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) °.

KEYWORDS:

• Monotropic nematic phase
• thiophene derivatives
• chalcone based liquid crystal
• the effect of molecular flexibility

Acknowledgement

The authors are thankful to the Head, Department of Chemistry, The Maharaja Sayajirao University of Baroda, for providing the necessary Instrumental and laboratory facilities required to carry out this work. NMR and POM facilities from the Department of Science and Technology under the FIST program and single-crystal X-ray diffraction from DST under the PURSE program are gratefully acknowledged.

Disclosure statement

No potential conflict of interest was reported by the author(s).