Coordination chemistry of vanadium in biological systems

Coordination chemistry of metallodrugs: insights into biological speciation from NMR spectroscopy☆

Electron spin resonance (ESR) spectroscopy and 51V nuclear magnetic resonance (NMR) spectroscopy have been used to study the interaction of vanadate with aqueous solutions of humic substances (HS) at different pH values and at different concentrations. Under acidic pH conditions, ESR spectra show that humic substances reduce vanadium(V) to vanadium(IV) without further reduction to vanadium(III). The reduced vanadium(IV) ion is bound to oxygen donor atoms, probably at carboxylic acid sites in the humic substances. 51V NMR spectra show that the VO2+ cation is immediately reduced and that the decavanadate cation decomposes to the VO2+ cation prior to reduction. The overall rate of reduction depends on both concentration and pH. There is no reduction above pH 6, which suggests that the standard reduction potential of humic substances is about +0.65 V. Near pH 7, vanadate is stabilized by binding to humic substances. As the concentration of humic substances increases, the total vanadium NMR signal intensity de...

Reaction of Vanadate with Aquatic Humic Substances: An ESR and 51V NMR Study

A large variety of oxovanadium(V) complexes, mononuclear VO2+ and VO3+ in addition to the dinuclear VO3+, of the structural type (VOL)2, (VOHL)2, VOLHQ, K(VO2HL), K(VO2H2L), or (salampr) (VO2L) {wh...

M. J. Danzitz

Papers

Vanadium-51 NMR as a probe of metal-ion binding in metalloproteins