Journal of Electroanalytical Chemistry, Vol.370, No.1-2, 203-211, 1994
Competitive Self-Assembly and Electrochemistry of Some Ferrocenyl-N-Alkanethiol Derivatives on Gold
Three ferrocenyl-alkanethiol derivatives with different functional groups linking ferrocene to an alkanethiol chain have been synthesized and characterized electrochemically in bulk solution and in self-assembled monolayer films on gold electrodes. Relative affinities of the ferrocenyl-alkanethiols and of the corresponding n-alkanethiols for the electrode surface were evaluated by the competitive self-assembly method. The affinity of the ferrocenyl-alkanethiols for the surface, relative to that of the corresponding alkanethiols, is a function of the polarity of the functional group linking ferrocene to the alkanethiol chain. In general, nonpolar linking groups (methylene) show a stronger affinity for the surface than do polar groups (carboxamides) and especially charged groups (quaternary ammonium salts). It is postulated that electrostatic effects are critically important during self-assembly. Redox potentials for the three ferrocenyl-alkanethiol derivatives scale approximately with the electron donating/withdrawing effects of the functional groups on the cyclopentadiene rings. However, redox potentials for the surface-confined molecules are consistently more positive than for the identical molecules in bulk solution.
Keywords:ELECTRON-TRANSFER KINETICS;OLIGOIMIDE MONOLAYERS;METAL-SURFACES;ORGANIC THIOLS;REDOX CENTERS;COADSORPTION;SPECTROSCOPY;SOLVENT;FUNCTIONALIZATION;VOLTAMMETRY