Synthesis, antibacterial, antifungal activity and interaction of CT-DNA with a new benzimidazole derived Cu(II) complex

The ligand [C16H10O2N4S2] L has been synthesized by the condensation reaction of 2-mercaptobenzimidazole and diethyloxalate. The ligand L was allowed to react with bis(ethylenediamine)CuII/NiII complexes to yield [C20H22N8S2Cu]Cl21 and [C20H22N8S2Ni]Cl22 complexes. The Ni(II) complex was synthesized only to elucidate the structure of the complex. The complexes 1 and 2 were characterized by elemental analyses, IR, NMR, EPR, UV-vis spectroscopy and molar conductance measurements. Both the complexes are ionic in nature and possess square-planar geometry. The binding of the complex 1 to calf thymus DNA was investigated spectrophotometrically. The absorption spectra of complex 1 exhibits a slight red shift with “hyperchromic effect” in presence of CTDNA. Electrochemical analysis and viscosity measurements were also carried out to ascertain the mode of binding. The complex 1 in the absence and in presence of CT DNA in aqueous solution exhibits one quasi-reversible redox wave corresponding to CuII/CuI redox couple at a scan rate of 0.2 V s−1. The shift in ΔEp, E1/2 and Ipa/Ipc values ascertain the interaction of calf thymus DNA with copper(II) complex. There is decrease in viscosity of CTDNA which indicates that the complex 1 binds to CTDNA through a partial intercalative mode. The antibacterial and antifungal studies of the [C7H6N2S], [C4H16N4Cu]Cl2, [C16H10N4S2O2] and [C20H22N8S2Cu]Cl2 were carried out against S. aureus, E. coli and A. niger. All the results reveal that the complex 1 is highly active against the bacterial strains and also inhibits fungal growth.