THIO-MODIFIED PYRROLE MONOMERS - 3 - ELECTROCHEMISTRY OF 1-(2-THIOETHYL)PYRROLE AND 3-(2-THIOETHYL)PYRROLE MONOLAYERS IN PROPYLENE CARBONATE

The electrochemical oxidation of 1-(2-thioethyl)pyrrole (1-TEP) and 3- (2-thioethyl)pyrrole (3-TEP) monolayers on gold was studied. Their cyc lic voltammograms were different, with, for example, 1-TEP having thre e oxidation peaks and 3-TEP just one. Moreover, the cyclic voltammetry of both TEP monolayers was unusual and did not follow the expected be havior for simple electron transfer from an absorbed monolayer. The ch ronoamperometry 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 electrochemi cal cycling, all the pyrrole rings were absent. This demonstration tha t the molecules decompose calls into question the generality of the gr afting mechanism of adhesion promotion for this type of compound.