First biscyanovinyl diphenylfluorenone-based hexacatenars: synthesis, liquid crystal and photophysical properties

Abstract

ABSTRACT In this paper, a series of hexacatenars, where the central fluorenone is connected two α-cyanostilbene which is substituted with 3,4,5-trialkoxybenzyl, was synthesized by Pd-catalyzed Suzuki coupling and Knoevenagel reaction as key steps. The LC characteristics, photophysical and electrochemical behaviors were evaluated by using POM, DSC, TGA, XRD, DFT calculations, UV-vis spectroscopy, photoluminescence measurements and CV. A rare mesophase sequence from Colhex/p6mm to Colrec/p2mm was observed and the mesophase width increased upon terminal chain elongation. The photophysical behaviors in different solutions and aggregated states indicated that these compounds exhibited solvatochromism, fluorescence quantum yields and aggregation-induced emission (AIE) behaviors. The electrochemical behaviors in thin film indicated these compounds show low band gap. DFT calculations of the investigated hexacatenars were accomplished to determine the structural, electronic and intermolecular interaction properties.