Skip to main content
Large Molecular Weight Nitroxide Biradicals Providing Efficient Dynamic Nuclear Polarization at Temperatures up to 200 K
Journal of the American Chemical Socity (2013)
  • Alexandre Zagdoun, Université de Lyon
  • Gilles Casano, Aix-Marseille Université
  • Olivier Ouari, Aix-Marseille Université
  • Martin Schwarzwalder, ETH Zürich
  • Aaron J. Rossini, Université de Lyon
  • Fabien Aussenac, Bruker BioSpin
  • Maxim Yulikov, ETH Zürich
  • Gunnar Jeschke, ETH Zürich
  • Christophe Coperet, ETH Zürich
  • Anne Lesage, University of Lyon
  • Paul Tordo, Aix-Marseille Université
  • Lyndon Emsley, University of Lyon
A series of seven functionalized nitroxide biradicals (the bTbK biradical and six derivatives) are investigated as exogenous polarization sources for dynamic nuclear polarization (DNP) solid-state NMR at 9.4 T and with ca. 100 K sample temperatures. The impact of electron relaxation times on the DNP enhancement (ε) is examined, and we observe that longer inversion recovery and phase memory relaxation times provide larger ε. All radicals are tested in both bulk 1,1,2,2-tetrachloroethane solutions and in mesoporous materials, and the difference in ε between the two cases is discussed. The impact of the sample temperature and magic angle spinning frequency on ε is investigated for several radicals each characterized by a range of electron relaxation times. In particular, TEKPol, a bulky derivative of bTbK with a molecular weight of 905 g·mol–1, is presented. Its high-saturation factor makes it a very efficient polarizing agent for DNP, yielding unprecedented proton enhancements of over 200 in both bulk and materials samples at 9.4 T and 100 K. TEKPol also yields encouraging enhancements of 33 at 180 K and 12 at 200 K, suggesting that with the continued improvement of radicals large ε may be obtained at higher temperatures.
Publication Date
July 24, 2013
Publisher Statement
Reprinted (adapted) with permission from Journal of the American Chemical Society, 135(34); Doi: 10.1021/ja405813t. Copyright 2013 American Chemical Society.
Citation Information
Alexandre Zagdoun, Gilles Casano, Olivier Ouari, Martin Schwarzwalder, et al.. "Large Molecular Weight Nitroxide Biradicals Providing Efficient Dynamic Nuclear Polarization at Temperatures up to 200 K" Journal of the American Chemical Socity Vol. 135 Iss. 34 (2013) p. 12790 - 12797
Available at: