Metal complexes of the type ML 1 L 2 [M=Cu(II), Ni(II), and Co(II), L 1 =α,α'-dipyridyl(dipy.), L 2 =2-hydroxybenzalidine anthranilic acid (HBAA)] have been synthesized by using α,α'-dipyridyl(dipy.), 2-hdroxybenzalidine anthranilic acid (HBAA) and metal(II) acetate. The resulting mixed ligand metal complexes have been characterized on the basis of elemental analysis, IR-spectra, electronic spectra, magnetic susceptibilities and molar conductance measurements. The antifungal and antibacterial activities of ligands and there metal complexes have been screened against Aspergillus flavus, Aspergillus fumigatus, Aspergillus niger, Escherichia coli and Staphylococcus aureus.

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Heterometallic metal sulphur assemblies containing coinage metals and molybdenum as well as tungsten have already been studied in prebiotic condition of H2S and carcinogenic solvent like DMSO and DMF. Recently an attempt has been made to study the similar system under eco-friendly system using green–chemistry technique. The products were characterized on the basis of chemical and spectroscopic studies under a mimicking approach to a synthetic model system relevant to copper-molybdenum antagonism.

For the first time the conversion of trimeric {M3S4} 4+ to tetrameric (M4S4} 4+ core has been made for molybdenum complex. The complex, K5[Mo3S4(CN)9] (1) on using with strong reducing agent transformed into K8[Mo4S4(CN)12] (2) in near quantitative yield. The diamagnetic complex (1) containing {Mo3} 6 core can accommodate two electrons in its non bonding molecular orbital 2a1 under reducing environment to give a complex ion [Mo3S4(CN)9] 7with [Mo3] 8 electronic configuration. This reduced species undergoes re-oxidation by atmospheric air to give back the original compound with [Mo3] 6 core via a partially oxidized an intermediate species [Mo3S4(CN)9] 6with [Mo3] 7 core shows a characteristic EPR signal. However, under drastic reducing condition, the two electrons reduced species [Mo3S4(CN)9] 7with [Mo3] 8 core accommodate the next coming electron to its antibonding 2e orbital and thus achieve an unstable tri-nuclear [Mo3(III)] 9 core, where each metal centre has been reduced by one electron. The highly unstable and super reduced species [Mo3S4(CN)9] 8with [Mo3(III)] 9 configuration undergoes core transformation from cuboidal trinuclear [Mo3(IV)S4] 4+ to the cubane type tetranuclear core [Mo4(III)S4] 4+ of [Mo4S4(CN)12] 8complex ion. The corresponding tungsten-analogue though responses this reduction, but quickly oxidizes back to the starting material during work-up procedure.

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