ORIGINAL RESEARCH

Cation- and/or anion-directed reaction routes. Couldthe desolvation pattern of isostructural coordination compoundsbe related to their molecular structure?

Berta Hollo • Marko V. Rodic • Oskar Bera •

Mirjana Jovicic • Vukadin M. Leovac •

Zoran D. Tomic • Katalin Meszaros Szecsenyi

Received: 31 January 2013 / Accepted: 4 April 2013

� Springer Science+Business Media New York 2013

Abstract The crystal and molecular structure of

[Cu(ampf)(ClO4)(MeOH)2]ClO4, (1), ampf = N,N0-bis(4-

acetyl-5-methylpyrazol-3-yl)formamidine, determined by

X-ray crystallography is described and compared with the

structurally related copper(II) complexes, formed under

similar experimental conditions, using CuII salts with dif-

ferent anions. The complex formation is discussed in view

of the structures of cobalt(II) and nickel(II) complexes with

the same organic ligand and different anions, also formed

under similar reaction conditions. Solvent molecules

coordinated to the central atom play an important role in

biologic systems. To get a better insight into the desolva-

tion mechanism, in this study the desolvation pattern of 1 is

presented. As in literature little attention is paid to the

desolvation mechanism of solvate complexes, the desolv-

ation mechanism of three, potentially biologically active

isostructural pairs of octahedral NiII and CoII compounds

with ampf and dmpc (3,5-dimethyl-1H-pyrazole-1-carbox-

amidine) ligands are evaluated and compared with the

desolvation of 1. The results of the thermal data are

discussed on the basis of structural features of the com-

pounds. The minor differences in structures of the related

compounds cannot be straightforwardly connected with the

different solvent evaporation mechanism. To explain the

differences found in desolvation pattern in isostructural

CoII and NiII complexes the Jahn-Teller effect is proposed.

Keywords CuII perchlorate � Isostructural CoII and NiII

pyrazole complexes � Desolvation mechanism � Jahn-Teller

effect

Introduction

Pyrazole derivatives and their complexes are used in

numerous and various applications. Many of applications

are related to their remarkable biologic activity [1–4].

Some derivatives and/or complexes are used for construc-

tion of various artificial helical structures [5] or are can-

didates for nanocarriers [6] for drug delivery and imaging,

citing here only a few examples chosen from the last year’s

publications lists.

In drug design, small molecule compounds like pyra-

zoles [7, 8] can be used to characterize the shape and

charge preferences of macromolecular binding sites. In

complex compounds, small anions and/or solvent mole-

cules coordinated to the central atom usually might be

relatively easily exchanged for substrate [9–12]. Catalytic

and structural metal sites are present not only in enzymes

but also in metal finger DNA-binding proteins [13]

domains.

Isothermal titration calorimetry (ITC) is the most pow-

erful tool to obtain additional information on bio-macro-

molecule structure–function relationship [14]. The results

of ITC offers data which might help to better understand

Electronic supplementary material The online version of thisarticle (doi:10.1007/s11224-013-0270-9) contains supplementarymaterial, which is available to authorized users.

B. Hollo � M. V. Rodic � V. M. Leovac �K. Meszaros Szecsenyi (&)

Faculty of Sciences, University of Novi Sad, Trg D. Obradovica

3, 21000 Novi Sad, Serbia

e-mail: mszk@uns.ac.rs

O. Bera � M. Jovicic

Faculty of Technology, University of Novi Sad, Bulevar cara

Lazara 1, 21000 Novi Sad, Serbia

Z. D. Tomic

Vinca Institute of Nuclear Sciences, University of Belgrade,

P.O.Box 522, 11001 Belgrade, Serbia

123

Struct Chem

DOI 10.1007/s11224-013-0270-9

the binding properties and mechanisms of interaction

between reacting components [15, 16] and to determine the

binding parameters and conformational changes during the

interactions [17–19].

