Determination of the Singlet-Triplet Splitting and Electron Affinity of o-Benzyne by Negative Ion Photoelectron Spectroscopy

Article abstract of DOI:10.1021/ja00267a003

The photoelectron spectrum of the o-benzyne negative ion displays transitions to both the X/¹A₁ and a/³B₂ states of the neutral molecule.Results yield adiabatic electron affinities of 0.560(10) and 0.551(10) eV for C6H4 and C6D4, respectively.These values are consistent with extrapolations from studies of larger strained cycloalkynes and imply that the lowest unoccupied MO of o-benzyne is primarly an antibonding acetylenic orbital.The o-benzyne singlet-triplet splitting is determined to be 37.7(6) kcal/mol.Several new vibrational frequencies for the neutral and anionic species are reported.