First Mesomorphic and DFT Characterizations for supramolecular assemblies of 3 (or 4)-n-alkanoyloxy benzoic acids and their optical applications

Abstract

Successful preparation of new liquid crystalline 3 (or 4)-n-alkanoyloxy benzoic acids, were designed and fully characterized via experimental and theoretical approaches. Elucidation of their molecular structures were carried out by elemental analyses, NMR and FT-IR, spectroscopy. Thermal and mesomorphic properties of all symmetrical dimers having -symmetrical alkanoyloxy chain, were analyzed by differential scanning calorimetry (DSC) and their mesophases identified by polarized optical microscopy (POM). Results revealed that, the smectic mesophase covered all designed symmetrical dimers with thermal stability depending on the length of terminal alkanoyl moiety. Furthermore, the results of the Density Functional Theory (DFT) calculations supported the observed experimental data for the mesomorphic behaviour. The para-derivatives (In) of the alkanoyloxy benzoic acids were predicted to be stable with greater hydrogen bonding interactions than the meta (IIn) counterparts. The computed reactivity parameters revealed that the acids reactivity was influenced by the position of ester substituent. The absorbance spectra of both para and meso derivatives were noticed to be blue shifted with the increase of alky side, however, the energy band gap of meso-derivatives was found to be slightly higher than para-derivates. The synthesized materials exhibit broad photoluminescence spectrum which was noted to be red shifted with the increase of side chain length. The fluorescence lifetime was found to be increases with the increase of alkyl side chain length, and meso-derivatives have slightly longer lifetime as compared to the para-derivatives.