Variation of DNA photocleavage efficiency for [(TL)2Ru(dpp)]Cl2 complexes where TL = 2,2′-bipyridine, 1,10-phenanthroline, or 4,7-diphenyl-1,10-phenanthroline

Abstract The complexes [(bpy) 2 Ru(dpp)]Cl 2 , [(phen) 2 Ru(dpp)]Cl 2 , and [(Ph 2 phen) 2 Ru(dpp)]Cl 2 (where dpp = 2,3-bis(2-pyridyl)pyrazine, bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline, Ph 2 phen = 4,7-diphenyl-1,10-phenanthroline) have been investigated and found to photocleave DNA via an oxygen-mediated pathway. These light absorbing complexes possess intense metal-to-ligand charge transfer (MLCT) transitions in the visible region of the spectrum. The [(TL) 2 Ru(dpp)] 2+ systems populate 3 MLCT states after visible light excitation, giving rise to emissions in aqueous solution centered at 692, 690, and 698 nm for TL = bpy, phen, and Ph 2 phen respectively. The 3 MLCT states and emissions are quenched by O 2 , producing a reactive oxygen species. These complexes photocleave DNA with varying efficiencies, [(Ph 2 phen) 2 Ru(dpp)] 2+  > [(phen) 2 Ru(dpp)] 2+  > [(bpy) 2 Ru(dpp)] 2+ . The presence of the polyazine bridging ligand will allow these chromophores to be incorporated into larger supramolecular assemblies.