Dynamic Nuclear Polarization (DNP) can significantly enhance the sensitivity of solid-state NMR. In DNP, microwave irradiation induces polarization transfer from unpaired electron spins to 1H nuclear spins via hyperfine couplings and spin-diffusion. The structure of the polarizing agents that host the electron spins is key for DNP efficiency. Currently, only a handful of structures perform well at very high magnetic fields (≥18.8 T), and enhancements are significantly lower than those obtained at lower fields. Here, we introduce a new series of water-soluble nitroxide biradicals with a scaffold augmented by dihydroxypropyl antenna chains that perform significantly better than previous dinitroxides at 18.8 T. The new radical M-TinyPol(OH)4 yields enhancement factors of ∼220 at 18.8 T and 60 kHz MAS, which is a nearly factor 2 larger than for the previous best performing dinitroxides. The performance is understood through 2H ESEEM measurements to probe solvent accessibility, supported by Molecular Dynamics simulations, and by experiments on deuterated samples. We find that the deuterated glycerol molecules in the matrix are located mainly in the second solvation shell of the NO bond, limiting access for protonated water molecules, and restricting spin diffusion pathways. This provides a rational understanding of why the dihydroxypropyl chains present in the best-performing structures are essential to deliver the polarization to the bulk solution.

Efficient DNP at high fields and fast MAS with antenna-sensitized dinitroxides / Niccoli, Lorenzo; Casano, Gilles; Menzildjian, Georges; Yulikov, Maxim; Robinson, Thomas; Akrial, Salah-Eddine; Wang, Zhuoran; Reiter, Christian; Purea, Armin; Siri, Didier; Venkatesh, Amrit; Emsley, Lyndon; Gajan, David; Lelli, Moreno; Ouari, Olivier; Lesage, Anne. - In: CHEMICAL SCIENCE. - ISSN 2041-6520. - STAMPA. - 15:(2024), pp. 16582-16593. [10.1039/d4sc04473h]

Efficient DNP at high fields and fast MAS with antenna-sensitized dinitroxides

Niccoli, Lorenzo
Formal Analysis
;
Emsley, Lyndon
Membro del Collaboration Group
;
Lelli, Moreno
Writing – Review & Editing
;
2024

Abstract

Dynamic Nuclear Polarization (DNP) can significantly enhance the sensitivity of solid-state NMR. In DNP, microwave irradiation induces polarization transfer from unpaired electron spins to 1H nuclear spins via hyperfine couplings and spin-diffusion. The structure of the polarizing agents that host the electron spins is key for DNP efficiency. Currently, only a handful of structures perform well at very high magnetic fields (≥18.8 T), and enhancements are significantly lower than those obtained at lower fields. Here, we introduce a new series of water-soluble nitroxide biradicals with a scaffold augmented by dihydroxypropyl antenna chains that perform significantly better than previous dinitroxides at 18.8 T. The new radical M-TinyPol(OH)4 yields enhancement factors of ∼220 at 18.8 T and 60 kHz MAS, which is a nearly factor 2 larger than for the previous best performing dinitroxides. The performance is understood through 2H ESEEM measurements to probe solvent accessibility, supported by Molecular Dynamics simulations, and by experiments on deuterated samples. We find that the deuterated glycerol molecules in the matrix are located mainly in the second solvation shell of the NO bond, limiting access for protonated water molecules, and restricting spin diffusion pathways. This provides a rational understanding of why the dihydroxypropyl chains present in the best-performing structures are essential to deliver the polarization to the bulk solution.
2024
15
16582
16593
Goal 3: Good health and well-being
Goal 7: Affordable and clean energy
Goal 9: Industry, Innovation, and Infrastructure
Niccoli, Lorenzo; Casano, Gilles; Menzildjian, Georges; Yulikov, Maxim; Robinson, Thomas; Akrial, Salah-Eddine; Wang, Zhuoran; Reiter, Christian; Pure...espandi
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Utilizza questo identificatore per citare o creare un link a questa risorsa: https://hdl.handle.net/2158/1413953
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