples of mixed coordination polymers,

combining heterocyclic binding sites and carboxylate functionalities, remain rare in the

literature. Hence, it was a matter of interest to find easy pathways to suitable ligands with

both, heterocyclic binding sites and carboxylate groups. The structural modification of the

ligands should be easy. General synthetic strategies opening the path to a variety of ligands

should be worthwhile.

4.2.1 Imidazole-based N,N,O-ligands suitable for the synthesis of coordination

polymers

As described in Chapter 2 no mononuclear complexes were isolated if bmima was

reacted with simple transition metal salts. During complexation experiments with Zn(II) salts

highly insoluble powders were gained. No complex formation was detectable by mass

spectrometry. The NMR spectra of very diluted solutions showed only the signals of the

uncoordinated ligand. All these facts hinted to the formation of coordination polymers.68

Reacting the dihydrochlorides Hbmima × 2 HCl × H2O (1) and Hbmimabo × 2 HCl ×

0.5 H2O (2) 69 with Zn(OAc)2 and two equivalents of base resulted in the formation of

coordination polymers (Scheme 4.1). With 1, colorless crystals of [Zn(bmima)Cl]n (3)

precipitated from the reaction mixture within several days, which were characterized by

elemental analysis and IR spectroscopy.

In coordination polymer 3, the shift of the carboxylate absorption from 1719 cm–1 to

1637 cm–1 clearly indicates the coordination of the ligand through the carboxylate donor. This

shift is comparable to the shift recently reported for the coordination polymer

115Chapter 4

[Zn(bmip)Cl(OH2)]n (∆ vas(CO2) = 85 cm–1), which was obtained by reacting of potassium

bis(N-methylimidazol-2-yl)propionate (K[bmip]) with ZnCl2.40, 70

Scheme 4.1: Syntheses of [Zn(bmima)Cl]n and [Zn(bmimabo)Cl]n; i) Zn(OAc)2, H2O, rt.

The analogous reaction, between 2 and Zn(OAc)2 1, afforded [Zn(bmimabo)Cl]n (4).

The compound precipitated from the reaction mixture immediately and was obtained as a

colorless powder.

In coordination polymer 4 the IR band of the asymmetric carboxylate stretching

vibration is observed 1633 cm–1. The similarity of the νas(CO2) wavenumbers in 3 and 4

suggest identical coordination of the bmima and bmimabo ligands in both coordination

polymers. Unfortunately, experimental data of a corresponding zinc coordination polymer of

bis(N-methylbenzo[d]imidazol-2-yl)propionate are not available for comparison.

Crystals of 3 were studied by X-ray structure analysis (Figure 4.7), revealing the 1D

coordination polymer structure of [Zn(bmima)Cl]n. Within the chains of [Zn(bmima)Cl]n,

each zinc center is tetrahedrally coordinated by two bmima ligands – one binding through the

two imidazole rings, the other one through the carboxylate group – and one chlorido ligand,

respectively. Hence, each bmima ligand bridges two zinc atoms, which results in a distance

between the metal centers of 7.1113(5) Å. This is considerably shorter than the distance of

7.74 Å found for the coordination polymer [Zn(bmip)Cl(OH2)]n, where the Zn(II) centers are

N

N HN

N

O OH

2 Cl−

Zn(bmima)Cl n × n H2O Zn(bmimabo)Cl n

i)

1 (imidazole)2 (benzoimidazole)

43

+ +

116Chapter 4

in trigonal bipyramidal environment.40 Selected bond lengths and angles are given in Figure

4.7. Interestingly, independent of the metal to ligand ratio employed, bmima forms the

mono(ligand) complex 3 and thus favors a tetrahedral coordination sphere.

Figure 4.7: Cutout of the molecular structure of 3; hydrogen atoms have been omitted for

clarity; i) side-view of a chain; ii) front-view of a chain; thermal ellipsoids are drawn at the

50% probability level; selected bond lengths (Å) and angles (°): Zn-Zn 7.1113(5), Cl-Zn

2.775(8), N11-Zn 1.993(2), N21-Zn 2.001(2), O1-Zn 1.9636(19); O1-Zn-N11 102.41(9), O1-

Zn-N21 125.42(9), N11-Zn-N21 108.82(10), O1-Zn-Cl 102.04(4), N11-Zn-Cl 115.80(7),

N21-Zn-Cl 102.96(7).

117Chapter 4

Recent studies have shown that the real space structure of metal coordination

complexes can be investigated by scanning tunneling microscopy (STM) technique.68, 71

Therefore, the Zn(II) coordination polymer, which has excellent crystallization properties,

was also studied by STM and AFM (atomic force microscopy).72

A 10–9 M aqueous solution of 3 was drop coated on highly oriented pyrolytic graphite

(HOPG) and SiO2, and investigated by STM or AFM technique at ambient conditions. On

HOPG the coordination polymer 3 was found to form stable, straight lines as shown in Figure

4.8. This can be attributed to a template effect of the substrate, stabilizing the polymer in

positions of minimal energy along step edges and subsurface defect lines. Shorter strings of

[Zn(bmima)Cl]n form on SiO2. As seen in Figure 4.8ii the minimal width of the structures is

approximately 10 Å, roughly the diameter of a single chain.

Figure 4.8: Topographies of 3 on the surfaces; i-ii) STM topography of 3 on HOPG, iii) AFM

topography of 3 on Graphite, iv) AFM topography of 3 on SiO2.72

118Chapter 4

The measured periodicity along the chain is 7.5 Å, which is almost congruent with the

Zn-Zn-distance of 7.1113(5) Å measured by X-ray structure determination (Figure 4.7). Thus,

the formation of congruent structures on the HOPG surface and in the solid state can be

assumed. Future experiments including current imaging tunneling spectroscopy (CITS) and

theoretical studies are in progress.

4.2.2 Imidazole-based N,N-ligands suitable for the synthesis of coordination polymers

For the formation of the Zn(II) coordination polymers 3 and 4 the tetrahedral

environment of the metal center seemed to be essential. Since this geometry is also favored by

copper(I), Cu(I) coordination polymers with the ligand bmima were targeted as well. In situ

reduction of Cu(II) salts is generally used as a convenient way to Cu(I) coordination

polymers, as Cu(I) salts are known to be easily oxidized by air or spontaneously

disproportionate into Cu(0) and Cu(II) in aqueous solutions. The Cu(II)/Cu(I) couple has a

low standard electrode potential of E° = 0.16 V (Scheme 4.2) and a positive slope against

temperature, making temperature regulation an expedient tool for controlling reaction rates.73

Scheme 4.2: Redox potentials for the couples Cu(II)aq/Cu(I)aq and Cu(I)aq/Cu(0).

In an attempted synthesis of a Cu(I) coordination polymer, Cu(OAc)2 was reacted with

ligand 1 and two equivalents of KOH. Surprisingly, the formation of a coordination polymer

with bmima and Cu(I) or Cu(II) metal centers was not observed. An IR spectrum recorded of

the yellow crystals, which precipitated from the reaction mixture, showed not the

characteristic absorption band of an asymmetric carboxylate vibration. The fact that the

crystals were highly insoluble indicated the formation of a coordination polymer. Finally, a

0.16 V 0.52 VCu2+ (aq) Cu+ (aq) Cu

119Chapter 4

single crystal X-ray structure analysis revealed the molecular structure of the compound. A

coordination polymer of the composition [Cu2Cl2(bie)3]n (5) had formed, which consists of

Cu(I) cations, a novel imidazole-based N,N-donor ligand and chlorido ligands. The

coordination polymer features the new ligand trans-1,2-bis(imidazole-2-yl)ethylene (bie, 6),

which thus was discovered by serendipity (see also Scheme 4.3 and Scheme 4.5).

In 5, each Cu(I) center is coordinated by three independent bie ligands, which

coordinate through the nitrogen atom in the N2-position of the imidazole ring (Figure 4.9i-ii).

These three bie ligands bind each to one further Cu(I) center through the second imidazole

ring, which results in a 2D sheet structure of coordination polymer 5. Top and side views of

such a sheet are visualized in Figure 4.9iii and Figure 4.9iv, respectively. The coordination

polymer [Cu2Cl2(bie)3]n crystallizes in the space group R 3 , revealing hexagonal chair

structures, which are formed by the Cu(I) centers within the sheets. The coordinated

imidazole groups of six bie ligands extend into these “hexagons”, to give an inscribed

hexagon of imidazole rings in the Cu(I) centered “hexagon” structure as visualized in Figure

4.9iii.

120Chapter 4

Figure 4.9: Cutout of the molecular structure of 5; hydrogen atoms have been omitted for

clarity; i) view on the ligand geometry in the molecular structure of 5; ii) coordination

environment of the Cu(I) centers in the molecular structure of 5; iii) top view on the sheet

structure; iv) side view on a sheet; thermal ellipsoids are drawn at the 50% probability level;

selected bond lengths (Å) and angles (°): C1-C1 1.336(3), C1-C11 1.4476(14), Cu-N11

2.0465(11), Cu-Cl 2.6423(8); N11-Cu-N11 112.56(3), N11-Cu-Cl 106.17(3); N11-C11-C11-

N12 2.54(0).

121Chapter 4

As demonstrated by the formation [Cu2Cl2(bie)3]n (5), the N,N-donor ligand bie (6) is

an interesting building block for the synthesis of coordination polymers. Hence it was a

matter of fact, to establish a synthetic pathway to this ligand. It was assumed that 6 either was

formed during the redox and self-assembly reaction leading to coordination polymer 5 or it

was introduced as a side product of the one-pot synthesis of Hbmima × 2 HCl (1) as

visualized in Scheme 4.3, where it was generated in such small amounts that detection via

NMR failed. To elucidate the pathway of formation of 5, it was attempted to isolate 6 during

the synthesis of bmima. For this purpose, the two step synthesis of 6 with debmimm as an

intermediate (see Chapter 2), rather than the one-pot reaction was employed. Indeed, careful

column chromatography allowed 6 to be isolated from the reaction mixture containing

debmimm in a yield of 0.1%.

Scheme 4.3: Formation of bie (6) as side product of the synthesis of 1; i) 1. diethyl malonate,

NaH, THF, 0 °C to rt, 2. NaOH, H2O, reflux, 3. HCl, H2O, rt.

Hence, a rational method of synthesis for the novel bis(imidazole) ligand 6 was

targeted. Therefore, 1,2-bmie (see Chapter 2) was dehydrated with 1,8-diazabicyclo-

[5.4.0]undec-7-ene (DBU) and trifluoroacetic anhydride (TFAA), which furnished 6 in

satisfying yields of 68% (Scheme 4.4).

H+

N

N Cl

Cl−

N

NH+ +HN

N2 Cl−

OHO

1

+ N

NN

N

6

i)

122Chapter 4

Scheme 4.4: Rational synthetic pathway to 6; i) DBU, TFAA, THF, 50 °C.

The proton NMR spectrum of 6 exhibits only one set of signals for the two imidazole

groups, viz. one singlet for the methyl group at 3.73 ppm and two pseudosinglets at 6.90 ppm

and 7.09 ppm. The protons adjacent to the double bond are spectroscopically equivalent,

showing up as a singlet at 7.40 ppm. The strong absorption at 1478 cm–1 in the IR spectrum

(KBr) is attributed to the v(C=N) stretching vibration of the imidazoles. Finally, the molecular

structure of 6 was unequivocally established by single crystal X-ray structure analysis (Figure

4.10). The fully conjugated ligand bie adopts a flat geometry with torsion angles of nearly 180

°.

Figure 4.10: Molecular structure of 6; thermal ellipsoids are drawn at the 50% probability

level; hydrogen atoms have been omitted for clarity; selected bond lengths (Å) and angles (°):

C1-C1 1.333(2), C1-C11 1.4479(15), C11-N11 1.3293(14), C11-N12 1.3629(14); C1-C1-C11

123.86(14), N11-C11-N12 110.43(9), N11-C11-C1 126.45(10); N11-C11-C11-N12 1.43(15);

C1-C1-C11-N12 −175.79(13), C11-C1-C1-C11 180.00(11).

N

NN

N

6

N

N

N

NOH

i)

123Chapter 4

The coordination polymer 5 is now available by two different routes. Either the redox

and self assembly reaction between bie (6) and Cu(OAc)2 in which the addition of bmima is

essential can be employed to obtain single crystals of 5. By way of altenative, reaction of 1:1

mixtures of CuCl and 6 in MeCN yielded microcrystalline powders of this coordination

polymer (see Scheme 4.5). The identity of the compounds obtained by the two synthetic

pathways was checked by elemental analysis, IR (KBr) and powder X-ray diffraction.

Scheme 4.5: The two synthetic pathways leading to 5; i) Cu(OAc)2, 1, KOH, H2O, 80 °C; ii)

CuCl, MeCN, rt.

N

NN

N

6

i) or ii) [Cu2Cl2(bie)3]n

5

124Chapter 4

4.2.3 Triazole-based N,N,O-ligands suitable for the synthesis of coordination polymers

Previous research efforts by the Burzlaff group suggested a possible application of

triazole-based heteroscorpionates for the preparation of coordination polymers.68

Coordination experiments employing the bis(1,2,4-triazole-1-yl)propionate Na[btp] (7),

Zn(ClO4), and MeOH as solvent afforded highly insoluble powders of the composition

[Zn(btp)2]. Proton NMR spectroscopy (D2O), showed only the signals of the free ligand. X-

ray structure analysis of crystals of the compound obtained from saturated H2O solutions

finally revealed a linear polymeric structure of the complex [Zn(btp)2]n (8). A cutout of its

structure is sketched in Scheme 4.6.

Scheme 4.6: Synthesis of 8, cutout of a linear coordination polymer; i) Zn(ClO4)2, MeOH.

To study the binding motif of this novel triazole-based ligand in detail, btp was

coordinated to a selection of transition metals, namely Mn(II),74 Fe(II), Co(II), Ni(II), Cu(II).

Reaction of Na[btp] with the corresponding sulfates MSO4 (M = Mn, Fe, Co, Ni, Cu) in hot

aqueous solution for several days afforded insoluble solids of the composition [M(btp)2]n (M

= Mn (9), Fe (10), Co (11), Ni (12), Cu (13)) (see Scheme 4.7).

Zn

N

N

N

N

N

N

ZnO

ON

NN

N

NN

O

O

8

n

NN

N

N

NN

CO2−Na+

i)

7

125Chapter 4

Scheme 4.7: Syntheses of the complexes 9-13; i) MSO4, H2O, 70-80 °C.

The IR spectra (KBr) of the complexes 9-13 all show the vas(CO2) vibration in the

same range from 1612 cm–1 to 1621 cm–1. Interestingly, the complex [Zn(btp)2]n exhibits the

the vas(CO2) band at higher frequencies (1634 cm–1), which supports a coordination mode in

complexes 9-13 different from [Zn(btp)2]n (8). The same trends can be observed for the

v(C=N) vibrations. The ∆ (vas(CO2), vs(CO2)) of the carboxylate stretching vibrations of

complexes 9-13 lies in the range 217-226 cm–1, indicating a unidentate coordination mode of

the carboxylate donor.64, 75-76 An overview of the key IR signals in the complexes 8-13 and

those of the ligand Na[btp], respectively, is given in Table 4.1.

NN

N

N

NN

CO2−Na+

i)

7

[M(btp)2]n

9 (M = Mn)10 (M = Fe)11 (M = Co)12 (M = Ni)13 (M = Cu)

126Chapter 4

Table 4.1: Key IR vas(CO2) values of the ligand 7 and the coordination polymers 8-13a

Complex vas(CO2)b

v(C=N)b

vs(CO2)b

∆ (vas,vs)b

Na[btp]

(7) 1617 1512 1394 223

[Mn(btp)2]n

(9) 1621 1521 1395 226

[Fe(btp)2]n

(10) 1620 1521 1397 223

[Co(btp)2]n

(11) 1616 1523 1399 217

[Ni(btp)2]n × n H2O

(12) 1615 1525 1396 219

[Cu(btp)2]n

(13) 1612 1526 1386 226

[Zn(btp)2]n

(8) 163468 153068 – –

a All vas(CO2) values are given in cm–1; bKBr.

For complexes [Mn(btp)2]n (9),74 [Fe(btp)2]n (10), [Co(btp)2]n (11), and [Cu(btp)2]n (13),

crystals suitable for single crystal X-ray structure determination could be obtained from the

reaction mixtures. All these complexes exhibit isostructural configurations: Three different

metal centers coordinate the two triazolyl donors and the carboxylate functionality of each btp

ligand (Figure 4.11i). A cutout of the coordination geometry of one metal atom – exemplified

by the structure of [Fe(btp)2]n (10) – is visualized in Figure 4.11ii. Selected bond lengths and

angles for all the complexes are shown in Table 4.2.

The metal center is octahedrally coordinated by six different ligands. Two ligands

coordinate through the carboxylate functionalities in mutual trans-position. The remaining

127Chapter 4

coordination sites are occupied by the N-atoms of the 4-positions of four triazole rings,

belonging to four different btp ligands.

Recently, M. Du, S. R. Batten and coworkers reported on the coordination properties

of bis(triazol-1-yl)acetate (btza, XX).66 It is noteworthy that the reaction of M(OAc)2 (M =

Mn, Zn) with Hbtza afforded the isostructural coordination polymers [Mn(btza)2(OH2)2]n × 2

n H2O and [Zn(btza)2(OH2)2]n × 2 n H2O in which the metal centers are coordinated by four

independent ligands each, two coordinated by the carboxylates and two by the triazole rings.

Two further coordination sites are occupied by additional water molecules. On the contrary,

in coordination polymer [Cu(btza)2]n × n H2O the ligand btzp exhibits a binding motif similar

to that of btp in [Cu(btp)2]n. Evidently, by elongation of the carboxylate arm from acetate to

propionate, full occupation of the manganese coordination sites by all donor groups offered

by the ligands becomes possible, while a linear chain structure is then favored for Zn(II). For

the Cu(II) center, the coordination geometry is independent of the chain length of the

carboxylate arm of the heteroscorpionates. This results in an array of coordination polymer

sheets in complexes 9-13. Within the same sheet all the metal atoms are situated in one plane,

shielded by the ligands from above and from below. The top view on such a sheet is given in

Figure 4.11iii.

Interestingly, no solvent molecules are intercalated in any of the structures of

coordination polymers 8-11 and 13, notwithstanding that incorporated water molecules were

observed for the coordination polymers derived from btza, namely [Mn(btza)2(OH2)2]n × 2 n

H2O, [Cu(btza)2]n × n H2O, and [Cu(btza)2]n × n H2O, respectively.66 In coordination

polymers [M(btp)2]n (M = Mn, Fe, Co, Cu) (9-13), the stacked sheets are interlocked into each

other, leaving no larger spaces within the structure. Figure 4.11iii presents a side view on the

arrangement of the polymer sheets in the crystal structure, showing the coordination

polyhedra of the manganese atoms.

128Chapter 4

Figure 4.11: Cutout of the molecular structure of 9-11 and 13, exemplified by the molecular

structure of [Fe(btp)2]n (10); hydrogen atoms have been omitted for clarity; i) ligand geometry

in the molecular structure of 10; ii) surrounding of one Fe(II) center; iii) coordination polymer

sheet (top view); iv) three adjacent coordination polymer sheets (side view); thermal

ellipsoids are drawn at the 50% probability level; selected bond lengths and angles are given

in Table 4.2.

129Chapter 4

Table 4.2: Selected bond lengths and angles for the complexes 9-11 and 13.

Bond lenghsa [Mn(btp)2]n [Fe(btp)2]n [Co(btp)2]n [Cu(btp)2]n

M-M

8.0636(4),

8.2794(5),

9.5378(5)

7.9974(4),

8.1601(3),

9.4562(6),

7.9366(5),

8.0779(3),

9.4223(6)

7.9366(5),

8.0779(3),

9.4223(6)

M-O1 2.1297(11) 2.0618(11) 2.0794(14) 2.3175(9)

M-N13 2.2806(13) 2.2308(12) 2.1708(15) 2.0205(10)

M-N23 2.2678(13) 2.2064(12) 2.1474(16) 2.0295(9)

Angles

O1-M-O1 180.00 180.00 180.00 180.00

O1-M-N13 88.10(5),

91.90(5)

87.48(5),

92.52(5)

87.68(6),

92.32(6) 86.50(4),

93.50(4)

O1-M-N23 87.16(5),

92.84(5)

87.34(5),

92.66(5)

87.45(6),

92.55(6)

89.04(4),

90.96(4)

N13-M-N2389.44(5),

90.56(5)

89.82(5),

90.18(5)

89.98(6),

90.02(6)

89.66(4),

90.34(4)

N13-M-N13 180.00 180.00 180.00 180.00

N23-M-N23 180.00 180.00 180.00 180.00

a all bond lengths are given in Å; b all angles are given in deg.

