J. Indian Chern. Soc., Vol. 88, March 2011, pp. 421-424 NOTE Structural and antimicrobial studies of some newly synthesized mixed ligand complexes of Co 11 , Ni 11 , Cu 11 and znii R. C. Sharma*, P. P. Giri and D. Kumar Department of Chemistry, Institute of Basic Sciences, Dr. B. R. Ambedkar University, Khandari Road, Agra-282 002, Uttar Pradesh, India E-mail : dev_kumar26@indiatimes.com Ma•1uscript received 12 March 2010, revised 19 July 2010, accepted 20 July 2010 Abstract : Four new mixed ligand complexes of Co 11 , Ni 11 , Cull and znH with 2-furylglyoxal-2-amino thiophenol (FGATJ>) and diphenyl amine-2-hydroxy-2'-carboxylic arid (DPHC) wrre synthesized and characterized by their melting point de- termination of recrystallised samples, running TLC for single spot, elemental analyses, molar conductance, magnetir measurements, IR, III NMR and UV spectral data. All the synthesized compounds were screened for antimicrobial ac- tivities against two bacteria, Escllerichia coli (gram -ve) and Staphylococcus aure11s (gram + ve), and two fungi, As- pergillus niger and Aspergillus flavlls. Metal complexes exhibit several fold increase in their antimicrobial activity in comparison to that of the constituting ligand fragments as determined by Serial Dilution Method. Keywords : Mixed ligand complexes, spectral studies, antimicrobial activities. Introduction Transition metals in the form of their complexes are responsible for several biological transformations and re- dox reactions in life processes 1 • They also find applica- tions in analytical 2 , industrial3.4, pharmaceuticals and medicinal 6 fields. A survey of literature reveals that the compounds having nitrogen, oxygen and sulphur as do- nor sites behave as anticancer 7 , antiviral 8 , antimicrobiaJ9 agents. In addition to above, mixed ligand complexes of metals have been reported as effective biocidal agents 1 0-12. These facts prompted us to synthesize some new mixed ligand complexes of bivalent metal ions of biological im- portance to study the combined antimicrobial activities of the ligands in conjunction with metal ions. Results and discussion The analytical data of complexes (Table 1) suggested their (1 : 1 : 1) M: L 1 : Lz stoichiometry and the conduc- tivity measurements reveal their non-electrolytical nature. The ligand FGA TP revealed characteristic IR bands at 1620 cm- 1 (>C=N), 1490 cm- 1 (furan ring breathing vibrations), 1735 cm-1 (>C=O stretching vibrations) and 2650 cm- 1 (-SH thiophenol stretching vibrations). A nega- tive shift in the band positions of >C=N and >C=O stretching frequency by 30-40 cm- 1 and formation of new bands around 540-520 cm- 1 and 450-430 cm- 1 due to M-0 and M-N bonds 1 3 respectively indicates the coor- dination of ligand to metal through oxygen and nitrogen atoms. The disappearance of the -SH stretching vibra- tions of the ligand due to deprotonation and the appear- ance of a new band around 340-320 cm- 1 • due to forma- tion of M-S bond 13 , further confirm the coordination of the ligand to the metal through sulphur atom. The ligand DPHC exhibits IR bands at 1590 cm- 1 (-NH bending vi- bration), 3580 cm- 1 (-OH phenolic) and 1680 cm- 1 (>C=O) and 3480 cm- 1 (-OH) of carboxylic group. In the IR spectra of metal complexes, the -NH band has shifted to negative side by 20-40 cm- 1 , which indicates its involvement in bonding with metal. The disappear- ance of the band due to the carboxylic proton and the development of a new band in the region 540-520 cm- 1 , indicate the deprotonation of -COOH group and its coor- dination to metal ion through oxygen forming M-0 bond. The presence of coordinated water molecules within co- ordination sphere of all complexes is supported by the appearance of broad bands in the region 3500-3400 and 840-810 cm- 1 due to stretching and bending vibrations of -OH group respectively. 1 H NMR spectra of the ligands were recorded in DMSO-d 6 solvent using TMS as an internal standard. 421