Systematic Evaluation of Polarizing Agents for Dynamic Nuclear Polarization Enhanced NMR

Abstract Dynamic nuclear polarization (DNP) can significantly enhance the sensitivity of nuclear magnetic resonance (NMR) spectroscopy, via the transfer of polarization from unpaired electrons to nuclei. As a result, there is considerable interest in improving DNP efficiency, particularly through the development of new polarizing agents (PAs). Here, a series of 32 PAs, including 26 dinitroxide and 6 hetero biradicals, of which 11 are introduced for the first time, were evaluated for their performance in DNP NMR experiments at magnetic field strengths of 9.4 T, 14.1 T, and 21.1 T. The PAs that are soluble in aqueous media were compared for different proton concentrations. A detailed comparison of the enhancement factors, polarization build‐up times, contribution factors, and the resulting overall sensitivity factors is provided. We find that the class of narrow‐line‐broad‐line biradicals not only yield the best performance at high field (21.1 T and 14.1 T) but remain among the best at intermediate fields (9.4 T). Specifically, SNAPol‐1 and HyTEK2 are consistently among the best performing radicals at any field. Among the dinitroxides, notably at 9.4 T, the AsymPol‐POK and M‐TinyPol families stand out in proton‐dense aqueous matrices, and a newly developed dinitroxide, NaphPolCbo, is found to provide the best overall sensitivity factor in organic solvent.

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Publication Details

Journal
Angewandte Chemie
Published
2025-05-26
DOI
https://doi.org/10.1002/ange.202505944
Primary Topic
Advanced NMR Techniques and Applications
Type
article
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article

Systematic Evaluation of Polarizing Agents for Dynamic Nuclear Polarization Enhanced NMR

Jiaxin Zhou, Hakim Karoui, Ran Wei, Shubha S. Gunaga et al.
Angewandte Chemie
Advanced NMR Techniques and Applications
article

Systematic Evaluation of Polarizing Agents for Dynamic Nuclear Polarization Enhanced NMR

Jiaxin Zhou, Hakim Karoui, Ran Wei, Shubha S. Gunaga, Snorri Th. Sigurdsson, Lyndon Emsley, S. K. Chatterjee, Mingqiang Huang, Yangping Liu, Yu Rao, Frédéric Mentink‐Vigier, Yuxuan Zhang, Faith J. Scott, Olivier Ouari, Amrit Venkatesh, Gilles Casano, Gaël De Paëpe, Seema Kumari, Ivanska M. Gierbolini-Colón
article en

Abstract

Abstract Dynamic nuclear polarization (DNP) can significantly enhance the sensitivity of nuclear magnetic resonance (NMR) spectroscopy, via the transfer of polarization from unpaired electrons to nuclei. As a result, there is considerable interest in improving DNP efficiency, particularly through the development of new polarizing agents (PAs). Here, a series of 32 PAs, including 26 dinitroxide and 6 hetero biradicals, of which 11 are introduced for the first time, were evaluated for their performance in DNP NMR experiments at magnetic field strengths of 9.4 T, 14.1 T, and 21.1 T. The PAs that are soluble in aqueous media were compared for different proton concentrations. A detailed comparison of the enhancement factors, polarization build‐up times, contribution factors, and the resulting overall sensitivity factors is provided. We find that the class of narrow‐line‐broad‐line biradicals not only yield the best performance at high field (21.1 T and 14.1 T) but remain among the best at intermediate fields (9.4 T). Specifically, SNAPol‐1 and HyTEK2 are consistently among the best performing radicals at any field. Among the dinitroxides, notably at 9.4 T, the AsymPol‐POK and M‐TinyPol families stand out in proton‐dense aqueous matrices, and a newly developed dinitroxide, NaphPolCbo, is found to provide the best overall sensitivity factor in organic solvent.

Angewandte ChemieVol. 137(31)
Florida State University (US), Centre National de la Recherche Scientifique (FR), University of Iceland (IS), Aix-Marseille Université (FR), Commissariat à l'Énergie Atomique et aux Énergies Alternatives (FR), CEA Grenoble (FR), Institut de Recherche Interdisciplinaire de Grenoble (FR), Institut de Chimie Radicalaire (FR), Institut Nanosciences et Cryogénie (FR), National High Magnetic Field Laboratory (US), Office Public d'Aménagement et de Construction de l'Isère (France) (FR), École Polytechnique Fédérale de Lausanne (CH), University of Virginia (US), Tianjin Medical University (CN), Université Grenoble Alpes (FR)
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