The possibility to apply other methods of thermal

analysis to obtain data which could be related directly to a

given property is reduced. The usual observation is that

isostructural compounds follow a similar decomposition

pattern [20–22]. However, by increasing sensitivity of

thermal analysis equipments small differences in decom-

position of isostructural compounds could be detected [23].

Through the reviews ‘‘Interplay of Thermochemistry

and Structural Chemistry’’ an attempt is made to correlate

the experiments and theory [24, 25]. L. Que, Jr. said that

‘‘By piecing together the various clues derived from the

physical methods, bioinorganic chemists have been able to

form a coherent picture of the metal binding site and to

deduce the role of the metal ion in a number of biologic

processes’’ [26].

The aim of the work was to show how anions and cat-

ions affect the complex formation reaction with potentially

bioactive ligands. Namely, to see how the change of the

metal salt in reaction of 4-acetyl-3-amino-5-methylpyr-

azole (aamp) ligand precursor in the presence of triethyl

orthoformate (teof) would result in change of structure of

the forming compound [27, 28]. On the other hand, the

thermal properties of new compounds are of great impor-

tance for both structure-based and ligand-based drug

design. Therefore, a special attention is paid to the thermal

decomposition of the newly synthesized [Cu(ampf)

(ClO4)(MeOH)2]ClO4, especially to mechanism of solvent

evaporation. In addition, as solvation of metal cations has a

functional importance in biologic systems [29], in this

paper we would like to present the pieces concerning the

regularity found by means of thermal analysis in the sol-

vent evaporation pattern in isostructural octahedral NiII and

CoII complexes with ampf and dmpc ligands and coordi-

nated MeOH or water molecules, some of them showing

moderate cytotoxic activity [27]. In view of the desolvation

pattern, found in the former isostructural pairs, the

desolvation mechanism of 1 is discussed.

Experimental

General methods

Analytical reagent grade commercial chemicals were used

as supplied. The IR data were recorded on a Thermo

Nicolet NEXUS 670 FT-IR spectrometer at room temper-

ature using KBr disks in the range of 4,000–400 cm-1,

while in the far IR-region of 600–180 cm-1 using CsI

pellets. In all the measurements a resolution of 4 cm-1 was

applied. Simultaneous TG/DSC measurements were per-

formed using SDT Q600 TA Instruments thermal analyzer

at heating rate of 2 �C min-1 in nitrogen gas carrier

(100 cm3 min-1) and alumina sample pan with corre-

sponding empty reference pan. Sample mass: \1 mg.

The molar conductivity of freshly prepared 1 9 10-3

mol dm-3 solution was determined at room temperature

using a Jenway 4010 digital conductivity meter.

Crystal structure determination and refinement

A suitable crystal of 1 was selected and glued to a

glass fiber. Diffraction measurements were performed

with a Gemini S j-geometry diffractometer equipped with

Sapphire3 CCD area detector (Agilent Technologies) using

graphite-monochromated Mo Ka radiation with the x scan

method. Data collection, reduction, absorption correction

(multi-scan), and cell refinement was performed with

CRYSALISPRO [30]. The structure was solved by the direct

method using SIR92 [31] and refined on F2 with SHELXL-97

[32] integrated in SHELXLE [33]. All non-hydrogen atoms

were refined with anisotropic displacement parameters.

H-atoms bonded to carbons were placed in idealized

positions and refined as riding with Uiso set as 1.2 or 1.5

Ueq of their parent atoms. The positions of H-atoms bonded

to hetero atoms were determined from DF map and refined

using the riding model. Molecular graphics were produced

with ORTEP-3 [34] and PLATON [35]. Relevant crystallo-

graphic data together with data collection and structure

refinement details are listed in Table 1.

Computation details

Deconvolution of DTG curves was performed by applying

the Gaussian function using Magic Plot 2.0 software. All

calculations were preformed in Mathcad 15.

