Molecular structure, vibrational spectra, first hyperpolarizability and HOMO–LUMO analysis of p-acetylbenzonitrile using quantum chemical calculation

The FT-IR and FT-Raman spectra of p-acetylbenzonitrile (p-ABN) are recorded in the solid phase. The fundamental vibrational frequencies, intensity of vibrational bands and the optimized geometrical parameters of the compound are evaluated using MP2 and DFT (B3PW91) methods with 6-31G basis set. The theoretical frequencies are scaled down and compared with experimental values which showed good agreement. Comparison of the simulated spectra with experimental spectra provides important information about ability of the hybrid computational method to describe the vibrational modes. The investigation of non-linear optical properties, the electric dipole moment μ, polarizability α, anisotropy of polarizability Δα, and molecular first hyperpolarizability β were computed. The linear polarizabilities and first hyperpolarizabilities of the studied molecule indicate that the molecule can be a candidate of non-linear optical material. The HOMO, LUMO, chemical hardness (η), chemical potential (μ), electrophilicity value (ω), total energy, and dipole moment are calculated by MP2 and DFT/B3PW91 using 6-31G basis set. The molecular electrostatic potential (MESP) is also calculated and corresponding graphs are drawn. Stability of the molecule arising from hyper conjugative interactions, charge delocalization has been analyzed using natural bond orbital analysis. Finally, some thermodynamic parameters are also calculated and discussed.