Isomeric effect on the oxidative formation of bilayers of benzenedimethanethiol on Au(111)

We report on the oxidative electrodeposition of the three isomers of benzenedimethanethiol (BDMT) on Au(111) from an alkaline aqueous solution. All isomers are found to adsorb onto gold via one sulfur and to form a complete monolayer. The IRAS spectra of the monolayers indicate that the isomers adopt an orientation that maximizes the exposure of the unreacted thiolate to the electrolyte solution. The monolayers can be made to react with dithiolates in solution by applying a sufficiently positive potential to the gold substrate. The extent of the monolayer that can react to form bilayer, through the oxidative formation of a disulfide, is related to the availability of the second sulfur endgroup of the adsorbed dithiolate. The orientation of the BDMT isomers in the bilayer also seems to favour the exposure of the unreacted thiolate to the electrolyte solution.