VANADIUM(III) COMPLEXES WITH L-HISTIDINE IN AQUEOUS-SOLUTION

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, ML2H2, M LH2, ML2H4 and ML were observed and their stability constants were eva luated. More complex equilibria in the vanadium(III)-L-histidine syste m were observed at higher pH values, where mixed hydroxy- and/or ore-s pecies appeared in solution. At pH 6-8.5 range V2OL4 species predomina ntly exists in solution. CD spectra has confirmed the low symmetry of this species, because of the distinct splitting of T-3(1g) --> t(3)T(2 g)d-d transition of V-III. (C) 1997 Elsevier Science Ltd.