|Sonntag, M.; Strohriegl, P.: Synthesis of a novel liquid crystalline bisindenocarbzole derivative, Liquid Crystals 34(1), 49-57 (2007)|
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.