The electrochemical oxidation of 2-amino-3-cyano-4-phenylthiophene: evidence for a new class of photoluminescent material

The electrooxidation of 2-amino-3-cyano-4-phenylthiophene on platinum electrodes was investigated for the first time in acetonitrile by cyclic voltammetry, controlled potential electrolysis, and spectrometric methods. The voltammetric responses were similar to those of common aromatic amino compounds. Two types of dimers were observed as intermediates in the early stages of oxidation. Ethlyamine and phenol were added to an electrolytic solution in order to determine the electrochemical behavior of 2-amino-3-cyano-4-phenylthiophene under basic and acidic conditions. We propose an E(CE)n mechanism to account for this electrochemistry. 2-Amino-3-cyano-4-phenylthiophene is first oxidized to a cation radical, followed by chemical coupling to form dimers, which are electroactive. Controlled potential electrolysis gave a new class of π-conjugated oligoaminothiophenes exhibiting an absorbance at 432 nm and photoluminescence at 538 nm.