Tautomeric forms of azolide anions: vertical electron detachment energies and dyson orbitals

Abstract

Several decouplings of the electron propagator, including the relatively new P3+ approximation for the self-energy, have been used to calculate vertical electron detachment energies of tautomeric forms of closed-shell, pentagonal, aromatic anions in which ring carbons without bonds to hydrogens appear. This study extends previous work in which the most stable forms of anionic, five-member rings with one to five nitrogens were considered. Whereas the lowest electron detachment energies sometimes are assigned by Koopmans's theorem results to π orbital vacancies, electron propagator calculations always obtain π orbital vacancies for the ground states of the doublet radicals. Higher electron detachment energies that correspond to excited doublets with π vacancies also are presented. The predicted transition energies are in good agreement with low-intensity peaks in recent anion photoelectron spectra that have been assigned to less stable, tautomeric forms of these anions.