Unidirectional Electron Transfer at Self-Assembled Monolayers of 11-Ferrocenyl-1-undecanethiol on Gold

Abstract The electron-exchange reaction between the ferrocenyl group of self-assembled monolayers of 11-ferrocenyl-1-undecanethiol on gold electrodes and Fe(III) species in solution is studied. The monolayer acts as an effective electron-transfer mediator for the reduction of Fe(ClO4)3 but inhibits the oxidation of Fe(ClO4)2 in HClO4 and NaClO4 solution. This behavior is also observed in HClO4 solutions containing FeIII(edta) but only when the concentration of HClO4 is higher than 0.5 M. Absorption spectra and spectroelectrochemical and electrochemical measurements show that FeIII(edta) dissociates in highly acidic solutions and generates Fe3+aq, which acts as an electron-accepting species.