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Solid state NMR

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Over the years, NMR spectroscopy has emerged as a powerful methodology to characterize the structure of molecules and materials. While solution NMR for spin-1/2 nuclei is widely used for deciphering the structure of organic molecules, it only provides averaged information due to Brownian motion in liquids and is not readily applicable to functional materials such as heterogeneous catalysts. In contrast, solid-state NMR (ssNMR) is perfectly suited for addressing this issue. Furthermore, ssNMR provides unique element-specific quantitative information about local surrounding and electronic structure, necessary to enable molecular-level understanding of molecules and materials.[1-6] Descriptors such as the chemical shift anisotropy and electric field gradient tensors (for quadrupolar nuclei, which represent most NMR active nuclei in the periodic table), are unique for solid-state NMR and are directly linked to the structure, which ultimately could be related to performance/reactivity of the material/catalyst, respectively.[7-8] Intrinsically, the main challenge in NMR is sensitivity due to weak polarization of nuclear spins by the external magnetic field, which is significantly worsened by a low amount of nuclei of interest when it comes to surface active sites. This can be overcome by hyperpolarization techniques such as DNP-SENS, developed and commonly applied in the Copéret group.[9]

Figure 1. Field and magic angle spinning (MAS) dependence of a prototypically quadrupole NMR signature with respect to field and spinning speed.
Figure 1. Field and magic angle spinning (MAS) dependence of a prototypically quadrupole NMR signature with respect to field and spinning speed.  

The solid-state NMR equipment available in the group includes a 600 MHz DNP NMR spectrometer with an array of probes with rotor sizes from 1.3 to 3.2 mm, covering nuclei in the range between 1H and 89Y, allowing to conduct NMR measurements in the temperature interval between 100 K and 300 K. Additionally, the Copéret group has access to the shared LAC NMR facility as well as spectrometers within the broad collaboration network (within ETHZ, or with EPFL, CRMN Lyon, NHFML Tallahassee, Iowa State University… etc.).

Figure 2. Left: 600 MHz spectrometer connected to the respective LT cabinet and gyrotron allowing to conduct DNP and LT measurements at the temperatures down to 100 K. Right: 3.2 HXY low-gamma DNP probe for 600 MHz spectrometer.
Figure 2. Left: 600 MHz spectrometer connected to the respective LT cabinet and gyrotron allowing to conduct DNP and LT measurements at the temperatures down to 100 K. Right: 3.2 HXY low-gamma DNP probe for 600 MHz spectrometer.

Early efforts in Copéret group were focused on characterization of ligands bound to surface sites in materials and heterogeneous catalysts, i.e. 1H, 13C, 15N, and 31P NMR.[6, 10-14] In the last years, the focus of the group has shifted towards direct observation of metal sites, allowing to gain unprecedented insights into the geometry and electronic structure, because NMR chemical shift directly probes frontier molecular orbitals, hence reactivity. Currently, Copéret group uses state-of-the art methodologies to characterize industrially relevant catalysts at the molecular level with the ultimate goal of contributing to their rational development, e.g. supported metathesis catalysts, zeolites or complex hybrid organic inorganic materials like the Ziegler-Natta Catalysts shown below. [7, 8, 15, 16]

Figure 3. 47/49Ti NMR spectrum of Ziegler-Natta catalysts (olefin polymerization) and 95Mo NMR spectra of MoOx@SiO2 (olefin metathesis catalysts). [8,15,16]
Figure 3. 47/49Ti NMR spectrum of Ziegler-Natta catalysts (olefin polymerization) and 95Mo NMR spectra of MoOx@SiO2 (olefin metathesis catalysts). [8,15,16]  

Selected References 

1. S. P. Brown, ‘Advanced solid-state NMR methods for characterising structure and self-assembly in supramolecular chemistry, polymers and hydrogels’, Curr. Opin. Colloid Interface Sci. 2018, 33, 86–98.


2. D. Lalli, M. N. Idso, L. B. Andreas, S. Hussain, N. Baxter, S. Han, B. F. Chmelka, G. Pintacuda, ‘Proton-Based Structural Analysis of a Heptahelical Transmembrane Protein in Lipid Bilayers’, J. Am. Chem. Soc. 2017, 139, 13006–13012.

3. D. Lacabanne, B. H. Meier, A. Böckmann, ‘Selective labeling and unlabeling strategies in protein solid-state NMR spectroscopy’, J. Biomol. NMR 2018, 71, 141–150.

4. L. Piveteau, T. C. Ong, B. J. Walder, D. N. Dirin, D. Moscheni, B. Schneider, J. Bär, L. Protesescu, N. Masciocchi, A. Guagliardi, L. Emsley, C. Copéret, M. V. Kovalenko, ‘Resolving the Core and the Surface of CdSe Quantum Dots and Nanoplatelets Using Dynamic Nuclear Polarization Enhanced PASS-PIETA NMR Spectroscopy’, ACS Cent. Sci. 2018, 4, 1113–1125.

