Vanadate system speciation

Elvingson, K., A.G. Baro, and L. Pettersson. 1996. Speciation in vanadium bioinorganic systems. 2. An NMR, ESR, and potentiometric study of the aqueous H+-vanadate-maltol system. Inorg. Chem. 35 3388-3393. 

Elvingson, K., M. Fritzsche, D. Rehder, and L. Pettersson. 1994. Speciation in vanadium bioinorganic systems. 1. A potentiometric and 51V NMR study of aqueous equilibria in the H+-vanadate(V)-L-a-alanyl-L-histidine system. Angew. Chem., Int. Ed. Engl. 48 878-885. 

The aqueous speciation of the vanadate-maltol system has been characterized, describing complexes which chelate the vanadium(V) in a bidentate manner (16,17).131 The formation of the corresponding vanadium(V) complex of 2-hydroxycyclohexanone (analogous to 17) has been proposed as an intermediate in the oxidation of cyclohexanone.132 Squaric acid forms a series of mono- and dinuclear complexes with vanadium(IV) and (V).133 Subtle differences in the structure are observed depending on the oxidation state of the vanadium, and are induced by the rigid ligand structure. 

Speciation diagram for the vanadate-peroxide system. c(Vtotai) = lOmM, c(H202)/c(V) = 2, ionic strength 0.15 m Na(Cl), 25°C. Species containing less than 2% of are not shown. Courtesy of L. Pettersson, Umea University, Sweden. 

The speciation in the aqueous system containing vanadate, H2O2 and L-alanyl-L-histidine (ala-his) as a ligand modelling the VFlPOs active site histidine (see also Figure 2.15) has... 

The speciation of vanadate in aqueous systems is found to be both concentration and pH dependent. The NMR spectrum of the vanadate solution contains four main peaks at —542, —564, —574 and —582 ppm, which are attributed to vanadate monomer, dimer, tetramer and pentamer, respectively [166,167]. A dynamic analysis combined with exchange rates determined by using the 2D EXSY NMR spectrum, allowed quantification of exchange pathways, and has yielded information about the kinetic stability of the vanadate oligomers (Figure 5.9) [167]. The major pathway for monomer formation is unimolecular decomposition of the dimer conversely, the major pathway for... 

A. Gorzsas, I. Andersson and L. Pettersson, Speciation in Aqueous Vanadate-Ligand and Peroxovanadate-Ligand Systems , J. Inorg. Biochem., 2009, 103, 517. 

---