Solid state nuclear magnetic resonance最新文献

{"title":"Protonation tuned dipolar order mediated 1H→13C cross-polarization for dissolution-dynamic nuclear polarization experiments","authors":"Stuart J. Elliott ,&nbsp;Quentin Stern,&nbsp;Olivier Cala,&nbsp;Sami Jannin","doi":"10.1016/j.ssnmr.2021.101762","DOIUrl":"https://doi.org/10.1016/j.ssnmr.2021.101762","url":null,"abstract":"<div><p><span>A strategy of dipolar order mediated nuclear spin polarization transfer has recently been combined with dissolution-dynamic nuclear polarization (</span><em>d</em><span>DNP) and improved by employing optimized shaped radiofrequency pulses and suitable molecular modifications. In the context of </span><em>d</em>DNP experiments, this offers a promising means of transferring polarization from high-gamma ¹H spins to insensitive ¹³C spins with lower peak power and lower energy compared with state-of-the-art cross-polarization schemes. The role of local molecular groups and the glassing matrix protonation level are both postulated to play a key role in the polarization transfer pathway via an intermediary reservoir of dipolar spin order. To gain appreciation of the mechanisms involved in the dipolar order mediated polarization transfer under <em>d</em>DNP conditions, we investigate herein the influence of the pivotal characteristics of the sample makeup: (<em>i</em>) revising the protonation level for the constituents of the DNP glass; and (<em>ii</em>) utilizing deuterated molecular derivatives. Experimental demonstrations are presented for the case of [1–¹³<span>C]sodium acetate. We find that the proton sample molarity has a large impact on both the optimal parameters and the performance of the dipolar order mediated cross-polarization sequence, with the </span>¹³C signal build-up time drastically shortened in the case of high solvent protonation levels. In the case of a deuterated molecular derivative, we observe that the nearby ²<span>H substituted methyl group is deleterious to the </span>¹H→¹³C transfer phenomenon (particularly at low levels of sample protonation). Overall, increased solvent protonation makes the dipolar order governed polarization transfer significantly faster and more efficient. This study sheds light on the influential sample formulation traits which govern the dipolar order-controlled transfer of polarization and indicates that the polarization transfer efficiencies of deuterated molecules can be boosted and reach high performances simply by adequate solvent protonation.</p></div>","PeriodicalId":21937,"journal":{"name":"Solid state nuclear magnetic resonance","volume":"116 ","pages":"Article 101762"},"PeriodicalIF":3.2,"publicationDate":"2021-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91640813","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A toolbox for improving the workflow of NMR crystallography","authors":"Patrick M.J. Szell ,&nbsp;Sten O. Nilsson Lill ,&nbsp;Helen Blade ,&nbsp;Steven P. Brown ,&nbsp;Leslie P. Hughes","doi":"10.1016/j.ssnmr.2021.101761","DOIUrl":"10.1016/j.ssnmr.2021.101761","url":null,"abstract":"<div><p>NMR crystallography is a powerful tool with applications in structural characterization and crystal structure verification, to name two. However, applying this tool presents several challenges, especially for industrial users, in terms of consistency, workflow, time consumption, and the requirement for a high level of understanding of experimental solid-state NMR and GIPAW-DFT calculations. Here, we have developed a series of fully parameterized scripts for use in Materials Studio and TopSpin, based on the .magres file format, with a focus on organic molecules (e.g. pharmaceuticals), improving efficiency, robustness, and workflow. We separate these tools into three major categories: performing the DFT calculations, extracting &amp; visualizing the results, and crystallographic modelling. These scripts will rapidly submit fully parameterized CASTEP jobs, extract data from the calculations, assist in visualizing the results, and expedite the process of structural modelling. Accompanied with these tools is a description on their functionality, documentation on how to get started and use the scripts, and links to video tutorials for guiding new users. Through the use of these tools, we hope to facilitate NMR crystallography and to harmonize the process across users.