Theoretical investigations of the cyanogen anion

Large ab initio calculations are performed on neutral cyanogen (C2N2) and its negatively charged ion (C2N2-). Four stable isomers are found on the lowest doublet potential energy surface of the anion: trans NCCN−X∼ 2Bu, trans CNCN−X∼ 2A′, trans CNNC−X∼ 2Bu and trans NNCC−X∼ 2A′. A set of spectroscopic data is derived for them at the RCCSD(T)/aug cc-pVTZ level of theory. The vertical and the adiabatic electron affinities are also deduced. High level ab initio calculations show that no metastable electronically excited states may exist either in the doublet or in the quartet states manifolds of C2N2- species.