Infrared spectra of Dewar 4-picoline in low-temperature argon matrices and vibrational analysis by DFT calculation

Dewar 4-picoline produced by UV irradiation on 4-picoline in a low-temperature argon matrix was monitored by FT-IR spectroscopy. The observed infrared bands were assigned to an isomer which has a C–C bridging bond with the aid of DFT (density functional theory) calculation, where the 6-31++G** basis set was used to optimize the geometrical structure. No other isomer bands were observed. A systematic comparison of the scaling factors derived from the observed and calculated wavenumbers for pyridine, 2-picoline, 4-picoline and their corresponding Dewar isomers indicates a linear relationship between the scaling factors and the vibrational wavenumbers.