Vanadium (IV and V) complexes of reduced Schiff bases derived from the reaction of aromatic o-hydroxyaldehydes and diamines containing carboxyl groups

Abstract

The reduced Schiff bases of salicylaldehyde [and o-vanillin (o-van)] with D,L- and L-diaminopropionic acid (DPA), designated by salDPA, and L-2,4-diaminopentanoic acid [ornithine (Orn)], designated by salOrn, as well as the VIVO2+ and VVO2+ complexes of salDPA were prepared. The compounds were characterised in the solid state and in solution. The structure of H4salDPA+Cl - was determined by X-ray diffraction. Complexation of V IVO2+ and VVO2+ with salDPA and salOrn (only the VIVO system) in aqueous solution was studied by potentiometry, UV/Visible spectroscopy and circular dichroism, as well as by EPR spectroscopy for the VIVO-salDPA system and by 1H- and 51V NMR spectroscopy for the VVO 2-salDPA system. Stoichiometries and complex formation constants were determined by potentiometry at 25°C and I = 0.2 M KCl. Practically only 1:1 complexes were formed in both systems with composition (VO)LH2 and (VO)L in the VIVO-salDPA system, and with composition (VO 2)LH and (VO2)L in the VVO2-salDPA system. Spectroscopic data provided information about the most probable binding modes of each stoichiometry. © Wiley-VCH Verlag GmbH & Co. KGaA, 2006.