Accuracy in Homonuclear Distance Determinations by Solid-State NMR Spectroscopy: The Benefits of Fast Magic-Angle Spinning up to 100 kHz

ChemRxiv

Abstract

Homonuclear distance measurements by solid-state nuclear magnetic resonance (NMR) spectroscopy under magic-angle spinning (MAS) conditions are key to structural analysis in complex materials. While a wide variety of dipolar recoupling techniques involving the excitation of double quantum (DQ) coherences is available, the excitation efficiency is critically affected by the chemical-shift anisotropy (CSA) and the (often unknown) relative orientations between chemical-shift and dipolar-coupling tensors of the involved nuclei. Here, we demonstrate that a previously reported DQ-based sequence, Constant-Time Dipolar Recoupling Effects Nuclear Alignment Reduction (CT-DRENAR), enables robust and highly accurate homonuclear distance determinations for 19F and 31P nuclei under fast MAS conditions up to 100 kHz. We establish a numerical simulation approach to investigate the uncertainties in such distance measurements arising from the orientational effects and show that they become negligible when the MAS frequency exceeds approximately twice the spectral dispersion due to the CSA. Using this numerical simulation approach for data analysis, 31P–31P and 19F–19F effective distances in crystalline model systems with shortest internuclear contacts of 3–5 Å and CSA magnitudes exceeding 100 ppm are determined with accuracies of 0.1–0.5 Å. The experiment is applied to probe the conformational change of a phosphine ligand upon ruthenium coordination in a heterogeneous solid molecular ruthenium-polyphosphine catalyst. These results demonstrate the suitability of CT-DRENAR as a reliable strategy for precise homonuclear distance measurements in complex functional materials.

Authors 11

1. Yufei Wu Aachen Institute of Technical and Macromolecular Chemistry

   Max Planck Institute for Chemical Energy Conversion · RWTH Aachen University

   Affiliation as printed

   Institute of Technical and Macromolecular Chemistry, RWTH Aachen University, Worringerweg 2, Aachen, Germany, 52074

   Max Planck Institute for Chemical Energy Conversion

2. Julius Schlüter Aachen Institute of Technical and Macromolecular Chemistry

   RWTH Aachen University

   Affiliation as printed

   Institute of Technical and Macromolecular Chemistry, RWTH Aachen University, Worringerweg 2, Aachen, Germany, 52074

3. Felix J. Byn Aachen Institute of Technical and Macromolecular Chemistry

   RWTH Aachen University

   Affiliation as printed

   Institute of Technical and Macromolecular Chemistry, RWTH Aachen University, Worringerweg 2, Aachen, Germany, 52074

4. Janine C. Baums Aachen Institute of Technical and Macromolecular Chemistry

   RWTH Aachen University

   Affiliation as printed

   Institute of Technical and Macromolecular Chemistry, RWTH Aachen University, Worringerweg 2, Aachen, Germany, 52074

5. Jonas Koppe

   ETH Zurich

   Affiliation as printed

   Laboratory of Inorganic Chemistry, ETH Zürich, Vladimir-Prelog-Weg 2, Zürich, Switzerland, 8049

6. Tom Gabler

   Leipzig University

   Affiliation as printed

   Institute of Organic Chemistry

   Leipzig University

7. Kirsten Zeitler

   Leipzig University

   Affiliation as printed

   Institute of Organic Chemistry

   Leipzig University

8. Peter J. C. Hausoul Aachen Institute of Technical and Macromolecular Chemistry

   RWTH Aachen University

   Affiliation as printed

   Institute of Technical and Macromolecular Chemistry, RWTH Aachen University, Worringerweg 2, Aachen, Germany, 52074

9. Regina Palkovits Aachen Institute of Technical and Macromolecular Chemistry

   Forschungszentrum Jülich · Max Planck Institute for Chemical Energy Conversion · RWTH Aachen University

   Affiliation as printed

   Institute for a Sustainable Hydrogen Economy, Forschungszentrum Jülich, Wilhelm-Johnen-Straße, Jülich, Germany, 52428

   Institute of Technical and Macromolecular Chemistry, RWTH Aachen University, Worringerweg 2, Aachen, Germany, 52074

   Max Planck Institute for Chemical Energy Conversion

10. Hellmut Eckert

    Federal Institute For Materials Research and Testing

    Affiliation as printed

    Bundesanstalt für Materialforschung und -Prüfung, Richard Willstätter-Strasse 11, Berlin, Germany, 12489

11. Thomas Wiegand Aachen Institute of Technical and Macromolecular Chemistry

    Max Planck Institute for Chemical Energy Conversion · RWTH Aachen University

    Affiliation as printed

    Institute of Technical and Macromolecular Chemistry, RWTH Aachen University, Worringerweg 2, Aachen, Germany, 52074

    Max Planck Institute for Chemical Energy Conversion