Research Article Synthesis, Characterization, and...

Research ArticleSynthesis Characterization and Antimicrobial Activities ofCoordination Compounds of Aspartic Acid

T O Aiyelabola12 D A Isabirye2 E O Akinkunmi3 O A Ogunkunle1 and I A O Ojo1

1Department of Chemistry Obafemi Awolowo University Ife Central Ile-Ife 220282 Osun State Nigeria2Department of Chemistry NWU Mafikeng Campus Private Bag X2046 Mmabatho 2735 South Africa3Department of Pharmaceutics Obafemi Awolowo University Ife Central Ile-Ife 220282 Osun State Nigeria

Correspondence should be addressed to T O Aiyelabola tt1hayeyahoocom

Received 1 September 2015 Accepted 27 October 2015

Academic Editor Nigam P Rath

Copyright copy 2016 T O Aiyelabola et alThis is an open access article distributed under the Creative CommonsAttribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Coordination compounds of aspartic acid were synthesized in basic and acidic media with metal ligand M L stoichiometricratio 1 2 The complexes were characterized using infrared electronic and magnetic susceptibility measurements and massspectrometry Antimicrobial activity of the compounds was determined against three Gram-positive and three Gram-negativebacteria and one fungus The results obtained indicated that the availability of donor atoms used for coordination was a functionof the pH of the solution in which the reaction was carried out This resulted in varying geometrical structures for the complexesThe compounds exhibited a broad spectrum of activity and in some cases better activity than the standard

1 Introduction

Much attention is being paid to coordination compounds aspotential antimicrobial agents in recent times This is due tothe improved activity of drugs administered as complexes[1ndash6] It has been suggested that ligands with nitrogen andoxygen donor systemsmight inhibit enzyme productionThisis because the enzymes which require these groups for theiractivity appear to be especially more susceptible to deactiva-tion by the metal ion upon chelation [2] Such compoundsinclude coordination compounds of amino acids such asaspartic acid Aspartic acid (Figure 1) is a naturally occurringamino acid and a component of the active centre of someenzymes It possesses three potential donor sites (one aminegroup and two carboxyl ones) [7 8] Aspartic acid has beenreported as bidentate as tridentate and as a bridging ligand[9ndash15] Its coordination behaviour may therefore be studiedby comparing the complexes it forms with a series of metalions of the same valency at relevant pH ranges [12 14 15] Var-ious structural possibilities for the correspondingmetal com-plexes are thus expected [16ndash20] Coordination compoundsof amino acids such as histidine [21] arginine glutamicacid [14 16] and aspartic acid [13 22] have been studied

These coordination compounds were reported to demon-strate activity varying from marginal to significantly goodantimicrobial properties However little attention has beenfocused on coordination compounds of aspartic acid as atridentate ligand As a result of resistance to the drugscurrently in use and the emergence of new diseases thereis a continuous need for the synthesis and identification ofnew compounds as potential antimicrobial agents Thereforewe considered it necessary to study the effects of the possiblevarying structures of coordination compounds of asparticacid on their antimicrobial activity as this would yieldinformation useful for designing antimicrobial agents Wetherefore report the syntheses of coordination compounds ofaspartic acid in acidic and basic media and their characteri-zation and antimicrobial activities

2 Experimental

21 Materials and Methods All reagents and solventsused were of analytical grade The infrared spectra wererecorded on a Genesis II FTIR spectrophotometer in therange 450ndash4200 cmminus1 The electronic absorption spectra of

Hindawi Publishing CorporationJournal of ChemistryVolume 2016 Article ID 7317015 8 pageshttpdxdoiorg10115520167317015

2 Journal of Chemistry

CH C

O

C

OH

O

+H3N

CH2

Ominus

Figure 1

the complexes in the range 200ndash1000 nm were obtained witha Genesis 10 UV-Vis spectrophotometer solid reflectanceMelting points or decomposition temperatures (mpdt)were measured using open capillary tubes on a Gallenkamp(variable heater)melting point apparatusThe in vitro antimi-crobial properties of the complexes were determined usinga modification of the literature procedure [23] Magneticsusceptibility was obtained using a Gouy balance at roomtemperatureMass spectrometry for one of the complexeswascarried out using Fisons VG Quattro spectrophotometer

22 Syntheses of Complexes The complexes were preparedaccording to a modification of literature procedure [13 2425] The general equations for the reactions are as follows

ML2

complexesMCl2

+ 2H2

LrarrMHL2

+ 2HClNa2

[ML2

] complexesMCl2

+ 2H2

L + 2NaOHrarrNa2

[ML2

] + 2HCl + 2H2

Owhere M = Co(II) Cu(II) Mn(II) Ni(II) Cd(II) L =(+)-aspartic acid

221 ML2

Complexes A solution of (+)-aspartic acid(002M 267 g) was added to 001M of appropriate metal(II)chloride salt (162 217 243 251 and 269 g) for coppercadmium nickel cobalt and manganese respectively anddissolved in 20mL of distilled water with stirring pH rangefor the reactionswas 201ndash221Themixtures were heatedwithstirring for 2 h using a water bath The resultant solutionswere further concentrated until a scum was formed andthen cooled Crystals obtained were filtered and washed withmethanol and then dried in a vacuum oven at 60∘C

222 Na2

[ML2

] Complexes Appropriate metal(II) chloridesalt solutions (002M 331 447 488 505 and 534 g) forcopper cadmium nickel cobalt and manganese respec-tively were dissolved in minimal amount of distilled waterwith warming until a clear solution was obtained (+)-Aspartic acid (004M 542 g) was dissolved in distilled waterandwarmed over a steambath 004MNaOHwas then addedwith stirring such that the pH range of the reactionwas about8ndash10 The metal(II) solution was then added and the mixturewas refluxed for 2 h The product obtained was allowed tocool overnight with the formation of crystals The crystalsobtained were filtered washed with methanol and dried inan oven at 60∘C

Figure 2 Infrared spectrum for Na2

[Co(asp)2

]


[Cu(asp)2

]

23 Antimicrobial Activity Using Disc Diffusion Assay Thein vitro antimicrobial screening effects of the ligand andcomplexes were evaluated using the disc diffusion method aspreviously reported [26] The strains used were Escherichiacoli NCTC 8196 Pseudomonas aeruginosa ATCC 19429Staphylococcus aureus NCTC 6571 Proteus vulgaris NCIBBacillus subtilis NCIB 3610 and one Methicillin resistant Saureus clinical isolate for bacteria and C albicans NCYC 6for fungi All the tests were performed in triplicate

