Reduction of vanadium(V) by L-ascorbic acid at low and neutral pH: kinetic, mechanistic, and spectroscopic characterization.
L-Ascorbic acid interacts with vanadium(V) over the pH range of 0.4-7.0 to form three different coordination complexes. Both inner- and outer-sphere electron-transfer pathways are proposed to form vanadium(IV) complexes with L-ascorbate or dehydroascorbate, respectively. Effects of the pH on the coordination of L-ascorbic acid to the vanadium(V) center were observed and are presumably related to the speciation of the vanadium(V) ion. Three vanadium(IV) complexes were observed using ambient-temperature electron paramagnetic resonance spectroscopy. Two of these complexes are proposed to be vanadium(IV) L-ascorbate complexes, and one is consistent with a vanadium(IV) dehydroascorbic acid complex proposed earlier. These reduction reactions will occur under physiological conditions and could be important to the reduction of vanadium(V)-containing coordination complexes used as insulin-enhancing agents for treatment of diabetes.
Department of Chemistry and Biochemistry, New Mexico State University, Las Cruces, 88003, USA.
Patricia C
PC
Wilkins
Michael D
MD
Johnson
Alvin A
AA
Holder
Debbie C
DC
Crans
D001205:Ascorbic Acid / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D010084:Oxidation-Reduction; D014639:Vanadium / Q000737:chemistry*
D014639:Vanadium; D001205:Ascorbic Acid