Synthesis

The synthesis of [Cu(ampf)(ClO4)(MeOH)2]ClO4, (1), was

carried out by the reaction of Cu(ClO4)2�6H2O and the ligand

precursor, 4-acetyl-3-amino-5-methylpyrazole (aamp). Three

metal-to-ligand mole ratios were tested (0.5/1.0, 0.8/1.0,

and 1.0/1.0). Ratios of 0.8/1.0 and higher resulted in single-

crystal formation. The mixture of 0.8 mmol metal perchlo-

rate and 1.0 mmol ligand precursor were dissolved in 10 cm3

MeOH by mild heating. To the warm solution 3 cm3 triethyl

orthoformate (teof) was added continuing the heating for 5

additional minutes. In 3 days green crystalline solid is

precipitated. The crystals were filtered off, washed with

MeOH and air dried. Yield: 42 %, Km(dmf) = 151

S cm2 mol-1, Km(MeOH) = 195 S cm2 mol-1. The solu-

bility of the compounds in EtOH and acetone is low, but they

Struct Chem

123

are well-soluble in MeOH and dimethylformamide (dmf).

Selected FT-IR (KBr, cm-1): 1637(s), 1621(vs), 1601(vs),

1557(vs), 1530(s), 1503(s), 1467(vs), 1421(s), 1364(s),

1322(m), 1216(m), 1100–1078(s), 978(s), 966(s), 916(m),

739(m), 674(m), 625(s), 577(m), 447(m).

Compounds for comparison of composition [M(ampf)

(MeOH)2(NO3)]NO3 are marked with Ia (M = CoII, [36])

and Ib (M = NiII, [27]). Complexes of formula

[M(ampf)(H2O)3](ClO4)2�H2O [28] are denoted as IIa

(M = CoII) and IIb (M = NiII). The complex with com-

position [Co(dmpc)2(H2O)2](NO3)2 [37, 38] is referred as

IIIa and [Ni(dmpc)2(H2O)2](NO3)2 [37, 38] as IIIb.

Results and discussion

Crystal structure of [Cu(ampf)(ClO4)(MeOH)2]ClO4 (1)

Molecular structure of the complex is depicted in Fig. 1,

while selected geometrical parameters are listed in Table 2.

Asymmetric unit of 1 consists of discrete [Cu(ampf)

(MeOH)2(ClO4)]? cations and ClO4- anions.

Copper atom of the complex cation is situated in square

bipyramidal environment—the equatorial sites of the

coordination polyhedron are occupied by ONN tridentate

ampf and methanol molecule, while another methanol

molecule and perchlorate anion define the axial positions.

Copper–equatorial atom ligator bonds are similar in length

(1.949(4) - 2.019(4) A) and are in accordance with

those reported for structurally related [Cu(ampf)(NO3)2

MeOH]�MeOH [27]. The axial bonds are significantly

longer [2.289(5) and 2.621(6) A for Cu–O4 and Cu–O5,

respectively] than the equatorial ones, which is in accor-

dance with Jahn-Teller effect [39, 40].

The tridentate coordination mode of ampf is analogous

to those in the complexes Ia, Ib, IIa, and IIb [27, 28, 36]

