Vanadium(III) complexes with L-histidine in aqueous solution

Abstract

Complex compounds of vanadium(III) with L-histidine were studied using absorption, CD and potentiometric measurements in aqueous solutions. In solutions at pH 2–4.5 consecutive mononuclear species MLH, ML 2H 2, MLH 2, ML 2H 4 and ML were observed and their stability constants were evaluated. More complex equilibria in the vanadium(III)-L-histidine system were observed at higher pH values, where mixed hydroxy- and/or oxo-species appeared in solution. At pH 6–8.5 range V 2OL 4 species predominantly exists in solution. CD spectra has confirmed the low symmetry of this species, because of the distinct splitting of 3 T 1 g → 3 T 2 g d-d transition of V III.