nickel (ii) and iron (ii) complexes with azole derivatives: … · nickel (ii) and iron (ii)...

Hindawi Publishing CorporationInternational Journal of Inorganic ChemistryVolume 2013 Article ID 987574 6 pageshttpdxdoiorg1011552013987574

Research ArticleNickel (II) and Iron (II) Complexes with Azole DerivativesSynthesis Crystal Structures and Antifungal Activities

Emmanuel N Nfor1 Peter F Asobo2 Justin Nenwa3 Oswald N Nfor4 Julius N Njapba1

Romanus N Njong1 and Offiong E Offiong5

1 Department of Chemistry University of Buea PO Box 63 Buea SWR Cameroon2Department of Chemistry Higher Teachers Training College University of Bamenda Bambili NWR Cameroon3Department of Inorganic Chemistry Coordination Chemistry Laboratory University of Yaounde I PO Box 812 Yaounde Cameroon4Department of Veterinary Medicine National Chung Hsing University Taichung Taiwan5Department of Pure and Applied Chemistry University of Calabar PMB 1115 Calabar CRS Nigeria

Correspondence should be addressed to Emmanuel N Nfor nforemmangmailcom

Received 15 May 2013 Accepted 8 July 2013

Academic Editor Alfonso Castineiras

Copyright copy 2013 Emmanuel N Nfor et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

Two new complexes of nickel (II) with 4-amino-3 5-bis(pyridyl)-1 2 4-triazole (abpt) and iron (II) with 2-(3-phenyl-1H-pyrazole-5-yl) pyridine (phpzpy) have been synthesized and characterized by elemental analysis and IR spectroscopy The crystal structuresof the complexes have been determined by single crystal X-ray diffraction techniques In the nickel and iron complexes the ligandsare coordinated through nitrogen atoms in bidentate manner The ligands and their respective complexes have been tested fortheir antifungal activity against Aspergillus niger Aspergillus flavus and Candida albicans From the study the complexes showedenhanced activities against the tested organisms compared to the ligands

1 Introduction

Aromatic nitrogen heterocycles represent an important classof compounds which can act as ligands towards metalions [1] Azoles belong to this class and are five-memberedheterocyclic ligands containing two or more heteroatomsone of which must be nitrogen These compounds have beenpaid considerable attention due to their wide applicability inmedicine [2ndash4]

Pyrazole and triazole derivatives are subject of manyresearch studies due to their widespread potential biologi-cal activities such as antitumour [5 6] anti-inflammatory[7] antipyretic [8] antivirial [9] antimicrobial [10 11]anticonvulsant [12] antihistaminic [13] antidepressant [1415] insecticides and fungicides In coordination chemistrypyrazole-and triazole-derived ligands exhibit various coor-dination modes and have received considerable attentionfor the synthesis of transition metal complexes with variousnuclearities [16] Hereinwe report on the synthesis structural

determination and antifungal activities of Ni(II) and Fe(II)complexes of abpt and phpzpy respectively The crystalstructures of the complexes are described and compared withthose of closely related structures

2 Experimental

21 Materials and PhysicalMeasurements Elemental analysisfor carbon hydrogen and nitrogen was performed on aThermo Flash EA-1112 Series CHNS-O Elemental AnalyzerThe IR spectra were obtained from KBr pellets in the range4000ndash400 cmminus1 using a Perkin-Elmer Spectrum 100 FT-IRspectrometer

22 Single Crystal X-Ray Diffraction Analysis and Struc-ture Determination Suitable-single crystals of 1 and 2 wereselected and mounted in air onto a loop The data collectionfor 1 and 2was carried out with a Bruker DUOAPEX II CCD

2 International Journal of Inorganic Chemistry

diffractometer at 173(2)K using an Oxford cryostream 700Data reduction and cell refinement were performed usingSAINT-Plus [17ndash21] and the space group was determinedfrom systematic absences by XPREP [22] and further justifiedby the refinement results Graphite-monochromated Mo K120572(120582 = 071073 A) radiation was used in both cases The X-raydiffraction data have been corrected for Lorentz-polarizationfactor and scaled for absorption effects by multiscan usingSADABS [23] The structures were solved by direct methodsimplemented in SHELXS-97 [24] Refinement procedures byfull-matrix least-squares methods based on 1198652 values againstall reflections have been performed by SHELXL-97 [24]including anisotropic displacement parameters for all non-H atoms The positions of hydrogen atoms belonging to thecarbon atoms Csp2 were geometrically optimized by apply-ing a riding model Calculations concerning the moleculargeometry the affirmation of chosen space groups and theanalysis of hydrogen bonds were performed with PLATON[25] The molecular graphics were done with ORTEP-3[26]and Mercury (version 30) [27] The crystal parameters datacollection and refinement results for 1 and 2 are summarizedin Table 1

23 Antifungal Activity The synthesized abpt phpzpy andtheir metal complexes 1 and 2 were screened in vitro fortheir antifungal activity against three fungi Aspergillus nigerAspergillus flavus and Candida albicans and evaluated bypoisoned food technique [28 29] The molds were grown onSabouraud dextrose agar (SDA) at 25∘C for 7 days and usedas inocula DMSO was used as the negative control whilefluconazole was used as the positive controlThe experimentswere performed in triplicates Diameters of fungal colonieswere measured and expressed as percent mycelial inhibition

percent inhibition of mycelial growth = (119889119888 minus 119889119905)119889119888times 100

(1)

where dc is average diameter of fungal colony in negativecontrol sets and dt is the average diameter fungal colony inexperimental sets

24 Synthesis of Ligands The ligand 4-amino-3 5-bis(2-pyridyl)-12 4-triazole (abpt) was prepared in two steps fromcommercially available precursors as previously described[30ndash32] while its counterpart 2-(3-phenyl-1H-pyrazole-5-yl)pyridine(phpypz) was equally synthesized as previouslyreported [33]

25 Synthesis of [119873119894(119886119887119901119905)2

(119874119867)2

]1198621198971198744

2minus(1) To a solutionof 4-amino-3 5-bis(pyridyl)-124-triazole (abpt) (238mg1mmol) in methanol (20 cm3) Ni(ClO

4

)sdot6H2

O (0375mg1mmol) was added in watermethanol (1 1) solution (10 cm3)with continuous stirring for 2 hThe product was filtered andallowed to evaporate slowly at room temperature resulting theformation of dark red crystals suitable for single crystal X-raydiffraction studies after one week Yield 80 Anal Calcd C6417 H 267 N 374 Found C 6400 H 269 N 344 IR

absorption bands (KBr cmminus1) 3387s 3260s 2108m 2070s2041vs 1608s 1589s 1433 and 1088w 777s 731m 633s

26 Synthesis of [Fe (phpypz)2

(NCS)2

] (2) To a methanolicsolution (15mL) of [Fe(H

2

O)6

](ClO4

)2

(153mg 042mmol)(and a pinch of ascorbic acid) a solution of KNCS (82mg084mmol) was added in the same solvent (15mL) undernitrogen The mixture was stirred for 15min then filtered (toremove KClO

4

) via a cannula into a schlenk containing asolution of phpzpy (18mg 084mmol) in methanol Water(5mL) was added and the solution was stirred for 1 h at roomtemperature then left to evaporate under nitrogen Singlecrystal suitable for X-ray diffraction was obtained after twodays as yellow block Yield 75 Anal Calcd C 6794 H415 N 528 FoundC 6793 H 395 N 563 IR absorptionbands (KBr cmminus1) 3205sh 3053s 2084s 1615s 1571m 1510w1459w 1432m 1291w 1250w 1061w 968w 927w 772s 707w636w 471w

3 Results and Discussion

31 Antifungal Activity The ligands abpt and phpzpy theircomplexes standard drug (fluconazole) and DMSO solventwere screened separately for their antifungal activity againstAspergillus flavus Aspergillus niger and Candida albicansThe ligands were found to show antifungal activity andtheir metal complexes show enhanced activity compared tothe free ligands Of the four chemical compounds screenedfor their antifungal activity three of them showed morethan 50 inhibition of mycelial growth against the threefungal strains while one showed less than 50 mycelialgrowth against the fungi compared to the standard drugwith greater than 70 inhibition (Table 3) The overtonersquosconcept [34] and Tweedyrsquos chelation theory [35] can be usedto explain the enhancement in antifungal activity of themetalcomplexes Chelation considerably reduces the polarity of themetal ion because of partial sharing of its positive chargewith the donor group and possible 120587-electron delocalizationwithin the entire chelate ring system that is formed duringcoordination Such chelation could enhance the lipophiliccharacter of the central metal atom and hence increase thehydrophobic character and liposolubility of the complexfavouring its permeation through the lipid layers of the cellmembrane

32 Description of the Crystal Structures The structure ofcomplex 1 with the atomic numbering scheme is shown inFigure 1The bond lengths and bond angles for the complex 1are listed in Table 2 Complex 1 crystallizes in the monoclinicP21

n space group and the coordination geometry aroundthe Ni(II) center can be described as a six-coordinateddistorted octahedron where four nitrogen atoms from twobidentate abpt ligands and two oxygen atoms from watermolecule occupy the six coordination with the chlorate anionas the counter ion in the outer sphereThe average ClndashO bonddistance is 137(2) A

The NindashN1py and NindashN2trz bond length values are2105(8) A and 2039(7) A respectively while the NindashO1 bond

International Journal of Inorganic Chemistry 3

Table 1 Crystal data and structure refinement for compounds 1 and 2

Compound (1) (2)Empirical formula C20H10ClNNiO C30H22FeN2S2FW 37414 52997119879 (K) 293(2) 293(2)Space group P21n 1198622119888

Wavelength (A) 071073 071073Crystal system Monoclinic MonoclinicUnit cell dimensions119886 (A) 9937(2) 16839(3)119887 (A) 14363(3) 9671(19)119888 (A) 109218(3) 18496(6)119881 (A3) 153235(8) 285378(18)119885 4 4119863119883

(gcmminus3) 1624 1361120583 (mmminus1) 0092 0091119865(000) 532 528Crystal size (mm3) 020 times 025 times 013 020 times 020 times 025120579 range (deg) 177ndash2748 160ndash2748Index range (ℎ 119896 119897) minus1010 1312 minus2828 minus88 minus88 minus2529Reflection collected 4896 4791Independent reflections(119877int)

209501111

214400187

Datarestraintsparameter 35011224 25010187Goodness-of-fit on 1198652 0918 1034

Final 119877 indices [119868 gt 2120590 gt (119868)] 1198771

= 01435 1198771

= 005361199081198772

= 04235 1199081198772

= 01231

119877 indices (all data) 1198771

= 01604 1198771

= 008651199081198772

= 04365 1199081198772

= 01335Largest diff peak and hole (e Aminus3) 0243 and minus0275 0663 and minus0557

Figure 1 Molecular diagram of complex salt 1 with the atomnumbering scheme (hydrogen atoms are omitted for clarity)

length is 2109(6) A which are similar to those of othernickel complexes reported elsewhere [30 36 37] The NindashN

Table 2 Selected bond lengths (A) and bond angles (∘) of 1 and 2

Complex (1)Ni(1)-O(1) 2109(6) O(1)-Ni(1)-N(1) 898(3)Ni(1)-N(1) 2105(8) O(1)-Ni(1)-N(2) 904(3)Ni(1)-N(2) 2309(7) O(1)-Ni(1)-O(1) 1800(2)

N(1)-Ni(1)-N(1) 1800(3)N(1)-Ni(1)-N(2) 1008(3)N(2)-Ni(1)-N(2) 1800(3)

Complex (2)Fe(1)-N(2) 2133(2) N(2)-Fe(1)-N(1) 7366(8)Fe(1)-N(4) 2107(3) N(1)-Fe(1)-N(2) 9687(9)Fe(1)-N(1) 2250(2) N(2)-Fe(1)-N(4) 8761(1)N(4)-C(008) 1159(4) N(4)-Fe(1)-N(4) 9990(1)S(2)-C(008) 1618(4) N(4)-Fe(1)-N(1) 9090(1)N(2)-N(3) 1351(3) N(4)-Fe(1)-N(2) 8760(1)Symmetry transformations used to generate equivalent atoms for (1) 119909 119910119911 12minusz minus119909 minus119910 minus119911 12 +x 12minusy 12 +z (2) minus119909 119910 12minusz 12 +y 119911 12minusx119909 minus119910 minus119911 12 +z 12minusy


(a) (b)

Figure 2 (a) Intra- and intermolecular hydrogen bond of complex 1 (b) Packing diagram of the complex salt 1 where chlorate anions areshown in space-filling model

Table 3 Antifungal activity of synthesized compounds

Compound Mycelial growth inhibition ()A niger A flavus C albicans

abpt 542 572 556phpzpy 493 486 497[Ni(abpt)(OH2)2]ClO4 613 606 596[Fe(phpzpy)2(SCN)2] 582 578 574Fluconazole 811 777 795

distances of 2039(7) A to 2105(8) A are considerably shorterthan the NindashO1 of 2109(7) A indicating the stronger abilityof the nitrogen to bond to the Ni than the oxygen atomFurthermore the longer NindashNpy distance compared to its NindashNtrz counterpart is consistentwith other systems of this ligandtype [38]The twowatermolecules occupy the apical positionwhereas the two triazole ligands occupy the equatorial planeThe bond angles between apical axis and equatorial planein complex 1 vary from 90∘ indicating distortion of theoctahedral structureTheN1ndashNi1ndashN2bond angles varies from512(2)∘ to 792(3)∘ while theO1ndashNi1ndashN1 bond angle is 898(3)∘and O1ndashNindashN2 is 904(3)∘ Furthermore the O1ndashNindashO1 bondangle is 180(2)∘ which are all comparable to other nickel (II)complexes with similar ligands [36 37]There exists the intramolecular and intermolecular hydrogen bond in the complex1 The intra molecular hydrogen bond exists between N6ndashN5ndashH and the intermolecular bond betweenO4sdot sdot sdotO1ndashH andO3sdot sdot sdotN5ndashH as shown in Figure 2(a) The chlorate anions areheld in the vacant space between the abpt ligand wings of twocomplex cations by O3sdot sdot sdotN5ndashH and O3sdot sdot sdotO3 and O4sdot sdot sdotO1ndashH with bond distances of 287 3036 and 2309 A respectively

Figure 3 Molecular diagram of complex 2 with the atom-numbering scheme

as shown in Figure 2(b) An electrostatic interactionO3sdot sdot sdotO3with bond distance 304(2) A is observed

The structure of the complex 2 with the atom numberingscheme is depicted in Figure 3 The bond lengths and bondangles are listed in Table 2 This complex crystallizes in themonoclinic C2c space group The coordination geometryaround the Fe(II) is a six coordinate distorted octahedronwhere four nitrogen atoms from the two bidentate neutralphpzpy ligand and two nitrogen atoms from the thiocyanateligands occupy the six coordination sites The bond distanceof FendashNpy = 2250(2) A is longer than that of the FendashNpz =213(2) A as would be expected for ligands of this type [38]whereas the FendashNthio = 2107(3) A is considerably shorterthan the FendashNpz and FendashNpy counterpart due to the strongerability of the thiocyanate ion to bind the Fe in comparison


(a) (b)

Figure 4 (a) Intermolecular hydrogen bond of complex 2 (b) Packing diagram of complex 2 along the c-axis

to the neutral bidentate ligand The N4ndashC008 bond distanceis 1159(4) A and S2ndashC008 distance is 1618(4) A Theseobserved CndashN and CndashS bond length values which fall in the1133 A to 1159(4) A and 1612ndash1168(4) A range for complex2 have been reported in other thiocyanato complexes [39]

The ligand phpzpy is not completely planar The pyridyland phenyl groups are slightly twisted with respect to thepyrazole The angles between the rings py-pz = 2784(7)∘py-ph = 6351(6)∘ and pz-ph = 1997(5)∘ in the complexThe N2ndashFe1ndashN1 and N2ndashFe1ndashN4 bond angles are 7366(8)∘and 8764(1)∘ Furthermore the N4ndashFe1ndashN4 N4ndashFe1ndashN1 andN4ndashFe1ndashN2 are 999(1)∘ 909(1)∘ and 876(1)∘ respectivelyIn the crystal packing (Figure 4(a)) intermolecular hydrogenbonds C008-S1sdot sdot sdotH5 exist in the complex

4 Conclusion

Wehave synthesized and characterized by elemental analysisIR and XRD spectroscopic techniques Ni(II) and Fe(II)complexes with azole derivatives abpt and phpypz respec-tively The complexes and their ligands have been tested fortheir antifungal activity against three fungal strains A nigerA flavus and C albicans and the complexes have shownenhanced activity compared to their parent ligands

