Electronic Spectroscopy of Methylcyanodiacetylene (CH3 C5 N)

The results of a study devoted to the electronic spectroscopy of gaseous, solid, and cryogenic matrix-isolated methylcyanodiacetylene (CH₃ C₅ N) are reported. UV absorption and optical phosphorescence spectra of the compound are described here for the first time, and the corresponding vibronic assignments are proposed. UV absorption, studied directly or through the excitation of phosphorescence, revealed the B˜  ¹ E--X˜  ¹ A₁ system, very weak A˜  ¹ A₂ -X˜  ¹ A₁ bands, and a strong, broad absorption feature, tentatively identified as D˜  ¹ E-X˜  ¹ A₁ . Spectral measurements were assisted by quantum chemical calculations at the DFT and ab initio (coupled cluster) levels of theory.