COMPARISON OF THE COMPLEXING PROCESSES OF 1-BUTYL-2-HYDROXYMETHYLIMIDAZOLE AND 1-BUTYL-2-METHYLIMIDAZOLE IN AQUEOUS-SOLUTION

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 half right over half arrow left tetrahedron equilibrium in solution towards six-co-ordination.