ELECTROCHEMISTRY AND ELECTROCHROMIC PROPERTIES OF PHENANTHROLINE-IRON(II/III) COMPLEX FILMS

New films of the iron complexes with bis((2-hydroxyphenyl)methylaminosulfonyl)bathophenanthroline(HPBP) and bis((2-aminophenyl)methylaminosulfonyl)bathophenanthroline(APBP) ligands are prepared on the electrode surfaces by electrochemical polymerization. The resulting film-coated electrode shows a well-defined reversible voltammogram corresponding to the redox reaction of the Fe(II/III) complexes and an electrochromic change from red(absorption maximum: 540 nm) to colorless. The response rate of the color change to a potential step was found to be correlated to the apparent diffusion coefficient(Dapp) for the homogeneous charge-transport process within the film. The Dapp values estimated are (3 - 4) x 10(-9)cm2s-1 for the [Fe(APBP)3] film and(1 - 2) x 10(-8) cm2s-2 for the [Fe(HPBP)3] film, respectively, by potential-step chronoamperometric and chronocoulometric methods. The result of electrochemical quartz crystal microbalance(EQCM) measurements4) and dependence of the formal potential of the metal complex of the Fe(II/III) redox couple with activity of the supporting electrolyte anion in NaClO4 aqueous solution showed that anion, cation, and solvent move simultaneously across the polymer film/solution interface during the redox reaction. A piezoelectric admittance measurement4) of the poly[Fe(APBP)3] coated quartz crystal electrode showed that the viscosity of the film is affected by the oxidation state of iron.