Photoelectron Spectroscopy of the Aminomethoxide Anion, H₂C(NH₂)O^–

Abstract

We report the photoelectron spectrum of the aminomethoxide anion (HC(NH)O). The electron affinity (EA) of the aminomethoxy radical is determined to be 1.944(1) eV. Transitions to the ground (X̃ A″) and first excited (ÃA') electronic states of aminomethoxy are observed, with the term energy measured to be T(Ã ← X̃) = 0.085(1) eV. A long vibrational progression is observed for the transition to the ground X̃ A″ electronic state of aminomethoxy, primarily consisting of OCN bending and HNH wagging vibrations, leading to the assignment of these two fundamental vibrational frequencies of HC(NH)O· X̃ A″. The gas-phase acidity of aminomethanol is calculated at the G4 level of theory to be Δ H = 374.0 kcal mol, which, when combined with the experimental EA of aminomethoxy in a thermochemical cycle, provides a determination of the O-H bond dissociation energy, D(HC(NH)O-H) as 106(2) kcal mol. Comparisons of the EAs and T(Ã ← X̃) for the aminomethoxy, methoxy, ethoxy, and hydroxymethoxy radicals provides insight into how the substituent group affects the electronic structure of singly substituted alkoxy radicals.