Tailoring of Polarizing Agents in the bTurea Series for Cross‐Effect Dynamic Nuclear Polarization in Aqueous Media |
| |
| Authors: | Claire Sauvée Dr Gilles Casano Dr Sébastien Abel Prof Antal Rockenbauer Dr Dimitry Akhmetzyanov Dr Hakim Karoui Prof Didier Siri Dr Fabien Aussenac Dr Werner Maas Dr Ralph T Weber Prof Thomas Prisner Dr Mélanie Rosay Prof Paul Tordo Dr Olivier Ouari |
| |
| Institution: | 1. Aix-Marseille Université, CNRS, ICR UMR 7273, Marseille cedex 20, France;2. Institute of Materials and Environmental Chemistry, Hungarian Academy of Sciences, Department of Physics, Budapest University of Technology and Economics and MTA-BME Condensed Matter Research Group, Budapest, Hungary;3. Institute of Physical and Theoretical Chemistry, Goethe University Frankfurt, Frankfurt-am-Main, Germany;4. Bruker BioSpin S.A.S., Wissembourg, France;5. Bruker BioSpin Corporation, Billerica, Massachusetts, USA |
| |
| Abstract: | A series of 18 nitroxide biradicals derived from bTurea has been prepared, and their enhancement factors ? (1H) in cross‐effect dynamic nuclear polarization (CE DNP) NMR experiments at 9.4 and 14.1 T and 100 K in a DNP‐optimized glycerol/water matrix (“DNP juice”) have been studied. We observe that ? (1H) is strongly correlated with the substituents on the polarizing agents, and its trend is discussed in terms of different molecular parameters: solubility, average e–e distance, relative orientation of the nitroxide moieties, and electron spin relaxation times. We show that too short an e–e distance or too long a T1e can dramatically limit ? (1H). Our study also shows that the molecular structure of AMUPol is not optimal and its ? (1H) could be further improved through stronger interaction with the glassy matrix and a better orientation of the TEMPO moieties. A new AMUPol derivative introduced here provides a better ? (1H) than AMUPol itself (by a factor of ca. 1.2). |
| |
| Keywords: | dinitroxides molecular dynamics organic synthesis polarizing agents solvent effects |
|
|
