On the Possibility of Electronically Excited States in Stable Amine Anions: Dicyanoamine, Cyanoethynylamine, and Diethynylamine

Of the dicyanomine anion (NCNCN), cyanoethynylamine anion (NCNC2H-), and diethynylamine anion (HC2NC2H-), only the mixed, C-s NCNC2H- anion has are large enough dipole moment to support an electronically excited state at 3.0323 eV. This quantum chemical study shows that this value lies 0.0051 eV below the electron binding energy (eBE) and may have correlation to early-onset diffuse interstellar bands. None of these three anions possess further valence excited electronic states beyond the singlet ground states, and triplet excited states are all beyond their respective eBEs.