Unfortunately, [Ni(btp)2]n × n H2O (12) could only be obtained as a microcrystalline

powder. It is the one with the lowest solubility in water and instantaneously begins to

precipitate from the reaction mixture. However, the powder diffraction patterns of [Ni(btp)2]n

× n H2O and coordination polymers 9-11 and 13 are congruent (see Figure 5.20, Appendix

5.3.3). Furthermore [Ni(btp)2]n × n H2O exhibits key IR vibrations in the same region (see

Table 4.1). Hence, closely related structures of polymers 9-11, 13 and [Ni(btp)2]n × n H2O

130Chapter 4

(12) can be concluded and coordination of the intercalated water molecule towards the metal

center is unlikely.

To probe the electronic properties of the coordination polymers bearing btp, 9-13 were

investigated by electron spin resonance (9, 11-13) and Mössbauer spectroscopy (10). The

experimental and simulated Mössbauer spectra of the Fe(II) complex 10 are presented in

Figure 4.12. The Mössbauer spectrum of 10 recorded at −196 °C consists of a symmetric

doublet. Least-square fit (solid line) to the experimental points assuming a Lorentzian line

shape gives an isomer shift, δ = 1.29 mms–1, which is within the typical range of δ = 1.1-1.3

mms–1 for hexacoordinate high spin iron(II) complexes bearing N- and O-donors, as is the

quadrupole splitting of ∆EQ = 3.48 mms–1 (typical range 2.0-3.2 mms–1).77

Figure 4.12: Zero-field Mössbauer spectrum of 10 at −196 °C; the solid lines are least-

squares fit to the data; δ = 1.29(1) mms−1, ∆EQ = 3.48(1) mms−1, ΓFWHM = 0.36(1) mms−1.

Only compounds [Mn(btp)2]n 9 and [Cu(btp)2]n 13 exhibited resolved ESR spectra at

room temperature as well as at −181 °C. The ESR spectrum of 9 recorded for solid samples at

room temperature is given in Figure 4.13i. The spectrum of coordination polymer 9 exhibits

two g-values at g = 1.93 (main signal) and g = 4.32. The g value of 1.93 is quite in the range

131Chapter 4

of those typically observed for high spin Mn(II) (g = 2-6).78 Since the Mn(II) centers of

[Mn(btp)2]n (9) adopt an axially slightly compressed octahedral geometry (along the O-Mn-O

axis), the ESR spectrum of 9 should actually exhibit an oblate axial system. No fine structure

was resolved in the spectrum, which can be explained by the large line width of the signal of

90 mT. The small signal with g = 4.32 is tentatively assigned to a forbidden half-field

transition ∆ms = 2 between the |− 1> and |+ 1> levels.79-81 As expected from the X-ray data,

the ESR spectrum of 13 shows a prolate axial system with g┴ = 2.07 and g║ = 2.30 as

visualized in Figure 4.13ii. The Cu(II) centers in [Cu(btp)2]n (13) adopt an axially slightly

elongated octahedral geometry. The g values are in the range of those observed for similar

octahedrally coordinated Cu(II) complexes with four equatorial heterocyclic N-donors and

two axial carboxylates bound to the metal center.82-83

Figure 4.13: ESR spectra of i) [Mn(btp)2]n 9 and (ii) [Cu(btp)2]n 13, recorded at room

temperature (solid samples).

132Chapter 4

4.2.4 Triazole-based N,O-ligands suitable for the synthesis of coordination polymers

Stimulated by the excellent properties of btp with regard to the synthesis of

coordination polymers, further research efforts were turned on the development of ligands

exhibiting similar carbon backbone structures, while offering only two donor groups – one

carboxylate moiety and one triazolyl functionality. On the one hand, it was attempted to

obtain more open structures, in which guest molecules might intercalate, as observed in the

case of the coordination polymers with btza (XX) and taa (XIX).65-66 On the other hand, the

second N-donor group, which does not bind in coordination polymer [Zn(btp)]n (8), forms the

connection to the third metal center in the coordination polymers [M(btp)2] (M = Mn, Fe, Co,

Cu). Thus, the second triazole unit seems to be responsible for the sheet structure formation.

Employing mono(triazole)-based N,O-ligands, one-dimensional coordination polymers might

result, which exhibit similar coordination geometries as observed for [Zn(btp)]n. Meeting this

challenge, the ligands ta and tzp were developed.

4.2.4.1 Syntheses of the ligands

The ligands K[ta] and K[tzp] were synthesized employing a procedure similar to that

reported for Na[btp]. By analogy to the synthesis of methyl bis(1,2,4-triazol-1-yl)propionate,

which was first reported by Díez-Barra and coworkers,68, 84 methyl (1,2,4-triazol-1-yl)acrylate

(taMe, 14) was obtained by reacting 1,2,4-triazole with sodium hydride, followed by the

addition of methyl propiolate. Saponification of 14 in the presence of a deficit of KOH

resulted in the potassium salt 15. Remaining ester 14 may easily be recovered by extracting

the crude reaction product with CH2Cl2, yielding K[ta] as offwhite powder. Thus, potassium

(1,2,4-triazol-1-yl)acrylate K[ta] (15) was easily available in multi gram scale (Scheme 4.8).

133Chapter 4

Scheme 4.8: Synthesis of K[ta] (15); i) 1. NaH, THF, 0 °C, 2. HC≡CCO2Me,

reflux; ii) KOH, H2O, rt.

On the other hand, potassium 1,2,4-triazol-1-ylpropionate K[tzp] (17) was obtained by

reacting 1,2,4-triazole with sodium hydride and methyl acrylate, similar to the procedure

employed by Dallacker and Minn,85 followed by saponification in the presence of aqueous

KOH (Scheme 4.9).

Scheme 4.9: Synthesis of K[tzp] (17); i) 1. NaH, THF, 0 °C, 2. HC=CCO2Me,

reflux; ii) KOH, H2O, rt.

Both ligands were characterized by routine spectroscopic methods. The formation of

15 is clearly indicated by the 1H NMR spectrum. The loss of the methyl group singlet,

observed at 3.81 ppm in the 1H NMR spectrum of 2, indicates complete saponification. The

two singlets of the triazole protons appear at 8.18 ppm and 8.76 ppm. The olefinic protons

attached to the α and β carbon atoms of the carboxylate emerge as two doublets at 6.54 ppm

(CHacryl,α) and 7.86 ppm (CHacryl,β). Ligand 17 exhibits the two singlets of the triazole protons

at 7.75 ppm and 8.01 ppm. The propionic acid unit gives rise to two triplets at 2.76 ppm (α-

CH2) and 4.47 ppm (β-CH2).

N

CO2Me

NN

N

CO2-

NN

NN

NH i) ii)

K+

1514

N

CO2Me

NN

N

CO2−

NN

NN

NH i) ii)

K+

16 17

134Chapter 4

The ligands offer four donors which in principle are able to bind metal centers, two

nitrogen atoms – N2 and N4 of the triazole aromatic ring – and the two oxygen atoms of the

carboxylate functionality (see Figure 4.14).

Figure 4.14: Possible binding sites of the ligand ta and tzp.

4.2.4.2 Syntheses of the metal complexes and coordination polymers with the ligand ta

Initial experiments, in which the carboxylate K[ta] (15) was reacted with MSO4 (M =

Mn, Fe, Co, Zn) at 70 °C in aqueous solutions, demonstrated successfully that ligand ta favors

the formation of coordination polymers. From coordination of 15 to a number of transition

metal ions M2+ (M = Mn, Fe, Co, Ni, Cu, Zn) coordination polymers [Mn(ta)2]n (18),

[Fe(ta)2]n (19), [Co(ta)2(OH2)2]n (20), [Ni(ta)(OH2)2]n × 2 n H2O (21), [Cu(ta)2(OH2)2]n (22),

[Zn(ta)2]n (23), and [Ag(ta)]n (24) resulted. Depending on the solubility of the resulting

complexes, crystals of coordination polymers formed from the reaction solutions within

several days by slow evaporation of the aqueous solutions.

The reaction of ta with MgSO4 afforded the mononuclear complex [Mg(H2O)6](ta)2.

An overview of the synthesized compounds is depicted in Scheme 4.10.

NN

N

O

O

M

M

M

M

−

NN

N

O

O

M

M

M

M

−

ta tzp

135Chapter 4

Scheme 4.10: Overview of the synthesized metal complexes and coordination polymers

bearing the ligand ta; i) MSO4 or AgNO3, H2O.

The coordination polymers [Mn(ta)2]n (18), [Fe(ta)2]n (19) were synthesized by

reacting ligand 15 with manganese(II) sulfate and ferrous sulfate, respectively. The IR spectra

(KBr) show characteristic signals at ν~ = 1666 cm–1 (18 and 19) and ν~ = 1561 cm–1 (18) and

ν~ = 1558 cm–1 (19), respectively, which are assigned to the asymmetric carboxylate vibration

and the ν(C=N) absorption of the triazole (see Table 4.3). This indicates only one

coordination mode to be present in MOFs 18 and 19 for the carboxylate functionality as well

as for the triazolyl donor. The almost identical IR vibration values support the assumption of

18 and 19 to be isostructural.

N

CO2−

NN

K+

15

[M(ta)2]n

18 (M = Mn)19 (M = Fe)23 (M = Zn)

[M(ta)2(OH2)2]n

20 (M = Co)21 (M = Ni)22 (M = Cu)

[Ag(ta)]n[Mg(OH2)6](ta)2

2524

i)i)

136Chapter 4

Table 4.3: Key IR signals of the ligand K[ta] (3) and the coordination polymers and 18 to 25.a

Compound νas(CO2–)b

ν(C=N)b

vs(CO2)b

∆ (vas,vs)b

K[ta]

(15) 1668 1579 1375 293

[Mn(ta)2]n

(18) 1666 1561 1399 267

[Fe(ta)2]n

(19) 1666 1558 1395 271

[Co(ta)2(OH2)2]n

(20) 1675 1560 1398 277

[Ni(ta)2(OH2)2]n

× 2 n H2O (21) 1669 1533 1388 281

[Cu(ta)2(OH2)2]n

(22) 1671 1571 1381 284

[Zn(ta)2]n

(23) 1667, 1656 1592, 1583 1387 280, 269

[Ag(ta)]n

(24) 1665 1578 1378 287

[Mg(H2O)6](ta)2

(25) 1667 1560 1378 289

a All vas(CO2) and ν(C=N) values are given in cm–1; b KBr.

Reaction of K[ta] with ZnSO4 resulted in the formation of coordination polymer 23.

The IR spectrum shows two bands for the asymmetric carboxylate vibration at 1667 cm–1 and

1656 cm–1 and two for the triazole ν(C=N) at 1592 cm–1 and 1583 cm–1. This suggests the

ligand to exhibit two different coordination modes within the polymer.

137Chapter 4

Finally, compound 20, synthesized from CoSO4 seemed to incorporate water

molecules. The IR spectrum showed one signal for the carboxylate and one for the triazolyl

group. Thus, again only one coordination mode of the ligand seems to be present in the

coordination polymer (Table 1).

Sulfate ions are commonly non-coordinating in reactions leading to coordination

polymers if reaction conditions similar to the ones here described are employed.86 Chloride

ions, on the other hand, are well known to coordinate to metal centers in analogous reactions

with neutral triazole-based N,N-ligands. Thus, ligand 15 was also reacted with the

corresponding first row transition metal chlorides, to check if any formation of heteroleptic

coordination polymers occurs. Interestingly, no chloride incorporation into the networks was

observed. The crystals that resulted were characterized by IR spectroscopy and elemental

analysis and were shown to be identical in composition with the corresponding coordination

polymers obtained from the transition metal sulfates.

To probe the thermal stability of the coordination polymers 18-20 and 23

thermogravimetric analyses (TGA) were conducted. According to the thermogravimetric

measurements, most coordination polymers derived from ta are stable up to about 200 °C and

more (for graphical details see Figure 5.23, Appendix 5.3.4). In the case of [Co(ta)2(H2O)2]n

(20) a weight loss of approximately 10% occured between 150 °C and 225 °C, which can be

explained by loss of the two coordinated water molecules.

Of compounds 18-20, 23, and 25 single crystals could be harvested form the reaction

mixtures. Compounds 21-24 were obtained as microcrystalline powders.

Single crystal X-ray structure determination of 18 and 19 revealed their three

dimensional metal organic framework (MOF) structure. The metal centers are surrounded by

six independent (1,2,4-triazol-1-yl)acrylate ions. The ligand binds in a µ3-ta-κN4:O1:O2 mode

(Figure 4.15i). The metal centers are octahedrally coordinated by two nitrogen donors N4 in

cis position. The four remaining coordination sites are occupied by the oxygen atoms of four

different carboxylate donors. Figure 4.15ii visualizes the coordination environment of the

138Chapter 4

metal centers in 18 and 19, as exemplified by structure 18. Selected bond lengths and angles

are given in Table 4.4.

Figure 4.15: Cutout of the molecular structure in 18 and 19, exemplified by the molecular

structure of 18; hydrogen atoms have been omitted for clarity; i) Coordination environment of

the metal centers; ii) ligand coordination; iii) 3D framework structure (top view); iv) view on

the 3D framework, revealing the channel-like cavities within the network.

139Chapter 4

Table 4.4: Selected bond lengths and angles for 18 and 19.

Bond lenghsa [Mn(ta)2]n [Fe(ta)2]n

M-M (µ2-O1:O2) 6.001(1)87 5.916(1)87

M-M (µ2-N4:O2) 9.2801(5) 9.220(2)

M-M (µ2-N4:O2) 9.9943(3) 9.897(2)

M-O1 2.3113(8), 2.050(5), 2.053(5)

M-O2 2.1503(9) 2.137(5), 2.144(5)

M-N3 2.3000(11), 2.222(6), 2.225(6)

O1-M-O1 174.52(6) 172.73(19)

O1-M-O2 88.64(3),

87.96(3)

88.3(2), 88.6(19),

87.1(2), 87.4(2)

O2-M-O2 103.17(5) 103.23(16),

O1-M-N3 92.12(4), 92.03(4) 92.9(2), 92.6(2), 92.7(2)

O2-M-N3 169.10(4), 87.72(4) 170.1(2), 86.7(2),

170.0(2), 86.8(2),

N3-M-N3 81.39(6) 83.3(2)

O1-C1-C2-C3 5.4(2) 4.9(11)

C1-C2-C3-N1 –176.46(12) –176.4(7)

C2-C3-N1-N2 8.2(2) 8.2(12)

a all bond lengths are given in Å; b all angles are given in deg.

In the coordination polymers 18 and 19 the ligand features a conjugated double bond

system, resulting in a nearly flat conformation with torsion angels of almost 180 ° around the

double bond. Cutouts of the network structure are given in Figures 4.15iii and 4.15iv, in

which two different views are shown. A view of the 3D framework, depicted in Figure 4.15iv

reveals small channel-like gaps. The metal-metal distances reach from 5.916(1) Å (µ2-O1:O2

bridged, 19) to 9.9943(3) Å (µ2-N4:O2 bridged, 18).

140Chapter 4

Reaction of CoSO4 with 15 afforded [Co(ta)2(OH2)2]n (20), a 2D coordination polymer

with sheet structure. The ligand coordinates in a µ2-ta-κN4:O mode, as depicted in Figures

4.16i. The nitrogen donors N4 of the triazole rings are in trans-position regarding the metal

center, as are the carboxylate groups. The metal centers are each coordinated by four

independent (1,2,4-triazol-1-yl)acrylate ions (see Figure 4.16ii). Two additional water

molecules occupy the axial coordination sites of the metal(II) center.

Figure 4.16: Cutout of the molecular structure of 20; i) environment of the ligand moiety; ii)

coordination environment of the metal centers in the molecular structures of 20 (i and ii: most

hydrogen atoms have been omitted for clarity); iii) top view on the 2D network; iv) side view

on the 3D framework; thermal ellipsoids are drawn at the 50% probability level. Selected

bond lengths (Å) and angles (°): C1-O2 1.2578(13), C1-O1 1.2644(13), C1-C2 1.5013(14),

Co-O2 2.0862(8), Co-N13 2.1375(9), O2-C1-O1 123.61(11); intra-planar hydrogen bond

length (Å): O1…H10A 1.969(1).

141Chapter 4

Different views on the network structure of 20 as well as selected bond lengths and

angles are given in Figures 4.16iii-iv. The above described alignment of metal centers and

ligands affords polymer sheets with the coordinated water intercalating between the sheets.

The network structure is stabilized by inter-sheet hydrogen bonds, as visualized in Figures

4.16iii-iv, to create a rather compact structure without any larger cavities within the network.

Coordination of 15 towards ZnSO4 afforded coordination polymer [Zn(ta)2]n (23) with 1D

double stranded chains. The zinc(II) ion is coordinated by four independent ligands (Figure

4.17i). Three of them are bonded through the carboxylate functionality and one by the

nitrogen atom N4 of the triazolyl group. The zinc-zinc distance along the single strand was

determined as 9.659(2) Å (µ2-N4:O bridged).

As already indicated by the IR spectrum, two different coordination modes of the ta-

ligand are present in the structure. Half of the ligands are bonded in the µ2-ta-κN4:O mode,

which is also observed in coordination polymer 20 and results in linear chains of zinc centers.

The second half of the ligands is bound in a for the ta-ligand so far unprecedented µ2-ta-

κO1:O2 fashion, fusing each two single strings to the double strand through the carboxylate

functionality, while the triazole ring dangles freely. As a result, short distances d(Zn-Zn) of

4.06 Å (µ2-O1:O2 bridged) are observed for the adjacent zinc centers within the double

strand. The non-coordinating triazolyl groups from different double strands interdigitate

through π-π-stacking between the aromatic rings and the C=C-double bonds like a zipper,

building up the three-dimensional network visualized by Figure 4.17ii. The sheets of “zipped”

coordination polymer double strands then interlace into a tight network structure without

larger gaps between the chains as shown in Figure 4.17iii.

142Chapter 4

Figure 4.17: Cutout of the molecular structures of 23; hydrogen atoms have been omitted for

clarity; thermal ellipsoids are drawn at the 50% probability level; i) coordination environment

of the metal centers and the ligand moiety; ii) two “zipped” coordination polymer strings of

[Zn(ta)2]n; iii) structure of interdigitating polymer double strands (top view); selected bond

lengths (Å) and angles (°): Zn-Zn 4.141(9), Zn-Zn 9.659(2), C1-O2 1.262(5), C1-O1

1.269(5), C1-C2 1.487(6), C2-C3 1.337(6), C3-N1 1.392(6), Zn-O1 1.982(3), Zn-O2

2.018(3), Zn-O3 1.921(3), Zn-N6 1.985(4), O1-Zn-O2 103.95(13), O1-Zn-O3 96.87(13), O2-

Zn-O3 107.95(13), O1-Zn-N6 115.47(14), O2-Zn-N6 101.87(14), O3-Zn-N6 128.54(11).

143Chapter 4

All of the above described structures contain M2+ metal centers selected from the first

row transition metals, where the different final topologies are determined by the individual

geometrical preferences of the assembling metal ions. In an attempt to probe the metal-

directed assembly of ta-bridged MOF structures by alkaline earth metal ions, Mg(SO4)2 × 6

H2O was combined with K[ta] (15). In this reaction, no coordination polymer was gained.

Instead simple anion exchange occurred to give [Mg(H2O)6](ta)2 (25).

In the mononuclear magnesium complex the metal center is coordinated by six water

ligands, bearing the (1,2,4-triazol-1-yl)acrylate anion as counter ions. Each hydrogen atom of

the coordinated water molecules is part of a hydrogen bridge (Figure 4.18).