5 Further Material

Crystallographic data for the structures reported in this paperhave been deposited with Cambridge Crystallographic DataCenter as supplementary publication no CCDC-875789 and875790 Copies of the data can be obtained free of charge fromCCDC 12 Union Road Cambridge CB2 1EZ UK (fax (44)1223-336-033 e-mail depositccdccamacuk)

Acknowledgments

One of the authors Emmanuel N Nfor is thankful tothe Common wealth Scholarship Commission (CSC) forResearch Fellowship and Professor AndrewD Burrows of theDepartment ofChemistryUniversity of BathUK for hostingthe fellowship

References

[1] J Reedjik in Comprehensive Coordination Chemistry GWilkinson R D Gillard and J A McCleverty Eds vol 2Pergamon Press Oxford UK 1987

[2] D Sanglard K Kuchler F Ischer J-L Pagani M Monod andJ Bille ldquoMechanisms of resistance to azole antifungal agents inCandida albicans isolates from AIDS patients involve specificmultidrug transportersrdquo Antimicrobial Agents and Chemother-apy vol 39 no 11 pp 2378ndash2386 1995

[3] J E Sjostrom J Fryklund T Kuhler and H Larsson ldquoInvitro antibacterial activity of omeprazole and its selectivityfor Helicobacter spp are dependent on incubation conditionsrdquoAntimicrobial Agents and Chemotherapy vol 40 no 3 pp 621ndash626 1996

[4] F C Odds G Dams G Just and P Lewi ldquoSusceptibili-ties of Candida spp to antifungal agents visualized by two-dimensional scatterplots of relative growthrdquo AntimicrobialAgents and Chemotherapy vol 40 no 3 pp 588ndash594 1996

[5] H D H Showalter J L Johnson J M Hoftiezer et alldquoAnthrapyrazole anticancer agents Synthesis and structure-activity relationships against murine leukemiasrdquo Journal ofMedicinal Chemistry vol 30 no 1 pp 121ndash131 1987

[6] S A F Rostom M A Shalaby and M A El-DemellawyldquoPolysubstituted pyrazolesmdashpart 5 Synthesis of new 1-(4-chlorophenyl)-4-hydroxy-1H-pyrazole-3-carboxylic acid hy-drazide analogs and some derived ring systems A novel classof potential antitumor and anti-HCV agentsrdquo European Journalof Medicinal Chemistry vol 38 pp 959ndash974 2003

[7] A K Tewari and A Mishra ldquoSynthesis and anti-inflammatoryactivities of N4 N5-disubstituted-3-methyl-1H-pyrazolo[34-c]pyridazinesrdquo Bioorganic amp Medicinal Chemistry vol 9 pp715ndash718 2001

[8] R H Wiley and P Wiley Pyrazolones Pyrazolidones andDerivatives John Wiley and Sons New York NY USA 1964

[9] S L Janus A Z Magdif B P Erik and N Claus ldquoSynthesisof triazenopyrazole derivativesas potential inhibitors of HIV-1rdquoMonatshefte fur Chemie vol 130 pp 1167ndash1173 1999

[10] V Michon C Herve du Penhoat F Tombret J M Gillardin FLepage and L Berthon ldquoPreparation structural analysis andanticonvulsant activity of 3- and 5-aminopyrazole N-benzoylderivativesrdquo European Journal of Medicinal Chemistry vol 30no 2 pp 147ndash155 1995

[11] R Boehm and C Karow ldquoBiologically active triazolesrdquo DiePharmazie vol 36 no 4 pp 243ndash247 1981


[12] I Yildirim N Ozdemir Y Akcamur M Dincer and OAndac ldquo4-Benzoyl-15-diphenyl-1H-pyrazole-3-carboxylicacid methanol solvaterdquo Acta Crystallographica vol 61 pp256ndash258 2005

[13] D M Bailey P E Hansen A G Hlavac et al ldquo34-Diphenyl-1H-pyrazole-1-propanamine antidepressantsrdquo Journal of Medic-inal Chemistry vol 28 no 2 pp 256ndash260 1985

[14] C K Chu and S J Cutler ldquoChemistry and antiviral activitiesof acyclonucleosidesrdquo Journal of Heterocyclic Chemistry vol 23no 2 pp 289ndash319 1986

