Vanadium(IV) and vanadium(V) complexes of deferoxamine B in aqueous solution.

Complex formation between oxovanadium(IV) and vanadate(V) with deferoxamine B was investigated in aqueous solution by EPR, electronic absorption spectroscopy, 51V NMR, ans pH-potentiometry. The reaction scheme implies that in very acidic media, reversible oxygen displacement occurs on the metal ion to yield nonoxo V(IV) or V(V) complexes, which exhibit distinct EPR and 51V NMR spectral features, respectively. In these species, the bare vanadium ions are coordinated to the three hydroxamic functions of the ligand. With increasing pH, oxo coordination is restored and "normal" VO(IV) and VO2(V) complexes are formed with metal bonding to one or two hydroxamic functions of the ligand.