Vanadium(III) binding strengths of small biomolecules*
Péter Buglyó, Eszter Márta Nagy, and Imre Sóvágó
University of Debrecen, Department of Inorganic and Analytical Chemistry, P.O. Box 21, H-4010 Debrecen, Hungary
Abstract: The hydrolysis of vanadium(III) and the complex formation reactions between V(III) and weakly coordinating [glycine (GLY), DL-aspartic acid (ASP), D-penicillamine (PEN), DL-histidine (HIS)] or strongly coordinating [N,O] donor [picolinic (PIC) or 6‑methylpicolinic acid (MePIC)] and [O,O] donor [maltol (MALT), 1,2-dimethyl-3-hydroxy-4-(1H)-pyridinone (DHP), tiron (TIR)] ligands were studied at 25.0 °C and an ionic strength of 0.20 M (KCl) in aqueous solution using combined pH-potentiometric and UV-vis spectroscopic techniques. Although some interaction between the amino acids and V(III) was found, we could not obtain reliable models for these systems owing to the intensive hydrolysis of the metal ion and the formation of polynuclear hydroxo complexes. With pyridine carboxylates or [O,O] donor ligands 1:1, 1:2 (in the latter case, also 1:3 species) were found to be present as major complexes in solution. The similarities and differences in binding V(III) by these ligands are discussed.
Keywords: Vanadium(III); insulin mimetic complex; complex equilibria; picolinate; deferriprone; maltol; speciation.
*Paper based on a presentation at the 4th International Symposium on Chemistry and Biological Chemistry of Vanadium, 3-5 September 2004, Szeged, Hungary. Other presentations are published in this issue, pp. 1497-1640.