Comparison of the complexing processes of 1-butyl-2-hydroxymethylimidazole and 1-butyl-2-methylimidazole in aqueous solution

Abstract

The stability constants and structures of the complexes of Co^II, Ni^II, Cu^II and Zn^II with 1-butyl-2-methylimidazole (bmim) and 1-butyl-2-hydroxymethylimidazole (bhmim) in aqueous solution have been determined by potentiometric and spectrophotometric methods. The stability of transition-metal complexes of bhmim depends on the presence of the hydroxymethyl group the oxygen atom of which interacts with the metal ion. Cobalt(II) and Zn^II form both tetrahedral and octahedral species with either ligands. In the case of bhmim the additional interaction of the oxygen atom shifts the octahedron ⇌ tetrahedron equilibrium in solution towards six-co-ordination.