Ternary complexes of oxovanadium(IV) with L-histidine as primary ligand and some imidazoles as secondary ligands

Ternary complexes of oxovanadium(IV) with L-histidine and imidazoles have been investigated using potentiometry, UV-visible and electron paramagnetic resonance studies in aqueous medium at 25+/-1degreesC and mu=0.1M NaClO4. The experimental data have provided evidence for the following general species (A=L-histidine and B=imidazole):VO(A), VO(AH(-1)), VO(A)(B) along various hydroxy products. Stabilities of the ternary complexes follow the order: 2-methylimidazole approximate to 2-ethylimidazole > imidazole with respect to imidazoles. The order has been explained in term of electronic and molecular structure.