Synthesis, characterization, crystal structure and mesomorphic behavior of thiophene based homologous series

Abstract

Through condensation of 4-n-alkoxybenzaldehyde (n = 2 to 8, 10, 12, 14, 16, 18) with (E)-1-(4-aminophenyl)-3-(thiophen-2-yl)prop-2-en-1-one, new homologous series of rod shaped calamite liquid crystals that merge Schiff base, chalcone and thiophene units have been prepared. All synthesized compounds were characterized by FT-IR, 1H-NMR and 13C-NMR spectroscopy. The liquid crystalline properties of the synthesized compounds were investigated using a polarizing optical microscope (POM) and differential scanning calorimetry (DSC). The results indicate that n-heptyloxy (A7) to n-tetradecyloxy (A14) derivatives exhibited monotropic nematic phase while the remaining derivatives of homologous series are non mesomorphic. The n-ethoxy derivative (A2) crystallizes under monoclinic, space group P21/c with unit cell dimension a = 19.343(4) Å, b = 5.8353(9) Å, c = 16.574(4) Å, β = 98.78(2) °, V = 1848.8(7) Å3. The dihedral angle between two phenyl rings of imine linkage in compound A2 is 51.64 (2) °.