Efficient Dynamic Nuclear Polarization at 800 MHz/527 GHz with Trityl-Nitroxide Biradicals

Guinevere Mathies, Marc A. Caporini, Vladimir K. Michaelis, Yangping Liu, Kan Nian Hu, Deni Mance, Jay L. Zweier, Melanie Rosay, Marc Baldus, Robert G. Griffin

Research output: Contribution to journalArticlepeer-review

Abstract

Cross-effect (CE) dynamic nuclear polarization (DNP) is a rapidly developing technique that enhances the signal intensities in magic-angle spinning (MAS) NMR spectra. We report CE DNP experiments at 211, 600, and 800 MHz using a new series of biradical polarizing agents referred to as TEMTriPols, in which a nitroxide (TEMPO) and a trityl radical are chemically tethered. The TEMTriPol molecule with the optimal performance yields a record 1H NMR signal enhancement of 65 at 800 MHz at a concentration of 10 mM in a glycerol/water solvent matrix. The CE DNP enhancement for the TEMTriPol biradicals does not decrease as the magnetic field is increased in the manner usually observed for bis-nitroxides. Instead, the relatively strong exchange interaction between the trityl and nitroxide moieties determines the magnetic field at which the optimum enhancement is observed. Radical design: A series of biradicals consisting of a nitroxide radical chemically tethered to a trityl radical were employed for cross-effect dynamic nuclear polarization at 211, 600, and 800 MHz. The relatively strong exchange interaction between the trityl and nitroxide moieties determined the field strength at which the enhancement is optimized, and yielded a record 1H NMR signal enhancement of 65 at 800 MHz.

Original languageEnglish (US)
Pages (from-to)11770-11774
Number of pages5
JournalAngewandte Chemie - International Edition
Volume54
Issue number40
DOIs
StatePublished - Sep 1 2015
Externally publishedYes

Keywords

  • biradicals
  • cross-effect
  • dynamic nuclear polarization
  • polarizing agents
  • solid-state NMR spectroscopy

ASJC Scopus subject areas

  • Chemistry(all)
  • Catalysis

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