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Time-Resolved Resonance Raman Observation of the Dimerization of Didehydroazepines in Solution
journal contribution
posted on 2008-02-21, 00:00 authored by Jiadan Xue, Yong Du, Yung Ping Chuang, David Lee Phillips, Jin Wang, Calvin Luk, Christopher M. Hadad, Matthew S. PlatzTime-resolved resonance Raman (TR3) studies of the photochemistry of phenyl azide, 3-hyroxyphenyl azide,
3-methoxyphenyl azide and 3-nitrophenyl azide in acetonitrile:water solutions is reported. After photolysis
of these four aryl azides in room temperature solutions, only one species was observed in the TR3 spectra for
each azide, respectively at the probe wavelengths employed in the TR3 experiments. The species observed
after photolysis of 3-nitrophenyl azide was assigned to 3,3‘-dinitroazobenzene, an azo compound formed
from the dimerization reaction of triplet 3-nitrophenylnitrene. In contrast, the species observed after photolysis
of phenyl azide, 3-hydroxyphenyl azide and 3-methoxyphenyl azide were tentatively assigned to intermediates
formed from the dimerization of didehydroazepines that are produced from the ring expansion reaction of the
respective singlet arylnitrene. To our knowledge, this is the first time-resolved vibrational spectroscopic
observation of the dimerization reaction of didehydroazepines in solution. In addition, these are the first
resonance Raman spectra reported for dimers formed from didehydroazepines. We briefly discuss the structures,
properties and chemical reactivity of the dimer species observed in the TR3 spectra and possible implications
for the photochemistry of aryl azides.