3 Results and Discussion

31 Physicochemical Analysis All the complexes were insol-uble in major organic solvents however they were soluble inhot waterThemelting points or decomposition temperaturesfor the complexes are shown in Table 1Most of the complexesdecomposed before melting

32 Infrared Spectra The infrared spectrumof the free ligandexhibited a broad band at 3380 cmminus1 which was assignedto the NH

2

stretching frequency Intense bands at 1650 and1583 cmminus1 were observed and are attributed to COOminusasy andCOOminussy stretching frequencies respectively [27 28] TheCOOminus asymmetric and symmetric stretching frequencies oncoordination were shifted to higher and lower wave numbersfor Na

2

[ML2

] complexes indicating that the oxygen atom ofthe carboxylate group of the ligandwas used for coordinationFigures 2 and 3 [12 28] For the ML

2

complexes the COOminus

Journal of Chemistry 3

Table 1 Some physicochemical properties of the compounds

Compound Empirical formulae Colour mpdt (∘C) Yield ()Co(d-asp)

2

Co(C4

H8

O4

N) Lilac 217 7420Cu(d-asp)

2

Cu(C4

H8

O4

N) Blue 205 5721Mn(d-asp)

2

Mn(C4

H8

O4

N) White 304(119889) 8184Ni(d-asp)

2

Ni(C4

H8

O4

N) Green 197(119889) 6600Cd(d-asp)

2

Cd(C4

H8

O4

N) White 204(119889) 6240Na2

[Co(d-asp)2

] Na[Co(C4

H8

O4

N)] Purple gt320 6260Na2

[Cu(d-asp)2

] Na[Cu(C4

H8

O4

N)] Blue 215(119889) 8420Na2

[Mn(d-asp)2

] Na[Mn(C4

H8

O4

N)] White 301ndash303(119889) 6850Na2

[Ni(d-asp)2

] Na[Ni(C4

H8

O4

N)] Green 294(119889) 6270Na2

[Cd(d-asp)2

] Na[Cd(C4

H8

O4

N)] White 287(119889) 6960(119889) decomposition temperature

Table 2 Electronic spectra bands for the compounds

Compound Band I Band II Band III 119889-119889 Magnetic moment (BM)Aspartic acid 196 212 8231 mdashCu(asp)

2

241 259 391 628 667 247Cd(asp)

2

238 259 271 mdash 000Ni(asp)

2

232 265 mdash 517 328Co(asp)

2

mdash 259 mdash 499 517 520 535 540Mn(asp)

2

226 277 mdash 544 568shld 682 829 582Na2

[Cu(asp)2

] 226 238 259 667 220Na2

[Cd(asp)2

] 226 241 256 833 881 000Na2

[Ni(asp)2

] mdash 235 259 637 652 115Na2

[Co(asp)2

] 223 241 256 526 541 565 433Na2

[Mn(asp)2

] 223 235 265 526 541 673

asymmetric stretching frequencies were shifted to higherfrequencies compared with that of the ligand in the order CogtMngtNiwith the exception of the copper complex in whichan hypsochromic shift was observed No shift was observedfor the cadmium complex It is suggested that this arrange-ment may be as a result of the size of the metal ions [28ndash30]In some of theNa

2

[ML2

] complexes (Table 2) two bands wereobserved on coordination for the COOminus asymmetric andsymmetric stretching frequenciesThese indicate the possiblemode of coordination of aspartic acid to the central metalion via both oxygen atoms of the 120572- and 120573-carboxylate ionConsequently in these complexes aspartic acid may be saidto be tridentate an observation that is in agreement with thatobtained by previous workers [10] Hypsochromic shifts wereobserved for the ndashNH

2

frequencies on coordination for theML2

and Na2

[ML2

] complexes This indicates bond elonga-tion on coordination It therefore suggests probable squareplanar and distorted octahedral geometry for the complexesrespectively New bands in the spectra of the complexes at500ndash598 cmminus1 were assigned to (MndashN) stretching frequencyThe participation of the lone pairs of electrons on the N ofthe amino group in the ligand in coordination is supportedby these band frequencies [31] Bands in the region of 604ndash724 cmminus1 indicate the formation of MndashO bond and furthersupport the coordination of the ligand to the central metalions via the oxygen atom of the carboxylate group [29]

33 Electronic Spectra and Magnetic Moment The electronicspectra of the ligands showed three absorption bands at 196212 and 232 nm assigned as the 119899 rarr 120590lowast 119899 rarr 120587lowast and120587lowast

rarr 120587lowast transitions of the major chromophores NH

2

andCOOminus present in the ligand molecules On coordinationhowever shifts were observed in these bands in addition tod-d transitions bands (Table 3) These in conjunction withthe magnetic moment of the complexes were used to proposeprobable geometry of the complexes obtained

331 Na2[ML2] Complexes The spectrum for the copper(II)complex displayed a well resolved band at 667 nm Fig-ure 4 assigned as 2B

1g rarr2Eg transition which suggests

an octahedral geometry [32] This proposed geometry wascorroborated by its magnetic moment of 247 BM indicativeof a tetragonally distorted octahedral geometry [33] A weakband at 833 nmassigned as charge transfer bandwas observedin the spectrum for the cadmium(II) complex This wassupported by its magnetic moment of zero indicative of adiamagnetic Cd(II) complex with filled 4d orbital [32 33]The Ni(II) complex exhibited a shoulder at 637 nm and astrong band at 652 nm which were assigned to 3A

2g(F) rarr5T1g and

3A2g(F) rarr

1Eg transitions The magnetic momentof 328 BM however is suggestive of an octahedral geometry[34 35] The cobalt(II) complex gave a shoulder at 526 nm


Table 3 Relevant IR bands for the compounds

Band ]s(NH2) ]asy(COOminus) ]sy(COOminus) (cmminus1) ](MndashN) ](MndashO)Aspartic acid 3380w 1650s 1583s mdash mdashCu(asp)

2

3433m 1641w 1509w 552s 656mCd(asp)

2

3333w 1650s 1539s 549s 724sNi(asp)

2

3357w 1674s 1559s 548w 721wCo(asp)

2

3143br 1684s 1561s 566w 665mMn(asp)

