Vibrational Spectra of the Azabenzenes Revisited:  Anharmonic Force Fields

Anharmonic force fields and vibrational spectra of the azabenzene series (pyridine, pyridazine, pyrimidine, pyrazine, s -triazine, 1,2,3-triazine, 1,2,4-triazine, and s -tetrazine) and benzene are obtained using density functional theory (DFT) with the B97−1 exchange-correlation functional and a triple-ζ plus double polarization (TZ2P) basis set. Overall, the fundamental frequencies computed by second-order rovibrational perturbation theory are in excellent agreement with experiment. The resolution of the presently calculated anharmonic spectra is such that they represent an extremely useful tool for the assignment and interpretation of the experimental spectra, especially where resonances are involved.