Solution chemistry of vanadium-(IV) and -(V) with the bidentate ligand 1,2-dimethyl-3-hydroxy-4(1H)-pyridinone: Relevance to the treatment of diabetes

1,2-Dimethyl-3-hydroxy-4(1H)-pyridinone (HL) forms an unusually wide range of oxo, hydroxy and non-oxo complexes with vanadium(IV) and vanadium(V) in aqueous solution; the tris non-oxo vanadium(IV) complex [V(IV)L(3)](+) is the first such monocationic complex to be studied in aqueous solution and the monocationic tris hydroxyvanadium(V) complex [V-V(OH)L(3)](+) is the first such species to be reported; the neutral his complex [V-V(O)(OH)L(2)] is of physiological significance in the treatment of diabetes.