2

3309w 1678m 1547w 550s 598mNa2

[Cu(asp)2

] 3238 3142br 1678s 1595m 1503s 1371s 520m 623brNa2

[Cd(asp)2

] 3025br 1687s 1532br 598s 619sNa2

[Ni(asp)2

] 3190wbr 1667sh 1547s 500m 672sNa2

[Co(asp)2

] mdash 1684s 1584w 1512s 1375s 546s 604sNa2

[Mn(asp)2

] 3357br 1686s 1542m 550s 658sasp aspartic acid w weak m medium s strong

Figure 4 UV-Vis spectrum for Na2

[Cu(asp)2

]

a strong band at 541 nm and a weak band at 565 nm typical ofa six coordinate octahedral geometry for cobalt(II) and wereattributed to 4T

1g(F) rarr4A2g(F)

4T1g(F) rarr

4T2g(F) and

4T1g(F) rarr

4T1g(F) transitions This geometry was corrob-

orated by a magnetic moment of 540 BM [34ndash36] TheMn(II) complex exhibited weak absorption bands at 526541 and 673 nm which are consistent with a six-coordinateoctahedral geometry and were assigned to 6A

1g rarr4T2g(G)

6A1g rarr

4T1g(G) and

6A1g rarr

4Eg(G) transitions its mag-netic moment of 582 BM complements this [2]

332 ML2 Complexes The spectrum for the copper(II)complex displayed two bands at 628 and 667 nm Figure 5assigned to 2B

1g rarr2Eg and 2Eg rarr

2A1g transitions The

complex exhibited a magnetic moment of 22 BM indicativeof a mononuclear copper(II) complex with 4-coordinate

Figure 5 UV-Vis spectrum for Cu(asp)2

square planar geometry [37ndash39] The cadmium complexexhibited no d-d transition band Amagneticmoment of zerocorroborates this however based on valence bond theory atetrahedral geometry is proposed and this is in agreementwith previous reports [32 39]The nickel complex exhibited awell-defined band at 517 nm assigned as 3A

2g rarr1Eg A mag-

netic moment of 115 BM was observed for this complexThisis interpreted as a low spinndashhigh spin equilibriummixture oftetrahedral-square planar complex [40] The Co(II) complexexhibited two absorption bands at 499 and 520 nm assignedas 4A2g rarr

4T2g(F) and

4A2g rarr

4T1g(F) respectively typical

for a tetrahedral geometryThis is corroborated by amagnetic


Figure 6 Mass spectrum of Mn(asp)2

Mn

N

OO

N

C

CH

C

CH

O O

minusL

O

N

C

CH

O

Q

RS

Mn

N

OO C

CH

C

CH

O O

HOOCH2C HOOCH2C

HOOCH2C

H2 H2NH2

H2

H2

CH2COOH

minusH2O

minusCOOH

minusCOOL+

mz 132

mz 319

mz 88mz 70

mz 187

mz 274

mz 132

oplus

+Mn

+CH2

Figure 7 Proposed fragmentation pattern of Mn(asp)2

moment of 433 BM [38] Bands at 544 568 and 682 for theMn(II) complex were assigned to 6A

1g rarr4T1g6A1g rarr

4Egand 6A

1g rarr4Eg transitions and a charge transfer band at

829 nm [41]

34 Mass Spectrometry The electronic impact mass spec-trum of the complex Mn(asp)

2

(Figure 6) was obtained and aprobable fragmentation pattern was proposed (Figure 7)Thespectrum showed a weak peak at mz 319 (4) which coin-cides with the calculatedmolecular ionThe fragmentation ofthe molecular ion was proposed to occur via three pathwaysQ R and S Pathway Q corresponds to the loss of 120573-COOHto give a peak atmz 274 (9) Pathway R corresponds to theextrusion of a ligand as a radical to give a peak at mz 187(42)While for pathway S themolecular ion fragments withthe ligand as a positive ionwithmz 132 (4)This ion furtherfragmentedwith the loss of COO to yield a peak atmz 88 thebase peak It also fragmented giving a peak at mz 70 (92)with the loss of a water molecule

Thus from the foregoing it was proposed that the coordi-nation mode of aspartic acid is a function of the pH at whichthe reaction was carried out as this may invariably determinethe donor atoms of the ligand available for coordination[42 43] From previous reports it has been reported thatthe participation of a particular functional group in metalbinding depends partly on its acid dissociation constant [42]In this case aspartic acid has 120572-carboxylic acid moiety withpKa of 209 and a 120573-carboxylic acid moiety with pKa of 386This implies that for the donor atoms to be readily availablefor complex formation the pH of the reactionmust fall withinthese rangesThiswas evident in the complexes formed this isbecause at pH ranges greater than 40 both the oxygen donoratoms from the 120572- and 120573-carboxylic group were available forbinding [9ndash11] It therefore acts as a tridentate ligand [9ndash11 42]

It is further suggested that energy consideration as aresult of the stability of the chelate ring also enhanced thecoordinationmode of the ligandThis is because although theNH3

+ ion has a pKa value of 982 (Figure 8) even at low pH


Table 4 Antimicrobial activities of the compounds

Microorganisms E coli P aeruginosa P vulgaris S aureus B subtilis MRSA C albicansAspartic acid 60 plusmn 02 60 plusmn 07 60 plusmn 00 60 plusmn 01 60 plusmn 01 60 plusmn 05 80 plusmn 10Cu(asp)

2

60 plusmn 00 120 plusmn 03 60 plusmn 02 120 plusmn 07 120 plusmn 00 160 plusmn 05 60 plusmn 03Cd(asp)

2

80 plusmn 02 80 plusmn 00 60 plusmn 06 110 plusmn 01 80 plusmn 03 110 plusmn 00 170 plusmn 0Ni(asp)

2

60 plusmn 05 60 plusmn 01 60 plusmn 07 60 plusmn 10 60 plusmn 09 60 plusmn 02 60 plusmn 02Co(asp)

2

60 plusmn 06 60 plusmn 01 60 plusmn 01 60 plusmn 00 60 plusmn 00 60 plusmn 08 60 plusmn 06Mn(asp)

2

80 plusmn 05 80 plusmn 08 80 plusmn 03 140 plusmn 02 200 plusmn 05 100 plusmn 03 60 plusmn 04Na2

[Cu(asp)2

] 90 plusmn 10 60 plusmn 03 100 plusmn 07 360 plusmn 08 160 plusmn 03 230 plusmn 08 160 plusmn 09Na2

[Cd(asp)2


[Ni(asp)2


[Co(asp)2


[Mn(asp)2

] 60 plusmn 07 60 plusmn 09 130 plusmn 00 60 plusmn 02 60 plusmn 07 130 plusmn 03 60 plusmn 01C 200 plusmn 04 60 plusmn 00 150 plusmn 06 200 plusmn 02 60 plusmn 09 60 plusmn 07 190 plusmn 01C Acriflavine+ Gram-positive bacteriaminus Gram-negative bacteria

