Interaction of vanadium(III) with imidazole carboxylic acids

Complex formation between vanadium(III) and several imidazole carboxylic derivatives (urocanic acid, imidazole-4-carboxylic and imidazole-4,5-dicarboxylic acid) was studied using pH-potentiometric and spectroscopic (UV–Vis absorption and fluorescence) methods. The results show that urocanic acid is a weak ligand in aqueous solution and hydrolysis of vanadium(III) effectively competes with the complexation processes. Imidazole mono and di-carboxylate are relatively stronger donor (N,O) ligands and are able to prevent, to some degree, the hydrolysis processes. The main complex species in the vanadium(III)–imidazole-4,5-dicarboxylic acid system is the dinuclear μ-oxo bridged V₂OL₂ species.