Cryogenic and Dissolution DNP NMR on γ-Irradiated Organic Molecules

Area of Science:

• Nuclear Magnetic Resonance Spectroscopy
• Chemical Physics
• Materials Science

Background:

• Nuclear magnetic resonance (NMR) is crucial for chemical structure determination but suffers from low sensitivity.
• Dissolution dynamic nuclear polarization (dDNP) enhances NMR sensitivity by polarizing nuclei using electron spins.
• Conventional dDNP requires specific radical-containing glasses and cryogenic conditions.

Purpose of the Study:

• To investigate the efficacy of gamma-irradiated radicals for dynamic nuclear polarization (dNP).
• To evaluate the enhancement of 1H and 13C nuclei in solid-state and solution-state NMR.
• To compare gamma-irradiation-based dNP with conventional glass-based dNP methods.

Main Methods:

• Generation of radicals in powders via gamma irradiation.
• Solid-state NMR measurements at 1-5 K with microwave irradiation.
• Rapid dissolution of irradiated samples for solution-state NMR analysis.

Main Results:

• Gamma-irradiated radicals yielded higher 1H solid-state NMR signal enhancements than conventional dNP.
• Significant enhancements in solution-state 1H NMR signals were achieved after rapid dissolution.
• Modest but notable 700-800-fold enhancements in specific 13C solution NMR sites were observed at 11.7 T.

Conclusions:

• Gamma-irradiated radicals are effective for dNP, enhancing both solid-state and solution-state NMR signals.
• This method offers an alternative to conventional dNP, with potential advantages in radical preparation and stability.
• The study highlights the potential and limitations of using gamma-irradiated radicals for advanced NMR spectroscopy.