Figure 4.18: Molecular structure of 25; thermal ellipsoids are drawn at the 50% probability

level; selected bond lengths (Å): O11…H1 1.860(3), O11…H2E 1.869(7), O11…H6B

2.094(8), O12…H5 1.761(2), N2…H3D 2.455(5), N3…H4C 1.968(3).

While the coordination polymers [Mn(ta)2]n, [Fe(ta)2]n, [Co(ta)2(H2O)2]n, and

[Zn(ta)2]n could be characterized by single crystal X-ray structure analysis, reactions of

CuSO4, NiSO4 and AgNO3 with 15 afforded 21, 22, and 24 only as microcrystalline powders

of the composition [Ni(ta)2(OH2)2] × 2 n H2O, [Cu(ta)2(OH2)2], and [Ag(ta)], respectively.

144Chapter 4

Although their structure could not be established in detail, some conclusions can be drawn

from their compositions, IR spectra and powder diffraction patterns.

As the low solubility of compounds 21, 22, and 24 is probably due to their polymeric

structure, these products are denoted as [Ni(ta)2(OH2)2]n × 2 n H2O (21), [Cu(ta)2(OH2)2]n

(22), and [Ag(ta)]n (24).

Elemental analysis of the coordination polymer [Cu(ta)2(OH2)2]n (22) shows the same

composition as [Co(ta)2(OH2)2]n (20), the structure of which was discussed above. However, a

congruence of the key IR vibrations of compounds 20 and 22, which could be proved for the

isostructural MOFs 18 and 19, is not observed. Although, the signals for the νas(CO2–)

vibration are observed at rather similar values at 1671 cm–1 in 22 and at 1675 cm–1 in 20,

which points to related binding motifs of the carboxylate unit, the powder diffraction patterns

of 20 and 22 vary as well, which definitely excludes congruent structures (see Figure 5.21,

Appendix 5.3.3).

It is concluded that coordination polymers 20 and 22 adopt different structures,

notwithstanding, their identical composition. This underlines once more how sensitive the

binding motif of the ligand depends on the geometrical preference of the metal center, to

which it is coordinated.

Ni(II) compound 21 seems to contain an exceptional large amount of water. The

stretching frequencies for the carboxylate group (vas(CO2) = 1669 cm–1, vs(CO2) = 1388 cm–1)

are in good agreement with the signals observed for 23 (vas(CO2) = 1669 cm–1, vs(CO2) = 1388

cm–1), hinting to a similar µ2-ta-κN4:O coordination of the carboxylate group. However, the

v(C=N) vibration appears at 1533 cm–1 which is the lowest value observed for all coordination

polymers bearing the ta ligand. This suggests a new, within this work unprecedented

coordination mode of the triazolyl moiety. The powder X-ray diffraction pattern shows no

similarity to any of the coordination polymers described in this study (see Figure 5.21,

Appendix 5.3.3).

145Chapter 4

In Ag(I) complex [Ag(ta)]n (24) the two carboxylate bands and the v(C=N) absorption

are nearly congruent with those observed for the ligand salt K[ta] (15). Hence, simple salt

exchange, as observed for 25, cannot be excluded. Though, the high insolubility of the

resulting compound – which precipitates at once from the reaction mixture – favors a

polymeric structure of 25. Again, the powder X-ray diffraction pattern shows no similarity to

any of the coordination polymers described here (see Figure 5.21, Appendix 5.3.3).

To probe the electronic properties of the coordination polymers bearing the ligand ta, 18-22

were investigated by electron spin resonance (18, 20-22) and Mössbauer spectroscopy (19).

The experimental and simulated Mössbauer spectra of [Fe(ta)2]n (19) are presented in Figure

4.19. The Mössbauer spectrum of 19 at −196 °C consists of a symmetric doublet. Least-

square fit (solid line) to the experimental points, assuming a Lorentzian line shape, gives an

isomer shift of δ = 1.38 mms–1, which is roughly within the typical range of δ = 1.1-1.3 mms–1

for hexa-coordinate high spin iron(II) complexes bearing N- and O-donors. The same is true

for the quadrupole splitting of ∆EQ = 3.27 mms–1 (typical range 2.0-3.2 mms–1).77

Figure 4.19: Zero-field Mössbauer spectrum of 10 at −196 °C; the solid lines are least-

squares fit to the data; δ = 1.38(1) mms−1, ∆EQ = 3.27(1) mms−1, ΓFWHM = 0.40(1) mms−1.

146Chapter 4

Only compounds [Mn(ta)2]n (18) and [Cu(ta)2(OH2)2]n (22) exhibit resolved ESR

spectra at room temperature, as well as at −181 °C. The ESR spectrum of 18, recorded for

solid samples at room temperature is given in Figure 4.20i. Coordination polymer 18 displays

the spectrum of an isotropic system with g = 2.00 and a line width of 4.8 mT. No fine

structure was resolved, as already observed for compound 9. The g value is quite in the range

of those typically observed for high spin Mn(II) (g = 2-6).78 Actually, the single crystal X-ray

structure analysis of 18 revealed the Mn(II) centers of 18 to adopt an axially slightly

compressed octahedral geometry (along the O-Mn-O axis), and the ESR spectrum of 18

should exhibit the spectrum of an oblate axial system. However, the missing g║ can be

explained by poor resolution, as already observed for the Mn(II) coordination polymer 9.

In fact the ESR spectrum of 22 shows an oblate axial system with g┴ = 2.17 and g║ =

2.07 (Figure 4.20ii), which agrees with the assumption of an axially compressed octahedral

geometry of the Cu(II) centers in the molecular structure of 18. The g values are in the range

of Cu(II) complexes in a octahedrally distorted coordination environment.82-83

Figure 4.20: ESR spectra of [Mn(ta)2]n (18) (ii) and [Cu(ta)2(OH2)2]n (22) (ii), recorded at

room temperature (solid samples).

147Chapter 4

4.2.4.3 Syntheses of metal complexes and coordination polymers with the ligand tzp

To study the influence of the ligand flexibility on the formation of MOF structures,

coordination polymer syntheses analogous to those established with the ligand ta were studied

with use of the more flexible ligand potassium 1,2,4-triazol-1-ylpropionate (17) were targeted.

Reaction of K[tzp] (17) with MSO4 (M = Co, Ni, Zn) and AgNO3 afforded crystals of

[Co(tzp)2(OH2)2]n × 2 n H2O (27), [Ni(tzp)(OH2)]n × 2 n H2O (28), [Zn(tzp)2]n × 0.25 n H2O

(30), and [Ag3(tzp)2(NO3)]n (31) growing from the reaction mixture. The combination of

MnSO4 CuSO4 with 17 produced [Mn(tzp)2]n (26) and [Cu(tzp)2(OH2)]n (29) as

microcrystalline powders. An overview of the synthesized coordination polymers containing

the ligand tzp is given in Scheme 4.11.

Scheme 4.11: Overview of the coordination polymers synthesized with the ligand tzp; i)

MSO4 or AgNO3, H2O, 70 °C.

The IR data of ligand 17 and coordination polymers 26-31 are summarized in Table

4.5. Compounds 26-28, and 31 exhibit the asymmetric carboxylate stretching vibrations in the

range of 1577 cm–1 to 1587 cm–1, which is at lower wavenumbers, than observed for the btp-

and the ta-derived MOFs.

Only one set of key IR signals is observed for 26-31, indicating one common

coordination mode of the ligand in each MOF. Most remarkably, coordination polymers

[Co(tzp)2(OH2)2]n× 2 n H2O (27) and [Ni(tzp)(OH2)]n × 2 n H2O (28) exhibit the asymmetric

N

CO2−

NN

K+

17

i) i)

[M(tzp)2]n

26 (M = Mn)30 (M = Zn)

[M(tzp)2(OH2)2]n

27 (M = Co)28 (M = Ni)29 (M = Cu)[Ag3(tzp)2(NO3)]n

31

148Chapter 4

carboxylate stretching vibration both at 1577 cm–1, and the symmetric one at 1412 cm–1 (27)

and 1411 cm–1 (28); the ν(C=N) vibrations are observed at 1523 cm–1 (27) and 1524 cm–1

(28). This coincidence of the IR vibrations clearly indicates that the networks are

isostructural.

In compounds [Cu(tzp)2(OH2)2]n 29 and [Zn(tzp)2]n × 0.25 H2O (30), the νas(CO2)

signals appear at 1620 cm–1 and 1628 cm–1, which is rather similar to those observed for the

corresponding btp-based coordination polymers [Zn(btp)2]n (8) (νas(CO2–) = 1634 cm–1) and

[Cu(btp)2]n (13) (νas(CO2) = 1612 cm–1).

Table 4.5: Key IR signals of the ligand 17 and the coordination polymers and 26-31.a

Compound νas(CO2–)b ν(C=N)b vs(CO2)

b ∆ (vas,vs)b

K[tzp]

17 1586 1513 1400 186

[Mn(tzp)2]n

26 1584 1517 1421 163

[Co(tzp)2(OH2)2]n× 2 n H2O

27 1577 1523 1412 165

[Ni(tzp)(OH2)]n × 2 n H2O

28 1577 1524 1411 166

[Cu(tzp)2(OH2)2]n

29 1628 1529 1401 227

[Zn(tzp)2]n × 0.25 H2O

30 1620 1529 1434 186

[Ag3(tzp)2(NO3)]n

31 1587 1513 1385 202

a All vas(CO2), ν(C=N), and vs(CO2) values are given in cm–1; b KBr.

149Chapter 4

A close similarity is also observed for the key IR vibrations of [Zn(tzp)2]n × 0.25 H2O

(30), with νas(CO2) = 1620 cm–1, ν(C=N) = 1529 cm–1, and those in [Zn(btp)2]n (8), with

νas(CO2) = 1634 cm–1, ν(C=N) = 1530 cm–1. This is easy to understand, since btp and tzp

possess the same carbon backbone and the molecular structure of 8 exhibits a µ2-ta-κN4:O

binding mode of btp with one triazole ring dangling. This results in a tetrahedral N,N,O,O-

coordinated Zn(II) center. This supports an analogous coordination of tzp to the Zn(II) centers

in the coordination polymer 30.

As no further correlations were evident from the IR signals of the tzp-based

coordination polymers, the only conclusion that can be drawn from the spectra is that 26 and

29-31 exhibit structures different from 27 and 28 and different from each other.

As already observed for coordination polymers 20-22, elemental analyses revealed

coordination polymers 27-30 to incorporate water molecules. In 27 and 28 and 21 four

equivalents of H2O per formula unit are present, while 20-22 and 29 contain only two

equivalents of H2O. Polymer 30 contains 0.25 H2O per formula unit.

A single crystal X-ray structure determination of [Co(tzp)2(OH2)2]n× 2 n H2O (27) and

[Ni(tzp)(OH2)]n × 2 n H2O (28) revealed their isostructural two dimensional polymer

structure. The ligand coordinates in a µ2-tzp-κN4:O mode, analogous to the coordination of ta

in Co(II) polymer 20. The nitrogen donors N4 of the triazole rings are in trans-position

regarding the metal center, as are the carboxylate groups. The alignment of the metal centers

and the ligands affords coordination polymer sheets with the coordinated water inserted

between the sheets. However, in contrast to the polymers of ta, the more flexible ligand tzp

allows more porous networks, leaving additional space within the layers, which can be

occupied by two further uncoordinated, co-crystalized H2O molecules. Different cutouts and

views on the network structure in 27 and 28, exemplified by the structure of 27 are shown in

Figure 4.21i-iv. Selected bond lengths and angles are given in Table 4.6.

150Chapter 4

Figure 4.21: Cutout of the molecular structures of [Co(tzp)2(OH2)2]n× 2 n H2O (27) and

[Ni(tzp)(OH2)]n × 2 n H2O (28), exemplified by the molecular structure of 27; thermal

ellipsoids are drawn at the 50% probability level; i) environment of the ligand moiety; ii)

coordination environment of the metal centers (i and ii: most hydrogen atoms have been

omitted for clarity); iii) top view on the 2D network; iv) side view on a 2D sheet.

151Chapter 4

Table 4.6: Selected bond lengths and angles for 27 and 28.

Bond lengths

[Co(tzp)2(OH2)2]n

× 2 n H2O

[Ni(tzp)(OH2)]n

× 2 n H2O

M-M (intra-planar) 10.2898(11)

13.944(2)

10.2578(8),

13.0875(13)

M-M (sheet-to-sheet) 8.0176(10) 8.0582(4)

M-O1 2.0929(14) 2.0725(10)

M-O3 2.1049(14) 2.925(11)

M-N3 2.144(17) 2.0898(11)

Angles

O1-M-O1 180.00 180.00

O1-M-O3 88.04(6),

91.96(6)

87.13(4),

92.87(4)

O3-M-O3 180.00 180.00

O1-M-N3 88.74(6),

91.26(6),

90.55(4),

89.45(4)

O3-M-N3 93.20(6),

86.80(6)

86.85(4),

93.15(4)

N3-M-N3 180.00 180.00

a all bond lengths are given in Å; b all angles are given in deg.

As already indicated by the key IR vibrations of [Zn(tzp)2]n × 0.25 H2O (30) and

[Zn(btp)2]n (8), the Zn(II) coordination polymers with btp and tzp show some similarities.

Each zinc atom is tetrahedrally coordinated by four ligands. The ligand is bonded in

the µ2-tzp-κN4:O mode, which was already observed for 27 and 28. Thus, linear chains of

Zn(II) centers result, with the links consisting of two ligands each. Two different types of zinc

chains (A and B), with slightly different d(Zn-Zn) values are present in the network, though

152Chapter 4

they have basically the same structure (Figure 4.22i-ii). This is due to the fact that every

second triazole nitrogen atom N2 in one of these chains (A-part) forms hydrogen bridges to

the co-crystallized H2O molecules, which results in slightly shorter metal-to-metal distances

within the chain (d(Zn1-Zn1) = 7.359(1) Å). In the other chain (B-part) no interactions to co-

crystallized solvent are observed resulting in longer distances d(Zn2-Zn2) of 7.380(1) Å. The

chains are aligned in a parallel fashion, exhibiting an ABBA sequence of the chains (Figure

4.22iii). A top view on the chains in the 3D framework is given in Figure 22iv.

The bond distances and angles are similar to those observed in [Zn(btp)2]n (8).

Selected bond lengths and angles of 30 and 8 are summarized in Table 4.7.

153Chapter 4

Figure 4.22: Cutout of the 1D molecular structure of 30; thermal ellipsoids are drawn at the

50% probability level; i) structure of chain A; ii) structure of chain B; iii) network structure of

30, depicted is the ABBA sequence of the chains.

154Chapter 4

Table 4.7: Selected bond lengths and angles in 30 and 8.

Bond lengths

30 (chain A) 30 (chain B) 868

Zn-Zn 7.3799(6) 7.3585(6) 6.773

N1-Zn 2.0282(18) 2.0186(16) 2.0045(13)

O1-Zn 1.9642(15) 1.9632(14) 1.9494(11)

N2-Zn 2.0142(17) 2.0271(16) 2.0045(13)

O2-Zn 1.9442(15) 1.9506(14) 1.9494(11)

Anglesb

O2-Zn-O1 110.04(7) 109.15(6) 100.41(7)

O2-Zn-N2 121.82(7) 122.62(6) 121.34(5)

O1-Zn-N2 102.10(7),

111.22(6)

102.30(6),

110.60(6) 104.48(5)

O2-Zn-N1 101.17(7),

110.17(7)

101.80(6),

110.32(7) 106.02(8)

N...H – 1.944(55) –

a all bond lengths are given in Å; b all angles are given in deg.

155Chapter 4

The single crystal structure analysis of the Ag(I) coordination polymer

[Ag3(tzp)2(NO3)]n (31) revealed its 3D metal organic framework structure. Two different

anions are present in the structure. The asymmetric unit consists of three Ag(I) centers. The

cationic charge is balanced by two tzp ligands and one nitrate, resulting in the formula unit

[Ag3(tzp)2(NO3)]n. In 31 all tzp ligands adopt the same µ5-tzp-κN4:N2:O1:O1:O2

coordination mode (Figure 4.23i), as anticipated from the IR data. This pentadentate

coordination mode of tzp is unique for coordination polymer 31, in which both the triazole

nitrogen atom N4 and the triazole nitrogen atom N2 bind to metal centers. The two O-atoms

of the carboxylate group are coordinated to three different Ag(I) ions, one donating with one

lone pair and the other one with both. The inorganic ligand NO3– is coordinated µ3-tzp-

κO1:O2:O2 and acts bridging between three different metal centers (Figure 4.23ii).

The Ag(I) ions adopt two different coordination spheres. One third of the Ag(I) centers

is coordinated by two triazole-N4, two O-donors of two different carboxylate groups and one

O-donor belonging to the nitrate ligand. This results in a square pyramidal coordination

sphere, slightly distorted toward a trigonal bipyramid (τ = 0.11). The other two thirds of the

Ag(I) centers are tetrahedrally coordinated by one triazole-N2, two O-donors belonging to

two different carboxylates and one nitrate-O. Figure 4.23ii visualizes the different metal

geometries. In the network structure, layers of Ag(I) atoms are made up, which are connected

by the ligands (Figure 4.23iii). Selected bond lengths and angles are given in Table 4.8 The

sequence of the different Ag(I) centers within the layers is ABACABA. Short distances

between the silver centers Ag2 and Ag3 of d(Ag2-Ag2) = 2.9406(5) and d(Ag3-Ag3) =

2.9646(5) are indicative of metal-metal interactions within the network structure, which are

not unusual in Ag(I) MOFs.88-90

156Chapter 4

Figure 4.23: Molecular structure of 31; hydrogen atoms have been omitted for clarity; i)

coordination environment of tzp; ii) overview of the coordination geometries of the Ag(I)

centers Ag1, Ag2, and Ag3; iii) view on the network structure; selected bond lengths an

angles are given in Table 4.8.

157Chapter 4

Table 4.8: Selected bond lengths and angles of 31.

Bond lengths

Ag1 Ag2 Ag3

Ag1-N23 2.176(2) Ag2-O1 2.284(2) Ag3-O22 2.266(2)

Ag1-N3 2.182(2) Ag2-O2 2.318(2) Ag3-O21 2.280(2)

Ag1-O2 2.644(5) Ag2-N2 2.363(2) Ag3-N22 2.433(2)

Ag1-O22 2.690(7) O41-Ag2 2.627(5) Ag3-O43 2.562(2)

Ag1-O41 2.859(4) Ag2-Ag2 2.9406(5) Ag3-Ag3 2.9646(5)

Anglesb

Ag1 Ag2 Ag3

N23-Ag1-N3 177.85(9) O1-Ag2-O2 135.90(8) O22-Ag3-O21 135.92(8)

O22-Ag1-O2 171.05(7) O1-Ag2-N2 123.89(8) O22-Ag3-N22 92.46(8)

O41-Ag1-O22 98.44(7) O2-Ag2-N2 91.57(8) O21-Ag3-N22 124.46(8)

O41-Ag1-N23 98.86(8) O1-Ag2-O41 110.32(7) O22-Ag3-O43 110.97(8)

O41-Ag1-N3 80.97(8) O2-Ag2-O41 83.03(8) O22-Ag3-O43 96.23(7)

O41-Ag1-O2 73.21(7) N2-Ag2-O41 101.90(9) N22-Ag3-O43 85.94(7)

O22-Ag1-N23 77.74(9)

N23-Ag1-O2 100.04(9)

O2-Ag1-N3 81.98(9)

N2-Ag1-O22 100.15(9)

a all bond lengths are given in Å; b all angles are given in deg.

While coordination polymers 27, 28, 30 and 31 could be characterized by single

crystal X-ray structure analysis, 26 and 29 were obtained as microcrystalline powders of the

composition [Mn(tzp)2]n (26) and [Cu(tzp)2(OH2)]n (29), respectively. Though their structures

could not be exactly predicted, their low solubility is indicative of MOF structures. The

powder X-ray diffraction patterns of both compounds reveal them to exhibit structures

158Chapter 4

different from the molecular structures with tzp described above. However, the powder X-ray

diffraction pattern of 26 shows some similarity to that of [Mn(ta)2]n (18) (for graphical details

see Figure 5.22, Appendix 5.3.3). Thus, a closely related structure can be assumed. As the

powder X-ray diffraction pattern of 29 shows no congruence to any of coordination polymers

discussed above, it must have a structure different from those described in this work.