[15] S C Bahal B L Dubey N Nath and J K Srivastava ldquoSyn-thesis characterisation and fungitoxicity of the complexes ofHg(II) Cd(II) Cu(II) and Ag(I) with 3-o-tolyoxymethyl-4-aryl-5-mercapto-124-triazolerdquo Inorganica Chimica Acta vol91 pp L43ndashL45 1984

[16] M R Grimmett in Obshchaya Comprehensive Organic Chem-istry D Barton andW D Ollis Eds vol 8 Pergamon OxfordUK 1979

[17] A L Gavrilova and B Bosnich ldquoPrinciples of mononucleatingand binucleating ligand designrdquo Chemical Reviews vol 104 no2 pp 349ndash383 2004

[18] P J Steel ldquoAromatic nitrogen heterocycles as bridging ligands asurveyrdquo Coordination Chemistry Reviews vol 106 pp 227ndash2651990

[19] R Mukherjee ldquoCoordination chemistry with pyrazole-basedchelating ligands molecular structural aspectsrdquo CoordinationChemistry Reviews vol 203 pp 151ndash218 2000

[20] J Klingele S Dechert and F Meyer ldquoPolynuclear transitionmetal complexes of metal-bridging compartmental pyrazolateligandsrdquoCoordinationChemistry Reviews vol 253 no 21-22 pp2698ndash2741 2009

[21] S Trofimenko Scorpionates The Coordination Chemistry ofPolypyrazolylborate Ligands University College Press LondonUK 1999

[22] SAINT-Plus Version 712 ldquoBruker AXS Incrdquo Madison WisUSA 2004

[23] Bruker XPREP2Version 614 ldquoBrukerAXS IncrdquoMadisonWisUSA 2003

[24] G M Sheldrick SADABS University of Gottingen Germany1996

[25] G M Sheldrick ldquoA short history of SHELXrdquo Acta Crystallo-graphica A vol 64 pp 112ndash122 2008

[26] A L J Spek ldquoSingle-crystal structure validation with theprogram PLATONrdquo Applied Crystallography vol 36 pp 7ndash132003

[27] L J Farrugia ldquoORTEP-3 for Windowsmdasha version of ORTEP-III with a Graphical User Interface (GUI)rdquo Journal of AppliedCrystallography vol 30 p 565 1997

[28] K Singh Y Kumar P Puri C Sharma and K R AnejaldquoSynthesis spectroscopic thermal and antimicrobial studiesof Co(II) Ni(II) Cu(II) and Zn(II) complexes with Schiffbase derived from 4-amino-3-mercapto-6-methyl-5-oxo-124-triazinerdquoMedicinal Chemistry Research vol 21 no 8 pp 1708ndash1716 2012

[29] AW BauerWMKirby J C Sherris andM Turck ldquoAntibioticsusceptibility testing by a standardized single disk methodrdquoAmerican Journal of Clinical Pathology vol 45 no 4 pp 493ndash496 1966

[30] M H Klingele P D W Boyd B Moubaraki K S Mur-ray and S Brooker ldquoProbing the dinucleating behaviourof a Bis-bidentate ligand synthesis and characterisation of

some di- and mononuclear Cobalt(II) Nickel(II) Copper(II)and Zinc(II) complexes of 35-Di(2-pyridyl)-4-(1H-pyrrol-1-yl)-4H-124-triazolerdquo European Journal of Inorganic Chemistryvol 2006 pp 573ndash589 2006

[31] S K Mandal H J Clase J N Bridson and S Ray ldquoSynthesisstructure and electrochemistry of a novel dinuclear cobalt(II)complex containing pyrrole units an unusual reductive elec-tropolymerization of the dinuclear cobalt(II) complexrdquo Inor-ganica Chimica Acta vol 209 no 1 pp 1ndash4 1993

[32] J F Geldard and F Lions ldquoThe organic chemistry of a newweak field tridentate chelating agent 35-Di(2-pyridyl)-124-triazolerdquoThe Journal of Organic Chemistry vol 30 pp 318ndash3191965

[33] J Pons A Chadghan J Casabo A Alvarez-Larena J FrancescPiniella and J Ros ldquoSynthesis and structural characterisation ofnew binuclear Pd(II) complexes with both bridging and termi-nal pyrazolate ligandsrdquo Inorganic Chemistry Communicationsvol 3 no 6 pp 296ndash299 2000

