Design, synthesis, spectroscopic characterization, biological screening, and DNA nuclease activity of transition metal complexes derived from a tridentate Schiff base

A new series of transition metal complexes of Cu(II), Ni(II), Co(II), Mn(II), Zn(II), Cd(II), Hg(II), and VO(IV) have been designed and synthesized from the Schiff base derived from cinnamidene-4-aminoantipyrine and 2-aminophenol by involving the carbonyl group of 4-aminoantipyrine. The structural features have been arrived from their elemental analyses, magnetic susceptibility, molar conduction, FAB mass, IR, UV-Vis, H-1 NMR and ESR spectral studies. The data show that the complexes have composition of the ML2 type. The UV-Vis, magnetic susceptibility, and ESR spectral data of the complexes suggest an octahedral geometry around the central metal ion except the VO(IV) complex, which has a square-pyramidal geometry. The redox behavior of the copper and vanadyl complexes has been studied by cyclic voltammetry. The antimicrobial activity of the ligand and its complexes has been extensively studied on microorganisms such as Salmonella typhi, Staphylococcus aureus, Escherichia coli, Bacillus subtilis, Aspergillus niger, and Rhizoctonia bataicola. It has been found that most of the complexes have higher activities than that of the free ligand. The nuclease activity of the above metal complexes shows that the complexes cleave DNA through redox chemistry. In the presence of H2O2, the complexes are capable of cleaving calf thymus DNA.