O

O

O

O

HO

O

H H O

O(a) (b) (c) (d)

OH

OH OHNH3

+NH3+ NH3

+OminusOminus

NH2minusOminusO minusO

(minusNH3+)

pKa = 982pKa = 386pKa = 209

Figure 8 Coordination behaviour of aspartic acid a function of the pH of the reaction (a) In strong acid (below pH 1) net charge = +1 (b)Around pH 3 net charge = 0 (c) Around pH 6ndash8 net charge = minus1 (d) In strong alkali (above pH 11) net charge = minus2

the nitrogen atom may be used for coordination Previousstudies have shown this to be due to the strong electron-donor(basic) character of theN atomof theNH

2

group and stabilityof the chelate ring [42ndash44] This in addition is supported bythe flexibility of the amino acid ligand It was also observedthat the geometry of the complexes was not determined onlyby the ligand but the metal ions as well [13 16ndash20] This isbecause the complexes assume geometries better suited forthe metal ions resulting in the variations observed for someof the complexes

35 Antimicrobial The results obtained indicated that thecompounds exhibited a broad spectrum of activity againstthe tested bacteria and fungi strains and in some cases betteractivity compared to the standard Some of the complexesexhibited better activity compared to the ligand consequentlylending support to the chelation theory [2 26 45ndash50] Inline with previous reports the compounds exhibited bet-ter activity generally against Gram-positive bacteria Thishas been attributed to the increased hydrophobic characterof these molecules in crossing the cell membrane of themicroorganism As a consequence the utilization ratio of thecompounds is enhanced [1ndash6 26 45]

Generally the ML2

complexes exhibited better activitycompared to the Na

2

[ML2

] complexes with the exception ofthe copper and manganese complexes The better activity ofthe ML

2

complexes compared to the Na2

[ML2

] complexes insome cases may be ascribed to the enhanced lipophilicity of

the former as a result of its nonionic nature as against the pos-itively charged latter [2 26 45ndash50] The Na

2

[Cd(asp)2

] com-plex gave good activity against C albicans while Cd(asp)

2

exhibited marginal activity against the fungi (Table 4) Thisindicates the activity of the metal ion as an antifungal agentIt also points to the fact that enhanced lipophilicity as aresult of the tridentate nature of the ligand may increasethe activity of the complex [2 26 45ndash50] It is suggestedthat the size and number of chelate rings may play a rolein the enhanced activity of these compounds in this caseThe Cu(asp)

2

complex exhibited the best activity contraryto that obtained in previous report for similar coordinationcompounds [24 26 51] The Na

2

[Cu(asp)2

] exhibited goodactivity against S aureus indicating the effect of the metalion as an antimicrobial agent [51] The activity of some ofthe complexes against B subtilis MRSA Ps Aeruginosaand C Albicans (Table 4) was significantly higher than thestandard drug (119901 lt 005) This indicates their potentials asantimicrobial agents against these microbes

4 Conclusion

In this study coordination compounds of aspartic acid weresynthesized in both acidic and basic media It was concludedthat the geometry assumed by the synthesized compoundswas a function of available donor atoms of the ligandand this is dependent on the relevant pH in which thereaction was carried out The complexes exhibited a broad


spectrum of activity In some cases complexes synthesizedin basic medium exhibited better activity compared to theircounterpart complexes obtained in acidic medium This wasattributed to their enhanced lipophilicity as a result of theincreased number of chelate rings

Competing Interests

The authors declare that they have no competing interests

Acknowledgments

T O Aiyelabola is grateful to NWU for a postdoctoral fellow-ship and the Sasol Inzalo NRF fellowship

References

[1] D Kumar A Kumar and D Dass ldquoSyntheses and characteri-zation of the coordination compounds of N-(2-hydroxymeth-ylphenyl)-C-(3rsquo-carboxy-2rsquo-hydroxyphenyl)thiazolidin-4-onerdquoInternational Journal of Inorganic Chemistry vol 2013 ArticleID 524179 6 pages 2013

[2] Z H Chohan M Arif M A Akhtar and C T SupureanldquoMetal-based antibacterial and antifungal agents synthesischaracterization and in vitro biological evaluation of Co(II)Cu(II) Ni(II) and Zn(II) complexes with amino acid-derivedcompoundsrdquoBioinorganic Chemistry andApplication vol 2009Article ID 83131 13 pages 2006

[3] I Bertini H B Gray E I Stiefel and J S Valentine BiologicalInorganic Chemistry Structure and Reactivity University Sci-ence Books Sausalito Calif USA 1st edition 2007

[4] N P Farrell ldquoMetal-based chemotherapeutic drugsrdquo inTheUsesof Inorganic Chemistry inMedicineTheRoyal Society of Chemi-stry Cambridge UK 1999

[5] A F Husseiny E S Aazam and J Al Shebary ldquoSynthesischaracterization and antibacterial activity of schiff-base ligandincorporating coumarin moiety and it metal complexesrdquo Inor-ganic Chemistry vol 3 pp 64ndash68 2008

[6] N P Farrell ldquoCatalysis bymetal complexesrdquo in TransitionMetalComplexes as Drugs and Chemotherapeutic Agents B R Jamesand R Ugo Eds vol 11 p 304 Reidel-Kluwer Academic PressDordrecht Netherlands 1989

[7] R Bregier-Jarzebowska A Gasowska and L Lomozik ldquoCom-plexes of Cu(II) ions and noncovalent interactions in systemswith L-aspartic acid and cytidine-5rsquo-monophosphaterdquo Bioinor-ganic Chemistry and Applications vol 2008 Article ID 25397110 pages 2008

[8] A L Lehninger D L Nelson and M M Cox ldquoAmino acidsbuilding blocks of proteinsrdquo in Principles of Biochemistry pp71ndash95 W H FreemanCBS New York NY USA 3rd edition2005

[9] L Kryger and S E Rasmussen ldquoWalden inversion III Thecrystal structure and absolute configuration of Zn(II) (+)-aspartate trihydraterdquo ActaChimie Scandinavian vol 27 pp2674ndash2676 1973

[10] L Antolini L Menabue G C Pellacani and G MarcotrigianoldquoStructural spectroscopic and magnetic properties of dia-qua(L-aspartato)nickel(II) hydraterdquo Journal of the ChemicalSociety Dalton Transactions no 12 pp 2541ndash2543 1982

