Long-Lived Nuclear Spin States in Methyl Groups and Quantum-Rotor-Induced Polarization

Long-Lived Nuclear Spin States in Methyl Groups and Quantum-Rotor-Induced Polarization

Substances containing rapidly rotating methyl groups may exhibit long-lived states (LLSs) in solution, with relaxation times substantially longer than the conventional spin-lattice relaxation time T 1. The states become long-lived through rapid internal rotation of the CH3 group, which imposes an ap...

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Bibliographic Details
Published in:Journal of the American Chemical Society Vol. 135; no. 50; pp. 18746 - 18749
Main Authors: Meier, Benno, Dumez, Jean-Nicolas, Stevanato, Gabriele, Hill-Cousins, Joseph T, Roy, Soumya Singha, Håkansson, Pär, Mamone, Salvatore, Brown, Richard C. D, Pileio, Giuseppe, Levitt, Malcolm H
Format: Journal Article
Language:English
Published: United States American Chemical Society 18-12-2013
Online Access:Get full text
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Summary:Substances containing rapidly rotating methyl groups may exhibit long-lived states (LLSs) in solution, with relaxation times substantially longer than the conventional spin-lattice relaxation time T 1. The states become long-lived through rapid internal rotation of the CH3 group, which imposes an approximate symmetry on the fluctuating nuclear spin interactions. In the case of very low CH3 rotational barriers, a hyperpolarized LLS is populated by thermal equilibration at liquid helium temperature. Following dissolution, cross-relaxation of the hyperpolarized LLS, induced by heteronuclear dipolar couplings, generates strongly enhanced antiphase NMR signals. This mechanism explains the NMR signal enhancements observed for 13C-γ-picoline (Icker, M.; Berger, S. J. Magn. Reson. 2012, 219, 1–3).
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ISSN:0002-7863
1520-5126
DOI:10.1021/ja410432f