VOLTAMMETRY AT 115-K 180-K FOR SELF-ASSEMBLED FERROCENE-TAGGED ALKANETHIOL MONOLAYERS ON GOLD AND SILVER ELECTRODES IN BUTYRONITRILE ETHYL CHLORIDE SOLVENT

We report cyclic voltammetry from 115 to 180 K in butyronitrile/ethyl chloride solvent for monolayer films of ferrocene-terminated alkanethiols chemisorbed on gold electrode surfaces. The alkyl spacers between thiol and ferrocene contained 4, 8, and 12 methylene units, and the ferrocene moieties were diluted with alkanethiols of equal chain length during self-assembly of the monomolecular films onto the gold electrodes. The self-assembled ferrocene films display highly stable voltammetry at low temperatures. The magnitudes of the voltammetric peak potential separations (DELTAE(peak)) are dominated by slow electron-transfer kinetics as opposed to uncompensated solution resistance. Qualitatively, the electron-transfer rates decrease with decreasing temperature and with increasing alkyl chain length. The ferrocene alkanethiols retain some degree of order and enforcement of a spacing between the electrode and the ferrocene sites in spite of their use in a non-water medium. We also report the voltammetry of ferrocene alkanethiol monolayers chemisorbed on silver electrodes at 170 K and below, which is kinetically separated from oxidation of the silver substrate.