Mesomorphic behaviour, optical and quantum computational study: Effect of electron density on newly synthesized liquid crystalline positional isomers

Abstract

Effect of position isomer in newly synthesized two liquid crystalline series having nitro and chloro groups at terminal and lateral position, with imine and cinnamoyloxy linkages was studied. The nitro and chloro groups in the aromatic end of the molecule are interchanged with each other at terminal and lateral position, giving rise to positional isomers. All synthesized compounds were characterized with standard spectroscopic techniques, Infrared, Ultra-Violet and Proton magnetic resonance spectroscopy. The mesophase behaviour was observed by a Polarizing optical microscope equipped with a heating stage and was confirmed by Differential scanning calorimetry with respective transition enthalpies of mesophase transition. The mesogenic derivative of both prepared series showed nematic and smectic A mesophase. DFT method was used to obtain optimized geometry of the molecules. The optimized geometry was used to obtain the Molecular electrostatic potential map, dipole moment, HOMO-LUMO and twist angle of the prepared series. The interaction between the molecules was studied on the base of electrostatic potential and HOMO-LUMO. The phase transition of the present two series is compared with each other and with three structurally related compounds to evaluate the effect of planarity, central linkage and position of substitution on their mesophase behaviour.