</p></div>","PeriodicalId":21937,"journal":{"name":"Solid state nuclear magnetic resonance","volume":"116 ","pages":"Article 101761"},"PeriodicalIF":3.2,"publicationDate":"2021-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"39695597","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Study of the structure and dynamics at various parts of the antibacterial drug molecule cefpodoxime proxetil","authors":"Krishna Kishor Dey ,&nbsp;Manasi Ghosh","doi":"10.1016/j.ssnmr.2021.101752","DOIUrl":"10.1016/j.ssnmr.2021.101752","url":null,"abstract":"<div><p><span>The structure and dynamics of cefpodoxime proxetil<span> are elucidated by measuring chemical shift anisotropy (CSA) tensor, spin-lattice relaxation time, and local correlation time at twenty-one crystallographically different </span></span>¹³C nuclei sites. The principal components of CSA tensor of cefpodoxime proxetil are extracted by the two-dimensional phase adjusted sinning sideband (2DPASS) cross-polarization magic angle spinning (CP-MAS) solid-state NMR experiment, and the spin-lattice relaxation time is measured by the method outlined by Torchia(T1CP). The local correlation time is calculated by bearing in mind that the spin-lattice relaxation mechanism of ¹³C nuclei is mainly governed by the CSA interaction and the heteronuclear dipole-dipole interaction. The aminothiazole ring, <span><math><mrow><mi>β</mi></mrow></math></span><span>-lactam ring, and dihydrothiazine ring provide stability to the drug molecule and increase the affinity of the drug to penicillin-binding proteins (PBPs) receptors. The principal components of CSA parameters, spin-lattice relaxation time, and local correlation time vary substantially for carbon nuclei residing on these three rings. These signify that not only the electronic environment, but the molecular conformation<span>, and the local dynamics are also altered within the ring. The substitution of the acyl side chain, oxime group, and the aminothiazole ring at the C7 position of the </span></span><span><math><mrow><mi>β</mi></mrow></math></span><span><span>-lactam ring enhances the antibacterial activity<span> and the binding affinity of the drug. A huge variation of the spin-lattice relaxation time and local correlation time is observed in those regions. The change in the electron </span></span>charge distribution and nuclear spin dynamics at different parts of the drug molecule is clear by CSA and spin-lattice relaxation measurements, which will enrich the field “NMR crystallography”.</span></p></div>","PeriodicalId":21937,"journal":{"name":"Solid state nuclear magnetic resonance","volume":"115 ","pages":"Article 101752"},"PeriodicalIF":3.2,"publicationDate":"2021-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.ssnmr.2021.101752","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"39269282","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"125Te NMR for structural investigations in phase change materials: Optimization of experimental conditions coupled to NMR shift prediction","authors":"J. Lizion ,&nbsp;A. Piarristeguy ,&nbsp;R. Laskowski ,&nbsp;P. Blaha ,&nbsp;R. Escalier ,&nbsp;M. Ménétrier ,&nbsp;A. Pradel ,&nbsp;G. Silly","doi":"10.1016/j.ssnmr.2021.101751","DOIUrl":"10.1016/j.ssnmr.2021.101751","url":null,"abstract":"<div><p><span><span>Phase Change Materials as those of the Ge-Sb-Te </span>ternary system are of great interest for technological applications. Properties of these compounds are strongly related to presence of vacancies and structural investigations remain challenging. In this paper we evidence that </span>¹²⁵<span>Te NMR in natural abundance and using commercial systems at intermediate field (14.1 ​T) together with NMR parameters prediction can contribute to improve understanding of electronic structure of such systems. GeTe is a typical phase change material, whose structure contains germanium vacancies, even in its stoichiometric form, giving it metallic properties. Here, we use nominal Ge</span>₅₀Te₅₀ and Ge₄₈Te₅₂<span> crystalline samples as an example to optimize the WURST-CPMG technique, a powerful technique to record wide NMR spectra which has not yet been used on </span>¹²⁵Te. The goal was to minimize the time devoted to experiments as well as maximize the signal-to-noise ratio in order to detect small intensity signals directly linked to vacancies. Virtual Crystal Approximation (VCA) calculations performed with WIEN2K helped to interpret the NMR spectra. For Te-based crystalline conducting samples the best experimental results were obtained using 3.2 ​mm thin wall rotors with diluted samples 40 ​vol% GeTe-60 ​vol% SiO₂<span>. In addition to the WURST-CPMG technique, high