Pub Date : 2026-02-01Epub Date: 2025-11-27DOI: 10.1016/j.ssnmr.2025.102052
Alexandre J.D. Pauletto, Ryan J. Bragg, Richard I. Walton, Michael A. Hope
Ag–Bi double perovskites are of interest as lead-free alternatives to halide perovskite optoelectronic materials. The properties can be tuned by halide mixing or dimensional reduction, but to understand how this changes the atomic structure requires a local structural probe. 209Bi NMR spectroscopy is extremely sensitive to the local environment but suffers from severe quadrupolar broadening. Here, we show that the combination of ultra-high field (28.2 T), fast magic angle spinning (50 kHz), and a sideband separation pulse sequence enables all seven local [BiX6] configurations to be distinguished in the 209Bi NMR spectra of mixed chloride–bromide Cs2AgBi(Cl1−xBrx)6 (0 ≤ x ≤ 1) double perovskites. The 81Br NMR spectrum of Cs2AgBiBr6 was further measured at 28.2 T using ultra-wideline methods. Finally, variable field experiments (11.7, 20.0, and 28.2 T) enabled the 209Bi CSA and quadrupolar parameters to be determined for the lower symmetry BA4AgBiBr8 layered double perovskite (BA+ = n-butylammonium). This work demonstrates the promise of ultra-high field NMR spectroscopy for challenging nuclei such as 209Bi in complex contemporary materials.
{"title":"Resolving 209Bi sites in mixed-halide double perovskites at 28 T","authors":"Alexandre J.D. Pauletto, Ryan J. Bragg, Richard I. Walton, Michael A. Hope","doi":"10.1016/j.ssnmr.2025.102052","DOIUrl":"10.1016/j.ssnmr.2025.102052","url":null,"abstract":"<div><div>Ag–Bi double perovskites are of interest as lead-free alternatives to halide perovskite optoelectronic materials. The properties can be tuned by halide mixing or dimensional reduction, but to understand how this changes the atomic structure requires a local structural probe. <sup>209</sup>Bi NMR spectroscopy is extremely sensitive to the local environment but suffers from severe quadrupolar broadening. Here, we show that the combination of ultra-high field (28.2 T), fast magic angle spinning (50 kHz), and a sideband separation pulse sequence enables all seven local [BiX<sub>6</sub>] configurations to be distinguished in the <sup>209</sup>Bi NMR spectra of mixed chloride–bromide Cs<sub>2</sub>AgBi(Cl<sub>1−<em>x</em></sub>Br<sub><em>x</em></sub>)<sub>6</sub> (0 ≤ <em>x</em> ≤ 1) double perovskites. The <sup>81</sup>Br NMR spectrum of Cs<sub>2</sub>AgBiBr<sub>6</sub> was further measured at 28.2 T using ultra-wideline methods. Finally, variable field experiments (11.7, 20.0, and 28.2 T) enabled the <sup>209</sup>Bi CSA and quadrupolar parameters to be determined for the lower symmetry BA<sub>4</sub>AgBiBr<sub>8</sub> layered double perovskite (BA<sup>+</sup> = <em>n</em>-butylammonium). This work demonstrates the promise of ultra-high field NMR spectroscopy for challenging nuclei such as <sup>209</sup>Bi in complex contemporary materials.</div></div>","PeriodicalId":21937,"journal":{"name":"Solid state nuclear magnetic resonance","volume":"141 ","pages":"Article 102052"},"PeriodicalIF":2.4,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145608811","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}
Pub Date : 2026-02-01Epub Date: 2025-12-20DOI: 10.1016/j.ssnmr.2025.102060
J.W. Zwanziger
A simple method for computing couplings from first principles is proposed, implemented, and tested. In this approach the coupling, which is just the mixed second derivative of the energy with respect to two nuclear magnetic dipoles, is evaluated non-perturbatively by computing the total energy with different fixed dipoles of various orientations, combined in a finite difference scheme. The approach is equally applicable to molecules and solids. Details of the implementation are presented, and a variety of examples in molecules and solids are provided.
