Coumarin-based emissive hexacatenars: synthesis, 2D and 3D self-assembly and photodimerization

Abstract

The first examples of unsymmetric coumarin polycatenar liquid crystals consisting of a coumarin central core with 1,2,3-triazole dendritic wings on both sides were synthesized via click reaction. Their properties were investigated using POM, DSC, XRD, SEM, IR, UV-vis spectra and photoluminescence measurements. Such polycatenars can self-assemble into different columnar liquid crystalline phases ranging from p4mm via p2mm to p6mm in their bulk states and into organogels with nanobelt or porous morphologies in different solvents. These polycatenars can exhibit highly fluorescent emission with large Stokes shifts (90–118 nm) in solution and as films. Most interestingly, the photodimerization in both LC and non-LC phases led to the formation of absolutely hexagonal columnar LC phases, while photodimerization in gel states led to the formation of flowerlike or 3D porous morphologies. Either columnar phases or gels with flowerlike or ordered porous morphologies were first observed in coumarin based derivatives.