Synthesis, mesomorphic properties and X-ray diffraction studies on 7-alkyloxy-3-(4-alkyloxyphenyl-4H-1-benzopyran-4-one: Crystal structure of 7-hexyloxy-3-(4-hexyloxyphenyl)-4H-1-benzopyran-4-one

Abstract

Eight new compounds, 7-alkyloxy-3-(4-alkyloxyphenyl)-4H-1-benzopyran-4-one incorporating isoflavone core and identical terminal side chains, OR (where R = C n H 2 n +1 with n ranging from 4 to 18 in even parity) have been synthesized and isolated. The thermal stability in relation to the phase behaviour and respective enthalpy values of these compounds were analyzed using differential scanning calorimetry. The texture of the preferred molecular orientation at different temperatures was observed under polarized light wherein all compounds exhibited nematic (N), smectic A (SmA) and smectic C (SmC) phases. The difference in mesogenicity of these compounds was also investigated from the viewpoints of conformation and polarity of the side chains which contributed remarkably towards the change in the intermolecular interaction within the mesophase. X-ray diffraction technique was employed to investigate the molecular packing associated with the intermolecular interaction as well as the correlation between the thermal behaviour of these compounds with their anisotropy properties within a mesophase. The molecular structure of compound 7-hexyloxy-3-(4-hexyloxyphenyl)-4H-1-benzopyran-4-one in crystal phase was confirmed by single-crystal X-ray diffraction.