To probe the electronic properties of the coordination polymers bearing the ligand tzp,

coordination polymers 26-29 were investigated by electron spin resonance. Only the

compounds [Mn(tzp)2]n (26) and [Cu(tzp)2(OH2)2]n (29) exhibited resolved ESR spectra at

room temperature as well as at −181 °C.

The ESR spectrum of 26, recorded for solid samples at room temperature is given in

Figure 4.24i. Coordination polymer 26 shows the spectrum of an isotropic system with g =

2.00. The g value is quite in the range of those typically observed for high spin Mn(II) (g = 2-

6)78 and congruent to that determined for 18 (g = 2.00). Also similar line widths are observed

for 26 (5.6 mT) and 18 (4.8 mT). This further supports the assumption that 18 and 22 form

related structures. As already observed for 9, no fine structure is resolved in the ESR spectra

of the Mn(II) coordination polymers.

The ESR spectrum of 29 shows a prolate axial system with g┴ = 2.07 and g║ = 2.29

(Figure 4.24ii). This agrees well with g values determined for [Cu(btp)2]n 13 (g┴ = 2.07 and

g║ = 2.30), in which the Cu(II) centers adopt an axially elongated octahedral geometry.

Hence, an elongated octahedron as observed for 13 might be assumed for 29 for as well.

159Chapter 4

Figure 4.24: ESR spectra of [Mn(tzp)2]n (26) (ii) and [Cu(tzp)2(OH2)]n (29) (ii), recorded at

room temperature (solid samples).

160Chapter 4

4.3 Conclusion

Different from the ligands 2,2-bmie, 1,2-bmie, and bmidta discussed in Chapter 2, the

novel N,N,O-ligands bmima and bmimabo were recognized as valuable building blocks for the

syntheses of coordination polymers, such as [Zn(bmima)Cl]n (3) and [Zn(bmimabo)Cl]n (4).

By serendipity, the N,N-ligand trans-bie (6) was discovered as a side product of the synthesis

of bmima and was found to form the 2D coordination polymer [Cu2Cl2(trans-bie)3]n (5).

Related N,N-donor ligands, such as 4,4’-bipyridines, pyrazines, and ligands based on

4-pyridine donors bridged by olefinic or aromatic bridges, were reported to form 1D

coordination polymers.91-97 Hence, linear coordination polymers bearing trans-bie might be

accesible employing 6, as well.

The coordination behavior of the ligand btp, which was already known to form 1D

coordination polymers with Zn(II), was investigated in detail. Reaction of btp with divalent

3d metal ions yielded the isostructural 2D coordination polymers [M(btp)2]n (M = Mn, Fe, Co,

Ni, Cu, Zn).

Following a procedure similar to the synthesis of btp, the novel mono(triazole)-based

N,O-ligands ta and tzp were developed. Contrary to the isostructural coordination polymers

resulting from the reaction of btp with various transition metals, similar reactions of ta and tzp

afforded molecular structures with varying topologies, basically depending on the metal

cations employed.

The novel ligand ta offers two carboxylate O-donors and two triazole N-donors (in

position 2 and 4 of the heterocycle) as four potential binding sites. If three of these donors

took part in metal coordination, 3D metal organic frameworks formed as represented by

[Mn(ta)2]n (18) and [Fe(ta)2]n (19). A coordination polymer built by interdigitating polymer

double strands was observed in the case of [Zn(ta)2]n (23), in which half of the ta ligands are

coordinated only through the carboxylate O-donors in a µ2-ta-κO1:O2 coordination mode. On

the other hand µ2-ta-κN4:O1 coordination of the ligand ta was observed in the case of

161Chapter 4

[Co(ta)2(OH2)2]n (20), in which two water molecules occupy two trans-positions of the

octahedral Co(II) center. All MOFs containing the ligand ta exhibit rather compact structures.

The coordination polymers [Ni(ta)(OH2)2]n × 2 n H2O (21), [Cu(ta)2(OH2)2]n (22), and

[Ag(ta)]n (24) were only obtained as microcrystalline powders. According to their powder

diffraction pattern, all three exhibit structures different from the other ones described here.

The new ligand tzp offers the same donor groups, while possessing a more flexible

structure. In the 1D coordination polymer [Zn(tzp)2]n × 0.25 H2O (30) tzp adopts a µ2-tzp-

κN4:O1 binding mode. Its structure shows similarities to that observed for [Zn(btp)2]n (8).

However, the linear chains in 30 are not connected via π-π-bonding. Furthermore, 0.25 equiv.

H2O are contained per formula unit. In the isostructural coordination polymers

[Co(tzp)2(OH2)2]n× 2 n H2O (27) and [Ni(tzp)(OH2)]n × 2 n H2O (28) the ligand binds in a µ2-

tzp-κN4:O1 fashion, similar to the ligand ta in [Co(ta)2(OH2)2]n (20).

Polymers [Mn(tzp)2]n (26) and [Cu(tzp)2(OH2)]n (29), were obtained as

microcrystalline powders. From their powder X-ray diffraction patterns, a structure of 26

related to [Mn(ta)2]n (18) was inferred.

Isostructural frameworks were observed for the 3D MOFs [Mn(ta)2]n (18) and

[Fe(ta)2]n (19) as well as the 2D coordination polymers [Co(tzp)2(OH2)2]n× 2 n H2O (27) and

[Ni(tzp)2(OH2)2]n × 2 H2O [Ni(tzp)(OH2)]n × 2 n H2O (28), which are structurally closely

related to [Co(ta)2(OH2)2]n (20), but incorporate solvent molecules.

Generally, more open structures are accessible with the ligand tzp, in which H2O

molecules are intercalated. Future experiments should concentrate on the removal of the co-

crystallized water molecules from the structures. This might lead to porous networks, which

could be able to store guest molecules, such as hydrogen. Networks containing larger cavities

might be generated, if ligands related to K[ta] (15) or K[tzp] (17) with rigid aryl- or

poly(aryl)-bridges were employed, since particularly the aryl- and poly(aryl)-bridged bi- and

trivalent aromatic carboxylic acids are well known to form highly porous structures.98

162Chapter 4

The 3D MOF [Ag3(tzp)2(NO3)]n (31) is the only example, in which the triazole-based

ligand tzp uses all of its binding sites, to bind in a κ5-N2,N4,O,O,O´ mode, with formation of

a compact structure without larger spaces for guest molecules.

However, Ag(I) containing coordination polymers have been described, which exhibit

antimicrobial activity and some of them even found applications in creams to prevent

bacterial infections in case of severe burns.99-100 Recently, some examples of Ag(I) containing

imidazole- and triazoles-based coordination polymers with antibacterial and antifungal

properties were reported, as well.101-102 Hence, future work on [Ag(ta)]n (24) and

[Ag3(tzp)2(NO3)]n (31) should also include tests of the antimicrobial activity of these

compounds.

163Chapter 4

4.4 Experimental section

4.4.1 General remarks

Experiments were carried out under nitrogen atmosphere using standard Schlenk

techniques only if noted. Solvents used in these syntheses (analytical-grade purity) were

degassed and stored under nitrogen atmosphere. Reported yields refer to analytically pure

substances and were not optimized. 1H and 13C{1H}

NMR spectra: Bruker DPX 300 AVANCE, δ values relative to the residual solvent

signal (1H: CHCl3, 7.26 ppm; HDO, 4.79 ppm; 13C{1H}: CHCl3, 77.2 ppm; CHD2OD, 49.0

ppm. IR spectra: Varian Excalibur FTS-3500 FT-IR spectrometer, CaF2 cuvett (d = 0.2 mm)

or KBr matrix. Mass spectra: Jeol JMS-700 using FD technique or FAB technique with 4-

NBOH as matrix. Elemental analysis: Elemental Analyser Euro EA 3000 Euro Vector

instrument. Melting points: Electrothermal digital melting point apparatus (capillary). X-ray

structure determination: Bruker Nonius Kappa CCD, Smart APEX II, or STOE IPDS 2T

diffractometer (graphite monochromator, Mo-Kα radiation, λ = 0.71073 Å). Powder XRD

analysis: Philips X’Pert powder diffractometer with Cu Kα radiation (40 kV, 40 mA). EPR

spectra: JEOL continuous wave spectrometer JES-FA200 equipped with an X-band Gunn

oscillator bridge, a cylindrical mode cavity and a Helium cryostat. 57Fe Mößbauer

spectroscopy: WissEl Mößbauer spectrometer (MRG-500) at 77 K in constant acceleration

mode. 57Co/Rh was employed as the radiation source. WinNormos was used for Igor Pro

software was used for the quantitative evaluation of the spectral parameters (leasts quares

fitting to Lorentzian peaks). The minimum experimental line widths were 0.23 mms−1. The

temperature of the samples was controlled by an MBBC-HE0106 MÖSSBAUER He/N2

cryostat within an accuracy of ±0.3 K. Isomer shifts were determined relative to α-iron at 298

K. N-methyl-2-imidazolecarboxaldehyde, Na[btp] (7)68 and tzpMe (16)85 were prepared

according to published procedures. The compounds 1,2-Hbmie, H[bmima] × 2 HCl × H2O (1)

164Chapter 4

and H[bmimabo] × 2 HCl × 0.5 H2O (2) were prepared as described in Chapter 269. All other

chemicals were used as purchased.

4.4.2 Syntheses of the ligands

bie (6): Under nitrogen atmosphere a Schlenk flask was charged with 1,2-bmie

(1.00 g, 4.85 mmol), THF (100 mL), and TFAA (2.02 ml, 3.05 g, 14.6 mmol). After stirring

for 30 min at room temperature, DBU (4.35 mL, 4.43 g, 29.1 mmol) was added. The mixture

was heated to 50 °C for 1 h. Subsequently, all volatiles were removed by rotary

evaporation.103 The brown residue was dissolved in CH2Cl2 (100 mL) and water (100 mL).

The phases were separated and the water phase was extracted with CH2Cl2 (3 × 100 mL). The

combined organic layers were dried (Na2SO4) and the solvent was removed by rotary

evaporation. The residue was fractionated by column chromatography (silica, 3 × 20 cm,

CH2Cl2/MeOH/NEt3 = 1000/50/1). All fractions containing product were collected and the

solvent was removed in vacuum. After recrystallization from hot water, the product was dried

in vacuum to give an offwhite powder (0.623 g, 3.31 mmol, 68%). M. p.: 223°C (dec.);

C10H12N4 (188.23 g mol–1): calcd. C 63.81, H 6.43, N 29.77; found C 63.99, H 6.43, N

29.68%.

1H NMR (CDCl3): δ = 3.73 (s, 6H, CH3), 6.90 (s, 2H, CHIm), 7.09 (s, 2H, CHIm), 7.40

(s, 2H, CH2) ppm; 13C{1H} NMR (CDCl3): δ = 32.9 (CH3), 116.2 (CHIm), 122.1 (CH2), 129.2

(CHIm), 145.5 (CIm) ppm;

FAB MS (4-NBOH): m/z (%) = 189 (100) [MH]+, 188 (56) [M]+; IR (CH2Cl2): ν~ =

3111 (w), 3046 (w), 2958 (w), 1521 (m), 1479 (s), 1457 (m), 1415 (m), 1289 (s), 1128 (m),

1082 (w), 1043 (w), 957 (m), 924 (w) cm–1. IR (KBr): ν~ = 3432 (br), 3107 (m), 3098 (m),

2953 (w), 2883 (w), 1802 (w), 1521 (w), 1478 (s), 1455 (m), 1413 (s), 1289 (s), 1267 (m),

1131 (m), 1088 (w), 1043 (w), 962 (s), 925 (m), 770 (s), 729 (s), 658 (s), 541 (m) cm–1.

165Chapter 4

Selected data for Nabtp (7):68 IR (KBr): ν~ = 3442 (br), 3113 (m), 1617 (s, CO2

–),

1512 (m), 1432 (m), 1394 (s), 1282 (m), 1207 (w), 1133 (m), 1015 (w), 974 (w), 678 (s) cm–1.

taMe (14): To a suspension of NaH (60% suspension in mineral oil, 1.19 g, 29.8

mmol) in THF (30 ml) was added 1,2,4-triazol (4.11 g, 59.5 mmol) under nitrogen

atmosphere and stirred for 1h. Methylpropiolate (2.65 ml, 2.50 g, 29.8 mmol) was added by

syringe and the mixture was stirred for 20 h under reflux. The solvent was removed in

vacuum and the residue was extracted with CH2Cl2 (250 ml) and the extracts filtered over

celite.103 The solvent was removed and the residue was recrystallized from toluene yielding

colorless crystals (4.13 g, 27.9 mmol, 94 %). M. p.: 155 °C; C6H7N3O2 (153.14 g mol–1):

calcd. C 47.06, H 4.61, N 27.44; found C 46.99, H 4.66, N 27.54%.

1H NMR (CDCl3): δ = 3.81 (s, 3H, CH3), 6.59 (d, 3JH,H = 13.7 Hz, 1H, CHacryl,α), 8.01

(d, 3JH,H = 14.0 Hz, 1H, CHacryl,β), 8.06 (s, 1H, CH5-tz), 8.34 (s, 1H, CH3-tz) ppm; 13C{1H}

NMR (CDCl3): δ = 52.2 (CH3), 110.1 (CHacryl,α), 135.3 (CHacryl,β), 144.7 (CH5-tz), 153.8 (CH3-

tz), 166.2 (CO2) ppm;

FD MS (Aceton): m/z (%) = 153 (100) [M+]; IR (CH2Cl2): ν~ = 1725 (s), 1665 (s),

1511 (w), 1303 (m), 1199 (m) cm–1. IR (KBr): ν~ = 3114 (w), 1713 (s), 1664 (s), 1518 (m),

1369 (m), 1341 (w), 1312 (m), 1266 (m), 1193 (s), 1170 (m), 1137 (m), 997 (m), 966 (w), 952

(w), 861 (w), 803 (w), 701 (w), 670 (m), 642 (w), 518 (w) cm–1.

K[ta] (15): To a solution of taMe (14) (3.00 g, 19.6 mmol) in H2O (50 mL) was added

KOH (0.880 g, 15.7 mmol) and the mixture was stirred for 24 h. The mixture was washed

with CH2Cl2 (3 × 50 mL) to remove the excess of taMe and the water phase was dried in

vacuum to yield an offwhite powder (2.42 g, 13.7 mmol, 87%). M. p.: 221 °C (dec.);

C5H4KN3O2 (177.20 g mol–1): calcd. C 33.89, H 2.28, N 23.71; found C 33.59, H 2.27, N

23.69%.

166Chapter 4

1H NMR (D2O): δ = 6.54 (d, 3JH,H = 14.1 Hz, 1H, CHacryl,α), 7.86 (d, 3JH,H = 14.0 Hz,

1H, CHacryl,β), 8.18 (s, 1H, CH5-tz), 8.76 (s, 1H, CH3-tz) ppm; 13C{1H} NMR (10% MeOH-

d4/D2O): δ = 117.7 (CHacryl,α), 133.4 (CHacryl,β), 146.2 (CH5-tz), 153.3 (CH3-tz), 174.0 (CO2)

ppm.

IR (KBr): ν~ = 3485 (m), 3249 (sh), 3133 (w), 1668 (s), 1579 (s), 1520 (m), 1433 (w),

1375 (s), 1353 (m), 1269 (m), 1224 (m), 1143 (m), 1006 (w), 994 (m), 865 (w), 671 (m), 644

(w), 539 (w) cm–1.

K[tzp] (17): A flask was charged with tzpMe (16) (7.50 g, 48.3 mmol,) and H2O (100

mL), and KOH (2.44 g, 43.5 mmol) was added with stirring. After 24 h, the water phase was

washed with CH2Cl2 (2 × 100 mL) and dried by rotary evaporation to yield a colorless solid

powder (6.14 g, 34.7 mmol, 80%). M. p.: 152 °C; C6H9N3O2 (155.15 g mol–1): calcd. C 46.45,

H 5.85, N 27.08; found C 46.27, H 6.15, N 27.00%.

1H NMR (D2O): δ = 2.76 (t, 3JH,H = 6.7 Hz, 2H, CH2CO2), 4.47 (t, 3JH,H = 6.7 Hz, 2H,

NCH2), 7.75 (s, 1H, CH5-tz), 8.01 (s, 1H, CH3-tz); 13C{1H} NMR (10% MeOH-d4/D2O): δ =

37.1 (CH2CO2), 46.6 (NCH2), 144.1 (CH5-tz), 151.0 (CH3-tz), 178.7 (CO2) ppm;

IR (KBr): ν~ = 3412 (br), 1586 (s), 1513 (m), 1400 (s), 1277 (m), 1210 (w), 1142 (m),

1014 (w), 868 (w), 680 (m) cm–1.

4.4.3 Syntheses of the complexes and coordination polymers

[Zn(bmima)Cl]n × H2O (3): A flask was charged with Hbmima × 2 HCl × H2O (1)

(0.200 g, 0.590 mmol), KOH (0.066 g, 1.18 mmol), and H2O (5 mL), and Zn(OAc)2 (0.108 g,

0.589 mmol) was added with stirring. After 5 min, stirring was stopped. The mixture was

stored at room temperature for 3 d. The colorless solid that formed was separated by filtration,

washed with ether and dried in an oil pump vacuum to yield a colorless powder (0.115 g,

167Chapter 4

0.314 mmol, 53%). M. p.: 337 °C (dec.); C12H15ClN4O2Zn × H2O (366.15 g mol–1): calc. C

39.36, H 4.68, N 15.30; found C 39.19, H 4.54, N 15.22.

IR (KBr): ν~ = 3537 (w), 1637 (s), 1505 (s), 1382 (m), 1303 (m), 1239 (m), 1220 (w),

1128 (m), 1091 (w), 973 (w), 778 (w), 743 (w), 646 (w) cm–1.

[Zn(bmimabo

)Cl]n (4): A flask was charged with Hbmimabo × 2 HCl × 0.5 H2O (2)

(0.200 g, 0.465 mmol), KOH (0.050 g, 0.891 mmol), and water (10 ml), and Zn(OAc)2 (0.082

g, 0.447 mmol) was added with stirring. After 20 h, the colorless solid that formed was

separated by filtration, washed with water (2 × 10 ml) and diethylether (2 × 10 ml), and was

dried in an oil pump vacuum to yield a colorless powder (0.153 g, 0.341 mmol, 77%). M. p.:

259 °C (dec.); C20H19ClN4O2Zn (448.25 g mol–1): C 53.59 H 4.27 N 12.50; found: C 12.34 H

4.37 N 12.34.

IR (KBr): ν~ = 2947 (w), 1633 (s), 1485 (m), 1457 (m), 1410 (w), 1379 (w), 1336 (w),

1298 (w), 1239 (w), 900 (w), 748 (w) cm–1.

[Cu(bie)1.5Cl]n (5), method A (redox and self assembly reaction): A flask was

charged with trans-bie (6) (0.055 g, 0.295 mmol) and Hbmima × 2 HCl × H2O (1) (0.500 g,

1.474 mmol), and a solution of KOH (0.165 g, 2.948 mmol) in water (20 mL) was added with

stirring. After 5 min, Cu(OAc)2 × 2 H2O (0.147 g, 0.737 mmol) was added with stirring.

Subsequently, stirring was stopped and the mixture was heated slowly to 80 °C for. After 1 d,

the mixture was cooled to room temperature. The yellow solid that formed was separated by

filtration, washed with water (2 × 20 mL) and Et2O (10 mL) and dried in an oil pump vacuum

to yield a yellow solid (0.053 g, 0.139 mmol, 71 %).

Method B: Under nitrogen atmosphere a Schlenk flask was charged with CuCl (0.036

g, 0.354 mmol) and MeCN (25 mL). After 15 min, trans-bie (6) (0.133 g, 0.71 mmol) was

added. The solid that formed within 1h was separated by filtration, washed with Et2O (2 × 20

mL), and dried in an oil pump vacuum to yield a yellow powder (0.072 g, 0.189 mmol. 53 %).

