DFT computation and spectroscopic analysis of N-(p-methoxybenzylidene)aniline, a potentially useful NLO material

FT-Raman and IR spectra of the biologically active molecule N-(p-methoxybenzylidene)aniline (NpMBA) have been recorded and analyzed. The molecular geometry of the title compound in the ground state have been calculated by density functional theory (DFT) with 6-31+G(d) and 6-311++G(d, p) basis sets. The harmonic vibrational frequencies calculated for NpMBA at B3LYP level using higher basis set 6-311++G(d, p). There are four conformers, C1, C2, C3 and C4 for this molecule. The computational results diagnose the most stable conformer of NpMBA as the C4 form. In order to obtain the information about the influence of intramolecular interaction on the molecule the calculated geometries of NpMBA molecule was compared with experimental data. The results of the optimized molecular structure gave clear evidence for the intramolecular charge transfer (ICT). The electric dipole moment (μ) and first hyper polarizability (β) values of the investigated molecule were computed using density functional theory calculations. The calculated results also show that the NpMBA molecule might have microscopic non-linear optical (NLO) behavior with non-zero values. The effects of methoxy and central bond substituent in benzene ring in the vibrational wave numbers have been analyzed. NBO analysis is useful to understand the intra molecular hyper conjugative interaction between lone pair N and σ*(CC) bond orbital. The overlapping of atomic orbitals along with their predicted energy is explained on the basis of HOMO–LUMO energy gap calculations. The MEP surface and thermodynamic parameters are also predicted.