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Site Directed Spin Labeling and EPR Spectroscopic Studies of Pentameric Ligand-Gated Ion Channels
Published on: July 4, 2016
EPR studies on branched high-spin arylnitrenes
Sergei V Chapyshev1, Denis V Korchagin, Mikhail F Budyka
1Institute of Problems of Chemical Physics, Russian Academy of Sciences, 142432 Chernogolovka, Moscow Region, Russia. chap@icp.ac.ru
UV photolysis of triazide selectively produces triplet mononitrene, quintet dinitrene, and septet trinitrene. Dinitrene and trinitrene are the major products, with rotational isomers influencing magnetic parameters and EPR spectra.
Area of Science:
- Photochemistry
- Quantum Chemistry
- Spectroscopy
Background:
- Nitrenes are reactive intermediates with diverse electronic structures.
- Understanding the magnetic properties of nitrenes is crucial for their application in materials science and catalysis.
- Previous studies have explored the generation and characterization of various nitrene species.
Purpose of the Study:
- To investigate the UV photolysis of triazide in a low-temperature matrix.
- To characterize the resulting mononitrene, dinitrene, and trinitrene species using Electron Paramagnetic Resonance (EPR) spectroscopy.
- To determine the magnetic parameters (zero-field splitting) and analyze the influence of rotational isomers on these properties.
Main Methods:
- UV photolysis of triazide (3) in 2-methyl-tetrahydrofuran glass at 7 K.
- Analysis of photoproducts using Electron Paramagnetic Resonance (EPR) spectroscopy.
- Line-shape spectral simulations to determine magnetic parameters and rotational isomer distributions.
- Theoretical calculations (PBE/DZ(COSMO)//UB3LYP/6-311+G(d,p)) for magnetic parameter estimation.
Main Results:
- Selective production of triplet mononitrene (4), quintet dinitrene (6), and septet trinitrene (8).
- Dinitrene (6) and trinitrene (8) were the major products after 45 min irradiation, in a ~1:2 ratio.
- EPR spectral simulations revealed line-broadening parameters indicating rotational isomer variations of ±1° for dinitrene and ±3° for trinitrene.
- Calculated magnetic parameters showed good agreement with experimental values, with minor overestimations.
Conclusions:
- UV photolysis of triazide provides a route to generate multiple nitrene species with varying spin multiplicities.
- The zero-field splitting parameters (D) of these nitrenes are comparable to those with nitrene centers on the same aryl ring, despite larger distances.
- Spin-spin interactions play a significant role in determining the magnetic properties of branched nitrenes.
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