Infrared and Raman Spectroscopy of Methylcyanodiacetylene (CH₃C₅N)

Abstract

A spectroscopic study combining IR absorption and Raman scattering is presented for methylcyanodiacetylene (CH C 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.

Electronic Spectroscopy of Methylcyanodiacetylene (CH3C5N)

“…Values implied by the – origin frequency of 34 925±10 cm −1 . [b] As reported by Szczepaniak et al., with the exception of ν 16 , presently derived from the dispersed phosphorescence spectrum. [c] As derived from the phosphorescence excitation spectrum, this work.…”

“…The – vibrationless origin is assumed to be at 34 092±10 cm −1 , based on the gas‐phase ν 12 frequency. [d] Modes ν 2 and ν 3 are in a strong anharmonic interaction . [e] Derived from the difference of 12 1 0 and 8 1 0 12 1 0 transition frequencies.…”

“…[e] Derived from the difference of 12 1 0 and 8 1 0 12 1 0 transition frequencies. [f] Tentative assignment . [g] Assumed to be equal to the gas‐phase value (cf.…”

“…[e] Modes ν 2 and ν 3 are in a strong anharmonic interaction, presumably together with ν 6 +ν 7 (see Ref. ).…”

“…Several literature reports also hint at their possible prebiotic importance . Recently, our attention has been directed toward methylated members of the cyanoacetylene family, especially as an effective method of laboratory synthesis of the title compound has been recently developed …”