The complete harmonic vibrational force field and the diagonal and semidiagonal cubic force field elements have been computed for pyridine at the 4-21 Hartree-Fock level. The harmonic constants were scaled by using scale factors previously derived by fitting the computed force field of benzene to the observed benzene vibrational spectrum. The scaled force field was then used to predict the vibrational spectrum of pyridine. Comparison with experimental spectra, after a few corrections in the experimental assignments, shows a mean deviation of 5.7 cm-1 for the non-CH frequencies. Computed intensities are qualitatively in agreement with experiment. This successful a priori accurate prediction of the vibrational spectrum of a moderately complex molecule offers hope that completely unknown spectra of such molecules can be computed to harmonic oscillator accuracy if the spectrum of a related substance is known.
ASJC Scopus subject areas
- Colloid and Surface Chemistry