and is realized through acetyl oxygen, azomethine nitro-

gen, and pyrazole nitrogen atoms. This leads to the for-

mation of two six-membered metallocycles that are slightly

puckered and can be described as half-chair conformers

(see Table S1 in the supplementary material). The ampf

deviates from planarity and can be considered as consti-

tuted of the two approximately planar 4-acetyl-5-meth-

ylpyrazol moieties connected through formamidine bridge,

with dihedral angle of 13.3(3)� between the mean planes of

4-acetyl-5-methylpyrazol moieties. Planarity of the ligands

parts is consistent with delocalization of electrons evi-

denced by the bond lengths in ligand backbone. One of the

two 4-acetyl-5-methylpyrazol moieties of the ampf is

coordinated through pyridinic nitrogen atom N2, the other

one through the acetyl oxygen atom O1. The difference in

coordination mode is due to stereochemically directed

reaction path, as the alternative hypothetical tridentate

coordination could not lead to formation of stable metal-

locycles. Different coordination pattern of ligand moieties

Table 1 Crystallographic data and structure refinement details for 1

Crystal data

Molecular formula C15H24Cl2CuN6O12

Formula weight 614.84

Crystal system, space group Monoclinic, P 21/n

Unit cell dimensions a = 14.530(1) A

b = 12.6543(9) A

c = 15.377(1) A

b = 114.607(9)�V = 2570.6(3) A3

Z 4

Dx 1.589 g cm-3

Absorption coefficient

(Mo Ka)

1.125 mm-1

F(000) 1,260

Crystal size 0.44 mm 9 0.41 mm 9 0.34 mm

Data collection

Temperature 298 K

Radiation type, wavelength Mo Ka, 0.71073 A

h range for data collection 3.01� - 25.00�No. reflections collected,

unique

11,385, 4,517

Rint 0.036

No. reflections with I [ 2rI 3,342

Refinement

Restraints, parameters 0, 335

Goodness-of-fit on F2 1.068

R1, wR2 [I [ 2rI] 0.077, 0.194

R1, wR2 [all data] 0.105, 0.212

Fig. 1 Molecular structure of [Cu(ampf)(ClO4)(MeOH)2]ClO4 (1)

showing the atomic numbering scheme. Displacement ellipsoids are

drawn at 50 % probability level

Struct Chem

123

is associated with different bond lengths in both pyrazole

rings, and to elongation of C4–O1 compared to C10–O2

bond (1.241(7) and 1.210(9) A, respectively).

Geometry of hydrogen bonding is shown in Table 3.

Complex cations are connected through the formamidine

NH- and methanolic OH-groups groups while pyrazole

NH-groups are hydrogen bonded to anionic perchlorates,

connecting thus cationic with anionic layers. Therefore,

crystal packing of the structural units can be described as

made of cation–anion sheets parallel to 1 0 �1 plane (Fig. S1

in the Supplementary material).

Compound 1 has analog composition as [M(ampf)

(MeOH)2(NO3)]NO3 (M = CoII in Ia and NiII in Ib). The

overall shape and relative position of hydrogen-bond

donors and acceptors in 1 is similar to those observed in Ia

and Ib. However, supramolecular arrangement in crystal

lattice is different for 1 and Ia or Ib, which could be

attributed to different counter ions.

The effects of cation and anion change on complex

formation reactions

The template synthesis of transition metal coordination

compounds using 4-acetyl-3-amino-5-methylpyrazole

(aamp) ligand precursor and teof dehydration and ligand

forming agent is already described [27, 28, 36]. By

changing the metal-to-ligand ratio the optimal conditions

were found for single-crystal formation that is favored

when the ligand precursor is added in a slight excess [28].

Despite the almost identical experimental conditions, the

composition and the structure of the newly obtained com-

pound are different from those found for the corresponding

NiII and CoII perchlorate compounds. While nickel and

cobalt form isostructural compounds with nitrate or per-

chlorate, with copper(II) the complex formation is anion

directed (see Scheme 1; Fig. 3).

Thermal decomposition of 1

The thermal decomposition curves for 1 were recorded in

an inert atmosphere of N21. TG, DTG, and DSC curves are

presented in Fig. 2. The stability of the desolvated com-

pound is low (*10 �C) and its decomposition takes place

with a very slow endothermic fragmentation of the organic

ligand. At around 250 �C a rapid, highly exothermic pro-

cess begins. Above 300 �C the decomposition turns into

slow endothermic transformations and it is not finished up

to 700 �C in nitrogen atmosphere (see Fig. 2).

