Revisiting Indolo[3,2-b]carbazole: Synthesis, Structures, Properties and Applications.

Indolo[3,2-b]carbazole presents a pi-skeleton with a remarkable electronic structure and interesting potential applications. It is, however, also associated with ambiguity and controversy. Herein, new derivatives of indolo[3,2-b]carbazole are reported and they have enabled a comprehensive study on the electronic structure of indolo[3,2-b]carbazole and the development of a new n-type organic semiconductor. Experimental and computational studies show that indolo[3,2-b]carbazole has a largely localized p-benzoquinonediimine moiety and significant antiaromaticity. When substituted with (4-silylethynyl)phenyl groups, the indolo[3,2-b]carbazole exhibits one-dimensional pi-pi stacking and functions as an n-type organic semiconductor in solution-processed field effect transistors.