STRUCTURAL AND ELECTROCHEMICAL STUDIES OF DICOPPER COMPLEXES OF A BINUCLEATING LIGAND INVOLVING SULFIDES AND BENZIMIDAZOLES

The reaction of malondialdehyde with mercaptoacetic acid furnishes a t etraacid which upon condensation with 1,2-diaminobenzene gives the tet rathioethertetrabenzimidazole binucleating ligand (L). One copper(I) a nd three copper(II) complexes of this ligand have been isolated. The l atter are not stable in solution where they are reduced by the solvent or the ligand itself. An investigation of the structures of the compo unds by EXAFS and XANES techniques has shown that in the copper(I) com plex the metal is in an N2S environment of T-shaped geometry. The copp er(II) derivatives are square pyramidal and there is no sulfur atom in the tetragonal plane. This situation is in agreement with the absence of magnetic interaction between the two copper(II) ions in the oxidiz ed compounds. All complexes exchange electrons at high potentials of t he Cu(I)/Cu(II) couple in the range 0.2-0.6 V-sce.