Phenylnitrene: energetics, vibrational frequencies, and molecular structures

Upon the generation of phenylnitrene (C 6 H 5 N) by photolysis of phenyl azide, it is possible for the conversion to the cyanocyclopentadienyl radical (C 5 H 4 CN) or dehydroazepine (seven-membered ring) to take place, depending on experimental conditions. Little is known about the mechanisms or electronic states involved. Characterization of these species by spectroscopic means is difficult because it is frequently unknown which of these intermediates is predominant. For example, a recent analysis of high-resolution electronic spectra leads to the conclusion that the electronic spectrum long attributed to triplet phenylnitrene is due to the cyanocyclopentadienyl radical. This conclusion is supported by the present research