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Suppressing 1H spin diffusion in fast MAS proton detected heteronuclear correlation solid-state NMR experiments
Solid State Nuclear Magnetic Resonance
  • Amrit Venkatesh, Iowa State University and Ames Laboratory
  • Ivan Hung, National High Magnetic Field Laboratory (NHMFL)
  • Kasuni C. Boteju, Iowa State University and Ames Laboratory
  • Aaron D. Sadow, Iowa State University and Ames Laboratory
  • Peter L. Gor'kov, National High Magnetic Field Laboratory (NHMFL)
  • Zhehong Gan, National High Magnetic Field Laboratory (NHMFL)
  • Aaron J. Rossini, Iowa State University and Ames Laboratory
Document Type
Article
Disciplines
Publication Version
Accepted Manuscript
Publication Date
2-1-2020
DOI
10.1016/j.ssnmr.2019.101636
Abstract

Fast magic angle spinning (MAS) and indirect detection by high gyromagnetic ratio (γ) nuclei such as proton or fluorine are increasingly utilized to obtain 2D heteronuclear correlation (HETCOR) solid-state NMR spectra of spin-1/2 nuclei by using cross polarization (CP) for coherence transfer. However, one major drawback of CP HETCOR pulse sequences is that 1H spin diffusion during the back X→1H CP transfer step results in relayed correlations. This problem is particularly pronounced for the indirect detection of very low-γ nuclei such as 89Y, 103Rh, 109Ag and 183W where long contact times on the order of 10–30 ms are necessary for optimal CP transfer. Here we propose two methods that eliminate relayed correlations and allow more reliable distance information to be obtained from 2D HETCOR NMR spectra. The first method uses Lee-Goldburg (LG) CP during the X→1H back-transfer step to suppress 1H spin diffusion. We determine LG conditions compatible with fast MAS frequencies (νrot) of 40–95 kHz and show that 1H spin diffusion can be efficiently suppressed at low effective radiofrequency (RF) fields (ν1,eff ≪ 0.5νrot) and also at high effective RF fields (ν1,eff ≫ 2νrot). We describe modified Hartmann-Hahn LG-CP match conditions compatible with fast MAS and suitable for indirect detection of moderate-γ nuclei such as 13C, and low-γ nuclei such as 89Y. The second method uses D-RINEPT (dipolar refocused insensitive nuclei enhanced by polarization transfer) during the X→1H back-transfer step of the HETCOR pulse sequence. The effectiveness of these methods for acquiring HETCOR spectra with reduced relayed signal intensities is demonstrated with 1H{13C} HETCOR NMR experiments on l-histidine•HCl•H2O and 1H{89Y} HETCOR NMR experiments on an organometallic yttrium complex.

Comments

This is a manuscript of an article published as Venkatesh, Amrit, Ivan Hung, Kasuni C. Boteju, Aaron D. Sadow, Peter L. Gor'kov, Zhehong Gan, and Aaron J. Rossini. "Suppressing 1H spin diffusion in fast MAS proton detected heteronuclear correlation solid-state NMR experiments." Solid State Nuclear Magnetic Resonance 105 (2020): 101636. DOI: 10.1016/j.ssnmr.2019.101636. Posted with permission.

Creative Commons License
Creative Commons Attribution-NonCommercial-No Derivative Works 4.0 International
Copyright Owner
Elsevier Inc.
Language
en
File Format
application/pdf
Citation Information
Amrit Venkatesh, Ivan Hung, Kasuni C. Boteju, Aaron D. Sadow, et al.. "Suppressing 1H spin diffusion in fast MAS proton detected heteronuclear correlation solid-state NMR experiments" Solid State Nuclear Magnetic Resonance Vol. 105 (2020) p. 101636
Available at: http://works.bepress.com/aaron_sadow/69/