Electrochemical and infrared analysis of alkoxyaniline derivative monolayers on gold

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Monolayers of 2-(6-mercaptohexan-1-oxy)aniline (AnC6SH) and 2-(7-mercaptoheptan-1-oxy)aniline (AnC7SH) on Au were characterized by reflection-absorption infrared (RAIR) spectroscopy and electrochemistry. Electrochemical oxidation of AnC6SH/Au and AnC7SH/Au in aqueous acidic solution leads to complex voltammetry indicative of oligomerization and degradation reactions of the aniline functionality. Scanning of the potential between 0.0 and +0.9 V vs. SSCE leads to four surface-confined redox waves occurring at +0.2, +0.4, +0.5, and +0.6 V vs. SSCE. The oxidized monolayers were found to display voltammetry equivalent in nature to that observed for poly(o-phenetidine), which exhibits redox waves for the leucoemeraldine/emeraldine (+0.2 V) and emeraldine/pernigraniline (+0.6 V) transformations and the formation of some quinonemonoimine degradation products (+0.4 V) in the polymer. A redox wave attributed to a quinonediimine dimer (+0.5 V) was also found for the oxidized monolayers. Further oxidation of this species leads to increased polymer production and degradation product formation. To reduce degradation product formation, AnC6SH/Au and AnC7SH/Au were oxidized in non-aqueous solution. This method led to production of only surface confined dimers as indicated by electrochemical analysis.

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ACS Symposium Series

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