Quantum Chemical and Spectroscopic (FT-IR, FT-Raman) Study, First Order Hyperpolarizability, NBO, Analysis HOMO and LUMO Analysis of Selegiline by abinitio HF and DFT Method

The FT-IR and FT-Raman vibrational spectra of selegiline were recorded. The optimized geometry and wavenumbers in the ground state were calculated using density functional (B3LYP) method with standard 6-31G(d,p) basis set. The computed B3LYP/6-31G(d,p) results show the best agreement with the experimental values over the other methods. Natural bond orbital analysis of selegiline is also carried out, which confirms the occurrence of strong intermolecular bonding, stability of the molecule arising from hyperconjugative interactions, and charge delocalization. The electric dipole moment (α), polarizability (α), and first hyperpolarizability (β0) which results also show that the selegiline might have microscopic non-linear optical behavior with non-zero values. The calculated HOMO and LUMO energies show that charge transfer occur in the molecule. The results of the calculations were applied to simulated spectra of the title compound, which show excellent agreement with observed spectra.