Synthesis and characterization of α-cyanostilbene-based bent-core hexacatenar mesogens with different central groups

Abstract

Two series of bent-core hexacatenars containing a diphenyl ketone/diphenylmethylene malononitrile as central group and two α-cyanostilbene units as molecular arm were synthesized by Suzuki coupling and Knoevenagel reactions. The effect of the central groups on the liquid crystalline and photophysical behaviors was investigated in detail. POM, DSC and XRD results indicated that all the compounds could self-assemble into hexagonal columnar mesophases and diphenylmethylene malononitrile-based hexacatenars show much wider range of mesophase. The introduction of malononitrile unit into aromatic core could induce more distinct solvatochromic effect. Both series of hexacatenars show aggregation-induced emission enhancement (AIEE) behaviors and the fluorescence intensity is affected by the size of spherical aggregates in the aggregated state. Additionally, the maximum emission bands, fluorescence intensity and fluorescence color in condensed state showed obvious transition upon rising temperature.