title: Spectrophotometric and ESR evidence for vanadium(IV) deferoxamine complexes.
abstract: Complexes of vanadium(IV), vanadyl, are reported to be formed with the trihydroxamic acid deferoxamine (H3DF+). One complex exhibits a reddish-violet color, with a major absorbance peak at 386 nm and a smaller peak at 520 nm. This complex is potentially useful for the microdetermination of vanadyl. The apparent molar absorptivity is 3.91 mM-1 cm-1, and the complex obeys Beer's law in the concentration range of 0.6-63 ppm. Electron spin resonance studies indicate the formation of two vanadyl complexes that are 1:1 in vanadyl and deferoxamine, but have two or three bound hydroxamate groups. ESR and spectrophotometric evidence indicate that the red, low pH form, involves an octahedral vanadium (4+) ion coordinated by three hydroxamate ligands. One of these hydroxamates is displaced by an oxygen at pH greater than 2.8 according to the following equilibria: VO2+ + H3DF+ in equilibrium with VIV(DF)2+ + H3O+, VIV(DF)2+ + H2O in equilibrium with VO(HDF)+ + H+, where pk2 = 2.8.
authors.affiliation: UAMS Division of Toxicology, Little Rock 72205.
authors.forename: R J
authors.initials: RJ
authors.lastname: Keller
authors.forename: J D
authors.initials: JD
authors.lastname: Rush
authors.forename: T A
authors.initials: TA
authors.lastname: Grover
mesh_terms: D003676:Deferoxamine / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D013053:Spectrophotometry; D014639:Vanadium / Q000737:chemistry*
chemical_list: D014639:Vanadium; D003676:Deferoxamine