Spectroscopic, DNA cleavage and antimicrobial studies of Co(II), Ni(II) and Cu(II) complexes of sulfur donor Schiff bases

A series of Co(II), Ni(II) and Cu(II) complexes of the type ML2 of Schiff bases derived from methylthiosemicarbazide and isatin/chloroisatin have been synthesized. Schiff bases exhibit thiol–thione tautomerism wherein sulfur plays an important role in the coordination. In view of analytical, spectral (IR, NMR, UV-vis, ESR, FAB-Mass) and magnetic studies, it has been concluded that all the metal complexes possess octahedral geometry. The measured molar conductance values in DMF indicate that the complexes are non-electrolytes in nature. The redox behaviors of the metal complexes are investigated by using cyclic voltammetry. The Schiff bases and their metal complexes have been screened for their antibacterial (Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and Salmonella typhi) and antifungal activities (Aspergillus niger, Aspergillus flavus and Cladosporium) by the minimum inhibitory concentration method. The DNA cleavage studies showed the cleavage of DNA by the agarose gel electrophoresis method.