Campus Units
Chemistry
Document Type
Article
Publication Version
Submitted Manuscript
Publication Date
9-25-2018
Journal or Book Title
Journal of the American Chemical Society
DOI
10.1021/jacs.8b08081
Abstract
Dynamic Nuclear Polarization (DNP) solid-state NMR has developed into an invaluable tool for the investigation of a wide range of materials. However, the sensitivity gain achieved with many polarizing agents suffers from an unfavorable field and Magic Angle Spinning (MAS) frequency dependence. We present a series of new hybrid biradicals, soluble in organic solvents, that consist of an isotropic narrow EPR line radical, BDPA, tethered to a broad line nitroxide. By tuning the distance between the two electrons and the substituents at the nitroxide moiety, correlations between the electron-electron interactions and the electronic spin relaxation times on one hand, and the DNP enhancement factors on the other hand are established. The best radical in this series has a short methylene linker and bears bulky phenyl spirocyclohexyl ligands. In a 1.3 mm prototype DNP probe, it yields enhancements of up to 185 at 18.8 T (800 MHz 1H resonance frequency) and 40 kHz MAS. We show that this radical gives enhancement factors of over 60 in 3.2 mm sapphire rotors at both 18.8 and 21.1 T (900 MHz 1H resonance frequency), the highest magnetic field available today for DNP. The effect of the rotor size and of the microwave irradiation inside the MAS rotor is discussed. Finally, we demonstrate the potential of this new series of polarizing agents by recording high field 27Al and 29Si DNP Surface Enhanced NMR spectra (DNP SENS) of amorphous aluminosilicates and 17O NMR on silica nanoparticles.
Copyright Owner
American Chemical Society
Copyright Date
2018
Language
en
File Format
application/pdf
Recommended Citation
Wisser, Dorothea; Karthikeyan, Ganesan; Lund, Alicia; Casano, Gilles; Karoui, Hakim; Yulikov, Maxim; Menzildjian, Georges; Pinon, Arthur C.; Purea, Armin; Engelke, Frank; Chaudhari, Sachin R.; Kubicki, Dominik; Rossini, Aaron; Moroz, Ilia B.; Gajan, David; Copéret, Christophe; Jeschke, Gunnar; Lelli, Moreno; Emsley, Lyndon; Lesage, Anne; and Ouari, Olivier, "BDPA-Nitroxide Biradicals Tailored for Efficient Dynamic Nuclear Polarization Enhanced Solid-State NMR at Magnetic Fields up to 21.1 T" (2018). Chemistry Publications. 1071.
https://lib.dr.iastate.edu/chem_pubs/1071
Comments
This document is the unedited Author’s version of a Submitted Work that was subsequently accepted for publication in Journal of the American Chemical Society, copyright © American Chemical Society after peer review. To access the final edited and published work see DOI: 10.1021/jacs.8b08081. Posted with permission.