[11] T Yasui and T Ama ldquoMetal complexes of amino acids VIIICarbon-13 nuclear magnetic resonances of cobalt(III) com-plexes containing l-aspartic and l-glutamic acidsrdquo Bulletin ofthe Chemical Society of Japan vol 48 no 11 pp 3171ndash3174 1975

[12] K Bukietynska H Podsiadły and Z Karwecka ldquoComplexes ofvanadium(III) with L-alanine and L-aspartic acidrdquo Journal ofInorganic Biochemistry vol 94 no 4 pp 317ndash325 2003

[13] K Nomiya andH Yokoyama ldquoSyntheses crystal structures andantimicrobial activities of polymeric silver(I) complexes withthree amino-acids [aspartic acid (H

2

asp) glycine (Hgly) andasparagine (Hasn)]rdquo Journal of the Chemical Society DaltonTransactions no 12 pp 2483ndash2490 2002

[14] A V Legler A S Kazachenko V I Kazbanov O V PerrsquoyanovaandO FVeselova ldquoSynthesis and antimicrobial activity of silvercomplexes with arginine and glutamic acidrdquo PharmaceuticalChemistry Journal vol 35 no 9 pp 501ndash503 2001

[15] T Komiyama S Igarashi and Y Yukawa ldquoSynthesis of polynu-clear complexes with an amino acid or a peptide as a bridgingligandrdquo Current Chemical Biology vol 2 no 2 pp 122ndash1392008

[16] R F See R A Kruse andWM Strub ldquoMetal-ligand bond dis-tances in first-row transition metal coordination compoundscoordination number oxidation state and specific ligandeffectsrdquo Inorganic Chemistry vol 37 no 20 pp 5369ndash5375 1998

[17] D A Buckingham ldquoStructure and stereochemistry of coordina-tion compoundsrdquo in Inorganic Biochemistry G Eichhorn Edpp 3ndash61 Elsevier London UK 1973

[18] J J R F da Silva and R J P WilliamsThe Biological Chemistryof the Elements Oxoford University Press Oxford UK 2ndedition 1984

[19] R H Holin G W Everett Jr and A Chakravorty ldquoMetalcomplexes of schiff bases and 120573-ketoaminerdquo in Progress inInorganic Chemistry F A Cotton Ed vol 7 pp 83ndash214 Wiley-Interscience New York NY USA 3rd edition 2009

[20] D PMellor ldquoHistorical background and fundamental conceptrdquoin Chelating Agents and Metal Chelate F P Dwyer and DMellor Eds pp 1ndash48 Academic Press New York NY USA1964

[21] K Nomiya S Takahashi R Noguchi S Nemoto T Takayamaand M Oda ldquoSynthesis and characterization of water-solublesilver(I) complexes with l-histidine (H

2

his) and (S)-(minus)-2-pyrrolidone-5-carboxylic acid (H

2

pyrrld) showing a widespectrum of effective antibacterial and antifungal activitiesCrystal structures of chiral helical polymers [Ag(Hhis)]n and[Ag(Hpyrrld)]

2

n in the solid staterdquo Inorganic Chemistry vol39 no 15 pp 3301ndash3311 2000

[22] Y Hui H Qizhuang Z Meifeng X Yanming and S JingyildquoSynthesis characterization and biological activity of rare earthcomplexes with L-aspartic acid and o-phenanthrolinerdquo Journalof the Chinese Rare Earth Society vol 2 pp 3ndash4 2007

[23] P R Murray E J Baroon M A Pfaller F C Tenover and RH YolkeManual of ClinicalMicrobiology American Society forMicrobiology Washington DC USA 6th edition 1995

[24] T O Aiyelabola O Isaac and A Olugbenga ldquoStructural andantimicrobial studies of coordination compounds of phenylala-nine and glycinerdquo International Journal of Chemistry vol 4 no2 article 49 2012

[25] S Yamada J Hidaka and B E Douglas ldquoCharacterization ofthe three isomers of sodium bis(L-aspartato)cobaltate(III)rdquoInorganic Chemistry vol 10 no 10 pp 2187ndash2190 1971

[26] T O Aiyelabola I A Ojo A C Adebajo et al ldquoSynthesischaracterization and antimicrobial activities of some metal(II)


amino acidsrsquo complexesrdquo Advances in Biological Chemistry vol2 pp 268ndash273 2012

[27] D Pavia G Lampman and G Kriz ldquoInfrared spectroscopyrdquoin Introduction to Spectroscopy A Guide for Students of OrganicChemistry pp 22ndash368 Brooks and Cole New York NY USA3rd edition 2001

[28] K Nakamoto ldquoComplexes of amino acidsrdquo in Infrared andRaman Spectra of Inorganic and Coordination Compounds KNakamoto Ed pp 66ndash74 Wiley Interscience New York NYUSA 2009

[29] W Kemp ldquoInfrared spectroscopyrdquo in Organic Spectroscopy pp22ndash38 Macmillan Hong Kong 1991

[30] L J Bellamy The Infrared Spectra of Complex MoleculesChapman amp Hall London UK 1975

[31] A A Osunlaja N P Ndahil and J A Ameh ldquoSynthesis phy-sico-chemical and antimicrobial properties of Co(II) Ni(II) andCu(II) mixed-ligand complexes of dimethylglyoxime-part IrdquoAfrican Journal of Biotechnology vol 8 no 1 pp 4ndash11 2009

[32] N N Greenwood and A Earnshaw ldquoCoordination com-poundsrdquo in Chemistry of the Elements pp 1060ndash1090 Butter-worth-Heinemann Oxford UK 2nd edition 1997

[33] A A Osowole G A Kolawole and O E Fagade ldquoSynthe-sis characterization and biological studies on unsymmetricalSchiff-base complexes of nickel(II) copper(II) and zinc(II) andadducts with 221015840-dipyridine and 110-phenanthrolinerdquo Journalof Coordination Chemistry vol 61 no 7 pp 1046ndash1055 2008

[34] A B P Lever ldquoCrystal field spectrardquo in Inorganic ElectronicSpectroscopy pp 481ndash579 Elsevier London UK 1986

[35] F A Cotton G Wilkinson and C A Murillo ldquoChemistry ofthe transition elementsrdquo in Advanced Inorganic Chemistry pp420ndash1375 Wiley Interscience New York NY USA 6th edition1999

