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Observing Nearby Nuclei on Paramagnetic Trityls and MOFs via DNP and Electron Decoupling |
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| Authors: | Prof Kong Ooi Tan Dr Luming Yang Michael Mardini Dr Choon Boon Cheong Prof Benoit Driesschaert Prof Mircea Dinc? Prof Robert G Griffin |
| Institution: | 1. Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA-02139 USA
Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA-02139 USA Laboratoire des Biomolécules, LBM, Département de Chimie, École Normale Supérieure, PSL University, Sorbonne Université, CNRS, 75005 Paris, France;2. Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA-02139 USA Research Group EPR Spectroscopy, Max Planck Institute for Multidisciplinary Sciences, Göttingen, 37077 Germany;3. Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA-02139 USA Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA-02139 USA;4. Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA-02139 USA Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA-02139 USA Institute of Sustainability for ChemicalsEnergy and Environment, 1 Pesek Road, Jurong Island, Singapore, 627833 Singapore;5. Department of Pharmaceutical Sciences, School of Pharmacy, West Virginia University, Morgantown, WV-2650 USA;6. Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA-02139 USA |
| Abstract: | Dynamic nuclear polarization (DNP) is an NMR sensitivity enhancement technique that mediates polarization transfer from unpaired electrons to NMR-active nuclei. Despite its success in elucidating important structural information on biological and inorganic materials, the detailed polarization-transfer pathway from the electrons to the nearby and then the bulk solvent nuclei, and finally to the molecules of interest-remains unclear. In particular, the nuclei in the paramagnetic polarizing agent play significant roles in relaying the enhanced NMR polarizations to more remote nuclei. Despite their importance, the direct NMR observation of these nuclei is challenging because of poor sensitivity. Here, we show that a combined DNP and electron decoupling approach can facilitate direct NMR detection of these nuclei. We achieved an ～80 % improvement in NMR intensity via electron decoupling at 0.35 T and 80 K on trityl radicals. Moreover, we recorded a DNP enhancement factor of  ～90 and ～11 % higher NMR intensity using electron decoupling on paramagnetic metal-organic framework, magnesium hexaoxytriphenylene (MgHOTP MOF). |
| Keywords: | dynamic nuclear polarization electron decoupling hyperpolarization metal-organic framework |