The valence and dipole-bound states of the cyanomethide ion, CH2CN−

The electronic and geometrical structures of the cyanomethyl radical, CH2CN, and cyanomethide ion, CH2CN−, are investigated with the Hartree-Fock method, Møller-Plesset perturbation theory and coupled cluster theory. It is found that the lowest singlet and triplet dipole-bound states (1B1 and 3B1) of the anion correspond to a σ-attachment of the extra electron to the ground (2B1, C2v state of the CH2CN radical. The ground valence (1A′, Cs) anionic state results from a π-attachment, which leads to some pyramidalization of the flat configuration of the neutral parent. The calculated electron affinities of CH2CN with respect to both anionic states are in good agreement with the experimental data.