Characterization and Effects of the pH on the Oxidation Potentials of Oxovanadium(IV)-Citrate Complex

Abstract

The electrochemical behavior of binuclear oxovanadium complex with citric acid has been studied at a glassy carbon working electrode (GCE) in aqueous 0.1 M NaClO4 as a supporting electrolyte at pH 5.9 and 8.0. It was found that (VO(Cit.))2.6H2O complex is irreversibly oxidized (VO 2+/3+ ) with anodic peak potential, Epa=+899 mV to +1260 mV vs. Ag/AgCl for scan rate 10 to 500 mVs -1 . It should be mentioned that dependence of Ipa on  1/2 is linear without any intercept, suggesting that the anodic process is diffusion controlled. It is observed that the oxidation of the complex, (VO(Cit.))2.6H2O becomes more difficult with increasing pH. IR bands at 934 cm -1 indicating the presence of oxovanadium(IV)complex. The title complex shows two absorption peaks, one in UV region at 300 nm and second peak at 567 nm in visible region in their electronic absorption spectra.