168Chapter 4

M. p.: 273°C (dec.); C15H18ClCuN6 (381.35 g mol–1): calcd. C 47.24, H 4.76, N 22.04; found

C 46.94, H 4.78, N 21.97%.

IR (KBr): ν~ = 3130 (w), 3087 (m), 3038 (w), 1529 (m), 1473 (m), 1413 (m), 1300

(w), 1279 (s), 1147 (m), 1100 (w), 958 (m), 795 (m), 785 (m), 771 (m), 732 (s), 669 (m), 524

(w) cm–1.

[Mn(btp)2]n (9): A test tube was charged with Na[btp] (7) (0.101 g, 0.44 mmol) and

MnSO4 × H2O (0.037 g, 0.22 mmol), and water (5 mL) was added. The mixture was heated

slowly to 70 °C. After 4 d, the mixture was cooled to room temperature. The pale yellow solid

that formed was separated of the supernatant, triturated with water (5 × 5 mL), and dried in an

oil pump vacuum at 80 °C to yield a pale yellow powder (0.066 g, 0.141 mmol, 64%). M. p.:

311 °C (dec.); C14H14MnN12O4 (469.28 g mol–1): calcd. C 35.83, H 3.01, N 35.82; found C

35.85, H 3.05, N 35.95 cm–1.

IR (KBr): ν~ = 3436 (br), 3114 m, 1621 (s), 1521 (m), 1438 (w), 1395 (s), 1340 (w),

1266 (w), 1199 (w), 1131 (m), 1007 (w), 908 (w), 822 (w), 673 (m), 552 (w) cm–1.

[Fe(btp)2]n (10): Under nitrogen atmosphere a test tube was charged with 7 (0.230 g,

1.00 mmol), and FeSO4 × 7 H2O (0.139 g, 0.50 mmol) and fitted into a Schlenk flask.

Degassed water (20 mL) was added under nitrogen atmosphere with stirring. After 5 min,

stirring was stopped and the mixture was slowly heated to 80 °C. After 6 d, the mixture was

cooled to room temperature. The colorless solid that formed was separated by decantation of

the supernatant and dried in an oil pump vacuum to give a colorless powder (0.154 g, 0.328

mmol, 66%). M. p.: 311 °C (dec.); C14H14FeN12O4 (470.18 g mol–1): calcd. C 35.76, H 3.00,

N 35.75; found C 35.72, H 3.00, N 35.47.

IR (KBr): ν~ = 3447 (br), 3118 (m), 1620 (s), 1521 (m), 1435 (w), 1397 (s), 1341 (w),

1266 (w), 1199 (w), 1130 (m), 1008 (w), 907 (w), 823 (w), 674 (m), 551 (w) cm–1.

169Chapter 4

[Co(btp)2]n (11): A test tube was charged with 7 (0.300 g, 1.30 mmol) and CoSO4 × 7

H2O (0.183 g, 0.651 mmol), and water (20 mL) was added. The mixture was slowly heated to

70 °C. After 3 d, the mixture was cooled to room temperature. The pink solid that formed was

separated by decantation of the supernatant and dried in an oil pump vacuum at 80 °C to give

a pink powder (0.189 g, 0.399 mmol, 61%). M. p.: 210 °C (dec.); C14H14CoN12O4 (473.27 g

mol–1): calcd. C 35.53, H 2.98, N 35.51; found C 35.27, H 3.01, N 35.39 cm–1.

IR (KBr): ν~ = 3430 br, 3116 m, 1616 (s), 1523 m, 1438 w, 1399 m, 1342 w, 1267 w,

1200 w, 1129 m, 1008 w, 911 w, 734 w, 674 m, 551 w cm–1.

[Ni(btp)2]n × n H2O (12): A test tube was charged with 7 (0.300 g, 1.30 mmol) and

water (10 mL). The solution was layered with a solution of NiSO4 × 5 H2O (0.159 g, 0.649

mmol) in water (10 mL). The test tube was slowly heated to 70 °C. After 3 d, the mixture was

cooled to room temperature. The pale blue solid that formed was separated by decantation of

the supernatant, triturated with water (5 × 20 mL), and dried in an oil pump vacuum at 80 °C

to yield a pale blue powder (0.195 g, 0.397 mmol, 61%). M. p.: 151 °C (dec.); C14H14NiN12O4

× H2O (491.05 g mol–1): calcd. C 34.24, H 3.28, N 34.23; found C 34.59, H 3.17, N 34.59.

IR (KBr): ν~ = 3431 (br) 3117 (m), 3005 (w), 2991 (w), 1615 (s), 1525 (m), 1439 (w),

1396 (s), 1343 (w), 1271 (w), 1201 (w), 1128 (m), 1008 (w), 968 (w), m 913 (w), 822 (w),

735 (w), 675 (m), 551 (w) cm–1.

[Cu(btp)2]n (13): A test tube was charged with 7 (0.230 g, 1.00 mmol) and CuSO4 × 5

H2O (0.125 g, 0.50 mmol), and water (20 mL) was added. The mixture was slowly heated to

70 °C. After 5 d, the mixture was cooled to room temperature. The pale blue solid that formed

was separated by filtration, triturated with water (5 × 20 mL), and dried in an oil pump

vacuum at 80 °C to yield a pale blue powder (0.178 g, 0.372 mmol, 74%). M. p.: 158°C

(dec.); C14H14CuN12O4 (477.88 g mol–1): calcd. C 35.19, H 2.95, N 35.17; found C 35.21, H

2.96, N 35.08.

170Chapter 4

IR (KBr): ν~ = 3429 (br), 3136 (m), 3102 (m), 3001 (w), 2985 (w), 1612 (s), 1526 (m),

1447 (w), 1386 (s), 1344 (w), 1272 (w), 1199 (w), 1127 (m), 997 (w), 968 (w), 918 (w), 817

(w), 734 (w), 673 (m), 620 (w), 554 (w) cm–1.

[Mn(ta)2]n (18): A test tube was charged with K[ta] (15) (0.177 g, 1.00 mmol) and

MnSO4 × H2O (0.084 g, 0.50 mmol), and H2O (20 mL) was added. The mixture was slowly

heated to 70 °C. After 8 d, the mixture was cooled to room temperature. The colorless solid

that formed was separated by filtration and dried in an oil pump vacuum to yield a colorless

powder (0.132 g, 0.399 mmol, 80%). M. p.: 351 °C (dec.); C10H8MnN6O4 (331.15 g mol–1):

calcd. C 36.27, H 2.44, N 25.38; found C 36.42, H 2.24, N 25.48.

IR (KBr): ν~ = 3104 (w), 1666 (s, νas(CO2–)), 1561 (s), 1456 (w), 1399 (s), 1382 (m),

1362 (m), 1294 (w), 1269 (w), 1227 (w), 1133 (w), 997 (m), 976 (w), 951 (w), 927 (w), 864

(w), 701 (m), 673 (m), 640 (w), 549 (w) cm–1.

[Fe(ta)2]n (19): Under nitrogen atmosphere a test tube was charged with 15 (0.200 g,

1.13 mmol), and FeSO4 × 7 H2O (0.117 g, 0.421 mmol). The test tube was fitted into a

Schlenk flask, and H2O (15 mL) was added under nitrogen atmosphere. Bright orange crystals

of 19 formed by slow evaporation of the solvent at 70 °C under reduced pressure within 8 d

(0.082 g, 0.247 mmol, 59%). M. p.: 302 °C (dec.); C10H8FeN6O4 (332.05 g mol–1): calcd. C

36.17, H 2.43, N 25.31; found C 35.93, H 2.37, N 25.39.

IR (KBr): ν~ = 3435 (br), 3126 (w), 3104 (w), 1666 (s), 1558 (s), 1453 (w), 1395 (s),

1362 (m), 1293 (w), 1269 (m), 1228 (m), 1190 (w), 1134 (m), 998 (m), 951 (w), 930 (w), 862

(w), 745 (w), 700 (m), 674 (m), 639 (w), 551 (w) cm–1.

[Co(ta)2(OH2)2]n (20): A test tube was charged with 15 (0.150 g, 0.847 mmol), CoSO4

× 7 H2O (0.119 g, 0.423 mmol) and H2O (10 mL). Pink crystals of 20 were deposited by slow

evaporation of the solvent at 70 °C within 6 d (0.132 g, 0.356 mmol, 84%). M. p.: 205 °C

171Chapter 4

(dec.); C10H12CoN6O6 (371.17 g mol–1): calcd. C 32.36, H 3.26, N 22.64; found C 32.26, H

3.29, N 22.75.

IR (KBr): ν~ = 3348 (m), 3109 (m), 3042 (sh), 1675 (s), 1662 (sh), 1560 (s), 1534 (s),

1452 (m), 1398 (s), 1385 (s), 1360 (m), 1296 (m), 1271 (w), 1227 (w), 11945 (w), 1136 (m),

1002 (m), 990 (w), 935 (m), 901 (w), 858 (w), 734 (w), 698 (m), 670 (m), 645 (w), 534 (w)

cm–1.

[Ni(ta)2(OH)2]n ×2 n H2O (21): A flask was charged with 15 (0.500 g, 2.82 mmol)

and water (30 ml), and heated to 70 °C. A solution of NiSO4 × 5 H2O (0.346 g, 1.41 mmol)

was added dropwise, while stirring at 70 °C. After stopping the stirring and slow cooling of

the solution to room temperature, pale green crystals of 21 formed within 1 d (0.256 g, 0.629

mmol, 45 %). M. p.: 153 °C (dec.); C10H16NiN6O8 (406.96 g mol–1): calcd. C 29.51, H 3.96, N

20.65; found C 29.67, H 3.91, N 20.52.

IR (KBr): ν~ = 3179 (m), 3178 (m), 3177 (m), 3127 (s), 3102 (s), 3060 (s), 3049 (s),

1669 (s), 1636 (w), 1533 (s), 1456 (w), 1388 (s), 1358 (s), 1295 (m), 1272 (m), 1230 (m),

1195 (w), 1135 (w), 997 (m), 965 (w), 946 (m), 913 (w), 905 (w), 874 (w), 817 (w), 780 (w),

751 (w), 689 (m), 671 (m), 642 (m), 550 (w) cm–1.

[Cu(ta)2(OH2)2]n (22): A test tube was charged with 15 (0.050 g, 0.282 mmol) and

water (10 mL). The resulting solution was layered with a solution of CuSO4 × 5 H2O (0.035 g,

0.141 mmol) in H2O (10 mL). Blue crystals of 22 formed upon storing the test tube at 70 °C

within for 3 d (0.043 g, 0.114 mmol, 81%). M. p.: 195 °C (dec.); C10H12CuN6O6 (375.78 g

mol–1): calcd. C 31.96, H 3.22, N 22.36; found C 31.77, H 3.52, N 22.45.

IR (KBr): ν~ = 3417 (m), 3132 (w), 1671 (s), 1571 (s), 1530 (s), 1457 (w), 1381 (s),

1296 (w), 1272 (m), 1215 (w), 1185 (w), 1126 (m), 994 (m), 949 (w), 866 (w), 824 (w), 711

(w), 667 (w), 642 (w), 568 (w) cm–1;

172Chapter 4

[Zn(ta)2]n (23): A test tube was charged with 15 (0.177 g, 1.00 mmol) and ZnSO4 × 7

H2O (0.143 g, 0.50 mmol) and H2O (10 mL). Upon slow evaporation of the solvent at 70 °C

colorless crystals of 23 were produced over 10 d (0.119 g, 0.348 mmol, 70%). M. p.: 301 °C

(dec.); C10H8ZnN6O4 (341.62 g mol–1): calcd. C 35.16, H 2.36, N 24.60; found C 35.25, H

2.27, N 24.64.

IR (KBr): ν~ = 3448 (w), 3123 (m), 1667 (s), 1656 (s), 1592 (s), 1583 (s), 1533 (m),

1524 (w), 1448 (w), 1387 (s), 1360 (m), 1299 (w), 1291 (w), 1273 (m), 1267 (m), 1226 (w),

1218 (w), 1194 (m), 1184 (w), 1134 (m), 1126 (m), 990 (m), 958 (w), 952 (w), 898 (w), 867

(w), 819 (w), 747 (w), 715 (m), 670 (m), 667 (m), 647 (w), 642 (w), 549 (w) cm–1.

[Ag(ta)]n (24): A test tube was charged with 15 (0.177 g, 1.00 mmol) and H2O (10

mL), and a solution of AgNO3 (0.170 g, 1.00 mmol) in H2O (10 mL) was added. The

colorless solid that formed was filtered of, washed with water (3 × 5 mL), and dried in

vacuum to yield 24 as an offwhite powder (0.163 g, 0.663 mmol, 66%). M. p.: 195 °C (dec.);

C5H4AgN3O2 (245.97 g mol–1): calcd. C 24.41, H 1.64, N 17.08; found C 24.27, H 1.49, N

16.86.

IR (KBr): ν~ = 3472 (w), 3109 (w), 3092 (m), 1665 (s), 1578 (s), 1546 (s), 1524 (m),

1444 (w), 1378 (s), 1355 (m), 1285 (w), 1269 (w), 1224 (m), 1194 (w), 1138 (m), 1004 (m),

955 (m), 868 (w), 817 (w), 708 (m), 674 (m), 647 (w), 545 (w) cm–1.

[Mg(OH2)6](ta)2 (25): A test tube was charged with 15 (0.500 g, 2.82 mmol) and a

solution of MgSO4 × 7 H2O (0.350 g, 1.41 mmol) in water (10 mL) was added. The test tube

was stored at 70 °C for 1 d and subsequently cooled to 4 °C for 7 d. The colorless crystals that

formed during cooling were collected and dried in air (0.248 g, 0.607 mmol, 43%). M. p.: 101

°C (dec.); C10H20N6O10 (408.61 g mol–1): calcd. C 29.57, H 4.93, N 20.57; found C 29.18, H

4.93, N 20.45.

173Chapter 4

IR (KBr): ν~ = 3506 (s), 3394 (s), 3204 (s), 3124 (s), 3023 (sh), 2518 (w), 2455 (w),

2408 (w), 2382 (w), 1669 (s), 1560 (s), 1519 (s), 1442 (m), 1378 (s), 1354 (s), 1290 (m), 1269

(m), 1226 (m), 1187 (m), 1136 (m), 997 (m), 979 (w), 958 (m), 904 (w), 873 (m), 828 (m),

750 (m), 693 (s), 640 (m), 547 (m), 462 (w), 403 (w) cm–1.

[Mn(tzp)2]n (26): A test tube was charged with K[tzp] (17) (0.500 g, 2.79 mmol) and

MnSO4 × H2O (0.236 g, 1.39 mmol), and water (20 mL) was added. The mixture was slowly

heated to 70 °C. After 6 d, the mixture was cooled to room temperature. The colorless solid

that formed was separated of the supernatant and dried in an oil pump vacuum to give a

colorless powder (0.102 g, 0.304 mmol, 22%). M. p.: 267 °C (dec.); C10H12MnN6O4 (335.18 g

mol–1): calcd. C 35.83, H 3.61, N 25.07; found C 35.70, H 3.75, N 25.04.

IR (KBr): ν~ = 4623 (br), 3469 (br), 3123 (w), 1584 (s), 1517 (m), 1450 (m), 1421 (s),

1339 (w), 1321 (w), 1275 (m), 1134 (m), 980 (m), 956 (w), 677 (w), 650 (w), 594 (w), 531

(w) cm–1.

[Co(tzp)2(OH2)2]n × 2 n H2O (27): A test tube was charged with 17 (0.500 g, 2.79

mmol) and CoSO4 × 7 H2O (0.392 g, 1.39 mmol), and water (20 mL) was added. The mixture

was slowly heated to 70 °C. After 6 d, the mixture was cooled to room temperature. The pink

solid that formed was separated by filtration and dried in an oil pump vacuum to yield a pink

powder (0.208 g, 0.506 mmol, 36%). M. p.: 101 °C (dec.); C10H20CoN6O8 (411.23 g mol–1):

calcd. C 29.21, H 4.90, N 20.44; found C 29.32, H 4.99, N 20.48.

IR (KBr): ν~ = 3514 (m), 3302 (m), 3127 (m), 1577 (s), 1523 (m), 1412 (s), 1371 (w),

1286 (m), 1264 (m), 1208 (w), 1133 (m), 1011 (w), 987 (m), 919 (w), 885 (w), 739 (w), 674

(s), 653 (w), 604 (w), 534 (w), 472 (w) cm–1.

[Ni(tzp)2(OH2)2]n × 2 n H2O (28): A test tube was charged with 17 (0.500 g, 2.79

mmol) and NiSO4 × 5 H2O (0.340 g, 1.39 mmol), and water (10 mL) was added. The mixture

174Chapter 4

was slowly heated to 70 °C. After 6 d, the mixture was cooled to room temperature. The blue

solid that formed was separated by filtration and dried in an oil pump vacuum to yield a blue

powder (0.185 g, 0.450 mmol, 32%). M. p.: 151 °C (dec.); C10H20NiN6O8 (410.99 g mol–1):

calcd. C29.22, H 4.90, N 20.45; found C 29.27, H 5.08, N 20.67.

IR (KBr): ν~ = 3512 (m), 3466 (sh), 3323 (m), 3131 (m), 1577 (s), 1524 (m), 1411 (s),

1372 (w), 1288 (m), 1264 (w), 1207 (w), 1131 (m), 1011 (w), 990 (m), 919 (w), 833 (w), 747

(w), 675 (s), 655 (m), 608 (w), 538 (w), 468 (w) cm–1.

[Cu(tzp)2(OH2)2]n (29): A test tube was charged with 17 (0.500 g, 2.79 mmol) and

CuSO4 × 5 H2O (0.347 g, 1.39 mmol), and water (20 mL) was added. The mixture was slowly

heated to 70 °C. After 6 d, the mixture was cooled to room temperature. The blue solid that

formed was separated by filtration and dried in an oil pump vacuum to yield a blue powder

(0.225 g, 0.599 mmol, 43%). M. p.: 123 °C (dec.); C10H16CuN6O6 (375.78 g mol–1): calcd. C

31.62, H 4.25, N 22.13; found C 31.65, H 4.28, N 22.16.

IR (KBr): ν~ = 3513 (m), 3445 (s), 3143 (m), 1628 (s), 1529 (m), 1401 (s), 1315 (w),

1274 (m), 1125 (s), 1050 (w), 1001 (m), 942 (w), 806 (w), 671 (s) 651 (w), 567 (w) cm–1.

[Zn(tzp)2]n × 0.25 n H2O (30): A test tube was charged with K[tzp] (1.000 g, 5.58

mmol) and ZnSO4 × 7 H2O (0.800 g, 2.79 mmol), and water (10 mL) was added. The mixture

was slowly heated to 70 °C. After 6 d, the mixture was cooled to room temperature. The

colorless solid that formed was separated by filtration and dried in an oil pump vacuum to

yield a colorless powder (0.225 g, 0.651 mmol, 23%). M. p.: 268 °C (dec.); C10H12ZnN6O4

(345.65 g mol–1): calcd. C 34.30, H 3.60, N 24.00; found C 34.58, H 3.60, N 24.12.

IR (KBr): ν~ = 3462 (br), 3130 (m), 2963 (w), 1620 (s), 1529 (m), 1434 (m), 1398 (s),

1356 (w), 1311 (m), 1272 (s), 1210 (w), 1132 (s), 1056 (w), 1000 (m), 951 (w), 887 (w), 866

(w), 675 (w), 657 (m), 592 (w), 566 (w) cm–1.

175Chapter 4

[Ag3(tzp)2NO3] (31): A test tube was charged with K[tzp] (0.050 g, 0.279 mmol), and

water (10 mL) was added with stirring. After 5 min, stirring was stopped and a solution of

AgNO3 (0.071 g, 0.418 mmol) in water (10 mL) was layered on the mixture. Subsequently,

the test tube was slowly heated to 70 °C without stirring. After 1 d, the mixture was cooled to

room temperature. The colorless solid that formed was separated by filtration and dried in an

oil pump vacuum to yield a colorless powder (0.052 g, 0.078 mmol, 56%). M. p.: 196 °C

(dec.); C10H12Ag3N7O7 (665.85 g mol–1): calcd. C 18.04, H 1.82, N 14.73; found C 18.05, H

1.76, N 14.60.

