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Thiol-Modified Pyrrole Monomers:  3. Electrochemistry of 1-(2-Thioethyl)pyrrole and 3-(2-Thioethyl)pyrrole Monolayers in Propylene Carbonate

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journal contribution
posted on 08.05.1998 by Elisabeth Smela, Hans Kariis, Zhongping Yang, Michael Mecklenburg, Bo Liedberg
The electrochemical oxidation of 1-(2-thioethyl)pyrrole (1-TEP) and 3-(2-thioethyl)pyrrole (3-TEP) monolayers on gold was studied. Their cyclic voltammograms were different, with, for example, 1-TEP having three oxidation peaks and 3-TEP just one. Moreover, the cyclic voltammetry of both TEP monolayers was unusual and did not follow the expected behavior for simple electron transfer from an adsorbed monolayer. The chronoamperometry for 1-TEP was also surprising, showing nucleation-like peaks; this was not seen for 3-TEP. Air exposure left the 1-TEP, but not the 3-TEP, surface electrochemically inert. Spectroscopic data on the oxidation products of surface-bound pyrroles are presented for the first time. IRAS, XPS, and UV−vis−NIR showed that, after electrochemical cycling, all the pyrrole rings were absent. This demonstration that the molecules decompose calls into question the generality of the grafting mechanism of adhesion promotion for this type of compound.