Ruthenium(II) bipyridyl complexes as photolabile caging groups for amines

The synthesis and characterization of a series of ruthenium bis(bipyridine) complexes where the inorganic moiety acts as a photolabile protecting group is described. Complexes of the type [Ru(bpy)(2)L-2](+) where bpy = 2,2'-bipyridine and L = butylamine, gamma-aminobutyric acid, tyramine, tryptamine, and serotonin were studied by nuclear magnetic resonance, cyclic voltammetry, and electronic absorption spectroscopy. In all cases, ligands are coordinated by the amine group. The complexes are stable in water for several days and deliver one molecule of ligand upon irradiation with visible light (450 nm). These properties make them suitable for their use as biological caged compounds.