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 c omplex of hemin with a polymer ligand, poly(L-glutamic acid), possessi ng pendant imidazoles, and the other is a complex of hemin with a bide ntate ligand, bis-imidazolyl terephthalamide. Their electrochemical ch aracteristics were studied at an edge-plane graphite electrode (EPG) u sing voltammetric and electroreflectance (ER) methods in neutral solut ions. The ER method enabled us to determine whether or not the coordin ation of imidazole with hemin was retained in the complexes immobilize d on the EPG electrode surface. The coordination of imidazole ligands with the central iron atom of hemin in monomeric hemin-imidazole compl exes adsorbed on the electrode surface cannot be established in the ab sence of the imidazole ligands in the solution phase. In contrast, the coordination is much more stable in the novel hemin-imidazole complex es even in the absence of ligands in the solution phase.