Mesomorphic behaviour and photoluminescence study of novel homologous series of Schiff’s base derived from cholesteryl carbonate and thiadiazole moiety

Abstract

ABSTRACT The steroidal derivatives are widely known for their ability to display a variety of mesophases, including frustrated phases, depending on the structure of the steroidal skeleton and the substituents attached. In this report, thirteen new homologues Schiff’s base derivatives were synthesised by condensing 4-formyl phenyl cholesteryl carbonate with 5-(4’-n-alkoxy phenyl)-2-amino-1,3,4-thiadiazole. All the synthesised derivatives were characterised using elemental analysis, FT-IR, 1H-NMR and 13C-NMR. Optical texture studies were carried out using a polarising optical microscope in heating and cooling cycles to examine the liquid crystalline behaviour of the synthesised compounds. The derivatives displayed a variety of mesophases, including chiral nematic (N*), twist grain boundary-A (TGBA), smectic A (SmA) and chiral smectic C (SmC*) phases. The isotropic temperature of all the compounds within the homologous series seems to decline with the increase in carbon numbers on flexible chains. The thermal behaviour of all the synthesised compounds was checked using differential scanning calorimetry and thermogravimetric analysis. All the synthesised compounds are UV-active and exhibit photoluminescence in the blue emission band with a remarkable quantum yield. The radical-scavenging activity of the synthesised mesogenic derivatives was also evaluated using the DPPH assay.