An electroreflectance study of novel hemin-imidazole complexes at a pyrolytic graphite electrode

Two types of novel hemin-imidazole complexes were prepared: one is a complex of hemin with a polymer ligand, poly(l-glutamic acid), possessing pendant imidazoles, and the other is a complex of hemin with a bidentate ligand, bis-imidazolyl terephthalamide. Their electrochemical characteristics were studied at an edge-plane graphite electrode (EPG) using voltammetric and electroreflectance (ER) methods in neutral solutions. The ER method enabled us to determine whether or not the coordination of imidazole with hemin was retained in the complexes immobilized on the EPG electrode surface. The coordination of imidazole ligands with the central iron atom of hemin in monomeric hemin-imidazole complexes adsorbed on the electrode surface cannot be established in the absence of the imidazole ligands in the solution phase. In contrast, the coordination is much more stable in the novel hemin-imidazole complexes even in the absence of ligands in the solution phase.