The missing link: triplet fluorocarbonyl nitrene FC(O)N

Area of Science:

• Physical Chemistry
• Spectroscopy
• Photochemistry

Background:

• Carbonyl nitrenes are reactive intermediates with limited experimental characterization.
• Understanding their properties is crucial for reaction mechanisms and synthetic applications.
• Previous studies have faced challenges in isolating and characterizing these species.

Purpose of the Study:

• To generate and characterize the elusive triplet fluorocarbonyl nitrene (FC(O)N).
• To investigate the spectroscopic properties (IR, UV/Vis, EPR) of FC(O)N.
• To explore the reactivity of FC(O)N under different irradiation conditions.

Main Methods:

• Matrix isolation of FC(O)N(3) in an argon matrix at 16 K.
• ArF excimer laser photolysis (193 nm) to generate FC(O)N.
• Characterization using IR, UV/Vis, EPR spectroscopy, and quantum-chemical calculations.
• Isotopic labeling studies for vibrational analysis.
• Visible and near-UV light irradiation experiments to study reactivity.

Main Results:

• High yield generation of triplet FC(O)N from FC(O)N(3) photolysis.
• Detailed spectroscopic data including six fundamental vibrations and isotopic shifts.
• Detection of four electronic transitions with vibrational fine structures.
• Observed reactivity of FC(O)N with N(2) under visible light and formation of FNCO under near-UV light.
• Formation of FNCO as a side product during nitrene generation.

Conclusions:

• The triplet fluorocarbonyl nitrene (FC(O)N) has been successfully generated and spectroscopically characterized.
• The study provides comprehensive data on its vibrational and electronic properties.
• FC(O)N exhibits distinct photochemical reactivity, converting back to the azide or forming FNCO.
• Insights into singlet-triplet energy gaps of carbonyl nitrenes are discussed.