Electrochemical and Spectroscopic Properties of Cation Radicals: III . Reaction Pathways of Carbazolium Radical Ions

Previous work had elucidated the anodic oxidation pathways of carbazole and several N‐substituted derivatives. These studies have now been extended to seventy‐six ring‐substituted carbazoles using electrochemical and spectroscopic techniques to study the reactivity of the various substituted carbazole cation radicals. Generally, it was found that 3, 6, and 9 (N) positions are extremely reactive; if these sites are not blocked by inert substituents the cation radicals generated by electrolytic oxidation react rapidly via coupling‐deprotonation. In some cases, substituents are eliminated from the 3 and 6 positions in the cation radicals followed by coupling to form substituted bicarbazyls. In other cases, relatively stable cation radicals were obtained and their EPR and visible absorption spectra were recorded. It was found that the reactivities of substituted carbazole cation radicals are considerably greater than those of analogous di‐ and triphenylaminium ions due to the planarity of the carbazole aromatic rings.