Asymmetric metal complex as an active material of a flow battery

An asymmetrical metal complex comprising a metal center coordinated with between two and six hydrophilic ligands, wherein at least one of said hydrophilic ligands is chemically different than the other said hydrophilic ligands, and a cation selected from sodium, potassium, lithium, magnesium, calcium, pyridinium, imidazolium, and ammonium, wherein the metal center is selected from iron, cobalt, titanium, vanadium, chromium, manganese, nickel, copper, aluminum, and zinc, and wherein a first ligand of the between two and six hydrophilic ligands is 2,2′-bipyridine-4,4′-dicarboxylic acid (Dcbpy), and where a second ligand of the between two and six hydrophilic ligands is cyanide.