Synthesis of a novel liquid crystalline bisindenocarbazole derivative

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 degrees C, whereas the other derivatives are crystalline or form molecular glasses. All bisindenocarbazoles exhibit high thermal stabilities above 300 degrees C and show excellent electrochemical stability. HOMO and LUMO levels of 25.4 eV and 22.3 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.