Spectroscopic, in vitro antibacterial, and antifungal studies of Co(II), Ni(II), and Cu(II) complexes with 4-chloro-3-coumarinaldehyde Schiff bases

A series of metal complexes ML2 center dot 2H(2)O [M = Co(II), Ni(II), and Cu(II)] have been synthesized with Schiff bases derived from 3-substituted-4-amino-5-mercapto-1,2,4-triazole and 4-chloro-3-coumarinaldehyde. The structures of these metal complexes have been proposed from elemental analyses, spectral (IR, UV-Vis, FAB-mass, ESR, and fluorescence), magnetic, and thermal studies. Low molar conductance values in DMF indicate that the metal complexes are nonelectrolytes. Cyclic voltammetric studies suggested that the Ni(II) and Cu(II) complexes are single-electron transfer quasi-reversible. The Schiff bases and their metal complexes have been screened for in vitro antibacterial (Escherichia coli, Staphylococcus aureus, Bacillus subtilis, and Salmonella typhi) and antifungal activities (Candida albicans, Cladosporium, and Aspergillus niger) by the minimum inhibitory concentration method. The Schiff base I and its Co(II) and Ni(II) complexes exhibit DNA cleavage activity on isolated DNA of S. aureus and A. niger.