Investigation of crystalline 2-pyridone using terahertz spectroscopy and solid-state density functional theory

Crystalline 2-pyridone has been investigated using terahertz vibrational spectroscopy in the range of 10-90 cm^-1 (0.3-2.7 THz). Solid-state density functional theory (B3LYP, BP, and PW91 with the 6-311G(d,p) basis set) was used to simulate and assign both observed terahertz spectral features and a previously published far-infrared spectrum up to 400 cm^-1. The PW91 functional was found to provide the best combination of crystal structure and vibrational frequency reproduction. Observed spectral features below 150 cm^-1 are assigned to intermolecular movements of the 2-pyridone chains within the unit cell. The use of independent intramolecular and intermolecular frequency scalars is proposed.