Efficient DNA photocleavage by [Ru(bpy)2(dppn)]2+ with visible light.

The population and reactivity of two low-lying excited states in [Ru(bpy)(2)(dppn)](2+) (bpy = 2,2'-bipyridine, dppn = benzo[i]dipyrido[3,2-a:2',3'-c]phenazine), a weakly emissive (3)MLCT state and a long-lived ligand-centered (3)pipi* state, lead to efficient photoinduced DNA damage. Irradiation with visible light results in nearly complete DNA cleavage within 30 s (lambda(irr) > or = 455 nm), likely from the combined action of guanine oxidation and the production of reactive oxygen species derived from (1)O(2).