{"title":"J couplings in the solid state from direct energy computations","authors":"J.W. Zwanziger","doi":"10.1016/j.ssnmr.2025.102060","DOIUrl":"10.1016/j.ssnmr.2025.102060","url":null,"abstract":"<div><div>A simple method for computing <span><math><mi>J</mi></math></span> couplings from first principles is proposed, implemented, and tested. In this approach the coupling, which is just the mixed second derivative of the energy with respect to two nuclear magnetic dipoles, is evaluated non-perturbatively by computing the total energy with different fixed dipoles of various orientations, combined in a finite difference scheme. The approach is equally applicable to molecules and solids. Details of the implementation are presented, and a variety of examples in molecules and solids are provided.</div></div>","PeriodicalId":21937,"journal":{"name":"Solid state nuclear magnetic resonance","volume":"141 ","pages":"Article 102060"},"PeriodicalIF":2.4,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145786032","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}
Average Hamiltonian Theory (AHT) is a widely used framework for analyzing spin dynamics in magnetic resonance experiments. The application of radiofrequency or microwave pulses, together with sample spinning, renders the Hamiltonian explicitly time-dependent, complicating the description of spin-state evolution. AHT overcomes this challenge by employing the Magnus expansion to generate a time-independent effective Hamiltonian. In this review, we discuss applications of AHT to spin polarization transfer mechanisms in nucleus–nucleus, electron–nucleus, and electron–electron–nucleus spin systems. AHT analysis to obtain an effective Hamiltonian in an appropriate interaction frame followed by density matrix evolution reveals optimal conditions for polarization transfer. The expression of the final density matrix also provides insight into the efficiency of the polarization transfer mechanism and their dependencies on external as well as internal interactions. Such analysis guides the design of experimental protocols, enabling informed choices of field strength, irradiation frequency, and pulse schemes to enhance nuclear polarization and dynamic nuclear polarization (DNP) efficiency. Thus, AHT serves as a powerful tool for both interpreting and optimizing polarization transfer experiments.
{"title":"Applications of Average Hamiltonian Theory to spin polarization transfer in magnetic resonance","authors":"Suraj Halder, Shovik Ray , Shubham Kumar Debadatta , Sheetal Kumar Jain","doi":"10.1016/j.ssnmr.2025.102051","DOIUrl":"10.1016/j.ssnmr.2025.102051","url":null,"abstract":"<div><div>Average Hamiltonian Theory (AHT) is a widely used framework for analyzing spin dynamics in magnetic resonance experiments. The application of radiofrequency or microwave pulses, together with sample spinning, renders the Hamiltonian explicitly time-dependent, complicating the description of spin-state evolution. AHT overcomes this challenge by employing the Magnus expansion to generate a time-independent effective Hamiltonian. In this review, we discuss applications of AHT to spin polarization transfer mechanisms in nucleus–nucleus, electron–nucleus, and electron–electron–nucleus spin systems. AHT analysis to obtain an effective Hamiltonian in an appropriate interaction frame followed by density matrix evolution reveals optimal conditions for polarization transfer. The expression of the final density matrix also provides insight into the efficiency of the polarization transfer mechanism and their dependencies on external as well as internal interactions. Such analysis guides the design of experimental protocols, enabling informed choices of field strength, irradiation frequency, and pulse schemes to enhance nuclear polarization and dynamic nuclear polarization (DNP) efficiency. Thus, AHT serves as a powerful tool for both interpreting and optimizing polarization transfer experiments.</div></div>","PeriodicalId":21937,"journal":{"name":"Solid state nuclear magnetic resonance","volume":"141 ","pages":"Article 102051"},"PeriodicalIF":2.4,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145567208","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}
We review solid-state NMR of magnetically oriented microcrystals. Three-dimensional alignment makes experiments virtually equivalent to single-crystal NMR possible even if the sample of interest is polycrystalline. This leads to characterization of electronic structure through determination of chemical shift and electric-field gradient tensors. The magnetic alignment of microcrystals benefits materials for which it is desirable but difficult to grow a sufficiently large single crystal. Here, we summarize how three-dimensional orientation is achieved through application of a rotating magnetic field with appropriate modulation of amplitude or frequency. We also discuss the condition for alignment, how to experimentally realize spontaneous orientation of individual microcrystals in a common direction, and other expected advantages of this approach. Next, we provide an overview of the current applications of NMR of magnetically oriented microcrystals to 13C NMR and 14N NMR. These applications prove the feasibility of single-crystal NMR even with microcrystalline powder.
