New supramolecular liquid crystals induced by hydrogen bonding between pyridyl‐1,2,4‐oxadiazole derivatives and 2,5‐thiophene dicarboxylic acid

Supramolecular liquid crystalline complexes were obtained from binary mixtures of 3-(4-pyridyl)-5-(4- n -alkoxy)phenyl-1,2,4-oxadiazoles and 2,5-thiophene dicarboxylic acid. Although the oxadiazole derivatives and the dicarboxylic acid are non-mesomorphic, the H-bonded complexes exhibit mesomorphism. Their liquid crystalline properties were investigated by differential scanning calorimetry and polarizing optical microscopy. The complexes exhibit enantiotropic nematic phases. A structural study involving AM1 semi-empirical calculations is also described.