A COMPARATIVE ELECTROCHEMICAL STUDY OF THE COADSORPTION OF BIS-[10-(FERROCENYLCARBONYL) DECYL] DISULFIDE AND 10-FERROCENYLCARBONYLDECANETHIOL WITH LINEAR ALKANE DISULFIDE AND ALKANETHIOL COMPOUNDS ON VAPOR-DEPOSITED GOLD SURFACES

The competitive adsorption of bis-[10-(ferrocenylcarbonyl)decyl] disulfide (I) with n-octanethiol, n-dodecanethiol and n-hexa-decanethiol, and with di-n-dodecyl disulfide and 10-ferrocenylcarbonyldecanethiol (II) with n-dodecanethiol was investigated on vapor-deposited gold films in acetonitrile solutions. The resulting self-assembled monolayers were probed in aqueous HClO4 using cyclic voltammetry. Adsorption isotherm data for all the compounds examined in this study were in good agreement with the coupled Langmuir isotherm model recently proposed by Rowe and Creager. Electrochemically identical mixed monolayers with the same (within experimental error) equilibrium surface coverage Gamma(Fc) of ferrocenyl thiolate were obtained from solutions of I + n-dodecanethiol, I + di-n-dodecyl disulfide and II + n-dodecanethiol, provided that the mole fraction of ferrocene moieties X(Fc) was the same in each coating solution. In addition, there was no discernible difference in the global adsorption Gibbs energy term of the Langmuir isotherm model for the three mixtures described above.