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

We report the photoelectron spectrum of the aminomethoxide anion (H₂C(NH₂)O^-). The electron affinity (EA) of the aminomethoxy radical is determined to be 1.944(1) eV. Transitions to the ground (X̃ ²A″) and first excited (Ã ²A') electronic states of aminomethoxy are observed, with the term energy measured to be T₀(Ã ← X̃) = 0.085(1) eV. A long vibrational progression is observed for the transition to the ground X̃ ²A″ electronic state of aminomethoxy, primarily consisting of OCN bending and HNH wagging vibrations, leading to the assignment of these two fundamental vibrational frequencies of H₂C(NH₂)O· X̃ ²A″. The gas-phase acidity of aminomethanol is calculated at the G4 level of theory to be Δ_acid H_0K^o = 374.0 kcal mol^-1, which, when combined with the experimental EA of aminomethoxy in a thermochemical cycle, provides a determination of the O-H bond dissociation energy, D₀(H₂C(NH₂)O-H) as 106(2) kcal mol^-1. Comparisons of the EAs and T₀(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.