Synthesis and Characterization of Disubstituted 2,1,3-Benzothiadiazole Liquid Crystals

Liquid crystals are unique because of their properties combining molecular order and fluidity.1 Intensive research has focused on the functionalization of the liquid crystalline molecules to obtain different molecules with desirable mesomorphic and physical properties.2 In this work we present the synthesis, characterization, thermal and optical properties of six new disubstituted non-symmetric 2,1,3-benzothiadiazole liquid crystals.3 The structural characterization of the target compounds was given by NMR 1H and 13C, IR spectroscopy and mass spectrometry. The mesomorphic behavior was investigated by XRD, MOLP and DSC. These molecules presented nematic and smectic phases. The analysis of the thermal stability (TGA) indicated a good thermal stability for all materials up to 290 ºC under nitrogen. The compounds displayed strong photoluminescent properties in the visible region, with absorption patterns peaking around 400–475 nm and emission between 530–570 nm with excellent quantum yields (0.56-0.96). Also, solvatochromism studies were performed.