Three complexes of the general formula [Ru(TPA)L-2] (PF6)(2) [TPA = tris(((2-pyridylmethyl)amine)], where L = pyridine (1), nicotinamide (2), and imidazole (3), were prepared and characterized spectroscopically. Xray crystallographic data were obtained for 1 and 3. Complexes 1-3 show strong absorption in the visible region and selective release of heterocycles upon irradiation with visible light. Time-dependent density functional theory calculations are consistent with the presence of singlet metal-to-ligand charge-transfer bands in the visible region in 1-3. Caged heterocycles 1-3 are highly stable in solution in the dark, including in cell growth media. Cell viability data show no signs of toxicity of 1-3 against PC-3 cells at concentrations up to 100 mu M under light and dark conditions, consistent with Ru(TPA) acting as a nontoxic and effective photocaging group for aromatic heterocycles.