The Lowest Singlet and Triplet States of the Oxylallyl Diradical

Photodetachment of the oxyallyl radical anion leads to formation of the oxyallyl diradical, an elusive transient molecule involved in many organic reactions. As described by W. C. Lineberger et al. in their Communication on page 8509 ff., the photoelectron spectrum reveals that the oxyallyl ground state is singlet and the lowest triplet state is only 55 meV higher in energy. The spectral profile indicates that the planar singlet state is the transition state for ringopening of cyclopropanone, whilst the CCC bending motion is activated upon photodetachment to the triplet state.