5. S. H. Cho, S. Ghosh, Z. J. Berkson, J. A. Hachtel, J. Shi, X. Zhao, L. C. Reimnitz, C. J. Dahlman, Y. Ho, A. Yang, Y. Liu, J. C. Idrobo, B. F. Chmelka, D. J. Milliron, ‘Syntheses of Colloidal F:In 2 O 3 Cubes: Fluorine-Induced Faceting and Infrared Plasmonic Response’, Chem. Mater. 2019, 31, 2661–2676.

6. C. Copéret, W.-C. C. Liao, C. P. Gordon, T.-C. C. Ong, ‘Active Sites in Supported Single-Site Catalysts: An NMR Perspective’, J. Am. Chem. Soc. 2017, 139, 10588–10596

7. Y. Kakiuchi, S. R. Docherty, Z. J. Berkson, A. V. Yakimov, M. Wörle, C. Copéret, S. Aghazada, Origin of Reactivity Trends of an Elusive Metathesis Intermediate from NMR Chemical Shift Analysis of Surrogate Analogues, J. Am. Chem. Soc. 2024, 146, 29, 20168–20182

8. Z. J. Berkson, R. Zhu, C. Ehinger, L. Lätsch, S. P. Schmid, D. Nater, S. Pollitt, O. V. Safonova, S. Björgvinsdóttir, A. B. Barnes, Y. Román-Leshkov, G. A. Price, G. J. Sunley, C. Copéret, Active Site Descriptors from 95Mo NMR Signatures of Silica-Supported Mo-Based Olefin Metathesis Catalysts, J. Am. Chem. Soc. 2023, 145, 23, 12651–12662

9. Rossini, A.J., et al., Dynamic Nuclear Polarization Surface Enhanced NMR Spectroscopy. Accounts of Chemical Research, 2013. 46(9): p. 1942-1951.

10. M. Valla, A. J. Rossini, M. Caillot, C. Chizallet, P. Raybaud, M. Digne, A. Chaumonnot, A. Lesage, L. Emsley, J. A. Van Bokhoven, C. Copéret, ‘Atomic Description of the Interface between Silica and Alumina in Aluminosilicates through Dynamic Nuclear Polarization Surface-Enhanced NMR Spectroscopy and First-Principles Calculations’, J. Am. Chem. Soc. 2015, 137, 10710–10719.

11. C. P. Gordon, C. Raynaud, R. A. Andersen, C. Copéret, O. Eisenstein, ‘Carbon-13 NMR Chemical Shift: A Descriptor for Electronic Structure and Reactivity of Organometallic Compounds’, Acc. Chem. Res. 2019, 52, 2278–2289


12. M. Valla, R. Wischert, A. Comas-Vives, M. P. Conley, R. Verel, C. Copéret, P. Sautet, ‘Role of tricoordinate Al sites in CH3ReO3/Al2O3olefin metathesis catalysts’, J. Am. Chem. Soc. 2016, 138, 6774–6785.

13. P. S. Engl, C. B. Santiago, C. P. Gordon, W. C. Liao, A. Fedorov, C. Copéret, M. S. Sigman, A. Togni, ‘Exploiting and understanding the selectivity of Ru-N-Heterocyclic carbene metathesis catalysts for the ethenolysis of cyclic olefins to α,ω-Dienes’, J. Am. Chem. Soc. 2017, 139, 13117–13125.

14. I. B. Moroz, K. Larmier, W. C. Liao, C. Copéret, ‘Discerning γ-Alumina Surface Sites with Nitrogen-15 Dynamic Nuclear Polarization Surface Enhanced NMR Spectroscopy of Adsorbed Pyridine’, J. Phys. Chem. C 2018, 122, 10871–10882.

15. A. V. Yakimov, C. J. Kaul, Y. Kakiuchi, S. Sabisch, F. M. Bolner, J. Raynaud, V. Monteil, P. Berruyer, C. Copéret, Well-Defined Ti Surface Sites in Ziegler–Natta Pre-Catalysts from 47/49Ti Solid-State Nuclear Magnetic Resonance Spectroscopy, J. Phys. Chem. Lett. 2024, 15, 11, 3178–3184

16. L. Lätsch, C. J. Kaul, A. V. Yakimov, I. B. Müller, A. Hassan, B. Perrone, S. Aghazada, Z. J. Berkson, T. De Baerdemaeker, A. Parvulescu, K. Seidel, J. H. Teles, C. Copéret, NMR Signatures and Electronic Structure of Ti Sites in Titanosilicalite-1 from Solid-State 47/49Ti NMR Spectroscopy, J. Am. Chem. Soc. 2023, 145, 28, 15018–15023