Synthesis, characterization and DNA binding studies of two mixed ligand complexes of ruthenium(II)

Two mixed ligand complexes [Ru(bpy)2(DMHBT)]Cl2(1) and [Ru(phen)2(DMHBT)]Cl2 (2) (where DMHBT is 11,13-dimethyl-13H-4,5,9,11,14-hexaaza-benzo[b]triphenylene-10,12-dione) have been synthesized and characterized by electrospray ionization (ESI) mass, 1H-1H correlation spectroscopy (COSY), electronic spectroscopy, fluorescence spectroscopy and cyclic voltammetry. Spectroscopic titration and viscosity changes of calf thymus (CT)-DNA in the presence of incremental amount of complexes 1 and 2 clearly demonstrate that both these complexes bind intercalatively to DNA, with binding constant 2.87 ± 0.20 × 104M−1 and 1.01 ± 0.20 × 105M−1 for complexes 1 and 2, respectively. All the experimental evidences suggest that the ancillary ligand 2,2′-bipyridine (bpy) and 1,10-phenanthroline (phen) influences the intercalative binding of these complexes to DNA.