resolution spectra using MAS<span> as implemented in the pj-MAT technique allowed us to identify the distributions of chemical shift parameters in the high intensity contribution of the 1D spectra. The NMR spectra recorded on the samples showed that an addition of Tellurium in the stoichiometric Ge</span></span>₅₀Te₅₀ sample leads to an important broadening of the spectrum together with a shift of the lines. According to VCA calculations it could be attributed to a distribution of concentrations of germanium vacancies in the sample and it would appear that Knight Shift but also Chemical Shift could contribute in similar proportion to the NMR line position when metavalent bonding is invoked.</p></div>","PeriodicalId":21937,"journal":{"name":"Solid state nuclear magnetic resonance","volume":"115 ","pages":"Article 101751"},"PeriodicalIF":3.2,"publicationDate":"2021-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.ssnmr.2021.101751","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"39280602","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Accurate fragment-based 51-V chemical shift predictions in molecular crystals","authors":"Amanda Mathews,&nbsp;Joshua D. Hartman","doi":"10.1016/j.ssnmr.2021.101733","DOIUrl":"10.1016/j.ssnmr.2021.101733","url":null,"abstract":"<div><p><span>Nuclear magnetic resonance (NMR) spectroscopy plays a crucial role in determining molecular structure for complex biological and pharmaceutical compounds. NMR investigations are increasingly reliant on computation for mapping spectral features to chemical structures. Here we benchmark the accuracy of fragment-based </span>⁵¹<span>V chemical shielding tensor calculations using a training set comprised of 10 biologically and pharmaceutically relevant oxovanadium complexes. Using our self-consistent reproduction of the Madelung potential (SCRMP) electrostatic embedding model, we demonstrate comparable performance between fragment methods and computationally demanding cluster-based techniques. Specifically, fragment methods employing hybrid density functionals are capable of reproducing the experimental </span>⁵¹V isotropic chemical shifts with a training set rms error of <span><math><mrow><mo>~</mo></mrow></math></span><span>9 ​ppm, representing a 20% improvement over traditional plane wave techniques. We provide training set-derived linear regression models for mapping the absolute shieldings obtained from computation to the experimentally determined chemical shifts using four common density functionals; PBE0, B3LYP, PBE, and BLYP. Finally, we establish the utility of fragment methods and the reported regression parameters examining four oxovanadium structures excluded from the training set including the tetracoordinate oxovanadium silicate </span><span><math><mrow><msub><mrow><mo>(</mo><mrow><mi>P</mi><msub><mi>h</mi><mn>3</mn></msub><mi>S</mi><mi>i</mi><mi>O</mi></mrow><mo>)</mo></mrow><mn>3</mn></msub><mi>V</mi><mi>O</mi></mrow></math></span>, VO¹⁵NGlySalbz which contains redox-active ligands, and the solid-state form of the common ⁵¹V NMR reference compound <span><math><mrow><mi>V</mi><mi>O</mi><mi>C</mi><msub><mi>l</mi><mn>3</mn></msub></mrow></math></span>.</p></div>","PeriodicalId":21937,"journal":{"name":"Solid state nuclear magnetic resonance","volume":"114 ","pages":"Article 101733"},"PeriodicalIF":3.2,"publicationDate":"2021-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.ssnmr.2021.101733","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"38989309","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Determination of the chemical shift tensor anisotropy and asymmetry of strongly dipolar coupled protons under fast MAS","authors":"Takeshi Kobayashi ,&nbsp;Frédéric A. Perras ,&nbsp;Yusuke Nishiyama","doi":"10.1016/j.ssnmr.2021.101743","DOIUrl":"10.1016/j.ssnmr.2021.101743","url":null,"abstract":"<div><p><span><span><span>Orientationally-dependent interactions such as dipolar coupling, quadrupolar coupling, and </span>chemical shift anisotropy (CSA) contain a wealth of spatial information that can be used to elucidate </span>molecular conformations and dynamics. To determine the sign of the chemical shift tensor anisotropy parameter (</span><em>δ</em>_aniso), both the |<em>m</em>| ​= ​1 and |<em>m</em>| ​= ​2 components of the CSA need to be symmetry allowed, while the recoupling of the |<em>m</em>| ​= ​1 term is accompanied with the reintroduction of homonuclear dipolar coupling components. Therefore, previously suggested sequences which solely recouple