Phototoxicity of strained Ru(ii) complexes: is it the metal complex or the dissociating ligand?

A photochemically dissociating ligand in Ru(bpy)(2)(dmphen) Cl-2 [bpy = 2,2'-bipyridine; dmphen = 2,9-dimethyl-1,10-phenanthroline] was found to be more cytotoxic on the ML-2 Acute Myeloid Leukemia cell line than Ru(bpy)(2)(H2O)(2)(2+) and prototypical cisplatin. Our findings illustrate the potential potency of diimine ligands in photoactivatable Ru(II) complexes.