The synthesis, characterization, and water oxidation activity of mononuclear ruthenium complexes with tris(2-pyridylmethyl)amine (TPA), tris(6-methyl-2-pyridylmethyl)amine (Me(3)TPA), and a new pentadentate ligand N,N-bis(2-pyridinylmethyl)-2,2'-bipyridine-6-methanamine (DPA-Bpy) have been described. The electrochemical properties of these mononuclear Ru complexes have been investigated by both experimental and computational methods. Using Cent as oxidant, stoichiometric oxidation of water by [Ru(TPA) (H2O)(2)](2+) was observed, while Ru(Me(3)TPA)(H2O)(2)](2+) has much less activity for water oxidation. Compared to [Ru(TPA)(H2O)(2)](2+) and [Ru(Me(3)TPA)(H2O)(2)](2+), [Ru(DPA-BpY)(H2O)](2+) exhibited 20 times higher activity for water oxidation. This study demonstrates a new type of ligand scaffold to support water oxidation by mononuclear Ru complexes.