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

The ligand [C(16)H(10)O(2)N(4)S(2)] L has been synthesized by the condensation reaction of 2-mercaptobenzimidazole and diethyloxalate. The ligand L was allowed to react with bis(ethylenediamine)Cu(II)/Ni(II) complexes to yield [C(20)H(22)N(8)S(2)Cu]Cl(2)1 and [C(20)H(22)N(8)S(2)Ni]Cl(2)2 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 Cu(II)/Cu(I) redox couple at a scan rate of 0.2 V s(-1). The shift in DeltaE(p), E(1/2) and I(pa)/I(pc) 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 [C(7)H(6)N(2)S], [C(4)H(16)N(4)Cu]Cl(2,) [C(16)H(10)N(4)S(2)O(2)] and [C(20)H(22)N(8)S(2)Cu]Cl(2) 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.