COPPER(II), NICKEL(II), ZINC(II), AND MOLYBDENUM(VI) COMPLEXES OF DESFERRIOXAMINE-B IN AQUEOUS-SOLUTION

Based on pH-metric, spectrophotometric, and EPR measurements, stabilit y constants and bonding modes are reported for the complexes formed in aqueous solutions of the copper(II)-, nickel(II)-, zinc(II)-, and mol ybdenum(VI)-desferrioxamine B (DFA) systems. Besides the totally depro tonated species, several protonated mononuclear complexes were found i n the copper(II)-, nickel(II)-, and zinc(II)-DFA systems, and also the dinuclear species [Cu(2)AH](2+). All three hydroxamate groups are abl e to coordinate to nickel(II) and zinc(II), but only two of them to th e copper(II). Molybdenum(VI) yields only one complex species, [MoO2(H( 2)DFA)](+). This species, which exists below pH 7, involves two hydrox amate groups coordinated to the metal ion. DFA completely prevents the formation of polyoxomolybdates below pH 7, but MoO42- and free DFA ex ist above this pH. (C) 1997 Elsevier Science Inc.