الفهرس 
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Abstract
The second research involves methylthio moiety that 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. Schiff bases In were prepared via direct condensation reaction between 4-methylthiobenzaldehyde with alkyloxy anilines, as demonstrated in Scheme 2. 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. While n-hexyloxy and n-octyloxy derivatives show a nematic phase under a POM, nhexadecyloxy derivatives do not show any liquid crystal phase. 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. The length of the alkyl chain was discovered to affect the calculated thermodynamic parameters and zero-point energy of compounds In. They were expected to increase as the alkyl chain length in series In increased. As seen in compound I16 the longer nonpolar moiety provides high thermal stability. The DFT outcomes show that the dipole moment in series In decreases with increasing the non-polar part of alkyl chain indicating that the length of alkyl moiety has a significant impact on the reactivity of investigated compounds. The HOMO and LUMO electron clouds are evenly distributed over the two benzene rings, while HOMO located mainly on benzene ring come from alkoxy aniline, but LUMO in mainly distributed over arylidene moiety. Finally, in order to determine the chemical shape–mesomorphic property relationship, the present examined series was compared to other structurally comparable homologues.