Synthesis, DNA-binding and DNA-photocleavage properties of ruthenium(II) mixed-polypyridyl complex [Ru(tbz)2(dppz)]2+

A new ruthenium(II) complex [Ru(tbz)2(dppz)]2+ (tbz = 2-(4′-thiazolyl)benzimidazole, dppz = dipyrido-[3,2-a:2′,3′-c]phenazine) has been synthesized and characterized by elemental analysis, electrospray mass spectra and 1H NMR. The DNA-binding properties of the complex with calf thymus DNA was investigated by spectroscopic and viscosity measurements. The results suggest that the complex binds to DNA via an intercalative mode. Moreover, the complex has been found to promote the photocleavage of plasmid DNA pBR322 under irradiation at 365 nm. The mechanism studies reveal that singlet oxygen 1O2 plays a significant role in the photocleavage.