Nonsymmetric bent-core liquid crystals based on a 1,3,4-thiadiazole core unit and their nematic mesomorphism

The synthesis and thermotropic properties of novel V-shaped molecules having a central 1,3,4-thiadiazole core with a bend-angle of 160 are reported. The compounds consist of a shape-persistent oligo(phenylene ethynylene) scaffold with lateral alkyloxy substituents. One of the terminal aromatic units possesses an alkoxy chain capped by an ethyl ester group while the second terminus is a pyridyl group. They exhibit enantiotropic nematic phases and are characterized by polarized optical microscopy, differential scanning calorimetry, and X-ray diffraction. Results from conoscopy indicate a biaxial nature of the nematic phase near room temperature. DFT calculations of dipole moments and molecular polarizabilities are used to substantiate the experimental findings.