DNA-binding and photocleavage studies of ruthenium(II) complexes containing asymmetric intercalative ligand

A novel asymmetric ligand 2-(pyridine-2-yl)-1-H-imidazo[4,5-i]dibenzo[2,3-a:2′,3′-c]phenazine (pidbp) and its ruthenium complexes [Ru(L)2(pidbp)]2+ (L = bpy (2, 2′- bipyridine), phen (1, 10 – phenanthroline)), have been synthesized and characterized by elemental analysis, ES-MS, 1H NMR. Various methods support the conclusion that both Ru(II) complexes can intercalate into DNA base pairs. Complex [Ru(bpy)2(pidbp)]2+4 exhibits its DNA “molecular light switch” properties. Furthermore, the two complexes are efficient DNA-photocleavers under irradiation at 365 nm, and complex 5 exhibits a stronger DNA-photocleavage efficiency than complex 4. The mechanism of DNA cleavage is an oxidative process by generating singlet oxygen.

A novel asymmetric ligand and its two Ru(II) complexes, [Ru(bpy)2(pidbp)]2+ and [Ru(phen)2(pidbp)]2+, have been synthesized and characterized. And [Ru(bpy)2(pidbp)]2+ is demonstrated to be the first example of Ru(II) complexes with asymmetric ligand, as DNA “molecular light switch”.Figure optionsDownload as PowerPoint slideHighlights
► A novel asymmetric ligand and its two Ru(II) complexes [Ru(L)2pidbp]2+have been synthesized and characterized.
► The DNA-binding results suggest that both complexes can bind to DNA by intercalation.
► [Ru(bpy)2(pidbp)]2+ is the first example of Ru(II) complexes with asymmetric ligand, as DNA “molecular light switch”.
► Both complexes can promote cleavage of pBR322 DNA under irradiation.