Speciation in peroxovanadate systems
2003 (English)In: Coordination Chemistry Reviews, Vol. 237, no 1-2, 77-87 p.Article in journal (Refereed) Published
Detailed and thorough potentiometric and 51V-NMR spectroscopic investigations of H+–H2VO4−–H2O2–Ligand systems have been performed at 25 °C in 0.15 M Na(Cl) ionic medium. Extensive ranges of vanadate, hydrogen peroxide and ligand concentration and of pH have been covered. The medium was chosen to represent the physiological conditions in human blood. The computer program , designed to treat different types of data simultaneously, has been used to establish the entire speciation in the systems. Before studying systems containing the ligand (L), the complete speciation in the subsystem H+–H2VO4−–H2O2 must be known under the same experimental conditions. The formation constants in this subsystem have earlier been determined and it was found that hydrogen peroxide interacts with vanadate in the whole pH range studied (0.5–10.5). In all, 10 peroxovanadate species were identified and diperoxovanadate species were found to be exceptionally stable at physiological pH. The ligands studied so far include imidazole (Im), -α-alanyl--histidine (Ah), -α-alanyl--serine (As), picolinic acid (Pi), and -(+)-lactic acid (La). In these five systems, as many as 3, 8, 6, 8, and 5 different peroxovanadate—L species (isomers included) were identified. A feature common to all these systems is that V(H2O2)2L species are formed at physiological pH. Notably, the 51V chemical shift values of diperoxovanadate moieties are always found in the range −670 to −770 ppm, and those of monoperoxovanadate from −540 to −670 ppm. The equilibrium conditions are illustrated in distribution diagrams and the effectiveness of the different ligands as complexation agents are compared. In the case of diperoxovanadate complexes, ligands with aromatic nitrogen (Im, Pi, Ah) are the most effective, the one with both aliphatic nitrogen and oxygen (As) is less effective, and the one with oxygen only (La) is the least preferred.
Place, publisher, year, edition, pages
2003. Vol. 237, no 1-2, 77-87 p.
Potentiometry, 51V-NMR, Speciation, Bioinorganic chemistry, Insulin-mimetic activity, Peroxovanadate complexes
IdentifiersURN: urn:nbn:se:umu:diva-9294DOI: 10.1016/S0010-8545(02)00223-0OAI: oai:DiVA.org:umu-9294DiVA: diva2:148965