Synthesis, mesomorphic properties, and theoretical study of benzothiazole-aromatic molecules with ester- and azomethine-linking groups

Abstract

ABSTRACT Two novel groups of rod-like molecules with benzothiazole-aromatic systems: one group (group A) having an ester linkage with different thioalkyl chain length and the other (group B) ester- and azomethine-linkages with methoxy groups in the tip of the molecules were synthesised. The structures of the synthesised compounds were confirmed by using physicochemical techniques such as 1H NMR, mass spectra, FT-IR spectra, melting points, and elemental analyses. Differential scanning calorimeter and polarising optical microscopy have been employed to verify their liquid crystalline behaviours and transition temperatures. All the synthesised compounds (groups A and B) showed enantiotropic nematic phase except the compound 13d showed the nematic phase in cooling only. The mesomorphic properties of the present compounds were compared with some other structurally related compounds to understand the chemical structure–mesophase properties relationship. The thermal range of nematic phase for the compounds (group A) were decreased with the increase of the thioalkyl chain length. The liquid crystalline properties of the compounds (group B) were greatly affected by the position of terminal methoxy groups. The change of the position of terminal methoxy groups in the compounds (group B) was theoretically studied to investigate if the theoretical calculations possess an agreement with the practical results.