Proton hyperfine couplings and Overhauser DNP
Name
nihms-2079042.pdf
Description
Accepted version
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1.34 MB
Format
Adobe PDF
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Author(s)
Mardini, Michael
George, Christy
Palani, Ravi Shankar
Du, Xizi
Tan, Kong Ooi
Sergeyev, Ivan
Liu, Yangping
Griffin, Robert G
Date Issued
December 2024
Journal
Journal of Magnetic Resonance
Publisher
Elsevier BV
Version
Author's final manuscript
Abstract
We have prepared trityl radicals with protons at the positions of the -COOH group in the phenyl rings and examined their EPR spectra, which show large - hyperfine couplings, and their dynamic nuclear polarization (DNP) Zeeman field profiles . By assessing these polarizing agents for high-field and Overhauser effect DNP, we gain insight into the roles that these hyperfine couplings and other molecular properties play in the DNP performance of these radicals. Interestingly, we do not observe OE DNP in any of the three molecules we examined. This suggests that hyperfine couplings by themselves are not sufficient to support OE DNP. In this case the electron spin density is ∼75 % localized on the central carbon atom rather than being distributed uniformly over the aromatic rings. This is in contrast to BDPA where the distribution is delocalized. Our findings do not suggest that any of these radicals are particularly well-suited to high-field DNP. Furthermore, we emphasize that polarizing agents can be extremely sensitive to their solvent environment, even obscuring the intrinsic magnetic properties of the radical.
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Creative Commons Attribution-NonCommercial-NoDerivatives
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DOI of Published Version
https://doi.org/10.1016/j.jmr.2024.107797
