Reduction of vanadium(V) with ascorbic acid and isolation of the generated oxovanadium(IV) species

The interaction of sodium metavanadate and VOCl3 with ascorbic acid, one of the possible natural reducing agents of vanadium(V) to oxovanadium(IV), has been investigated. Three new VO2+ complexes could be isolated as microcrystalline powders. One of them, of composition K1.5Na0.5[VO(HAsc)(OH)3], contains ascorbic acid as a monodentate ligand. In the other two, K[VO(Diketo)(OH)] x H2O and Na3[VO(Diketo)2(OH)], the enolized form of 2,3-diketogulonic acid (one of the oxidation products of ascorbic acid), acts as a bidentate ligand. The complexes were characterized by means of electronic (absorption and reflectance) and infrared spectroscopy and magnetic susceptibility measurements. Their thermal behavior was investigated by thermogravimetric and differential thermal analyses. The interest of the investigated system in relation to vanadium detoxification is also discussed.