Synthesis, structural characteristics, DNA binding properties and cytotoxicity studies of a series of Ru(III) complexes

Four related ruthenium(III) complexes, with the formula mer-[RuCl3(dmso)(N−N)] (dmso = dimethyl sulfoxide; N−N = 2,2′-bipyridine (1), 1,10-phenantroline (2), dipyrido[3,2-f:2′,3′-h]quinoxaline (3) and dipyrido[3,2-a:2′,3′-c]phenazine (4)), have been reported. Complexes 3 and 4 are newly synthesized and characterized by X-ray diffraction. The hydrolysis process of 1–4 has been studied by UV–vis measurement, and it has been found that the extension of the N−N ligands can increase the stability of the complexes. The binding of these complexes with DNA has been investigated by plasmid cleavage assay, competitive binding with ethidium bromide (EB), DNA melting experiments and viscosity measurements. The DNA binding affinity is increased with the extension of the planar area of the N−N ligands, and complex 4 shows an intercalative mode of interaction with DNA. The in vitro anticancer activities of these compounds are moderate on the five human cancer cell lines screened.