Tentative identification of C₅N₂ in rare gas matrices

A new cyanocarbon is formed in a discharge of dicyanoacetylene (NC₄N) and studied in rare gas matrices through its visible absorption, laser-induced fluorescence, and laser excitation spectra. The spectrum, with origin at 22737 cm^-1 in an argon matrix, exhibits strong progressions in a vibrational mode around 2000 cm^-1, typical for a linear molecule with multiple bonds. Isotopic studies suggest that the carrier contains two equivalent nitrogen atoms and probably five carbons. They also point to a centro-symmetric molecule with two equivalent carbon atom pairs. Given this information, we assign the carrier of this spectrum tentatively to a linear cumulenic NC₅N or CNC₃NC. Chemical evidence suggests it may be formed by the reaction of C atoms with NC₄N or its isomer NC₃NC.