the |<em>m</em>| ​= ​2 term cannot determine the sign a ¹H's <em>δ</em>_aniso in a densely-coupled network. In this study, we demonstrate the CSA recoupling of strongly dipolar coupled ¹H spins using the <span><math><mrow><mi>C</mi><msubsup><mi>n</mi><mi>n</mi><mn>1</mn></msubsup><mrow><mo>(</mo><mrow><msub><mn>90</mn><mn>0</mn></msub><msub><mn>360</mn><mn>180</mn></msub><msub><mn>540</mn><mn>0</mn></msub><msub><mn>360</mn><mn>180</mn></msub><msub><mn>90</mn><mn>0</mn></msub></mrow><mo>)</mo></mrow></mrow></math></span> sequence. This pulse scheme recouples both the |<em>m</em>| ​= ​1 and |<em>m</em>| ​= ​2 CSA terms but the scaling factors for the homonuclear dipolar coupling terms are zeroed. Consequently, the sequence is sensitive to the sign of <em>δ</em>_aniso<span> but is not influenced by homonuclear dipolar interactions.</span></p></div>","PeriodicalId":21937,"journal":{"name":"Solid state nuclear magnetic resonance","volume":"114 ","pages":"Article 101743"},"PeriodicalIF":3.2,"publicationDate":"2021-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.ssnmr.2021.101743","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"39253050","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Efficient symmetry-based γ-encoded DQ recoupling sequences for suppression of t1-noise in solid-state NMR spectroscopy at fast MAS","authors":"Yusuke Nishiyama ,&nbsp;Vipin Agarwal ,&nbsp;Rongchun Zhang","doi":"10.1016/j.ssnmr.2021.101734","DOIUrl":"https://doi.org/10.1016/j.ssnmr.2021.101734","url":null,"abstract":"<div><p><span>Solid-state NMR spectroscopy has played a significant role in elucidating the structure and dynamics of materials and biological solids at a molecular level for decades. In particular, the </span>¹H double-quantum/single-quantum (DQ/SQ) chemical shift correlation experiment is widely used for probing the proximity of protons, rendering it a powerful tool for elucidating the hydrogen-bonding interactions and molecular packing of various complex molecular systems. Two factors, namely, the DQ filtering efficiency and <em>t</em>₁-noise, dictate the quality of the 2D ¹H DQ/SQ spectra. Experimentally different recoupling sequences show varied DQ filtering efficiencies and <em>t</em>₁-noise. Herein, after a systematic search of symmetry-based DQ recoupling sequences, we report that the symmetry-based γ-encoded <span><math><mrow><mi>R</mi><msubsup><mi>N</mi><mi>n</mi><mi>ν</mi></msubsup></mrow></math></span> sequences show superior performance to other DQ recoupling sequences, which not only have a higher DQ recoupling efficiency but can also significantly reduce <em>t</em>₁-noise. The origin of <em>t</em>₁-noise is further discussed in detail via extensive numerical simulations. We envisage that such γ-encoded <span><math><mrow><mi>R</mi><msubsup><mi>N</mi><mi>n</mi><mi>ν</mi></msubsup></mrow></math></span> sequences are superior candidates for DQ recoupling in proton-based solid-state NMR spectroscopy due to its capability of efficiently exciting DQ coherences and suppressing <em>t</em>₁-noise.</p></div>","PeriodicalId":21937,"journal":{"name":"Solid state nuclear magnetic resonance","volume":"114 ","pages":"Article 101734"},"PeriodicalIF":3.2,"publicationDate":"2021-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.ssnmr.2021.101734","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72249281","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Operando NMR characterization of a metal-air battery using a double-compartment cell design","authors":"Magali Gauthier,&nbsp;Minh Hoang Nguyen ,&nbsp;Lucie Blondeau,&nbsp;Eddy Foy,&nbsp;Alan Wong","doi":"10.1016/j.ssnmr.2021.101731","DOIUrl":"10.1016/j.ssnmr.2021.101731","url":null,"abstract":"<div><p>Applying <em>operando</em><span><span> investigations is becoming essential for acquiring fundamental insights into the reaction mechanisms and phenomena at stake in batteries currently under development. The capability of a real-time characterization of the charge/discharge electrochemical pathways and the reactivity of the electrolyte is critical to decipher the underlying </span>chemistries and improve the battery performance. Yet, adapting </span><em>operando</em> techniques for new chemistries such as metal-oxygen (<em>i.e.