FTIR and Raman spectra, electronic spectra and normal coordinate analysis of N,N-dimethyl-3-phenyl-3-pyridin-2-yl-propan-1-amine by DFT method

• Vibrational wave numbers were computed using DFT method.
• NLO behaviors were computed.
• Hyperpolarizability and HOMO, LUMO energy were calculated.
• The NBO analysis explained the intramolecular hydrogen bonding.

The Fourier transform infrared (FT-IR) and FT-Raman spectra of N,N-dimethyl-3-phenyl-3-pyridin-2-yl-propan-1-amine have been recorded in the range 4000–500 cm−1 and 4000–50 cm−1 respectively. The complete vibrational assignment and analysis of the fundamental modes of the compound were carried out using the observed FT-IR and FT Raman data. The vibrational frequencies experimentally determined, was compared with the theoretical frequencies computed by DFT gradient calculations (B3LYP method) employing the 6-31+G(d, p) basis set for the optimized geometry of the compound. The geometry and normal modes of vibration obtained from the DFT method are in good agreement with the experimental data. The assignments of the vibrational spectra have been carried out with the help of Normal Coordinate Analysis (NCA) following the Scaled Quantum Mechanical Force Field Methodology (SQMFF). The calculated infrared and Raman spectra of the title compounds were also stimulated utilizing the scaled force fields and the computed dipole derivatives for IR intensities and polarizability derivatives for Raman intensities. The change in electron density (ED) in the σ* and π* antibonding orbitals and stabilization energies E(2) have been calculated by Natural Bond Orbital (NBO) analysis to give clear evidence of stabilization originating in the hyper conjugation of hydrogen-bonded interaction. The electronic spectrum determined by TD-DFT method is compared with the observed electronic spectrum.

In this work, the complete vibrational assignment with PED of N,N-dimethyl-3-phenyl-3-pyridin-2-yl-propan-1-amine were calculated using Pulay’s density functional theory (DFT) based on scaled quantum chemical approach. The calculated HOMO and LUMO energies show that charge transfer occur within the molecule. Comparison of simulated spectra with the experimental spectra provides important information about the ability of the computational method to describe the vibrational modes.Figure optionsDownload as PowerPoint slide