New chair shaped supramolecular complexes-based aryl nicotinate derivative; mesomorphic properties and DFT molecular geometry

A new series of chair-shaped liquid crystalline complexes were formed through 1 : 1 intermolecular hydrogen bonding between 4-(4-(hexyloxyphenylimino)methyl)phenyl nicotinate and 4-alkoxybenzoic acids, with different alkoxy chains. The mesomorphic behaviour of these supramolecular hydrogen-bonded complexes was investigated through differential scanning calorimetry and polarizing optical microscopy. The Fermi bands of the hydrogen bonding formation were confirmed through Fourier-transform infrared spectroscopy. Schlieren textures of the nematic phase (N) were observed for all prepared complexes. These thermotropic supramolecular complexes were confirmed also using density functional theory calculations. It was found that as the akoxy chain length increased the predicted total energy of the H-bonded complex also increased. The predicted data of the charge distribution explained the nematic mesophase which covered all 1 : 1 mixtures and it could be attributed to more end-to-end aggregations of the alkoxy chains with longer chain lengths. Moreover, formation of the H-bonded complexes greatly affected polarizability with respect to the individual compounds. The polarizability increased three and one third times compared with that of the free acid and base, respectively.