[36] W E Estes D P Gavel W E Hatfield and D J HodgsonldquoMagnetic and structural characterization of dibromo- anddichlorobis(thiazole)copper(II)rdquo Inorganic Chemistry vol 17no 6 pp 1415ndash1421 1978

[37] C J Ballhausen In An Introduction to Ligand Field TheoryMcGraw Hill New York NY USA 1962

[38] N Raman K Pothiraj and T Baskaran ldquoSynthesis characteri-zation and DNA damaging of bivalent metal complexes incor-porating tetradentate dinitrogenndashdioxygen ligand as potentialbiocidal agentsrdquo Journal of Coordination Chemistry vol 64 no24 pp 4286ndash4300 2011

[39] J R Anacona T Martell and I Sanchez ldquoMetal complexesof a new ligand derived from 23-quinoxalinedithiol and 26-bis(bromomethyl)pyridinerdquo Journal of the Chilean ChemicalSociety vol 50 no 1 pp 375ndash378 2005

[40] G LMiessler andDA TarrCoordinationCompounds PearsonPrentice Hall New York NY USA 1999

[41] A A Osowole ldquoSynthesis characterization and magnetic andthermal studies on some metal(II) thiophenyl schiff base com-plexesrdquo International Journal of Inorganic Chemistry vol 2011Article ID 650186 7 pages 2011

[42] H C Freeman ldquoMetal complexes of amino acid and peptidesrdquoin Inorganic Biochemistry G Eichhorn Ed pp 121ndash150 Else-vier London UK 1973

[43] R Murray D Granner and V Rodwell ldquoBiochemistryrdquo inHarperrsquos Illustrated Lange Medical Books P J Kennelly and VW Rodwell Eds vol 77 McGraw-Hill London UK 2006

[44] E Fakas and I Solvago ldquoMetal complexes of amino acids andpeptidesrdquo in Amino Acids Peptides and Proteins J S Davies

Ed vol 35 pp 353ndash434 Royal Society of Chemistry LondonUK 2006

[45] Z H Chohan S H Sumrra M H Youssoufi and T B HaddaldquoSynthesis and in vitro cytostatic activity of new 120573-d-arabinofuran[110158402101584045]oxazolo- and arabino-pyrimidinone derivativesrdquoEuropean Journal of Medicinal Chemistry vol 45 no 2 pp 831ndash839 2006

[46] P K Panchal H M Parekh P B Pansuriya and M N PatelldquoBactericidal activity of different oxovanadium(IV) complexeswith Schiff bases and application of chelation theoryrdquo Journal ofEnzyme Inhibition and Medicinal Chemistry vol 21 no 2 pp203ndash209 2006

[47] N Raman VMuthuraj S Ravichandran andA KulandaisamyldquoSynthesis characterisation and electrochemical behaviour ofCu(II) Co(II) Ni(II) and Zn(II) complexes derived fromacetylacetone and p-anisidine and their antimicrobial activityrdquoJournal of Chemical Sciences vol 115 no 3 pp 161ndash167 2003

[48] N Raman and A Kulandaisany ldquoSynthesis spectral redoxand antimicrobial activities of Schiff base complexes derivedfrom 1-phenyl-23-dimethyl-4-aminopyrazol-5-one and ace-toacetaniliderdquoTransitionMetal Chemistry vol 26 no 1 pp 131ndash135 2001

[49] M Shakir S Hanif M A Sherwani O Mohammad andS I Al-Resayes ldquoPharmacologically significant complexes ofMn(II) Co(II) Ni(II) Cu(II) and Zn(II) of novel Schiff baseligand (E)-N-(furan-2-yl methylene) quinolin-8-amine syn-thesis spectral XRD SEM antimicrobial antioxidant and invitro cytotoxic studiesrdquo Journal ofMolecular Structure vol 1092Article ID 21396 pp 143ndash159 2015

[50] C Jayabalaknshnan R Kervembu and K Natarajan ldquoCatalyticand antimicrobial activities of new ruthenium(II) unsymmetri-cal Schiff base complexesrdquo Transition Metal Chemistry vol 27no 7 pp 790ndash794 2002

[51] G Grass G Rensing and M Solioc ldquoMetallic copper as anantimicrobial surfacerdquo Applied and Environmental Microbiol-ogy vol 77 no 5 pp 1541ndash1547 2011

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy


Carbohydrate Chemistry

International Journal of


Journal of

Chemistry


Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of


Chromatography Research International


Applied ChemistryJournal of



Theoretical ChemistryJournal of


Journal of

Spectroscopy

Analytical ChemistryInternational Journal of


Journal of


Quantum Chemistry


Organic Chemistry International

ElectrochemistryInternational Journal of



CatalystsJournal of


CH C

O

C

OH

O

+H3N

CH2

Ominus

Figure 1

the complexes in the range 200ndash1000 nm were obtained witha Genesis 10 UV-Vis spectrophotometer solid reflectanceMelting points or decomposition temperatures (mpdt)were measured using open capillary tubes on a Gallenkamp(variable heater)melting point apparatusThe in vitro antimi-crobial properties of the complexes were determined usinga modification of the literature procedure [23] Magneticsusceptibility was obtained using a Gouy balance at roomtemperatureMass spectrometry for one of the complexeswascarried out using Fisons VG Quattro spectrophotometer

22 Syntheses of Complexes The complexes were preparedaccording to a modification of literature procedure [13 2425] The general equations for the reactions are as follows

ML2

complexesMCl2

+ 2H2

LrarrMHL2

+ 2HClNa2

[ML2

] complexesMCl2

+ 2H2

L + 2NaOHrarrNa2

[ML2

] + 2HCl + 2H2

Owhere M = Co(II) Cu(II) Mn(II) Ni(II) Cd(II) L =(+)-aspartic acid

221 ML2

Complexes A solution of (+)-aspartic acid(002M 267 g) was added to 001M of appropriate metal(II)chloride salt (162 217 243 251 and 269 g) for coppercadmium nickel cobalt and manganese respectively anddissolved in 20mL of distilled water with stirring pH rangefor the reactionswas 201ndash221Themixtures were heatedwithstirring for 2 h using a water bath The resultant solutionswere further concentrated until a scum was formed andthen cooled Crystals obtained were filtered and washed withmethanol and then dried in a vacuum oven at 60∘C