IR (KBr): ν~ = 3394 (br), 3120 (w), 1587 (s), 1513 (m), 1385 (s), 1362 (s), 1277 (m),

1211 (m), 1139 (m), 1020 (w), 879 (w), 670 (w), 644 (w) cm–1.

176Chapter 4

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(72) These data were obtained in cooperation with Prof. Dr. Paul Müller, Uptal Mitra, and Dr. Viatcheslav Dremov, Department für Physik, University of Erlangen-Nürnberg.

(73) J.-P. Zhang, X.-M. Chen, in Design And Construction Of Coordination Polymers(Eds.: M.-C. Hong, L. Chen), John Wiley & Sons, Inc., Hoboken, 2009, pp. 63-86.

(74) These data were obtained in cooperation with Eike Hübner, Department of Chemistry and Pharmacy, University of Erlangen-Nürnberg.

(75) G. B. Deacon, R. J. Phillips, Coord. Chem. Rev. 1980, 33, 227-250. (76) V. Robert, G. Lemercier, J. Am. Chem. Soc. 2006, 128, 1183-1187. (77) E. Münck, in Physical Methods in Bioinorganic Chemistry: Spectroscopy and

Magnetism (Ed.: L. Que, Jr.), University Science Books, Sausalito, 2000, p. 291. (78) G. Palmer, in Physical Methods in Bioinorganic Chemistry: Spectroscopy and

Magnetism (Ed.: L. Que, Jr.), University Science Books, Sausalito, 2000, p. 123. (79) D. M. L. Goodgame, Y. Nishida, R. E. P. Winpenny, Bull. Chem. Soc. Jpn. 1986, 59,

344-346. (80) S. S. Eaton, K. M. More, B. M. Sawant, G. R. Eaton, J. Am. Chem. Soc. 1983, 105,

6560-6567. (81) R. D. Dowsing, J. F. Gibson, J. Chem. Phys. 1969, 50, 294-303. (82) P. C. A. Bruijnincx, M. Lutz, A. L. Spek, E. E. Van Faassen, B. M. Weckhuysen, G.

Van Koten, R. J. M. K. Gebbink, Eur. J. Inorg. Chem. 2005, 779-787. (83) E. Hübner, G. Türkoglu, M. Wolf, U. Zenneck, N. Burzlaff, Eur. J. Inorg. Chem.

2008, 1226-1235. (84) E. Diez-Barra, J. Guerra, V. Hornillos, S. Merino, J. Tejeda, Tetrahedron Lett. 2004,

45, 6937-6939.

179Chapter 4

(85) F. Dallacker, K. Minn, Chem.-Ztg. 1986, 110, 101-108. (86) H. A. Habib, A. Hoffmann, H. A. Höppe, G. Steinfeld, C. Janiak, Inorg. Chem. 2009,

48, 2166-2180. (87) Distances were calculated using Diamond 2.1e; K. Brandenburg, M. Berndt, Diamond

– Visual Crystal Structure Information System, Crystal Impact GbR, Bonn (Germany), 1999; for Software Review see: W. T. Pennington, J. Appl. Crystallogr. 1999, 32, 1028-1029.

(88) J.-X. Dai, H.-L. Zhu, A. Rothenberger, Q.-F. Zhang, Z. Naturforsch., B Chem. Sci. 2007, 62, 1112-1116.

(89) T. Zhang, C. Ji, K. Wang, D. Hu, X. Meng, C. Chen, Inorg. Chim. Acta 2007, 360, 1609-1615.

(90) D. Sun, G.-G. Luo, N. Zhang, Q.-J. Xu, C.-F. Yang, Z.-H. Wei, Y.-C. Jin, L.-R. Lin, R.-B. Huang, L.-S. Zheng, Inorg. Chem. Commun. 2010, 13, 290-293.

(91) S. Takamizawa, E.-i. Nakata, T. Akatsuka, C. Kachi-Terajima, R. Miyake, J. Am. Chem. Soc. 2008, 130, 17882-17892.

(92) M. Barquín, M. J. González Garmendia, L. Larrínaga, E. Pinilla, J. M. Seco, M. R. Torres, J. Coord. Chem. 2010, 63, 1652-1665.

(93) N. L. Toh, M. Nagarathinam, J. J. Vittal, Angew. Chem. 2005, 117, 2277-2281; Angew. Chem., Int. Ed. 2005, 44, 2237-2241.

(94) B. Li, J. Lang, S. Wang, Y. Zhang, J. Chem. Crystallogr. 2005, 35, 547-550. (95) J. Lewiński, M. Dranka, W. Bury, W. Śliwiński, I. Justyniak, J. Lipkowski, J. Am.

Chem. Soc. 2007, 129, 3096-3098. (96) J.-q. Sha, J. Peng, H.-s. Liu, J. Chen, A.-x. Tian, P.-p. Zhang, Inorg. Chem. 2007, 46,

11183-11189. (97) M. Wang, Y.-R. Zheng, K. Ghosh, P. J. Stang, J. Am. Chem. Soc. 2010, 132, 6282-

6283. (98) For more detailed information see Chapter 4.1.(99) Z. Guo, P. J. Sadler, Angew. Chem. 1999, 111, 1610-1630; Angew. Chem., Int. Ed.

1999, 38, 1512-1531. (100) K. Nomiya, S. Takahashi, R. Noguchi, J. Chem. Soc., Dalton Trans. 2000, 1343-1348. (101) K. Nomiya, S. Takahashi, R. Noguchi, S. Nemoto, T. Takayama, M. Oda, Inorg.

Chem. 2000, 39, 3301-3311. (102) X. Han, C. An, Z. Zhang, Appl. Organomet. Chem. 2008, 22, 565-572. (103) All following procedures were performed under airobic conditions.

180Chapter 5

5

Appendices

5.1 Appendices for Chapter 2

5.1.1 Additional details regarding the molecular structures of 23, 26, 27b, 28, and 29

Figure 5.1: Molecular structure of [ReBr(Hbmima)(CO)3] (23);1 thermal ellipsoids are drawn at

the 50% probability level; hydrogen atoms, apart from H1A3 and co-crystallized solvent

molecules have been omitted for clarity; only one enantiomer is shown; selected bond lengths (Å)

and angles (°): ReA-Br1A 2.6156(9), ReA-C31A 1.921(6), ReA-C32A 1.958(7), ReA-C33A

1.907(6), ReA-N21A 2.234(5), ReA-N11A 2.211(5), C31A-O31A 1.150(7), C32A-O32A

1.083(7), C33A-O33A 1.153(8), C4A-O2A 1.216(7), C4A-O1A 1.332(6), C2A-C4A 1.504(7),

181Chapter 5

C31-O31 1.157(7); C31-Re1B 1.929(8), C32-O32 1.151(8), C32-Re1B 1.794(7), N11-Re1B

2.183(7), N21-Re1B 2.353(6), O2-H2B 0.84, Re1B-C33B 1.748(18), Re1B-Br1B 2.647(5),

C33B-O33B 1.388(18), C33C-O33C 1.279(18); C33A-ReA-C31A 87.6(3), C33A-ReA-C32A

89.4(3), C31A-ReA-C32A 89.3(2), N11A-ReA-N21A 94.60(16), C32A-ReA-Br1A 176.19(15),

N11A-ReA-Br1A 84.45(13), N21A-ReA-Br1A 85.83(12); C33B-Re1B-C32 93.6(7), C33B-

Re1B-C31 89.9(7), C32-Re1B-C31 89.7(4), C33B-Re1B-N11 92.9(7), C32-Re1B-N11 92.5(3),

C31-Re1B-N11 176.3(3), C33B-Re1B-N21 87.9(7), C32-Re1B-N21 175.0(4), C31-Re1B-N21

85.6(3), N11-Re1B-N21 92.1(2), C33B-Re1B-Br1B 172.5(7), C32-Re1B-Br1B 93.6(3), C31-

Re1B-Br1B 88.1(3), N11-Re1B-Br1B 88.8(2), N21-Re1B-Br1B-84.67(16), O33B-C33B-Re1B

178.2(16).

182Chapter 5

Figure 5.2: Molecular structure of [MnCl2(debmimm)] (26); only one of the two molecules in the

asymmetric unit is shown; the thermal ellipsoids are drawn at the 50% probability level;

hydrogen atoms have been omitted for clarity. Selected bond lengths (Å) and angles (°): Cl1-Mn1

2.3110(10), Cl2-Mn1 2.3513(9), Cl3-Mn2 2.3381(9), Cl4-Mn2 2.3436(9), Mn1-N11 2.133(2),

Mn1-N21 2.149(3), Mn2-N41 2.132(3), Mn2-N51 2.138(3); N11-Mn1-N21 106.01(9), N11-

Mn1-Cl1 110.53(7), N21-Mn1-Cl1 111.66(8), N11-Mn1-Cl2 107.23(7), N21-Mn1-Cl2

105.74(7), Cl1-Mn1-Cl2 115.14(4), N41-Mn2-N51 106.77(10), N41- Mn2-Cl3 102.63(7), N51-

Mn2-Cl3 114.03(7), N41-Mn2-Cl4 107.79(7), N51-Mn2-Cl4 106.91(7), Cl3-Mn2-Cl4 117.96(4).

183Chapter 5

Figure 5.3: Molecular structure of [CoCl2(dmbmimm)] (27b); only one of the two molecules in

the asymmetric unit is shown; the thermal ellipsoids are drawn at the 50% probability level;

hydrogen atoms have been omitted for clarity. Selected bond lengths (Å) and angles (°): Cl1-Co1

2.2554(17), Cl2-Co1 2.2566(16), Cl4-Co2 2.2589(16), Cl5-Co2 2.2322(17), Co1-N11 2.015(5),

Co1-N21 2.021(4), Co2-N41 2.016(5), Co2-N51 2.033(5); N11-Co1-N21 108.82(18), N11-Co1-

Cl1 103.77(14), N21-Co1-Cl1 114.07(13), N11-Co1-Cl2 108.28(13), N21-Co1-Cl2 108.53(13),

Cl1-Co1-Cl2 113.08(7), N41-Co2-N51 108.34(19), N41-Co2-Cl5 112.63(14), N51-Co2-Cl5

109.46(14), N41-Co2-Cl4 106.94(13), N51-Co2-Cl4 106.77(14) Cl5-Co2-Cl4 112.45(7).

184Chapter 5

Figure 5.4: Molecular structure of [NiCl2(dmbmimm)] (28); the thermal ellipsoids are drawn at

the 50% probability level; hydrogen atoms have been omitted for clarity. Selected bond lengths

(Å) and angles (°): Cl2-Ni 2.2415(6), N11-Ni 1.9792(15); N11-Ni-N11 107.99(9), N11-Ni-Cl2

110.04(5), N11-Ni-Cl2 100.63(5), Cl2-Ni-Cl2 126.72(4).

185Chapter 5

Figure 5.5: Molecular structure of [CuCl2(dmbmimm)] (29); the thermal ellipsoids are drawn at

the 50% probability level; hydrogen atoms have been omitted for clarity. Selected bond lengths

(Å) and angles (°): Cl1-Cu 2.2398(12), Cl2-Cu 2.2514(13), Cu-N21 1.986(4), Cu-N11 1.998(4);

N21-Cu-N11 105.01(15), N21-Cu-Cl1 130.76(11), N11-Cu-Cl1 96.84(12), N21-Cu-Cl2

96.48(11), N11-Cu-Cl2 133.52(12), Cl1-Cu-Cl2 99.42(5).

186Chapter 5

Figure 5.6: Preliminary molecular structure of [ZnCl2(dmbmimm)] (30);2 Only one of the eight

molecules in the asymmetric unit are shown; the thermal ellipsoids are drawn at the 50%

probability level; hydrogen atoms have been omitted for clarity.

187Chapter 5

Selected bond lengths (Å) and angles (°) of Figure 5.6: Zn1-N1 2.008(3), Zn1-N2

2.014(3), Zn1-Cl2 2.2443(10), Zn1-Cl1 2.2665(11), Zn2-N5 2.015(3), Zn2-N6 2.1016(3), Zn2-

Cl4 2.2421(10), Zn2-Cl3 2.2670(10), Zn3-N12 2.013(3), Zn3-N9 2.022(3), Zn3-Cl6 2.2426(10),

Zn3-Cl5 2.2696(11), Zn4-N16 2.013(3), Zn4-N15 2.023(3), Zn4-Cl8 2.2442(10), Zn4-Cl7

2.2710(10), Zn5-N19 2.028(3), Zn5-N20 2.039(3), Zn5-Cl9 2.2299(11), Zn5-Cl10 2.2550(10),

Zn6-N23 2.030(3), Zn6-N24 2.041(3), Zn6-Cl11 2.2300(11), Zn6-Cl12 2.2554(11), Zn7-N28

2.022(3), Zn7-N26 2.037(3), Zn7-Cl14 2.2276(11), Zn7-Cl13 2.2533(11), Zn8-N31 2.019(3),

Zn8-N32 2.036(3), Zn8-Cl16 2.2289(10), Zn8-Cl15 2.2542(11); N1-Zn1-N2 108.95(12), N1-

Zn1-Cl2 112.75(9), N2-Zn1-Cl2 105.01(9), N1-Zn1-Cl1 108.60(9), N2-Zn1-Cl1 108.51(9), Cl2-

Zn1-Cl1 112.85(4), N5-Zn2-N6 109.10(12), N5-Zn2-Cl4 104.89(9), N6-Zn2-Cl4 112.84(9), N5-

Zn2-Cl3 108.46(9), N6-Zn2-Cl3 108.54(9), Cl4-Zn4-Cl3 112.83(4), N12-Zn3-N9 108.28(12),

N12-Zn3-Cl6 104.97(9), N9-Zn3-Cl6 114.63(9), N12-Zn3-Cl5 108.88(9), N9-Zn3-Cl5 107.75(9),

Cl6-Zn3-Cl5 113.14(4), N16-Zn4-N15 108.35(11), N16-Zn4-C18 104.89(9), N15-Zn4-Cl8

114.61(9), N16-Zn4-Cl7 108.97(9), N15-Zn4-Cl7 107.69(8), Cl8-Zn4-Cl7 112.14(4), N19-Zn5-

N20 108.34(12), N19-Zn5-Cl19 110.46(9), N20-Zn5-Cl9 110.96(9), N19-Zn5-Cl10 106.96(9),

N20-Zn5-Cl10 106.00(9), Cl9-Zn5-Cl10 113.85(4), N23-Zn6-N24 108.23(12), N23-Zn6-Cl11

110.48(9), N24-Zn6-Cl11 110.96(9), N23-Zn6-Cl12 107.09(9), N24-Zn6-Cl12 105.97(9), Cl11-

Zn6-Cl12 113.84(4), N28-Zn7-N26 107.40(12), N28-Zn7-Cl14 110.53(9), N26-Zn7-Cl14

112.32(9), N28-Zn7-Cl13 107.10(9), N26-Zn7-Cl13 106.93(9), Cl14-Zn7-Cl13 112.29(4), N31-

Zn8-Z32 107.59(12), N31-Zn8-Cl16 110.45(9), N32-Zn8-Cl16 112.28(9), N31-Zn8-Cl15

107.17(9), N32-Zn8-Cl15 106.80(9), Cl16-Zn8-Cl15 112.28(4).

188Chapter 5

5.1.2 Details of X-ray structure determinations

Single crystals of 5 were obtained by slow evaporation of a saturated solution of the

compound in CH2Cl2. Crystals of 6 × bmim were grown by recrystallization from hot MeOH.

Crystals of 8, 19, 25, 26, 27b, 28, 28b, 29, and 30 suitable for X-ray structure analysis were

deposited upon layering a solution of the complex in MeOH with Et2O. Crystals of 12 were

obtained by layering a solution of the compound in CH2Cl2 with n-pentane. Crystals of 21 were

grown by recrystallization from hot H2O. Crystals of 23 formed upon layering a solution of the

complex in acetone with n-hexane. Slow cooling of a saturated solution of the compound

dissolved in MeCN/CH2Cl2/n-pentane (1/20/50) to –20 °C afforded single crystals of 24.

Single crystals of 5, 6 × bmim, 8, 12, 19, 21, 25, 26, 27b, 28, 28b, 29, and 30 were

mounted with perfluorinated ether on a glass fibre. A Bruker Nonius Kappa CCD, a Smart APEX

II, or a STOE IPDS 2T diffractometer was used for data collection (graphite monochromator,

Mo-Kα radiation, λ = 0.71073 Å). The structures were solved by direct methods and refined by

full-matrix least-squares procedures against F2 {SHELX-97}.3 A weighting scheme was applied

in the last steps of the refinement with w =1/[σ2(Fo2) + (aP)2 + bP] and P = [2Fc2 +

max(Fo2,0)]/3. The OH protons in 5, 12, 19, 21, and 23 were found and refined free. All the other

hydrogen atoms were included in their calculated positions and refined in a riding model. The

molecular structure of 6 × bmim was disordered with occupancies of the two different

dithioacetate positions of 85:15. Thus, only a refinement in Pc instead of P2/c was possible. The

molecular structure of 21 was disordered concerning the carbon backbone structure with 70:30

split-occupancies for atoms C2 and C4. The molecular structure of 23 was largely disordered and

could not be sufficiently refined. The molecular structure of 28 was disordered concerning atoms

C4 and C5 with occupancies of 70:30. The molecular structure of 29 was disordered concerning

atoms C31, C32, C33, and C34 with occupancies of 50:50. The structure of 30 could be resolved

and reasonably refined in P21/c (monoclinic). However this is only a preliminary result, since

189Chapter 5

symmetry, cell dimensions and systematic absences indicate a crystal system of higher symmetry,

such as e.g., an orthorhombic system.

All details and parameters of the measurements are summarized in Tables 5.1-5. The

structures were visualized with Diamond 2.1e.4 CCDC-723078 (for 5) CCDC-728290 (for 6 ×

bmim) and CCDC-723079 (for 22) contain the supplementary crystallographic data.

These data can be obtained free of charge from The Cambride Crystallographic Data Centre via

www.ccdc.cam.ac.uk/datarequest/cif.

190Chapter 5

Table 5.1: Details of the structure determinations of 5, 6 and 12. 2,2-Hbmie

(5) Li[bmita] ×××× bmim

(6 × bmim)

1,2-Hbmie

(12)

CCDC 723078 728290 789371

Empirical formula C10H14N4O × H2O C19H23LiN8S2 C10H14N4O1

Formula mass 224.27 434.51 206.25

Crystal colour/habit colourless plate orange plate colorless block

Crystal system monoclinic monoclinic triclinic

Space group P21/n Pc P1a [Å] 7.4297(5) 9.4278(7) 7.6691(4)

b [Å] 19.3827(13) 7.7758(6) 8.1640(4)

c [Å] 8.1557(5) 14.5248(10) 9.1596(3)

α [°] 90 90 68.613(3)

β [°] 106.377(4) 102.843(6) 81.425(3)

γ [°] 90 90 77.672(4)

V [Å3] 1126.83(13) 1038.16(13) 520.08(4)

θ [°] 3.04–29.01 2.99–29.01 3.49–28.5

h –10 to 10 –12 to 12 –10 to 10

k –26 to 26 –10 to 10 –10 to 10

l –11 to 11 –19 to 19 –12 to 12

F(000) 480 456 220

Z 4 2 2

µ (Mo-Kα) [mm–1] 0.095 0.428 0.09

Crystal size [mm] 0.28 × 0.16 × 0.04 0.30 × 0.29 × 0.05 0.22 × 0.10 × 0.08

Dcalcd. [g cm–3], T [K] 1.322, 150(2) 1.39, 100(2) 1.317, 150(2)

Reflections collected 24953 27352 16165

Indep. reflections 2994 5463 2627 Obsd. Reflections

(I > 2σI) 2242 5066 2100

Parameter 154 306 136

Weight parameter a, b 0.0626, 0.3020 0.0386, 0.2588 0.0504, 0.2182

R1 (obsd.) 0.0440 0.0296 0.0434

R1 (overall) 0.0686 0.0346 0.0583

wR2 (obsd.) 0.1064 0.0728 0.1037

wR2 (overall) 0.1198 0.0748 0.1104

Diff. peak / hole [e/Å3] 0.258 / –0.22 0.287/–0.206 0.288/–0.259

191Chapter 5

Table 5.2: Details of the structure determinations of 18, 20 and 22.

