Surface-confined monomers on electrode surfaces. 11. Electrochemical and infrared spectroscopic characteristics of aniline-terminated alkanethiol monolayers on Au electrochemically treated in nonaqueous media

The stability and electrochemical properties in nonaqueous media of self-as sembled alkanethiol monolayers containing an alkoxyaniline tail group tethe red to a gold surface via a hexyl or heptyl chain were investigated. It was previously found that upon electrochemical oxidation in 1 M H2SO4, 2-(6-me rcaptohexan- 1-oxy)aniline (AnC6SH) and 2-(7-mercaptoheptan-1-oxy)aniline ( AnC7SH) monolayers on Au give rise to surface-confined dimeric and oligomer ic/polymeric anilines as well as surface-confined hydrolyzed aniline dimer. In the study at hand, AnC6SH/Au and AnC7SH/Au were electrochemically oxidi zed in 0.1 M LiClO4/CH3CN to discourage the formation of surface-confined h ydrolyzed aniline dimer. The resulting voltammetry was compared to that obs erved for monolayers oxidized in 1 M H2SO4 and that of dimeric model compou nds in 0.1 M LiClO4/CH3CN. Reflection-absorption infrared spectroscopy and electrochemical data reveal that upon oxidation in a nonaqueous electrolyte both AnC6SH/Au and AnC7SH/Au yield head-to-tail coupled, surface-confined oligomers and no detectable amounts of hydrolyzed products.