[34] Y Anjaneyulu and R P Rao ldquoPreparation characterization andantimicrobial activity studies on some ternary complexes ofCu(II) with acetylacetone and various salicylic acidsrdquo Synthesisand Reactivity in Inorganic Metal-Organic and Nano-MetalChemistry vol 16 no 3 pp 257ndash272 1986

[35] B G Tweedy ldquoPlant extracts with metal ions as potentialantimicrobial agentsrdquoPhytopathology vol 55 pp 910ndash914 1964

[36] F S Keij R A G de Graaff J G Haasnoot and JReedijk ldquoSynthesis and co-ordination chemistry of a noveldinucleating chelating triazole ligand The crystal struc-ture bis-120583-[4-amino-35-bis(pyridin-2-yl)-124-triazole-1198731015840 120583-N1120583-N1119873

10158401015840

]-bis[aquachloro-nickel(II)] dichloride tetrahy-draterdquo Journal of the Chemical Society Dalton Transactions pp2093ndash2097 1984

[37] P J Van Koningsbruggen D Gatteschi R A G De GraaffJ G Haasnoot J Reedijk and C Zanchini ldquoIsotropic andanisotropic magnetic exchange interactions through 120583-N1N2124-triazole and 120583-sulfato bridges X-ray crystal structuremagnetic properties and single-crystal EPR study of (120583-4-amino-35-bis(pyridin-2-yl)-124-triazole-N1015840N1N 2N10158401015840)(120583-sulfato-OO1015840)[(sulfato-O)aquacopper(II)] triaquacopper(II)hydraterdquo Inorganic Chemistry vol 34 no 21 pp 5175ndash51821995

[38] M H Klingele and S Brooker ldquoThe coordination chemistryof 4-substituted 35-di(2-pyridyl)-4H-124-triazoles and relatedligands rdquo Coordination Chemistry Reviews vol 241 pp 119ndash1322003

[39] J G Małecki J Mrozinski and K Michalik ldquoStructural spec-troscopic and magnetic properties of Mn(II) Co(II) and Ni(II)complexes with 2-hydroxy-6-methylpyridine ligandrdquo Polyhe-dron vol 30 pp 1806ndash1814 2011

Copyright of International Journal of Inorganic Chemistry is the property of HindawiPublishing Corporation and its content may not be copied or emailed to multiple sites orposted to a listserv without the copyright holders express written permission However usersmay print download or email articles for individual use


diffractometer at 173(2)K using an Oxford cryostream 700Data reduction and cell refinement were performed usingSAINT-Plus [17ndash21] and the space group was determinedfrom systematic absences by XPREP [22] and further justifiedby the refinement results Graphite-monochromated Mo K120572(120582 = 071073 A) radiation was used in both cases The X-raydiffraction data have been corrected for Lorentz-polarizationfactor and scaled for absorption effects by multiscan usingSADABS [23] The structures were solved by direct methodsimplemented in SHELXS-97 [24] Refinement procedures byfull-matrix least-squares methods based on 1198652 values againstall reflections have been performed by SHELXL-97 [24]including anisotropic displacement parameters for all non-H atoms The positions of hydrogen atoms belonging to thecarbon atoms Csp2 were geometrically optimized by apply-ing a riding model Calculations concerning the moleculargeometry the affirmation of chosen space groups and theanalysis of hydrogen bonds were performed with PLATON[25] The molecular graphics were done with ORTEP-3[26]and Mercury (version 30) [27] The crystal parameters datacollection and refinement results for 1 and 2 are summarizedin Table 1

23 Antifungal Activity The synthesized abpt phpzpy andtheir metal complexes 1 and 2 were screened in vitro fortheir antifungal activity against three fungi Aspergillus nigerAspergillus flavus and Candida albicans and evaluated bypoisoned food technique [28 29] The molds were grown onSabouraud dextrose agar (SDA) at 25∘C for 7 days and usedas inocula DMSO was used as the negative control whilefluconazole was used as the positive controlThe experimentswere performed in triplicates Diameters of fungal colonieswere measured and expressed as percent mycelial inhibition

percent inhibition of mycelial growth = (119889119888 minus 119889119905)119889119888times 100

(1)

where dc is average diameter of fungal colony in negativecontrol sets and dt is the average diameter fungal colony inexperimental sets

