AIE-active discotic LC containing tetraphenylethylene and α-cyanostilbene: Synthesis, self-assembly and photophysical properties

A novel α-cyanostilbene-containing tetraphenylethylene-based discotic LC with 3,4,5-tridecyloxy benzene units at the terminal was synthesized by Ti-catalyzed McMurry coupling, Pd-catalyzed Suzuki coupling and Knoevenagel reactions as key steps. The liquid crystal and photophysical properties were well demonstrated by polarizing optical microscopy (POM), differential scanning calorimetry (DSC), X-ray scattering (XRD), molecular dynamics (MD) and optical experiments. The compound could self-assemble into Colhex/p6mm mesophase in a wide temperature range. It is interesting that two discotic molecules formed one columnar slice, which was attributed to the twisted conformation of propeller-like TPE and α-cyanostilbene. The photophysical properties of the TPE-based DLCs including solvatochromism and aggregation-induced emission (AIE) behaviors were systematically investigated demonstrating large Stokes shifts, high fluorescence quantum yields and strong fluorescence in both solution and aggregated states. This work indicated that the combination of different AIE-active units into one LC molecule could induce complex self-assembly structure and excellent fluorescence properties.