Influence of polar substituent on central bending unit of bent core mesogens: Synthesis, photophysical, mesomorphism and DFT studies

Abstract

New five ring bent core mesogens derived from substituted 1,3-phenylenediamine (4-nitro-1,3-phenylenediamine, 4-chloro-1,3-phenylenediamine) were synthesized. Their molecular structures, photophysical properties and mesogenic behaviors were investigated. The molecular structures and the purity of the bent core molecule have been characterized by spectroscopic studies and elemental analysis respectively. Photophysical properties of bent core compounds were investigated in chloroform by using UV–visible and fluorescence spectroscopic studies. The phase transition temperatures were detected by differential scanning calorimetry analysis and the phases are confirmed by polarizing optical microscopy. The polar substituents on bent core unit of bent shaped molecule influence the mesomorphic behaviors of the bent core mesogens. The polar nitro group at 4-position of the bent core unit displays tilted smectic C phase and unknown smectic X phase whereas chloro group at 4-position exhibits orthogonal smectic A phase. The bent core mesogens are fluorescent in nature. The density functional theory calculation was carried out to obtain the stable molecular conformation and chemical reactivity of the bent core molecules. Orbitals involved in the electronic transitions and their corresponding energies together with oscillator strengths have been reported.