NC4NC2: A new isomer of dicyanodiacetylene isolated in a cryogenic matrix

The photoreactivity of the dicyanoacetylene:acetylene complex, trapped in an argon matrix at 10 K, has been studied at λ > 120 nm using FTIR spectroscopy and complemented by DFT calculations at the B3LYP/6-31G** level. Two products have been formed during the experiment. In addition to the spectral bands assigned to dicyanodiacetylene, NC6N, a second set of bands has been observed: its carrier is attributed to NC4NC2 ([3-cyanoprop-2-ynylidyne)ammonio]ethynide) based on DFT calculations and isotopic experiments. On the basis of this assignement, this is the first time that this C6N2 isomer has been identified.