{"title":"NMR of magnetically oriented microcrystals","authors":"Ryosuke Kusumi , Kazuyuki Takeda , Tsunehisa Kimura","doi":"10.1016/j.ssnmr.2025.102033","DOIUrl":"10.1016/j.ssnmr.2025.102033","url":null,"abstract":"<div><div>We review solid-state NMR of magnetically oriented microcrystals. Three-dimensional alignment makes experiments virtually equivalent to single-crystal NMR possible even if the sample of interest is polycrystalline. This leads to characterization of electronic structure through determination of chemical shift and electric-field gradient tensors. The magnetic alignment of microcrystals benefits materials for which it is desirable but difficult to grow a sufficiently large single crystal. Here, we summarize how three-dimensional orientation is achieved through application of a rotating magnetic field with appropriate modulation of amplitude or frequency. We also discuss the condition for alignment, how to experimentally realize spontaneous orientation of individual microcrystals in a common direction, and other expected advantages of this approach. Next, we provide an overview of the current applications of NMR of magnetically oriented microcrystals to <sup>13</sup>C NMR and <sup>14</sup>N NMR. These applications prove the feasibility of single-crystal NMR even with microcrystalline powder.</div></div>","PeriodicalId":21937,"journal":{"name":"Solid state nuclear magnetic resonance","volume":"140 ","pages":"Article 102033"},"PeriodicalIF":2.4,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144901775","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}
Pub Date : 2025-12-01Epub Date: 2025-08-05DOI: 10.1016/j.ssnmr.2025.102030
N. Vaisleib , M. Arbel-Haddad , A. Goldbourt
Geopolymers are aluminosilicate materials that exhibit effective immobilization properties for low-level radioactive nuclear waste, and more specifically for the immobilization of radioactive cesium. The identification of the cesium-binding sites and their distribution between the different phases making up the geopolymeric matrix can be obtained using solid-state NMR measurements of the quadrupolar spin 133Cs, which is a surrogate for the radioactive cesium species present in nuclear waste streams. For quadrupolar nuclei, acquiring two-dimensional multiple-quantum experiments allows the acquisition of more dispersed spectra when multiple sites overlap. However, 133Cs has a spin-7/2 and one of the smallest quadrupole moments, making multiple-quantum excitation highly challenging. In this work we present pulse schemes that enhance the excitation efficiency of 133Cs triple quantum coherences by a factor of ∼2 with respect to a two-pulse excitation scheme. The improved schemes were developed by using numerical simulation and verified experimentally by applying one and two-dimensional triple-quantum solid-state NMR experiments to a mixture of cesium-exchanged hydrated zeolites A and X, which possess dynamically averaged small quadrupolar coupling constants in the order of 10 kHz.
{"title":"Enhanced 133Cs triple-quantum excitation in solid-state NMR of Cs-bearing zeolites","authors":"N. Vaisleib , M. Arbel-Haddad , A. Goldbourt","doi":"10.1016/j.ssnmr.2025.102030","DOIUrl":"10.1016/j.ssnmr.2025.102030","url":null,"abstract":"<div><div>Geopolymers are aluminosilicate materials that exhibit effective immobilization properties for low-level radioactive nuclear waste, and more specifically for the immobilization of radioactive cesium. The identification of the cesium-binding sites and their distribution between the different phases making up the geopolymeric matrix can be obtained using solid-state NMR measurements of the quadrupolar spin <sup>133</sup>Cs, which is a surrogate for the radioactive cesium species present in nuclear waste streams. For quadrupolar nuclei, acquiring two-dimensional multiple-quantum experiments allows the acquisition of more dispersed spectra when multiple sites overlap. However, <sup>133</sup>Cs has a spin-7/2 and one of the smallest quadrupole moments, making multiple-quantum excitation highly challenging. In this work we present pulse schemes that enhance the excitation efficiency of <sup>133</sup>Cs triple quantum coherences by a factor of ∼2 with respect to a two-pulse excitation scheme. The improved schemes were developed by using numerical simulation and verified experimentally by applying one and two-dimensional triple-quantum solid-state NMR experiments to a mixture of cesium-exchanged hydrated zeolites A and X, which possess dynamically averaged small quadrupolar coupling constants in the order of 10 kHz.</div></div>","PeriodicalId":21937,"journal":{"name":"Solid state nuclear magnetic resonance","volume":"140 ","pages":"Article 102030"},"PeriodicalIF":2.4,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145020586","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}
Pub Date : 2025-12-01Epub Date: 2025-10-30DOI: 10.1016/j.ssnmr.2025.102048
Raphaële Coulon , David Gajan , Wassilios Papawassiliou , Andrew J. Pell , Judith Schlagnitweit , Franck Fayon , Pierre Florian , Dominique Massiot , Armin Afrough , Dennis W. Juhl , Thomas Vosegaard , Linda Cerofolini , Moreno Lelli , Massimo Lucci , Claudio Luchinat , Ruud L.E.G. Aspers , Jennifer S. Gómez , Arno P.M. Kentgens , Sander F.H. Lambregts , Y.T. Angel Wong , Anne Lesage
Solid-state nuclear magnetic resonance (solid-state NMR) is an essential tool for probing local structure and dynamics in complex materials, yet its uptake in the broader chemistry community has remained limited by technical and operational barriers. The PANACEA project established a pan-European infrastructure to transform solid-state NMR into a community-ready analytical technique by combining state-of-the-art instrumentation, coordinated user access, and targeted technological innovation. Over three years, PANACEA enabled over 90 user projects across chemistry and materials science, while driving advances in DNP methods, probe design, ultra-fast MAS, and interoperable software platforms such as EasyNMR and CHEMeDATA. This article presents the main outcomes of the initiative, illustrating how infrastructure-driven research and guided access can broaden the impact of solid-state NMR and integrate it into mainstream chemical workflows.
