Infrared and Raman Spectroscopy of Methylcyanodiacetylene (CH3 C5 N).

A spectroscopic study combining IR absorption and Raman scattering is presented for methylcyanodiacetylene (CH3 C5 N). Gas-phase, cryogenic matrix-isolated, and pure solid-phase substance was analyzed. Out of 16 normal vibrational modes, 14 were directly observed. The analysis of the spectra was assisted by quantum chemical calculations of vibrational frequencies, IR absorption intensities, and Raman scattering activities at density functional theory and ab initio levels. Previous assignments of gas-phase IR absorption bands were revisited and extended.