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 quantu...