DNA-binding, photocleavage studies of ruthenium(II) complexes with 2-(2-quinolinyl) imidazo[4,5-f][1,10]phenanthroline

Two new ruthenium complexes with [Ru(L)2(qip)]2+ (L = bpy (2,2′- bipyridine), phen (1,10-phenanthroline); qip = 2-(2-quinolinyl)imidazo[4,5-f][1,10]phenanthroline), have been synthesized and characterized by elemental analysis, ES-MS, 1H NMR. The binding properties of two complexes towards CT-DNA were investigated by various optical methods and viscosity measurements. The experiment results suggested that both Ru(II) complexes can intercalate into DNA base pairs. Strong quenching in emission intensity of two Ru(II) complexes were observed upon addition of Ag+ in the absence and presence of CT-DNA. Furthermore, the two complexes can promote cleavage of pBR322 DNA under irradiation at 365 nm, and complex 2 exhibits a stronger DNA-photocleavage efficiency than complex 1. The mechanism of DNA cleavage suggests that singlet oxygen (1O2) is likely to be the cleaving agent.

Graphical abstractTwo Ru(II) complexes, [Ru(bpy)2(qip)]2+ and [Ru(phen)2(qip)]2+, have been synthesized and characterized. Strong quenching in emission intensity of two Ru(II) complexes were observed upon addition of Ag+ in the absence and presence of CT-DNA.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Two novel Ru(II) complexes [Ru(L)2(qip)]2+ have been synthesized and characterized. ► Both complexes can interact with DNA in an intercalative mode. ► After binding to Ag+, two Ru(II) complexes exhibit strong luminescence quenching in the absence and presence of DNA. ► Both complexes can promote cleavage of pBR322 DNA under irradiation.