Electronic structure, FT-IR analysis and nematic behaviour studies of para-methoxybenzylidine p-ethylaniline: Ab-initio and DFT approach

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Electronic structure of para-methoxybenzylidine p-ethylaniline (MBEA), a pure nematic liquid crystal has been examined using ab–initio, HF/6-31G(d,p) and DFT B3LYP/6-31G(d,p) techniques with GAMESS program. MBEA transforms from crystal to nematic at 28°C and nematic to isotropic phase at 57°C. Potential Energy Surface (PES) in terms of various conformations and charge distribution analysis have been carried out. Molecular Electrostatic Potential (MEP), Highest Occupied Molecular Orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO) surfaces have been scanned. Ionization potential, electron affinity, electronegativity, global hardness and softness parameters of the liquid crystal molecule have been determined. Molecular and thermodynamic properties such as total energy, dipole moment, entropy, enthalpy and Gibbs free energy have been calculated at 298.15K temperature. FTIR showed that calculated and experimental frequencies are in agreement. Stacking, side by side and end to end interactions between a molecular pair have been evaluated employing modified second order perturbation theory along with multicentred-multipole expansion technique. Results have been used to elucidate the physico-chemical and liquid crystalline properties of the system.