24 Synthesis of Ligands The ligand 4-amino-3 5-bis(2-pyridyl)-12 4-triazole (abpt) was prepared in two steps fromcommercially available precursors as previously described[30ndash32] while its counterpart 2-(3-phenyl-1H-pyrazole-5-yl)pyridine(phpypz) was equally synthesized as previouslyreported [33]

25 Synthesis of [119873119894(119886119887119901119905)2

(119874119867)2

]1198621198971198744

2minus(1) To a solutionof 4-amino-3 5-bis(pyridyl)-124-triazole (abpt) (238mg1mmol) in methanol (20 cm3) Ni(ClO

4

)sdot6H2

O (0375mg1mmol) was added in watermethanol (1 1) solution (10 cm3)with continuous stirring for 2 hThe product was filtered andallowed to evaporate slowly at room temperature resulting theformation of dark red crystals suitable for single crystal X-raydiffraction studies after one week Yield 80 Anal Calcd C6417 H 267 N 374 Found C 6400 H 269 N 344 IR

absorption bands (KBr cmminus1) 3387s 3260s 2108m 2070s2041vs 1608s 1589s 1433 and 1088w 777s 731m 633s

26 Synthesis of [Fe (phpypz)2

(NCS)2

] (2) To a methanolicsolution (15mL) of [Fe(H

2

O)6

](ClO4

)2

(153mg 042mmol)(and a pinch of ascorbic acid) a solution of KNCS (82mg084mmol) was added in the same solvent (15mL) undernitrogen The mixture was stirred for 15min then filtered (toremove KClO

4

) via a cannula into a schlenk containing asolution of phpzpy (18mg 084mmol) in methanol Water(5mL) was added and the solution was stirred for 1 h at roomtemperature then left to evaporate under nitrogen Singlecrystal suitable for X-ray diffraction was obtained after twodays as yellow block Yield 75 Anal Calcd C 6794 H415 N 528 FoundC 6793 H 395 N 563 IR absorptionbands (KBr cmminus1) 3205sh 3053s 2084s 1615s 1571m 1510w1459w 1432m 1291w 1250w 1061w 968w 927w 772s 707w636w 471w

3 Results and Discussion

31 Antifungal Activity The ligands abpt and phpzpy theircomplexes standard drug (fluconazole) and DMSO solventwere screened separately for their antifungal activity againstAspergillus flavus Aspergillus niger and Candida albicansThe ligands were found to show antifungal activity andtheir metal complexes show enhanced activity compared tothe free ligands Of the four chemical compounds screenedfor their antifungal activity three of them showed morethan 50 inhibition of mycelial growth against the threefungal strains while one showed less than 50 mycelialgrowth against the fungi compared to the standard drugwith greater than 70 inhibition (Table 3) The overtonersquosconcept [34] and Tweedyrsquos chelation theory [35] can be usedto explain the enhancement in antifungal activity of themetalcomplexes Chelation considerably reduces the polarity of themetal ion because of partial sharing of its positive chargewith the donor group and possible 120587-electron delocalizationwithin the entire chelate ring system that is formed duringcoordination Such chelation could enhance the lipophiliccharacter of the central metal atom and hence increase thehydrophobic character and liposolubility of the complexfavouring its permeation through the lipid layers of the cellmembrane

32 Description of the Crystal Structures The structure ofcomplex 1 with the atomic numbering scheme is shown inFigure 1The bond lengths and bond angles for the complex 1are listed in Table 2 Complex 1 crystallizes in the monoclinicP21

n space group and the coordination geometry aroundthe Ni(II) center can be described as a six-coordinateddistorted octahedron where four nitrogen atoms from twobidentate abpt ligands and two oxygen atoms from watermolecule occupy the six coordination with the chlorate anionas the counter ion in the outer sphereThe average ClndashO bonddistance is 137(2) A

The NindashN1py and NindashN2trz bond length values are2105(8) A and 2039(7) A respectively while the NindashO1 bond






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N(1)-Ni(1)-N(1) 1800(3)N(1)-Ni(1)-N(2) 1008(3)N(2)-Ni(1)-N(2) 1800(3)



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5 Further Material


Acknowledgments


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10158401015840






nickel (ii) and iron (ii) complexes with azole derivatives: … · nickel (ii) and iron (ii)...

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