ELECTROCHEMICAL EVALUATION AND ENHANCEMENT VIA HETEROGENEOUS EXCHANGEOF THE PASSIVATING PROPERTIES AND STABILITY OF SELF-ASSEMBLED MONOLAYERS DERIVED FROM THE RIGID-ROD ARENETHIOLS, X-C6H4-C-C-C6H4-C-C-C6H4-SH (X=H AND F)

The passivating properties of self-assembled monolayers derived from t he chemisorption of the rigid rod arenethiols 1a-b on Au(lll) have bee n probed by electrochemical techniques in an aqueous electrolyte. Thes e studies suggest that the pure monolayers of 1a-b possess a high dens ity of unfilled defect sites, potentially as a result of the solvent r equired for their preparation. However, a heterogeneous ''patching'' p rocess, which involves both addition of hexadecanethiol at defect site s and exchange with the original monolayer, provides mixed monolayers that have superior passivating properties and which X-ray photoelectro n spectroscopy and grazing-angle IR reveal to be still predominantly c omposed of 1a-b. The ability to reproducibly obtain these highly block ing mixed monolayers in which 1a-b is the primary component now provid es a means by which to investigate, at the next level of study, electr on transfer/tunneling through these novel interfacial barriers.