Synthesis and Acid-responsive Electron-transfer Disproportionation of Non- and Tetramesityl-substituted 1,1′,9,9′-Bicarbazole

Non-substituted 1,1′,9,9′-bicarbazole and 3,3′,6,6′-tetramesityl-1,1′,9,9′-bicarbazole were synthesized through dimerization of carbazole derivatives and oxidative N–N bond formation reaction. Non-substituted 1,1′,9,9′-bicarbazole formed a stacking packing structure in crystal. Both bicarbazoles were found to undergo acid-responsive electron-transfer disproportionation. The radical cation generated from the non-substituted 1,1′,9,9′-bicarbazole was stable in solution under air at room temperature, even without protecting bulky substituents.