Synthesis, Characterization, DNA-Binding, and DNA-Photocleavage Properties of RuII Complexes

A new polypyridyl ligand 2-benzo[b]thiophen-3-yl-1H-1,3,7,8-tetraazacyclopenta[l]phenanthrene (BTCP) and its RuII complexes [Ru(bpy)2(BTCP)]2+ (1) (bpy = 2,2′-bipyridine), [Ru(phen)2(BTCP)]2+ (2) (phen = 1,10-phenanthroline), and [Ru(dmb)2(BTCP)]2+ (3) (dmb = 4,4′-dimethyl-2,2′-bipyridine), have been synthesized and characterized. The DNA-binding properties of the three complexes were investigated by spectroscopic methods and viscosity measurements. The results indicate that complexes 1, 2, and 3 bind to DNA by an intercalative mode and the ancillary ligands have a significant effect on the binding strengths of RuII complexes to DNA. When irradiated at 365 nm, complex 2 was found to be a more effective DNA-cleaving agent than complexes 1 and 3.