As the mechanism of decomposition in general is most

easily followed by DTG curves, the deconvolution of DTG

curves is performed. The determined Gaussian functions

for peaks were transformed into conversion versus tem-

perature curves using the following Eq. (1):

a Tð Þ ¼R T

0dm Tð ÞdT

R Tf

0dm Tð ÞdT

ð1Þ

where a is the degree of conversion, T stands for the

temperature, Tf is the final temperature of the selected

process, dm(T) is the mass function derivate obtained by

deconvolution. This procedure was applied to the processes

of solvent evaporation only, in the temperature range where

no fragmentation of the organic ligand occurs. The

deconvolution was started on the basis of the number of

coordinated solvent molecules, supposing that to every

molecule at least one evaporation peak belongs. The

number of peaks was increased to achieve an acceptable

agreement between the measured and calculated data.

As can be seen in Fig. 2, the solvent evaporation in 1

begins at room temperature and is finished around 170 �C.

The amount of methanol found (*7 %) is significantly less

than the calculated one (10.42 %). This means that a sig-

nificant amount of the coordinated MeOH evaporates

practically during the storage of the complex.

Mechanism of solvent evaporation

The temperature of the solvent evaporation is an indication

about its bonding energy. The way, the coordinated solvent

molecules evaporate during the thermal decomposition,

together with the evaporation temperature indirectly refer

to e.g., the possibility of its exchange by the substrate

binding to the metal center, catalyzing thus some specific

processes in biologic systems [41]. To exclude the effect of

the experimental conditions on the mechanism of the

Table 2 Selected bond lengths in 1

Bond Length, A Bond Length, A

Cu–O1 1.949 (4) C2–N5 1.319 (7)

Cu–O3 2.019 (4) N1–N2 1.363 (7)

Cu–N2 1.954 (5) N5–N6 1.372 (7)

Cu–N4 1.995 (5) C11–N1 1.337 (8)

Cu–O4 2.289 (5) C5–N6 1.302 (8)

Cu–O5 2.621 (6) C9–C11 1.387 (9)

C1–N4 1.300 (7) C3–C5 1.411 (8)

C1–N3 1.326 (7) C8–C9 1.407 (8)

C2–N4 1.412 (7) C2–C3 1.415 (8)

C8–N3 1.377 (7) C10–O2 1.210 (9)

C8–N2 1.320 (7) C4–O1 1.241 (7)

1 The repeatability of the measurements was also tested. Caution:

Most of the perchlorates belong to explosives therefore special

attention should be paid to protective measures. In the case of thermal

measurements, the sample mass (\1 mg) and the heating rate

(\20 �C min-1) should be kept low.

Struct Chem

123

solvent evaporation, the thermal decomposition of each

isostructural pair is compared at the same heating rate and

is registered under very similar reaction conditions (same

type of sample holder, atmosphere, sample mass, etc.). In

order to separate the simultaneous processes method of

deconvolution was applied to DTG curves. Unfortunately,

one cannot assign a defined physical meaning to the sep-

arated peaks. Only groups of processes affecting the

evaporation like different diffusion rate, the formation of a

new solid-phase and/or structural rearrangements around

the metal center in a given temperature range might be

proposed.

Scheme 1 Change of structure

due to change of metal cation

and/or anion in complexes of

ampf

Fig. 2 TG, DSC, and DTG curves for 1

Table 3 Geometry of intermolecular contacts relevant for the association of molecules in the crystal structure of 1

D–H���A D–H, A H���A, A D���A, A D–H���A, �

O3–H3���N5i 0.93 1.94 2.862 (7) 167.5

O4–H4���O8ii 1.00 1.82 2.814 (8) 171.4

N6–H6���O9iii 0.95 1.94 2.87 (1) 165.0

Symmetry codes: ði) � xþ 3=2; y� 1=2; �zþ 1=2; ðii) x� 1=2; �yþ 3=2; zþ 1=2: ðiii) x� 1=2; �yþ 1=2; zþ 1=2:

Struct Chem

123

One of our research aims for more than two decades is to

get the best possible insight into the correlation between

the structure and the predicted application. During these

years an interesting phenomenon came into sight: while

NiII and CoII under similar reaction conditions usually form

isostructural compounds, the structure of CuII complexes is

different (see Scheme 1). Comparing the desolvation

pattern of isostructural pairs of nickel(II) and cobalt(II)

coordination compounds with pyrazole derivatives con-

taining two or more solvent ligands we have found [27, 28,

36] that the solvent evaporation in NiII complexes

always consists of overlapped, sometimes hardly separable

Fig. 3 Molecular structure of isostructural pairs: Ia [36] and Ib [27]; IIa and IIb [28]; IIIa and IIIb [37, 38]

Fig. 4 DTG curve deconvolution for isostructural solvate pairs: Ia and Ib; IIa and IIb; IIIa and IIIb

Struct Chem

123

processes, while in the corresponding CoII compounds the

solvent evaporation takes place in a more complex way.

Similar behavior was found in isostructural CoII and NiII

coordination compounds in literature [42–44], also. How-

ever, it is important to note that the similarity between the

desolvation pattern of [Cu(ampf)(ClO4)(MeOH)2]ClO4 and

[Co(ampf)(MeOH)2(NO3)]NO3 is more emphasized than

that between Ia and the corresponding isostructural NiII

complex (Ib). To gain more insight to this phenomenon we

have compared the desolvation pattern of 1 with three

isostructural pairs of cobaltII and nickelII solvate com-

plexes with pyrazole-type ligands. The structures of the

isostructural pairs are presented in Fig. 3.

In all three isostructural pairs around the metal center

an octahedral surrounding is established. In compounds

Ia-b the ampf ligand is coordinated in tridentate NNO

fashion in the equatorial plane. The forth place in the

equatorial plain is occupied by a methanol molecule while

one MeOH and a nitrate ion take the axial positions. In

compounds IIa-b the same coordination mode of the

ligand is established. To the remaining three sites water

molecules are coordinated. In IIIa-b two dmpc ligands

coordinate to the metal center as bidentates with NN-

donor atoms. The axial positions are occupied by water

molecules. The thermal stability of all the desolvated

compounds is different, however, by controlled rate ther-

mal analysis all of them could be isolated.

The deconvolution results for DTG curves and the cor-

responding peaks are shown in Fig. 4, while the results of

calculations are given in Table 4.

The solvent evaporation in NiII compounds agrees with

loss of the molecules about one by one (except of IIb,

where all 3 water molecules depart almost simultaneously,

see Fig. 4). In CoII compounds the DTG curves show a

significantly higher degree of asymmetry and there is no

stoichiometric correlation in solvent departure.

Despite the similar [M(ampf)(MeOH)2A]A coordination

formula (M = Cu, A = ClO4 for 1; M = Co, Ni,

A = NO3 for Ia and Ib), the mechanism of desolvation in

1 is obviously different than that observed for Ia and Ib

(see Fig. 4). In Ia and Ib the methanol evaporation also

begins almost at room temperature. Regardless, the mea-

sured and calculated methanol contents are in the range of

experimental error, while in 1 the amount of MeOH

determined by thermogravimetry is somewhat more than

half of the theoretical one. For a better DTG curve fitting

the number of involved processes in cobalt(II) compounds

should be increased at least by one compared to the number

of corresponding solvent ligands. In 1 the desolvation

pattern is even more complicated.