Hbmima ×××× 2 HCl

(18)

Hbmimabo

(20)

[Re(2,2-bmie)(CO)3]

(22)

CCDC 775807 775808 723079

Empirical formula C12H18N4O2 2(Cl) C20H20N4O2 C13H13N4O4Re

Formula mass 321.2 348.4 475.47

Crystal colour/habit colorless block colorless prism pale yellow plate

Crystal system monoclinic monoclinic triclinic

Space group C2/c P21/c P1a [Å] 34.632(3) 11.9817(10) 7.8701(2)

b [Å] 6.5099(3) 16.5996(12) 9.0959(10)

c [Å] 13.8527(17) 8.7091(6) 11.2096(9)

α [°] 90 90 85.533(8)

β [°] 103.390(9) 89.344 76.987(5)

γ [°] 90 90 67.707(4)

V [Å3] 3038.2(5) 1732.1(2) 723.38(10)

θ [°] 2.98–28.51 2.99–25.34 2.86–29.5

h –46 to 46 –14 to 14 –10 to 10

k –8 to 8 –19 to 19 –12 to 12

l –18 to 18 –10 to 10 –15 to 15

F(000) 1344 736 452

Z 8 4 2

µ (Mo-Kα) [mm–1] 0.434 0.089 8.423

Crystal size [mm] 0.25× 0.23 × 0.14 0.42 × 0.16 × 0.05 0.21 × 0.16 × 0.06

Dcalcd. [g cm–3], T [K] 1.404 1.336, 150(2) 2.183, 150(2)

Reflections collected 35341 18423 24985

Indep. reflections 3869 3163 4023 Obsd. Reflections

(I > 2σI)3204 2419 3689

Parameter 190 253 199

Weight parameter a, b 0.0472, 2.8795 0.0898, 3.6975 0.0247, 0.1510

R1 (obsd.) 0.0316 0.0866 0.0166

R1 (overall) 0.0429 0.1117 0.0213

wR2 (obsd.) 0.0841 0.2123 0.0464

wR2 (overall) 0.0905 0.228 0.0476

Diff. peak / hole [e/Å3] 0.432/–0.306 0.831 / –0.603 0.881/–1.010

192Chapter 5

Table 5.3: Details of the structure determinations of 18, 20 and 22. [ReBr(Hbmima)(CO)3]

(23)1

[MnCl2(debmimm)]

(26)

[FeCl2(debmimm)]

(25)

CCDC

Empirical formula C15H16BrN4O5Re

× 3(C3H6O)2(C17H24Cl2MnN4O4)

× CH4O4(C17H24Cl2N4O4)

× C2H3NFormula mass 772.66 980.53 1941.66

Crystal colour/habit yellow prims colorless block colorless block

Crystal system triclinic orthorhombic orthorhombic

Space group P1 Pca21 Pbca

a [Å] 11.9482(12) 16.2070(9) 16.1498(11)

b [Å] 15.1039(14) 12.0496(12) 22.237(6)

c [Å] 17.914(2) 22.574(2) 24.951(3)

α [°] 109.806(9) 90 90

β [°] 102.458(11) 90 90

γ [°] 92.009(11) 90 90

V [Å3] 2949.3(5) 4408.4(6) 8960(3)

θ [°] 2.71-29.5 2.77–28.51 2.81–28.52

h –16 to 16 –21 to 21 –21 to 21

k –20 to 20 –16 to 16 –29 to 29

l –24 to 22 –30 to 30 –33 to 33

F(000) 1520 2032 4024

Z 4 4 4

µ (Mo-Kα) [mm–1] 5.525 0.874 0.942

Crystal size [mm] 0.28× 0.27 × 0.23 0.3 × 0.28 × 0.2 0.25 × 0.13 × 0.07

Dcalcd. [g cm–3], T [K] 1.74, 150(2) 1.477, 150(2) 1.439, 150(2)

Reflections collected 67332 70824 139432

Indep. reflections 16224 11159 11356 Obsd. Reflections

(I > 2σI)11812 9458 8857

Parameter 739 530 529 Weight parameter a, b

0.0459, 13.026 0.0576, 2.3017 0.0690, 10.5803

R1 (obsd.) 0.041 0.0408 0.0414

R1 (overall) 0.0744 0.0539 0.0594

wR2 (obsd.) 0.0956 0.1015 0.1199

wR2 (overall) 0.1153 0.1082 0.131 Diff. peak / hole [e/Å3]

2.583 / –3.162 0.928 / –0.464 1.897 / –0.661

193Chapter 5

Table 5.4: Details of the structure determinations of 24 (preliminary), 27 and 28. [Fe(OTf)2(debmimm)2]

(24)

[CoCl2(dmbmimm)]

(27)

[NiCl2(debmimm)]

(28)

CCDC

Empirical formula C36H48F6FeN8O14S2,

4(CH2Cl2) 2(C17H20Cl2CoN4O4)

× CH4OC17H24Cl2NiN4O4

Formula mass 1390.5 932.4 478.01

Crystal colour/habit colorless block blue prism blue block

Crystal system triclinic orthorhombic monoclinic

Space group P1 Pbca C2/c

a [Å] 15.2412(15) 15.9055(15) 7.0944(2)

b [Å] 15.9515(18) 22.533(2) 24.4695(6)

c [Å] 15.9883(8) 22.694(2) 12.5101

α [°] 115.143(7) 90 90

β [°] 114.641(5) 90 96.730(2)

γ [°] 96.353(9) 90 90

V [Å3] 2996.3(5) 8133.3(14) 2156.74(10)

θ [°] 2.8–25.35 1.79–27.18 1.66–27.92

h –18 to 18 –18 to 20 –8 to 9

k –19 to 19 –27 to 28 –32 to 32

l –19 to 19 –29 to 29 –16 to 16

F(000) 1424 3840 992

Z 2 8 4

µ (Mo-Kα) [mm–1] 0.761 1.138 1.177

Crystal size [mm] 0.29 × 0.25 × 0.24 0.2 × 0.08× 0.05 0.38 × 0.18 × 0.17

Dcalcd. [g cm–3], T [K] 1.541, 150(2) 1.523, 150(2) 1.472, 220(2)

Reflections collected 67219 118373 16238

Indep. reflections 10957 9032 2576 Obsd. Reflections

(I > 2σI)8640 6738 2234

Parameter 716 497 141

Weight parameter a, b 0.1098, 59.7330 0.0315, 61.4650 0.0351, 2.6799

R1 (obsd.) 0.1068 0.0709 0.0329

R1 (overall) 0.1262 0.098 0.0393

wR2 (obsd.) 0.323 0.181 0.0799

wR2 (overall) 0.3342 0.1657 0.0831

Diff. peak / hole [e/Å3] 2.950 / –1.033 0.804 / –0.936 0.774 / –0.736

194Chapter 5

Table 5.5: Details of the structure determinations of 28 ×××× 28b, 29 and 30 (preliminary). [NiCl2(debmimm)]2

××××2[NiCl2(debmimm)]

[CuCl2(debmimm)]

(29)

[ZnCl2(dmbmimm)]

(30)2

CCDC

Empirical formula C34H48Cl4Ni2N8O8 ×2(C17H24Cl2NiN4O4)

C17H24Cl2CuN4O4 C19H32Cl2N4O6Zn

Formula mass 1911.97 519.9 500.69

Crystal colour/habit brown plate orange plate colorless plate

Crystal system triclinic monoclinic monoclinic

Space group P1 P21/n P21/c

a [Å] 10.2597(2) 15.0147(17) 15.951(3)

b [Å] 14.3483(3) 6.6227(4) 24.693(5)

c [Å] 15.0905(3) 26.519(2) 22.439(5)

α [°] 96.2900 90 90

β [°] 104.4100(10) 105.847(8) 90.02(3)

γ [°] 96.4980(10) 90 90

V [Å3] 2115.74(7) 2536.8(4) 8838(3)

θ [°] 1.41–27.82 2.82–27.5 2.71–27.5

h –13 to 13 –19 to 19 –20 to 20

k –18 to 17 –8 to 8 –32 to 32

l –19 to 19 –33 to 34 –29 to 29

F(000) 992 1080 4144

Z 1 4 16

µ (Mo-Kα) [mm–1] 1.2 1.103 1.386

Crystal size [mm] 0.3 × 0.26 × 0.15 0.27 × 0.23 × 0.09 0.23 × 0.23 × 0.05

Dcalcd. [g cm–3], T [K] 1.501, 220(2) 1.361, 150(2) 1.505, 293(2)

Reflections collected 34563 42991 203544

Indep. reflections 9939 5835 40535 Obsd. Reflections

(I > 2σI)7899 4944 31550

Parameter 509 300 2130

Weight parameter a, b 0.0401, 0.6698 0.1689, 8.4641 0.0355, 4.1656

R1 (obsd.) 0.0347 0.0865 0.0395

R1 (overall) 0.0482 0.0972 0.0642

wR2 (obsd.) 0.0833 0.2421 0.0791

wR2 (overall) 0.0897 0.2574 0.0869

Diff. peak / hole[e/Å3] 0.0503 / –0.369 0.194 / –1.137 0.816 / –0.74

195Chapter 5

5.1.3 Powder X-ray diffraction patterns

Figure 5.7: Comparison of the powder X-ray diffraction patterns of 27-28 (i, ii, and iv were

calculated using Diamond 3.1b4): i) [NiCl2(debmimm)]2 × 2 [NiCl2(debmimm)], calculated (28 ×

28b); i) [NiCl2(debmimm)], calculated (28); iii) [NiCl2(debmimm)]; iv) [CoCl2(dmbmimm)],

calculated (27b); v) [CoCl2(debmimm)] (27).

196Chapter 5

5.1.4 Additional details of ESR investigations

Figure 5.8: ESR spectra of [CuCl2(debmimm)]: i) recorded in frozen CHCl3 solutions at

−181 °C; ii) adsorbed on silica, recorded at rt. A JEOL continuous wave spectrometer JES-FA200

was used, equipped with an X-band Gunn oscillator bridge, a cylindrical mode cavity and a

Helium cryostat.

197Chapter 5

5.1.5 Additional details of CV measurements

Figure 5.9: Cyclic voltammograms of [Fe(OTf)2(debmimm)2] (24); Conditions: Complex

0.002 M, [(n-Bu)4N]PF6 0.1 M in CH2Cl2 at 22.5 °C (nitrogen purged); Au working electrode, Pt

counter electrode vs. Ag/AgCl reference electrode; scanrate 500 mV/s; 2 scans. An Autolab

instrument with PGSTAT 30 potentiostat was used. A conventional three electrode arrangement

was employed consisting of a gold working disk electrode (Metrohm, geometric area: 0.07 cm2),

a platinum wire (Metrohm) as the auxiliary electrode and Ag wire as pseudo reference electrode.

During the measurements a nitrogen atmosphere was kept.

198Chapter 5

Figure 5.10: Cyclic voltammograms of [FeCl2(debmimm)] (25); Conditions: Complex 0.002 M,

[(n-Bu)4N]PF6 0.1 M in CH2Cl2 at 22.5 °C (nitrogen purged); Au working electrode, Pt counter

electrode vs. Ag/AgCl reference electrode; scanrate 100-500 mV/s; 2 scans. An Autolab

instrument with PGSTAT 30 potentiostat was used. A conventional three electrode arrangement

was employed consisting of a gold working disk electrode (Metrohm, geometric area: 0.07 cm2),

a platinum wire (Metrohm) as the auxiliary electrode and Ag wire as pseudo reference electrode.

During the measurements a nitrogen atmosphere was kept.

199Chapter 5

Figure 5.11: Cyclic voltammograms of [MnCl2(debmimm)] (26); Conditions: Complex 0.002 M,

[(n-Bu)4N]PF6 0.1 M in CH2Cl2 at 22.5 °C (nitrogen purged); Au working electrode, Pt counter

electrode vs. Ag/AgCl reference electrode; scanrate 100-500 mV/s; 2 scans. An Autolab

instrument with PGSTAT 30 potentiostat was used. A conventional three electrode arrangement

was employed consisting of a gold working disk electrode (Metrohm, geometric area: 0.07 cm2),

a platinum wire (Metrohm) as the auxiliary electrode and Ag wire as pseudo reference electrode.

During the measurements a nitrogen atmosphere was kept.

200Chapter 5

Figure 5.12: Cyclic voltammograms of [CoCl2(debmimm)] (27); Conditions: Complex 0.002 M,

[(n-Bu)4N]PF6 0.1 M in CH2Cl2 at 22.5 °C (nitrogen purged); Au working electrode, Pt counter

electrode vs. Ag/AgCl reference electrode; scanrate 100-500 mV/s; 2 scans. An Autolab

instrument with PGSTAT 30 potentiostat was used. A conventional three electrode arrangement

was employed consisting of a gold working disk electrode (Metrohm, geometric area: 0.07 cm2),

a platinum wire (Metrohm) as the auxiliary electrode and Ag wire as pseudo reference electrode.

During the measurements a nitrogen atmosphere was kept.

201Chapter 5

Figure 5.13: Cyclic voltammograms of [NiCl2(debmimm)] (28); Conditions: Complex 0.002 M,

[(n-Bu)4N]PF6 0.1 M in CH2Cl2 at 22.5 °C (nitrogen purged); Au working electrode, Pt counter

electrode vs. Ag/AgCl reference electrode; scanrate 100-500 mV/s; 2 scans. An Autolab

instrument with PGSTAT 30 potentiostat was used. A conventional three electrode arrangement

was employed consisting of a gold working disk electrode (Metrohm, geometric area: 0.07 cm2),

a platinum wire (Metrohm) as the auxiliary electrode and Ag wire as pseudo reference electrode.

During the measurements a nitrogen atmosphere was kept.

202Chapter 5

Figure 5.14: Cyclic voltammograms of [CuCl2(debmimm)] (29); Conditions: Complex 0.002 M,

[(n-Bu)4N]PF6 0.1 M in CH2Cl2 at 22.5 °C (nitrogen purged); Au working electrode, Pt counter

electrode vs. Ag/AgCl reference electrode; scanrate 100-500 mV/s; 2 scans. An Autolab

instrument with PGSTAT 30 potentiostat was used. A conventional three electrode arrangement

was employed consisting of a gold working disk electrode (Metrohm, geometric area: 0.07 cm2),

a platinum wire (Metrohm) as the auxiliary electrode and Ag wire as pseudo reference electrode.

During the measurements a nitrogen atmosphere was kept.

203Chapter 5

Figure 5.15: Cyclic voltammograms of [ZnCl2(debmimm)] (30); Conditions: Complex 0.002 M,

[(n-Bu)4N]PF6 0.1 M in CH2Cl2 at 22.5 °C (nitrogen purged); Au working electrode, Pt counter

electrode vs. Ag/AgCl reference electrode; scanrate 100-500 mV/s; 2 scans. An Autolab

instrument with PGSTAT 30 potentiostat was used. A conventional three electrode arrangement

was employed consisting of a gold working disk electrode (Metrohm, geometric area: 0.07 cm2),

a platinum wire (Metrohm) as the auxiliary electrode and Ag wire as pseudo reference electrode.

During the measurements a nitrogen atmosphere was kept.

204Chapter 5

5.2 Appendices for Chapter 3

5.2.2 Details of X-ray structure determination of 24

Crystals of 24 suitable for X-ray structure analysis were deposited upon layering a

solution of the complex in MeOH with Et2O. Single crystals of 24 were mounted with

perfluorinated ether on a glass fibre. A Bruker Nonius Kappa CCD was used for data collection

(graphite monochromator, Mo-Kα radiation, λ = 0.71073 Å). The structures were solved by

Patterson methods and refined by full-matrix least-squares procedures against F2 {SHELX-97}.3

A weighting scheme was applied in the last steps of the refinement with w =1/[σ2(Fo2) + (aP)2 +

bP] and P = [2Fc2 + max(Fo2,0)]/3. All hydrogen atoms were included in their calculated

positions and refined in a riding model. All details and parameters of the measurements are

summarised in Table 5.6. The structures were visualized with Diamond 2.1e.4

205Chapter 5

Table 5.6: Details of the structure determinations of 24. [MnCl2(bmimPh

4-OMe)]2

(24)

CCDC

Empirical formula C34H40Cl4Mn2N8O2

Formula mass 844.42

Crystal colour/habit colourless block

Crystal system triclinic

Space group P1a [Å] 8.9018(4)

b [Å] 9.5000(6)

c [Å] 12.5958(10)

α [°] 78.465(4)

β [°] 83.984(5)

γ [°] 63.856(4)

V [Å3] 936.73(10)

θ [°] 3.01–28.5

h –11 to 11

k –12 to 12

l –16 to 16

F(000) 434

Z 1

µ (Mo-Kα) [mm–1] 1.002

Crystal size [mm] 0.18× 0.14 × 0.1

Dcalcd. [g cm–3], T [K] 1.497, 150(2)

Reflections collected 29786

Indep. reflections 47729 Obsd. reflections

(I > 2σI)4200

Parameter 226

Weight parameter a, b 0.0271, 0.4523

R1 (obsd.) 0.0240

R1 (overall) 0.0295

wR2 (obsd.) 0.0583

wR2 (overall) 0.0608

Diff. peak / hole [e/Å3] 0.347/–0.083

206Chapter 5

5.2.3 Biological section

5.2.3.1 Materials and methods

Cytotoxicity was measured on HeLa S3 and Hep G2 cells using an AlamarBlue assay.

AlamarBlue was purchased from BioSource Europe.

5.2.3.2 Cell cultivation

Cells were cultivated at 37 °C in humidified 5% CO2

atmosphere using Dulbecco’s

DMEM-media (Invitrogen) containing 10% foetal calf serum, 1% penicillin and 1%

streptomycin. Cells were split every three days. Both cell lines were tested for mycoplasma

infections using a mycoplasma detection kit (Roche Applied Science).

5.2.3.3 AlamarBlue assay5

Cells were seeded in 96-well plates (4,000 HeLa S3 cells/well or 8,000 Hep G2 cells/well) and

allowed to attach for 24 h. The cells were then treated with different concentrations of the reagent

tested. Solutions of reagents were prepared by dissolving the respective complexes in a suitable

amount of DMSO and diluting with medium to give final concentrations with a maximum DMSO

content of 1 %. The cells were incubated for 48 h, AlamarBlue (10 µl) was added and the cells

were incubated for another hour. After excitation at 530 nm, fluorescence at 590 nm was

measured using a FL600 Fluorescence Microplate Reader (Bio-TEK). Cell viability is given in

percent with respective to a control containing only pure medium and 1 % DMSO. All

experiments were repeated for a minimum of three times with each experiment done in four

replicates. The resulting curves were fitted using Sigma plot 10.0.6

207Chapter 5

5.3 Appendices for Chapter 4

5.3.1 Additional details regarding the molecular structures of 11, 13, 19, and 28

Figure 5.16: Cutout of the molecular structure of [Co(btp)2]n (11) showing the metal geometry;

the thermal ellipsoids are drawn at the 50% probability level; hydrogen atoms have been omitted

for clarity. Selected bond lengths (Å) and angles (°): Co-O1 2.0794(14), Co-N23 2.1474(16), Co-

N13 2.1708(15); O1-Co-O1 180.00(5), O1-Co-N23 92.55(6), O1-Co-N23 87.45(6), N23-Co-N23

180.00(10), O1-Co-N13 87.68(6), O1-Co-N13 92.32(6), N23-Co-N13 90.02(6), N23-Co-N13

89.98(6), N13-Co-N13 180.00(9).

208Chapter 5

Figure 5.17: Cutout of the molecular structure of [Cu(btp)2]n (13) showing the metal geometry;

the thermal ellipsoids are drawn at the 50% probability level; hydrogen atoms have been omitted

for clarity. Selected bond lengths (Å) and angles (°):Cu-N13 2.0205(10), Cu-O2 2.3175(9), Cu-

N23 2.0295(9); N13-Cu-N13 180.0000(10), N13-Cu-N23 89.66(4), N13-Cu-N23 90.34(74),

N23-Cu-N23 180, N13-Cu-O2 86.50(4), N13-Cu-O2 93.50(4), N23-Cu-O2 89.04(4), N23-Cu-O2

90.96(4), O2-Cu-O2 180.00(4).

