Marked Improvement in Photoinduced Cell Death by a New Tris-heteroleptic Complex with Dual Action: Singlet Oxygen Sensitization and Ligand Dissociation

The new tris-heteroleptic complex [Ru(bpy)­(dppn)­(CH3CN)2]2+ (3, bpy = 2,2′-bipyridine, dppn = benzo[i]­dipyrido[3,2-a;2′,3′-c]­phenazine) was synthesized and characterized in an effort to generate a molecule capable of both singlet oxygen (1O2) production and ligand exchange upon irradiation. Such dual reactivity has the potential to be useful for increasing the efficacy of photo­chemo­therapy drugs by acting via two different mechanisms simultaneously. The photo­chemical properties and photo­induced cyto­toxicity of 3 were compared to those of [Ru(bpy)2­(dppn)]2+ (1) and [Ru(bpy)2­(CH3CN)2]2+ (2), since 1 sensitizes the production of 1O2 and 2 undergoes ligand exchange of the mono­dentate CH3CN ligands with solvent when irradiated. The quantum yield of 1O2 production was measured to be 0.72(2) for 3 in methanol, which is slightly lower than that of 1, Φ = 0.88(2), in the same solvent (λirr = 460 nm). Complex 3 also undergoes photo­induced ligand exchange when irradiated in H2O (λirr = 400 nm), but with a low quantum efficiency (