222 Na2

[ML2

] Complexes Appropriate metal(II) chloridesalt solutions (002M 331 447 488 505 and 534 g) forcopper cadmium nickel cobalt and manganese respec-tively were dissolved in minimal amount of distilled waterwith warming until a clear solution was obtained (+)-Aspartic acid (004M 542 g) was dissolved in distilled waterandwarmed over a steambath 004MNaOHwas then addedwith stirring such that the pH range of the reactionwas about8ndash10 The metal(II) solution was then added and the mixturewas refluxed for 2 h The product obtained was allowed tocool overnight with the formation of crystals The crystalsobtained were filtered washed with methanol and dried inan oven at 60∘C


[Co(asp)2

]


[Cu(asp)2

]

23 Antimicrobial Activity Using Disc Diffusion Assay Thein vitro antimicrobial screening effects of the ligand andcomplexes were evaluated using the disc diffusion method aspreviously reported [26] The strains used were Escherichiacoli NCTC 8196 Pseudomonas aeruginosa ATCC 19429Staphylococcus aureus NCTC 6571 Proteus vulgaris NCIBBacillus subtilis NCIB 3610 and one Methicillin resistant Saureus clinical isolate for bacteria and C albicans NCYC 6for fungi All the tests were performed in triplicate

3 Results and Discussion

31 Physicochemical Analysis All the complexes were insol-uble in major organic solvents however they were soluble inhot waterThemelting points or decomposition temperaturesfor the complexes are shown in Table 1Most of the complexesdecomposed before melting

32 Infrared Spectra The infrared spectrumof the free ligandexhibited a broad band at 3380 cmminus1 which was assignedto the NH

2

stretching frequency Intense bands at 1650 and1583 cmminus1 were observed and are attributed to COOminusasy andCOOminussy stretching frequencies respectively [27 28] TheCOOminus asymmetric and symmetric stretching frequencies oncoordination were shifted to higher and lower wave numbersfor Na

2

[ML2

] complexes indicating that the oxygen atom ofthe carboxylate group of the ligandwas used for coordinationFigures 2 and 3 [12 28] For the ML

2

complexes the COOminus




2

Co(C4

H8

O4


2

Cu(C4

H8

O4


2

Mn(C4

H8

O4

N) White 304(119889) 8184Ni(d-asp)

2

Ni(C4

H8

O4

N) Green 197(119889) 6600Cd(d-asp)

2

Cd(C4

H8

O4

N) White 204(119889) 6240Na2

[Co(d-asp)2

] Na[Co(C4

H8

O4


[Cu(d-asp)2

] Na[Cu(C4

H8

O4

N)] Blue 215(119889) 8420Na2

[Mn(d-asp)2

] Na[Mn(C4

H8

O4

N)] White 301ndash303(119889) 6850Na2

[Ni(d-asp)2

] Na[Ni(C4

H8

O4

N)] Green 294(119889) 6270Na2

[Cd(d-asp)2

] Na[Cd(C4

H8

O4




2

241 259 391 628 667 247Cd(asp)

2

238 259 271 mdash 000Ni(asp)

2

232 265 mdash 517 328Co(asp)

2


2

226 277 mdash 544 568shld 682 829 582Na2

[Cu(asp)2

] 226 238 259 667 220Na2

[Cd(asp)2

] 226 241 256 833 881 000Na2

[Ni(asp)2

] mdash 235 259 637 652 115Na2

[Co(asp)2

] 223 241 256 526 541 565 433Na2

[Mn(asp)2

] 223 235 265 526 541 673


2

[ML2


2


and Na2

[ML2




2





2g(F) rarr5T1g and

3A2g(F) rarr





2

3433m 1641w 1509w 552s 656mCd(asp)

2

3333w 1650s 1539s 549s 724sNi(asp)

2

3357w 1674s 1559s 548w 721wCo(asp)

2

3143br 1684s 1561s 566w 665mMn(asp)

2

3309w 1678m 1547w 550s 598mNa2

[Cu(asp)2

] 3238 3142br 1678s 1595m 1503s 1371s 520m 623brNa2

[Cd(asp)2

] 3025br 1687s 1532br 598s 619sNa2

[Ni(asp)2

] 3190wbr 1667sh 1547s 500m 672sNa2

[Co(asp)2

] mdash 1684s 1584w 1512s 1375s 546s 604sNa2

[Mn(asp)2



[Cu(asp)2

]


1g(F) rarr4A2g(F)

4T1g(F) rarr

4T2g(F) and

4T1g(F) rarr



1g rarr4T2g(G)

6A1g rarr

4T1g(G) and

6A1g rarr








2g rarr1Eg A mag-


4T2g(F) and

4A2g rarr





Mn

N

OO

N

C

CH

C

CH

O O

minusL

O

N

C

CH

O

Q

RS

Mn

N

OO C

CH

C

CH

O O

HOOCH2C HOOCH2C

HOOCH2C

H2 H2NH2

H2

H2

CH2COOH

minusH2O

minusCOOH

minusCOOL+

mz 132

mz 319

mz 88mz 70

mz 187

mz 274

mz 132

oplus

+Mn

+CH2




4Egand 6A


829 nm [41]


2








2


2


2


2


2


[Cu(asp)2


[Cd(asp)2


[Ni(asp)2


[Co(asp)2


[Mn(asp)2


O

O

O

O

HO

O

H H O

O(a) (b) (c) (d)

OH

OH OHNH3

+NH3+ NH3

+OminusOminus


(minusNH3+)

pKa = 982pKa = 386pKa = 209



2



Generally the ML2


2

[ML2


2


[ML2



2

[Cd(asp)2


2


2


2

[Cu(asp)2


4 Conclusion




Competing Interests


Acknowledgments


References














2










2


2


2












































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of




2

Co(C4

H8

O4


2

Cu(C4

H8

O4


2

Mn(C4

H8

O4

N) White 304(119889) 8184Ni(d-asp)

2

Ni(C4

H8

O4

N) Green 197(119889) 6600Cd(d-asp)

2

Cd(C4

H8

O4

N) White 204(119889) 6240Na2

[Co(d-asp)2

] Na[Co(C4

H8

O4


[Cu(d-asp)2

] Na[Cu(C4

H8

O4

N)] Blue 215(119889) 8420Na2

[Mn(d-asp)2

] Na[Mn(C4

H8

O4

N)] White 301ndash303(119889) 6850Na2

[Ni(d-asp)2

] Na[Ni(C4

H8

O4

N)] Green 294(119889) 6270Na2

[Cd(d-asp)2

] Na[Cd(C4

H8

O4




2

241 259 391 628 667 247Cd(asp)

2

238 259 271 mdash 000Ni(asp)

2

232 265 mdash 517 328Co(asp)

