DFT, FT-Raman, FT-IR and FT-NMR studies of 4-phenylimidazole

The experimental and theoretical vibrational spectra of 4-phenylimidazole (4-PI) were studied. The FT-IR, FT-Raman and FT-NMR spectra of 4-PI molecule was recorded in the powder form. The tautomeric, structural and spectroscopic analysis of the title molecule was made by using density functional harmonic calculations. For the title molecule, only one tautomeric form was found most stable structure by using B3LYP level with the 6-311G(d,p) and 6-311G++(d,p) as basis set. Selected experimental bands were assigned and characterized based on the scaled theoretical wave numbers by their total energy distribution (TED). Stability of the molecule arising from hyperconjugative interactions, charge delocalization has been analyzed using natural bond orbital (NBO) analysis. The results show that charge in electron density (ED) in the σ* anti-bonding orbitals and E2 energies confirms the occurrence of intermolecular charge transfer (ICT) within the molecule.The isotropic chemical shifts computed by 1H and 13C NMR analysis also show good agreement with experimental observations. The theoretically predicted FTIR and FT-Raman spectra of the title molecule have been constructed.