Synthesis of a novel liquid crystalline bisindenocarbazole derivative

Abstract

In this paper we describe the synthesis of four new bisindenocarbazole derivatives, prepared by selective bromination of bisindenocarbazole in the 7‐ and 7′‐positions, followed by Suzuki crosscoupling with alkyl‐substituted phenyl, biphenyl and fluorene units. From this new class of fused aromatics a liquid crystalline derivative is reported for the first time. The bisindenocarbazole with two 4‐hexylphenyl side groups exhibits a broad nematic phase between 180 and 250°C, whereas the other derivatives are crystalline or form molecular glasses. All bisindenocarbazoles exhibit high thermal stabilities above 300°C and show excellent electrochemical stability. HOMO and LUMO levels of −5.4 eV and −2.3 eV, respectively, were determined by cyclic voltammetry and optical spectroscopy. The bisindenocarbazoles display a strong blue fluorescence with up to 56% quantum yield in solution.

Acknowledgments

The authors would like to thank Andrea Jahreis for helping to prepare the starting materials, Andreas Timme for the SAXS measurement and Günter Lattermann for fruitful discussions. We are grateful to the Deutsche Forschungsgemeinschaft (SFB 481) and the BMBF (POLITAG programme) for financial support.