2


2

226 277 mdash 544 568shld 682 829 582Na2

[Cu(asp)2

] 226 238 259 667 220Na2

[Cd(asp)2

] 226 241 256 833 881 000Na2

[Ni(asp)2

] mdash 235 259 637 652 115Na2

[Co(asp)2

] 223 241 256 526 541 565 433Na2

[Mn(asp)2

] 223 235 265 526 541 673


2

[ML2


2


and Na2

[ML2




2





2g(F) rarr5T1g and

3A2g(F) rarr





2

3433m 1641w 1509w 552s 656mCd(asp)

2

3333w 1650s 1539s 549s 724sNi(asp)

2

3357w 1674s 1559s 548w 721wCo(asp)

2

3143br 1684s 1561s 566w 665mMn(asp)

2

3309w 1678m 1547w 550s 598mNa2

[Cu(asp)2

] 3238 3142br 1678s 1595m 1503s 1371s 520m 623brNa2

[Cd(asp)2

] 3025br 1687s 1532br 598s 619sNa2

[Ni(asp)2

] 3190wbr 1667sh 1547s 500m 672sNa2

[Co(asp)2

] mdash 1684s 1584w 1512s 1375s 546s 604sNa2

[Mn(asp)2



[Cu(asp)2

]


1g(F) rarr4A2g(F)

4T1g(F) rarr

4T2g(F) and

4T1g(F) rarr



1g rarr4T2g(G)

6A1g rarr

4T1g(G) and

6A1g rarr








2g rarr1Eg A mag-


4T2g(F) and

4A2g rarr





Mn

N

OO

N

C

CH

C

CH

O O

minusL

O

N

C

CH

O

Q

RS

Mn

N

OO C

CH

C

CH

O O

HOOCH2C HOOCH2C

HOOCH2C

H2 H2NH2

H2

H2

CH2COOH

minusH2O

minusCOOH

minusCOOL+

mz 132

mz 319

mz 88mz 70

mz 187

mz 274

mz 132

oplus

+Mn

+CH2




4Egand 6A


829 nm [41]


2








2


2


2


2


2


[Cu(asp)2


[Cd(asp)2


[Ni(asp)2


[Co(asp)2


[Mn(asp)2


O

O

O

O

HO

O

H H O

O(a) (b) (c) (d)

OH

OH OHNH3

+NH3+ NH3

+OminusOminus


(minusNH3+)

pKa = 982pKa = 386pKa = 209



2



Generally the ML2


2

[ML2


2


[ML2



2

[Cd(asp)2


2


2


2

[Cu(asp)2


4 Conclusion




Competing Interests


Acknowledgments


References














2










2


2


2












































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of




2

3433m 1641w 1509w 552s 656mCd(asp)

2

3333w 1650s 1539s 549s 724sNi(asp)

2

3357w 1674s 1559s 548w 721wCo(asp)

2

3143br 1684s 1561s 566w 665mMn(asp)

2

3309w 1678m 1547w 550s 598mNa2

[Cu(asp)2

] 3238 3142br 1678s 1595m 1503s 1371s 520m 623brNa2

[Cd(asp)2

] 3025br 1687s 1532br 598s 619sNa2

[Ni(asp)2

] 3190wbr 1667sh 1547s 500m 672sNa2

[Co(asp)2

] mdash 1684s 1584w 1512s 1375s 546s 604sNa2

[Mn(asp)2



[Cu(asp)2

]


1g(F) rarr4A2g(F)

4T1g(F) rarr

4T2g(F) and

4T1g(F) rarr



1g rarr4T2g(G)

6A1g rarr

4T1g(G) and

6A1g rarr








2g rarr1Eg A mag-


4T2g(F) and

4A2g rarr





Mn

N

OO

N

C

CH

C

CH

O O

minusL

O

N

C

CH

O

Q

RS

Mn

N

OO C

CH

C

CH

O O

HOOCH2C HOOCH2C

HOOCH2C

H2 H2NH2

H2

H2

CH2COOH

minusH2O

minusCOOH

minusCOOL+

mz 132

mz 319

mz 88mz 70

mz 187

mz 274

mz 132

oplus

+Mn

+CH2




4Egand 6A


829 nm [41]


2








2


2


2


2


2


[Cu(asp)2


[Cd(asp)2


[Ni(asp)2


[Co(asp)2


[Mn(asp)2


O

O

O

O

HO

O

H H O

O(a) (b) (c) (d)

OH

OH OHNH3

+NH3+ NH3

+OminusOminus


(minusNH3+)

pKa = 982pKa = 386pKa = 209



2



Generally the ML2


2

[ML2


2


[ML2



2

[Cd(asp)2


2


2


2

[Cu(asp)2


4 Conclusion




Competing Interests


Acknowledgments


References














2










2


2


2












































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of



Mn

N

OO

N

C

CH

C

CH

O O

minusL

O

N

C

CH

O

Q

RS

Mn

N

OO C

CH

C

CH

O O

HOOCH2C HOOCH2C

HOOCH2C

H2 H2NH2

H2

H2

CH2COOH

minusH2O

minusCOOH

minusCOOL+

mz 132

mz 319

mz 88mz 70

mz 187

mz 274

mz 132

oplus

+Mn

+CH2




4Egand 6A


829 nm [41]


2








2


2


2


2


2


[Cu(asp)2


[Cd(asp)2


[Ni(asp)2


[Co(asp)2


[Mn(asp)2


O

O

O

O

HO

O

H H O

O(a) (b) (c) (d)

OH

OH OHNH3

+NH3+ NH3

+OminusOminus


(minusNH3+)

pKa = 982pKa = 386pKa = 209



2



Generally the ML2


2

[ML2


2


[ML2



2

[Cd(asp)2


2


2


2

[Cu(asp)2


4 Conclusion




Competing Interests


Acknowledgments


References














2










2


2


2












































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of




2


2


2


2


2


[Cu(asp)2


[Cd(asp)2


[Ni(asp)2


[Co(asp)2


[Mn(asp)2


O

O

O

O

HO

O

H H O

O(a) (b) (c) (d)

OH

OH OHNH3

+NH3+ NH3

+OminusOminus


(minusNH3+)

pKa = 982pKa = 386pKa = 209



2



Generally the ML2


2

[ML2


2


[ML2



2

[Cd(asp)2


2


2


2

[Cu(asp)2


4 Conclusion




Competing Interests


Acknowledgments


References














2










2


2


2












































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of



Competing Interests


Acknowledgments


References














2










2


2


2












































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of






































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of

Research Article Synthesis, Characterization, and...

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