Comparison of metal–solvent distances, unit cell vol-

umes and H-bond interactions in the Co/Ni isostructural

pairs (Table 5) shows that despite of some minor differ-

ences, the structural data do not offer an acceptable

Table 4 Peak temperature (t, �C) and mass loss (Dm, % compared to the theoretical 100 %) for the separated desolvation processes

Samples

Peaks Ia Ib IIa IIb IIIa IIIb

1 Temperature, t,�C

86 80 67 99 134 151

Mass loss, Dm, % 73.1 45.0 55.1 26.1 62.7 45.7

2 Temperature, t,�C

97 110 93 111 146 168

Mass loss, Dm, % 8.2 55.0 2.1 58.2 29.1 54.3

3 Temperature, t,�C

126 – 119 116 155 –

Mass loss, Dm, % 18.7 – 4.3 15.6 8.2 –

4 Temperature, t,�C

– 146 – –

Mass loss, Dm, % – 38.4 – –

Table 5 Metal-solvent distances and unit cell volumes in Co/Ni isostructural pairs

[M(ampf)(MeOH)2(NO3)]NO3 [36] [M(ampf)(H2O)3](ClO4)2�H2O [28] [M(dmpc)2(H2O)2](NO3)2 [37, 38]

M–MeOH (A) V (A3) M–H2O (A) V (A3) M–H2O (A) V (A3)

Co 2.08(2) 1,100 2.11(3) 2,486 2.1736(8) 991

Ni 2.08(1) 1,126 2.08(7) 2,469 2.152(1) 985

Struct Chem

123

explanation for the different desolvation pattern observed

in isostructural pairs of compounds.

Only the loss of almost one MeOH in 1 at room tem-

perature could be explained by its significantly longer

distance from the metal center (Cu–MeOH: 2.289(5) A)

compared to the second one (Cu–MeOH 2.019(4) A,

Dr = 0.270(9) A). The higher similarity between the sol-

vent evaporation from 1 and the structurally most similar

Ia might be the consequence of the Jahn-Teller effect [39,

40] that is in octahedral complexes more pronounced with

odd number of electrons in e.g., orbitals (d9 and low spin

d7) compared to the d8 electron configuration in Ib. The

JTE offers good examples for structural instabilities and

dynamical processes in molecules and in the condensed

phase, and may help e.g., to understand the main trends in

molecular magnetism [45] or variation in coloration [46]

etc. However to our knowledge it was not yet applied to

explain the different desolvation pattern in isostructural

complexes. Namely, JTE may affect the energy of the new

solid-phase formation in a similar way in CuII and CoII

compounds, while NiII complexes are not affected by JTE

at all. The lower packing index may additionally facilitate

the MeOH evaporation in 1 (64.9 % compared to 71.0 %

in Ia).

Conclusions

In the reaction of copper(II) perchlorate with 4-acetyl-3-

amino-5-methylpyrazole ligand precursor in the presence

of teof, the complex of composition [Cu(ampf)(ClO4)

(MeOH)2]ClO4, ampf = N,N0-bis(4-acetyl-5-methylpyr-

azol-3-yl)formamidine is formed. The compound was

characterized by X-ray single-crystal diffraction and ther-

mal methods. In order to see how the cation and anion

affect the complex formation, the composition and the

structure of the new compound was compared to those

obtained for cobalt(II) and nickel(II) perchlorate and cop-

per(II), cobalt(II), and nickel(II) nitrates. While CoII and

NiII under similar experimental conditions usually give

isostructural compounds, the reaction with CuII salts is very

much affected be the anion.

Regularity in solvent removal processes in isostructural

complex compounds cannot be related to a specific struc-

tural parameter. Supposing that the heat transfer is similar,

both the different diffusion rates and new solid-phase for-

mation may be the rate determining steps. However, the

energy of the new solid-phase formation, due to Jahn-

Teller effect, most probably is more similar in CuII and

CoII compounds, compared to that in the complexes which

do not exhibit Jahn-Teller distortion.

The data presented here are collected on the basis of a

continuous experimental work and may be of a great

importance for building reliable data bases, necessary to

answer the question ‘‘how is substance formed?’’ [47].

Acknowledgments The authors thank to the Ministry of Education,

Science and Technological Development of the Republic of Serbia for

financial support (Projects No. ON172014 and III45022) and Secre-

tariat for Science and Technological Development, Autonomous

Province of Vojvodina, Republic of Serbia.

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