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Updated: May 11, 2026
08:22
Measurement of Ultrafast Vibrational Coherences in Polyatomic Radical Cations with Strong-Field Adiabatic Ionization
Published on: August 6, 2018
Hyperfine interactions of narrow-line trityl radical with solvent molecules
S N Trukhan1, V F Yudanov, V M Tormyshev
1Boreskov Institute of Catalysis, pr. Ak. Lavrentieva, 5, Novosibirsk 630090, Russia. trukhan@catalysis.ru
Summary
Electron nuclear dipolar interactions cause forbidden satellite lines in CW EPR spectra of trityl radicals. Deuterium substitution revealed solvent protons significantly contribute to dynamic nuclear polarization (DNP) via these interactions.
Area of Science:
- Electron Paramagnetic Resonance (EPR) Spectroscopy
- Dynamic Nuclear Polarization (DNP)
- Radical Chemistry
Background:
- Electron nuclear dipolar interactions are crucial for certain dynamic nuclear polarization (DNP) mechanisms.
- These interactions also lead to forbidden satellite lines in continuous-wave Electron Paramagnetic Resonance (CW EPR) spectra, involving simultaneous electron and nuclear spin flips.
- Trityl radicals, widely used as DNP reagents, exhibit these satellite lines originating from Hydrogen-1 (¹H) nuclei, which are resolvable in CW EPR.
Purpose of the Study:
- To investigate the role of electron nuclear dipolar interactions in DNP mechanisms using trityl radicals.
- To quantify the contribution of both the radical's own hydrogens and solvent hydrogens to these interactions.
- To determine the relative importance of different hydrogen pools in DNP enhancement.
Main Methods:
- CW EPR spectroscopy was employed to analyze trityl radicals.
- Spectra were simulated using hyperfine parameters to determine the intensity of satellite lines.
- Isotopic substitution, replacing Hydrogen-1 (¹H) with Deuterium (²H) in both the radical and solvent, was used to differentiate dipolar interactions.
- The parameter reff, representing the integrated intensity of dipolar interactions, was calculated.
Main Results:
- Satellite lines from ¹H nuclei in trityl radicals were observed and quantified using EPR spectral simulations.
- Isotopic substitution allowed for the distinct determination of dipolar interactions from trityl hydrogens and solvent hydrogens.
- For the Finland trityl in methanol, the reff values indicated stronger integrated dipolar interactions from solvent ¹H compared to trityl ¹H.
- Solvent ¹H were identified as a more significant contributor to the DNP mechanism than the radical's ¹H.
Conclusions:
- Forbidden satellite lines in CW EPR spectra of trityl radicals provide insights into electron nuclear dipolar interactions.
- Solvent ¹H play a critical role in DNP enhancement, often exceeding the contribution from the radical's own ¹H.
- The parameter reff effectively characterizes the integrated dipolar interaction strength, highlighting the importance of solvent effects in DNP processes involving trityl radicals.
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