Effect of regioisomerism on the self-assembly and photophysical behavior of 1,3,4-thiadiazole-based polycatenars

A new class of polycatenars, where the central benzene ring is connected to two arms derived from substituted 1,3,4-thiadiazoles at the 1,3- and 1,4-positions, was synthesized and characterized. These thiadiazole-based molecules are promising as they stabilize columnar phases over a wide temperature range, in comparison to their oxadiazole analogues. The para-substituted polycatenars exhibited a columnar hexagonal and/or a columnar oblique phase, while the meta-substituted polycatenars exhibited solely a columnar oblique phase. The para-substituted polycatenars exhibited green emission, while the meta-substituted polycatenars exhibited blue emission in solution and film states. Stabilization of a broad range columnar phase and luminescence in the solid state make these new compounds promising from the viewpoint of applications in emissive displays. The self-assembly and luminescence of these regioisomers was greatly influenced by the molecular structure.