Ab initio and density functional theory studies on vibrational spectra of 3-{[(4-methoxyphenyl)methylene]amino}-2-phenylquinazolin-4(3H)-one

The infrared and Raman spectra of 3‐{[(4‐methoxyphenyl)methylene]amino}‐2‐ phenylquinazolin‐4(3H)‐one have been recorded and analysed. Geo metry and harmonic vibrational wavenumbers were calculated theoretically using Gaussian 03 set of quantum chemistry codes. Calculations were performed at the Hartree‐Fock and DFT (B3LYP) levels of theory using the standard 6‐31G* basis. The calculated wavenumbers (B3LYP) agree well with the observed wavenumbers. The proposed assignments of normal modes are based on potential energy distribution (PED) analysis. Calculated infrar ed intensities and first hyperpolarizability are reported. The prepared compound was identified by NMR and mass spectra. The phenyl C‐C stretching modes are equally active as strong bands in both IR and Raman spectra, which are responsible for hyperpolarizability enhancement leading to nonlinear optical activity. The calculated first hyperpolarizability is comparable with the