Bicarbazoles: Systematic Structure?Property Investigations on a Series of Conjugated Carbazole Dimers

摘要

A large series of conjugated carbazole dimers, namelynbicarbazoles 1−12, were synthesized by Suzuki−Miyaura, Sonogashira,nHay, and McMurry coupling reactions. In 1−12, the two carbazole moietiesnare linked at the 1-, 2-, or 3-position directly or via an acetylenic or olefinicnspacer. The structure−property relationships, particularly the effects of thenconjugation connectivity and the π-conjugated spacers on the electronic,nphotophysical, and electrochemical properties of 1−12, were studied bynextensive UV−vis and fluorescence spectroscopic measurements, cyclicnvoltammetry (CV), and theoretical calculations as well as X-ray crystallographicnanalyses. The connection at the 1-position of carbazole ensures highnextent of π-conjugation, while that at the 3-position enhances the electrondonatingnability. Both acetylenic and olefinic spacers allow the extension ofnπ-conjugation, and the latter also causes the increase of the donor ability. Moreover, the structural variations were found to affectnthe fluorescence quantum yields significantly, which are up to 0.84.