209Chapter 5

Figure 5.18: Cutout of the molecular structure of [Fe(ta)2]n (19); the thermal ellipsoids are drawn

at the 50% probability level; hydrogen atoms have been omitted for clarity. Selected bond lengths

(Å) and angles (°): Fe-O1 2.050(5), Fe-O31 2.053(5), Fe-O2 2.137(5), Fe-O32 2.144(5), Fe-N33

2.222(6), Fe-N33 2.222(6), Fe-N3 2.225(6), O1-Fe-O31 172.73(19), O1-Fe-O2 88.3(2), O31-Fe-

O2 87.1(2), O1-Fe-O32 87.4(2), O31-Fe-O32 88.16(19), O2-Fe-O32 103.23(16), O1-Fe-N33

92.9(2), O31-Fe-N33 92.6(2), O2-Fe-N33 170.1(2), O32-Fe-N33 86.7(2), O31-Fe-N3 92.7(2),

O2-Fe-N3 86.8(2), O32-Fe-N3 170.0(2), N33-Fe-N3 83.3(2).

210Chapter 5

Figure 5.19: Molecular structure of [Ni(tzp)2(OH2)2]n × 2 H2O (28); the thermal ellipsoids are

drawn at the 50% probability level; hydrogen atoms apart from H13, H14, H15, and H16 have

been omitted for clarity. Selected bond lengths (Å) and angles (°): Ni-O1 2-0725(10), Ni-N3

2.0898 (11), Ni-O3 2.0925(11), O1-Ni-O1 180.00(6), O1-Ni-N3 90.55(4), O1-Ni-N3 89.45(4),

N3-Ni-N3 180, O1-Ni-O3 87.13(4), O1-Ni-O3 92.87(4), N3-Ni-O3 86.85(4), N3-Ni-O3

93.15(4), O1-Ni-O3 892.87(4).

211Chapter 5

5.3.2 Details of X-ray structure determinations

Crystals of 10, 11, 13, 18, 19, 20, 23, 25, 27, 28, 30, and 31 were obtained from the

mother liquors. Single crystals of 10, 11, 13, 18, 19, 20, 23, 25, 27, 28, 30, and 31 were mounted

with perfluorinated ether or Paratone N on a glass fibre. A Bruker Nonius Kappa CCD

diffractometer and a STOE IPDS 2T diffractometer were used for data collection (graphite

monochromator, Mo-Kα radiation, λ = 0.71073 Å). The structures were solved by direct methods

and refined by full-matrix least-squares procedures against F2 {SHELX-97}.3 A weighting

scheme was applied in the last steps of the refinement with w =1/[σ2(Fo2) + (aP)2 + bP] and P =

[2Fc2 + max(Fo2,0)]/3. The OH protons in 20, 23, 25, 27, 28, 30, and 31 were found and refined

free. All the other hydrogen atoms were included in their calculated positions and refined in a

riding model. All details and parameters of the measurements are summarized in Tables 5.7-5.11.

The structures were visualized with Diamond 2.1e.4 CCDC-775806 (for 3), CCDC-789373 (for

5), CCDC-789372 (for 6), CCDC-771286 (for 18), CCDC-771288 (for 20), CCDC-771289 (for

23) and CCDC-771290 (for 25), contain supplementary crystallographic data.

These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via

www.ccdc.cam.ac.uk/datarequest/cif

212Chapter 5

Table 5.7: Details of the structure determinations of 3, 5, and 6.

[Zn(bmima)Cl]n

(3)

[CuCl(trans-bie)1.5]n

(5)

trans-bie

(6)

CCDC 775806 789373 789372

Empirical formula C12H15ClN4O2Zn ×H2O

C15H18ClCuN6 C10H12N4 × 6 H2O

Formula mass 366.12 381.35 296.33

Crystal colour/habit colorless prism yellow prism colorless plate

Crystal system monoclinic trigonal Triclinic

Space group P21/n R 3 P1a [Å] 10.3660(4) 11.8428(8) 6.3699(2)

b [Å] 11.5626(8) 11.8428(8) 6.89390(10)

c [Å] 12.9848(7) 19.300(2) 10.0388(4)

α [°] 90 90 78.777(2)

β [°] 106.952(6) 90 76.601(2)

γ [°] 90 120 70.277(2)

V [Å3] 1488.71 2344.2(3) 400.41(2)

θ [°] 2.71-28.51 2.9-29.5 3.45-28.49

h –13 to 13 –16 to 16 –8 to 8

k –15 to 15 –16 to 16 –9 to 9

l –17 to 17 –26 to 26 –13 to 13

F(000) 752 1176 160

Z 4 6 1

µ (Mo-Kα) [mm–1] 1.844 1.576 0.101

Crystal size [mm] 0.21 × 0.18 × 0.08 0.18 × 0.16× 0.11 0.22 × 0.2 × 0.05

Dcalcd. [g cm–3], T [K] 1.633, 293(2) 1.621, 150(2) 1.229, 150(2)

Reflections collected 40724 18245 11224

Indep. reflections 3772 1450 2031 Obsd. Reflections

(I > 2σI) 2954 1331 1698

Parameter 197 73 127

Weight parameter a, b 0.0461, 1.6201 0.0205, 7.7439 0.0470, 0.1218

R1 (obsd.) 0.0386 0.0253 0.0366

R1 (overall) 0.0575 0.029 0.0473

wR2 (obsd.) 0.0954 0.0596 0.0917

wR2 (overall) 0.102 0.0612 0.0972

Diff. peak / hole [e/Å3] 1.111 / –0.456 1.052 / –1.086 0.315 / –0.039

213Chapter 5

Table 5.8: Details of the structure determinations of 10, 11, and 13. [Fe(btp)2]n

(10)

[Co(btp)2]n

(11)

[Cu(btp)2]n

(13)

CCDC

Empirical formula C14H14FeN12O4 C14H14CoN12O4 C14H14CuN12O4

Formula mass 470.22 473.30 477.92

Crystal colour/habit colorless block pink prism blue block

Crystal system triclinic triclinic triclinic

Space group P1 P1 P1a [Å] 7.7672(4) 7.8212(6) 7.88900(10)

b [Å] 7.9974(4) 7.9366(5) 7.9298(4)

c [Å] 8.1601(3) 8.0779(3) 7.9488(3)

α [°] 108.367(4) 107.925(4) 94.269(3)

β [°] 104.499(4) 104.638(4) 105.087(2)

γ [°] 92.936(4) 93.077(6) 106.334(2)

V [Å3] 461.05(4) 456.87(5) 454.86(3)

θ [°] 2.74-29.5 2.72-29.5 3.24-29.48

h –10 to 10 –10 to 10 –9 to 10

k –11 to 11 –10 to 10 –10 to 10

l –11 to 11 –11 to 11 –11 to 11

F(000) 240 241 243

Z 1 1 1

µ (Mo-Kα) [mm–1] 0.873 0.995 1.256

Crystal size [mm] 0.16 × 0.14 × 0.094 0.18 × 0.1 × 0.04 0.4 × 0.32 × 0.1

Dcalcd. [g cm–3], T [K] 1.694, 150(2) 1.72 1.745

Reflections collected 13840 15436 12340

Indep. reflections 2561 2529 2513 Obsd. Reflections

(I > 2σI)2350 2297 2439

Parameter 142 142 142

Weight parameter a, b 0.0431, 0.2041 0.0558, 0.1489 0.0171, 0.3496

R1 (obsd.) 0.0292 0.0302 0.0212

R1 (overall) 0.0334 0.0376 0.0219

wR2 (obsd.) 0.0824 0.0888 0.0521

wR2 (overall) 0.0841 0.1063 0.0518

Diff. peak / hole [e/Å3] 0.440/–0.318 0.607/–0.563 0.421/–0.288

214Chapter 5

Table 5.9: Details of the structure determinations of 18, 19, and 20. [Mn(ta)2]n

(18)

[Fe(ta)2]n

(19)

[Co(ta)2(OH2)2]n

(20)

CCDC 771286 771288

Empirical formula C10H8MnN6O4 C10H8N6O4 C5H6Co0.50N3O3

Formula mass 331.16 332.07 185.59

Crystal colour/habit colourless prism orange block pink prism

Crystal system orthorhombic monoclinic monoclinic

Space group F2dd Cc P21/n

a [Å] 11.3027(4) 11.224(2) 9.6572(4)

b [Å] 14.7218(11) 14.814(3) 6.6740(2)

c [Å] 15.2213(10) 9.2248(17) 11.6097(3)

α [°] 90.00 90 90.00

β [°] 90.00 127.499(12) 112.264(2)

γ [°] 90.00 90 90.00

V [Å3] 2532.8(3) 1216.9 692.48(4)

θ [°] 3.85-29.00 2.67-25.67 3.59-29.52

h –15 to 15 –13 to 13 –13 to 13

k –20 to 17 –17 to 17 –9 to 9

l –20 to 20 –11 to 11 –16 to 16

F(000) 1336 672 378

Z 8 4 4

µ (Mo-Kα) [mm–1] 1.070 1.268 1.284

Crystal size [mm] 0.16 × 0.16 × 0.14 0.4 × 0.333 × 0.3 0.18 × 0.16 × 0.14

Dcalcd. [g cm–3], T [K] 1.737, 150(2) 1.813, 100(2) 1.780, 150(2)

Reflections collected 11604 7681 25573

Indep. reflections 1687 2181 1937 Obsd. reflections

(I > 2σI) 1605 2100 1794

Parameter 97 191 112

Weight parameter a, b 0.0198, 0.6023 0.0444, 13.7807 0.0256, 0.3996

R1 (obsd.) 0.0186 0.0496 0.0193

R1 (overall) 0.0213 0.0541 0.0223

wR2 (obsd.) 0.0404 0.1365 0.0526

wR2 (overall) 0.0410 0.1376 0.0543

Diff. peak / hole [e/Å3] 0.230/–0.195 0.691/–0.594 0.465/–0.332

215Chapter 5

Table 5.10: Details of the structure determinations of 23, 25, and 27. [Znta2]n

(23)

[Mg(OH2)6](ta)2

(25)

[Co(tzp)2(OH2)2]

× 2 H2O (27)

CCDC 771289 771290

Empirical formula C10H8N6O4Zn C10H20MgN6O10C10H16CoN6O6

× 2 H2O Formula mass 341.59 408.63 411.26

Crystal colour/habit colourless block colourless block pink block

Crystal system triclinic triclinic monoclinic

Space group P1 P1 P21/a

a [Å] 7.1423(14) 6.8041(4) 7.3011(10)

b [Å] 9.659(2) 7.5250(5) 13.944(2)

c [Å] 9.9751(19) 9.6571(5) 8.0176

α [°] 61.515(14) 72.404(4) 90

β [°] 81.469(16) 76.679(5) 110.332(10)

γ [°] 72.789(15) 64.297(4) 90

V [Å3] 577.7(2) 421.84(4) 765.40(18)

θ [°] 2.32-25.54 3.35-29.00 2.71-25.95

h –8 to 8 –9 to 9 –8 to 8

k –11 to 11 –10 to 10 –17 to 17

l –12 to 12 –13 to 13 –9 to 9

F(000) 344 214 426

Z 2 2 2

µ (Mo-Kα) [mm–1] 2.156 0.174 1.18

Crystal size [mm] 0.2 × 0.2 × 0.2 0.39 × 0.25 × 0.15 0.3 × 0.3 × 0.3

Dcalcd. [g cm–3], T [K] 1.964, 100(2) 1.609, 150(2) 1.784, 100(2)

Reflections collected 7432 12084 9746

Indep. reflections 2159 2235 1495 Obsd. Reflections

(I > 2σI)1840 1999 1322

Parameter 190 164 131

Weight parameter a, b 0.0621, 0.0000 0.0397, 0.1299 0.0102, 0.8905

R1 (obsd.) 0.0581 0.0260 0.0279

R1 (overall) 0.046 0.0304 0.0343

wR2 (obsd.) 0.1152 0.0707 0.0569

wR2 (overall) 0.1112 0.0732 0.0585

Diff. peak / hole [e/Å3] 1.661/–1.197 0.429/–0.213 0.342/–0.369

216Chapter 5

Table 5.11: Details of the structure determinations of 28, 30, and 31. [Ni(tzp)2(OH2)2]

× 2 H2O (28)

[Zn(tzp)2]

× 0.25 H2O (30)

[Ag2(tzp)3(NO3)]

(31)

CCDC

Empirical formula C10H16NiN6O6

× 2 H2O 2 (C10H12N6O6Zn)

× 0.25 H2O C10H12Ag3N7O7

Formula mass 411.02 695.8 665.88

Crystal colour/habit blue prim colorless block colorless block

Crystal system monoclinic monoclinic monoclinic

Space group P21/a P21/a P21/a

a [Å] 7.3369(9) 14.6508(13) 14.3250(9)

b [Å] 13.803(2) 5.4459(2) 8.0282(4)

c [Å] 8.0582(4) 33.787(3) 14.6457(10)

α [°] 90 90 90

β [°] 110.598(8) 99.793(5) 112.974(5)

γ [°] 90 90 90

V [Å3] 763.89(15) 2656.5(3) 1550.72

θ [°] 2.7-29.5 3.09-28.52 2.81-26.79

h –10 to 10 –19 to 19 –18 to 18

k –19 to 19 –7 to 7 –10 to 10

l –11 to 11 –45 to 45 –18 to 18

F(000) 428 1418 1272

Z 2 4 4

µ (Mo-Kα) [mm–1] 1.329 1.877 3.809

Crystal size [mm] 0.35 × 0.24 × 0.15 0.36 × 0.16 × 0.09 0.3× 0.3 × 0.3

Dcalcd. [g cm–3], T [K] 1.787, 150(2) 1.74, 150(2) 2.852

Reflections collected 32467 45918 22127

Indep. reflections 2127 6728 3272 Obsd. Reflections

(I > 2σI)1946 5693 2988

Parameter 127 394 244

Weight parameter a, b 0.0473, 0.2768 0.0321, 1,9217 0.0202, 2.1621

R1 (obsd.) 0.0220 0.0311 0.0253

R1 (overall) 0.0254 0.0415 0.0300

wR2 (obsd.) 0.0783 0.0744 0.0492

wR2 (overall) 0.0801 0.0783 0.0506

Diff. peak / hole [e/Å3] 0.467/–0.519 0.514/–0.446 1.077/–0.806

217Chapter 5

5.3.3 Powder X-ray diffraction patterns

Figure 5.20: Comparison of the powder X-ray diffraction patterns of coordination polymers

bearing the ligand btp: i) [Cu(btp)2]n (13); ii) [Ni(btp)2]n × H2O (12); iii) [Co(btp)2]n (11); iv)

[Fe(btp)2]n (10); v) [Mn(btp)2]n (9).

218Chapter 5

Figure 5.21: Comparison of the powder X-ray diffraction patterns of coordination polymers

bearing the ligand ta: i) [Ag(ta)]n (24); ii) [Zn(ta)2]n (23); iii) [Cu(ta)2(OH2)]n (22); iv)

[Ni(ta)2(OH2)2]n × 2 n H2O (21); v) [Co(ta)2(OH2)]n (20); vi) [Fe(ta)2]n (19); vii) [Mn(ta)2]n (18).

219Chapter 5

Figure 5.22: Comparison of the powder X-ray diffraction patterns of coordination polymers

bearing the ligand tzp: i) [Ag3(tzp)2(NO3)]n (31); ii) [Zn(tzp)2]n × 0.25 n H2O (30); iii)

[Cu(tzp)2(OH2)]n (29); iv) [Ni(tzp)2(OH2)2]n × 2 n H2O (28); v) [Co(tzp)2(OH2)]n × 2 n H2O (27);

vi) [Mn(tzp)2]n (26).

220Chapter 5

5.3.4 Thermogravimetric analysis

For thermogravimetric measurements the instrument STD 2960 Simultaneous DSC-TGA (TA

Instruments) was used. About 15 mg of sample were heated in an air flow of 100 mL/min at 3

K/min to 500 °C.

Figure 5.23: Thermogravimetric analyses; i) [Zn(ta)2]n; ii) [Mn(ta)2]n; iii) [Fe(ta)2]n; iv)

[Co(ta)2(OH2)]n.

221Chapter 5

5.4 References

(1) This is only a preliminary result of the X-ray structure analysis. The molecular structure of 23 was largely disordered and could not be sufficiently refined. See also Appendix 5.1.2.

(2) The structure of 30 could be resolved and reasonably refined in P21/c (monoclinic). However this is only a preliminary result, since symmetry, cell dimensions and systematic absences indicate a crystal system of higher symmetry, such as e.g., an orthorhombic system.

(3) G. Sheldrick, Acta Crystallogr., Sect. A 2008, 64, 112-122. (4) K. Brandenburg, M. Berndt, Diamond – Visual Crystal Structure Information System,

Crystal Impact GbR, Bonn (Germany), 1999; for Software Review see: W. T. Pennington, J. Appl. Crystallogr. 1999, 32, 1028–1029.

(5) R. D. Fields, M. V. Lancaster, Am. Biotechnol. Lab. 1993, 11, 48-50. (6) Systat Software, Inc. 2006 (http://www.systat.com).

List of Publications

“Two new imidazole-based heteroscorpionate ligands”N. V. Fischer, F. W. Heinemann, N. Burzlaff, Eur. J. Inorg. Chem. 2009, 26, 3960-3965.

“Scorpionate complexes suitable for enzyme Inhibitor Studies” N. V. Fischer, G. Türkoglu, N. Burzlaff, Curr. Bioact. Compd. 2009, 5, 277-295.

“Metal-organic frameworks constructed with 1,2,4-triazol-1-ylacrylic acid ligand: Syntheses and crystal structures” N. V. Fischer, A. Inayat, W. Schwieger, N. Burzlaff, J. Coord. Chem. 2010, 63, 2831-2845.

“N,N,O Ligands based on triazoles and transition metal complexes thereof” E. Hübner, N. V. Fischer, F. W. Heinemann, U. Mitra, V. Dremov, P. Müller, N. Burzlaff, Eur. J. Inorg. Chem. 2010, doi: 10.1002/ejic.201000391.

Short lectures

“A new class of imidazole-based N,N,O-ligands: Synthesis, structure and reactivity” XIth International Seminar for Ph. D. Students on Organometallic and Coordination Chemistry (Sayda, Germany, 2008).

Contributed Presentations

Poster presentation, 4th EuCheMS Conference on Nitrogen Ligands in Coordination Chemistry, Metal-Organic Chemistry, Bioinorganic Chemistry & Homogeneous Catalysis(Garmisch-Partenkirchen, Germany, 2008).

Poster presentation, Heidelberg Forum of Molecular Catalysis (Heidelberg, Germany, 2009).

Poster presentation, Inorganic/Bioinorganic Reaction Mechanism Meeting (Kloster Banz, Germany 2010).

Poster presentation, 39th International Conference on Coordination Chemistry (Adelaide, Australia 2010).

CURRICULUM VITAE

Persönliche Daten

Nina Fischer

geboren am 09. 12. 1982 in Frankfurt am Main

Schulausbildung

1989-1993: Bachgrundschule Gössenheim

1993-2002: Frobenius-Gymnasium Hammelburg

Studium

10/02-09/07 Studium der Chemie (Diplom) An der Friedrich-Alexander-Universität Erlangen Nürnberg

09/04: Diplomvorprüfung

02/07: Diplomhauptprüfung

Diplomarbeit

03/07-09/07: Institut für Anorganische und Analytische Chemie der Friedrich-Alexander-Universität Erlangen Nürnberg unter Anleitung von Prof. Dr. N. Burzlaff zum Thema „Übergangsmetall-Komplexe mit Bis(N-alkylimidazolyl)propionsäure-liganden“

Dissertation

11/07-10/10: Institut für Anorganische und Analytische Chemie der Friedrich-Alexander-Universität Erlangen Nürnberg unter Anleitung von Prof. Dr. N. Burzlaff zum Thema „Novel Ligands based on Imidazole and Triazole: From Coordination Chemistry to Medicinal Applications and Material design”