Synthesis, characterization and electrochemical studies of mixed ligand complexes of ruthenium(ii) with DNA

Two mixed ligand complexes of ruthenium(ii) Ru(bzimpy)(bpy)(OH(2))](2+) (1) and Ru(bzimpy)(phen)(OH(2))](2+) (2) have been synthesized and characterized by FAB mass, (1)H NMR, cyclic voltammetry and spectroelectrochemical measurements. Controlled potential electrolysis of these complexes results in the conversion of ruthenium(ii) to ruthenium(iii) at 0.6 V and ruthenium(iii) to ruthenium(iv) at 0.8 V vs. SCE. The binding constant of these complexes with DNA has been determined electrochemically and found to be (3.58 +/- 0.25) x 10(4) and (2.87+/- 0.2) x 10(4) M(-1). Viscosity measurements suggest that these complexes bind with DNA through intercalation. Such intercalative binding to DNA has been found to induce chirality to the two complexes. Electrochemically generated ruthenium(iv) species of these complexes have been found to bring about oxidative cleavage in DNA.