</em> metal-air) batteries introduces challenges in the cell design due notably to the requirements of an oxygen gas supply at the cathode. Herein a simple <em>operando</em><span> cell is presented with a two-compartment cylindrical cell design for NMR spectroscopy. The design is discussed and evaluated. </span><em>Operando</em> ⁷Li static NMR characterization on a Li–O₂ battery was performed as a proof-of-concept. The productions of Li₂O₂<span>, mossy Li/Li dendrites and other irreversible parasitic lithium compounds were captured in the charge/discharge processes, demonstrating the capability of tracking the evolution of the anodic and cathodic chemistry in metal-oxygen batteries.</span></p></div>","PeriodicalId":21937,"journal":{"name":"Solid state nuclear magnetic resonance","volume":"113 ","pages":"Article 101731"},"PeriodicalIF":3.2,"publicationDate":"2021-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.ssnmr.2021.101731","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"25564712","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A new method to measure the temporal magnetic field instabilities in cryogen-free magnets for magnetic resonance","authors":"Eugeny Kryukov,&nbsp;Miroslaw Owczarkowski,&nbsp;David Phillipps,&nbsp;Angel Joaquin Perez Linde,&nbsp;Stephen Burgess,&nbsp;Jeremy Good","doi":"10.1016/j.ssnmr.2021.101732","DOIUrl":"10.1016/j.ssnmr.2021.101732","url":null,"abstract":"<div><p>Despite the obvious advantages of cryogen-free magnets for NMR such as independence of liquid helium supply and the possibility to use the same magnet at different fields, the practical application of those magnets remains limited because of temporal magnetic field distortions associated with cryogen-free cold head operation. A new experimental method for the simple and reliable detection of the temporal field distortions is described in this paper. The accuracy of the magnetic field measurements by this method is two orders of magnitude higher than by conventional MetroLab Tesla meter. This has enabled us to make improvements in the design of cryogen-free magnets by reducing the amplitude of such field distortions down to sub ppb level. This then results in cryogen-free magnets that are suitable for MRI and MAS NMR applications.</p></div>","PeriodicalId":21937,"journal":{"name":"Solid state nuclear magnetic resonance","volume":"113 ","pages":"Article 101732"},"PeriodicalIF":3.2,"publicationDate":"2021-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.ssnmr.2021.101732","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"38892003","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dipolar dephasing for structure determination in a paramagnetic environment","authors":"Rubin Dasgupta,&nbsp;Karthick B.S.S. Gupta,&nbsp;Derek Elam ,&nbsp;Marcellus Ubbink,&nbsp;Huub J.M. de Groot","doi":"10.1016/j.ssnmr.2021.101728","DOIUrl":"10.1016/j.ssnmr.2021.101728","url":null,"abstract":"<div><p>We demonstrate the efficacy of the REDOR-type sequences in determining dipolar coupling strength in a paramagnetic environment. Utilizing paramagnetic effects of enhanced relaxation rates and rapid electronic fluctuations in Cu(II)-(DL-Ala)₂.H₂O, the dipolar coupling for the methyl C–H that is 4.20 ​Å (methyl carbon) away from the Cu²⁺ ion, was estimated to be 8.8 ​± ​0.6 ​kHz. This coupling is scaled by a factor of ~0.3 in comparison to the rigid limit value of ~32 ​kHz, in line with partial averaging of the dipolar interaction by rotational motion of the methyl group. Limited variation in the scaling factor of the dipolar coupling strength at different temperatures is observed. The C–H internuclear distance derived from the size of the dipolar coupling is similar to that observed in the crystal structure. The errors in the dipolar coupling strength observed in the REDOR-type experiments are similar to those reported for diamagnetic systems. Increase in resolution due to the Fermi contact shifts, coupled with MAS frequencies of 30–35 ​kHz allowed to estimate the hyperfine coupling strengths for protons and carbons from the temperature dependence of the chemical shift and obtain a high resolution ¹H–¹H spin diffusion spectrum. This study shows the utility of REDOR-type sequences in obtaining reliable structural and dynamical information from a paramagnetic complex. We believe that this can help in studying the active site of paramagnetic metalloproteins at high resolution.</p></div>","PeriodicalId":21937,"journal":{"name":"Solid state nuclear magnetic resonance","volume":"113 ","pages":"Article 101728"},"PeriodicalIF":3.2,"publicationDate":"2021-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.ssnmr.2021.101728","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"25498679","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}