Synthesis and Computational Investigations of New Thioether/Azomethine Liquid Crystal Derivatives

Abstract

Methylthio moiety was observed to alter the mesomorphic features of rod-like Schiff-base-derived liquid crystalline materials. For this purpose, a new series of (E)-4-(alkoxy)-N-(4-(methylthio)benzylidene)aniline (In) liquid crystals were synthesized and examined using experimental and computational approaches. The compounds in the series differ from each other in the terminal alkoxy chain length that is attached to one end of the aromatic core. Various spectroscopic methods were used to verify the molecular structures of the produced derivatives. All compounds were checked for correct chemical structures using elemental analysis, FT-IR, 1H-NMR, and 13C-NMR. Both a polarized optical microscope (POM) and a differential scanning calorimeter (DSC) were used in order to study the behavior of liquid crystals. Both tested compounds I6 and I8 have monotropic nematogenic properties while the longer chain derivative I16 shows non-mesomorphic behavior. Computational studies were carried out using density functional theory (DFT) calculations to validate the experimental results. All of the analyzed compounds had their reactivity characteristics, dipole moments, and polarizability explained. Finally, in order to determine the chemical shape–mesomorphic property relationship, the present examined series was compared to other structurally comparable homologues.

Keywords

• thioether liquid crystal
• Schiff base
• nematic phase
• DFT
• (<i>E</i>)-4-(alkoxy)-<i>N</i>-(4-(methylthio)benzylidene)aniline