Thiol-Modified Pyrrole Monomers: 2. As-Deposited Monolayers of 1-(2-Thioethyl)pyrrole and 3-(2-Thioethyl)pyrrole

A combination of analytical techniques was used to examine monolayers of 1-(2-thioethyl)pyrrole (1-TEP) and 3-(2-thioethyl)pyrrole (3-TEP) adsorbed on gold, including infrared, UV−vis−NIR, mass spectroscopy, ellipsometry, wetting, and X-ray photoelectron spectroscopy. Both monolayers were found to undergo adsorption-catalyzed reactions. Monolayers of 1-TEP were disordered even after long deposition times, with an isotropic distribution (orientation) of the tails, from perpendicular to parallel to the substrate, as expected for a short chain thiolate with a relatively bulky tail group. Vapor and solution deposition methods produced the same results. The 1-TEP monolayers were quite sensitive to oxygen, and exposure to air resulted in the rapid formation of carbonyl species. In the bulk, 1-TEP did not react in this manner. Solution-deposited 3-TEP monolayers consisted predominantly of short-chain alkanethiolates and/or disulfides that had lost the pyrrole moiety, together with ca. 30% of intact, bound 3-TEP....