Sydnone Photochemistry: Formation of Nitrenes
Didier Bégué1, Maryam Miri2, Avat Arman Taherpour2
1CNRS/Université de Pau et des Pays de l'Adour/E2S UPPA, Institut des Sciences Analytiques et de Physicochimie pour l'Environnement et les Matériaux, UMR5254, Pau 64000, France.
Photolysis of sydnones generates triplet arylnitrenes. Imidoylnitrenes are key intermediates, dissociating to form nitrenes and nitriles or rearranging to carbodiimides.
Area of Science:
- Photochemistry
- Organic Chemistry
- Spectroscopy
Background:
- Sydnone photolysis in argon matrices yields bicyclic lactones, CO2, and carbodiimides.
- Laser photolysis of 3-arylsydnones generates triplet arylnitrenes, detectable via ESR spectroscopy.
Purpose of the Study:
- Investigate computational routes from various precursors to arylnitrenes.
- Elucidate the role of imidoylnitrenes in sydnone and tetrazole photolyses.
Main Methods:
- Laser photolysis of 3-arylsydnones in MTHF matrix at 5 K.
- Electron spin resonance (ESR) spectroscopy to characterize triplet arylnitrenes.
- Computational studies using M06-2X/6-311+G(d,p) level of theory.
Main Results:
- Triplet arylnitrenes were generated and characterized by zero-field splitting parameters.
- Imidoylnitrenes identified as key intermediates in matrix photolyses.
- Computational analysis revealed two competing pathways for imidoylnitrenes with similar activation energies.
Conclusions:
- Imidoylnitrenes are crucial intermediates in sydnone and tetrazole photochemistry.
- Dissociation to nitrene and nitrile, and rearrangement to carbodiimide, are energetically similar pathways.
- Understanding these pathways provides insight into arylnitrene generation.
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