SYNTHESIS, CHARACTERIZATION AND BIOLOGICAL STUDIES OF RUTHENIUM (II) COMPLEXES OF SUBSTITUTED 2-{4, 5-BIS[(E)-2-PHENYLETHENYL]-1H-IMIDAZOL-2-YL}-1H-BENZIMIDAZOLE

Ruthenium(II) complexes of the type [Ru(bpy) 2(L)](PF6)2, where L= 2-{4,5-bis[(E)-2-phenylethenyl]-1H-imidazol-2-yl}-1H-benzimidazole (1), 2-{4,5-bis[(E)-2-(4-chlorophenyl)ethenyl]-1H-imidazol-2-yl}-1H-benzimi-dazole (2), 2-{4,5-bis [(E)-2-(4-fluorophenyl) ethenyl]-1H-imidazol-2-yl} -1H-benzimidazole (3), 2-{4 ,5-bis[(E)-2- (4-methylphenyl) ethenyl] -1H-imidazol-2-yl }-1H-benzimidazole (4), 2-{4, 5-bis[(E)-2-(4-methoxyphenyl) ethenyl]-1H-imidazol-2-yl}-1H-benzimidazole (5) have been synthesized and characterized by elemental analyses and  spectral (IR, UV-vis, NMR, ESI-MS) techniques. The redox behavior of the complexes has been studied by cyclic and differential pulse voltammetry. In acetonitrile solution, all the complexes exhibit characteristic metal to ligand charge transfer (MLCT) absorptions and ligand-based transitions. The complexes showed efficient DNA cleavage activity in the presence of light at the wavelength of 480 nm. The complexes are also able to cleave supercoiled pUC19 plasmid DNA via guanine base oxidation in a concentration-dependent manner. In-vitro cytotoxic activity of the complexes shows that complex 1 has better anticancer activity against MCF7 human breast cancer cells with an IC₅₀ value of 7.9 µM. The antimicrobial activities of the ligand and their metal complexes were screened by agar diffusion method and found that the metal complexes have higher antimicrobial activity than the free ligand.