Coumarin derivatives containing schiff base and ester mesogenic core: Synthesis, mesomorphic behaviour and DFT calculations

Abstract

New coumarin esters, (E)-4-(((7-(octyloxy)-2-oxo-2H-chromen-3-yl)imino)methyl)phenyl-4-alkyloxybenzoate, CE-(2-18) containing Schiff base linkage in which octyloxy chain at one end and different long terminal alkoxy chains (C2-C18) at the other end have been synthesized and studied for their mesomorphic behaviour. New compounds were characterized using different analytical techniques such as FT-IR, 1H NMR, 13C NMR, and Mass spectral analysis. The transitions of phase and mesophase investigation were carried out using differential scanning calorimetry and Polarised Optical Microscope. The mesomorphic investigation revealed that all new derivatives CE-(2-14) exhibited an enantiotropic nematic phase whereas except CE-2 and CE-3 all other members have also displayed enantiotropic smectic C phase in addition to enantiotropic nematic phase. The new mesogens mesomorphic behaviour of all synthesized compounds were thoroughly studied and discussed, as well as compared with structurally comparable substances. Finally, the DFT theoretical calculations were studied and compared with the experimental to explain the relationship between the structural parameters and the mesomorphic behaviour.