Electrooxidation of N-methylindole

Abstract

The electrooxidation of N-methylindole (1-methylindole) results in the formation of soluble oligomers. Fluorescence spectroscopy and mass spectrometry indicate that the major product of this reaction is an asymmetric cyclic trimer, which is also shown to undergo a reversible one-electron redox reaction. The redox potential for this species is similar to that obtained for 5-methylindole asymmetric trimer. Also formed are significant fractions of a linear polymer; this is attributed to the steric hindrance of two of the methyl groups during the formation of the cyclic trimer, which decrease the propensity for cyclisation when compared with 5-substituted and unsubstituted indoles. Further oxidation of the trimer, in contrast to 5-substituted indoles, does not result in trimer coupling and electroactive film formation. This supports the hypothesis that coupling of 5-substituted indole trimers takes place at the ring nitrogens.