{"title":"Transforming solid-state nuclear magnetic resonance towards a chemistry-ready technique","authors":"Raphaële Coulon , David Gajan , Wassilios Papawassiliou , Andrew J. Pell , Judith Schlagnitweit , Franck Fayon , Pierre Florian , Dominique Massiot , Armin Afrough , Dennis W. Juhl , Thomas Vosegaard , Linda Cerofolini , Moreno Lelli , Massimo Lucci , Claudio Luchinat , Ruud L.E.G. Aspers , Jennifer S. Gómez , Arno P.M. Kentgens , Sander F.H. Lambregts , Y.T. Angel Wong , Anne Lesage","doi":"10.1016/j.ssnmr.2025.102048","DOIUrl":"10.1016/j.ssnmr.2025.102048","url":null,"abstract":"<div><div>Solid-state nuclear magnetic resonance (solid-state NMR) is an essential tool for probing local structure and dynamics in complex materials, yet its uptake in the broader chemistry community has remained limited by technical and operational barriers. The PANACEA project established a pan-European infrastructure to transform solid-state NMR into a community-ready analytical technique by combining state-of-the-art instrumentation, coordinated user access, and targeted technological innovation. Over three years, PANACEA enabled over 90 user projects across chemistry and materials science, while driving advances in DNP methods, probe design, ultra-fast MAS, and interoperable software platforms such as EasyNMR and CHEMeDATA. This article presents the main outcomes of the initiative, illustrating how infrastructure-driven research and guided access can broaden the impact of solid-state NMR and integrate it into mainstream chemical workflows.</div></div>","PeriodicalId":21937,"journal":{"name":"Solid state nuclear magnetic resonance","volume":"140 ","pages":"Article 102048"},"PeriodicalIF":2.4,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145404774","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}
Pub Date : 2025-12-01Epub Date: 2025-09-09DOI: 10.1016/j.ssnmr.2025.102046
Rose Gauttier, Colan E. Hughes, Benson M. Kariuki, Kenneth D.M. Harris
The development of NMR strategies for in-situ monitoring of crystallization processes has opened the opportunity to establish new mechanistic insights, including to understand the structural evolution of the solid phase produced in crystallization systems as a function of time. In this paper, we report the results of an in-situ solid-state 13C NMR study of crystallization from a solution containing 1,10-dihydroxydecane and urea in methanol, leading to the identification of two structurally diverse multicomponent crystalline phases that are formed at different stages of the crystallization process. The initially produced phase is a urea inclusion compound, in which 1,10-dihydroxydecane guest molecules are included within the well-known urea host tunnel structure. Subsequently, a second crystalline phase is formed, which is identified as a stoichiometric hydrogen-bonded co-crystal 1,10-dihydroxydecane-(urea)2. The in-situ solid-state 13C NMR results suggest that the urea inclusion compound is not an intermediate phase on the crystallization pathway to form the co-crystal, as the urea inclusion compound remains after the formation of the co-crystal phase. However, after the appearance of the co-crystal phase, the subsequent crystallization process is dominated by rapid growth of the co-crystal rather than growth of the urea inclusion compound. The results demonstrate the capability of in-situ solid-state NMR strategies to monitor the structural evolution of multicomponent solid phases during crystallization from solution.
{"title":"In-situ solid-state NMR spectroscopy reveals competing crystallization pathways for a system that forms structurally diverse multicomponent crystalline phases","authors":"Rose Gauttier, Colan E. Hughes, Benson M. Kariuki, Kenneth D.M. Harris","doi":"10.1016/j.ssnmr.2025.102046","DOIUrl":"10.1016/j.ssnmr.2025.102046","url":null,"abstract":"<div><div>The development of NMR strategies for <em>in-situ</em> monitoring of crystallization processes has opened the opportunity to establish new mechanistic insights, including to understand the structural evolution of the solid phase produced in crystallization systems as a function of time. In this paper, we report the results of an <em>in-situ</em> solid-state <sup>13</sup>C NMR study of crystallization from a solution containing 1,10-dihydroxydecane and urea in methanol, leading to the identification of two structurally diverse multicomponent crystalline phases that are formed at different stages of the crystallization process. The initially produced phase is a urea inclusion compound, in which 1,10-dihydroxydecane guest molecules are included within the well-known urea host tunnel structure. Subsequently, a second crystalline phase is formed, which is identified as a stoichiometric hydrogen-bonded co-crystal 1,10-dihydroxydecane-(urea)<sub>2</sub>. The <em>in-situ</em> solid-state <sup>13</sup>C NMR results suggest that the urea inclusion compound is not an intermediate phase on the crystallization pathway to form the co-crystal, as the urea inclusion compound remains after the formation of the co-crystal phase. However, after the appearance of the co-crystal phase, the subsequent crystallization process is dominated by rapid growth of the co-crystal rather than growth of the urea inclusion compound. The results demonstrate the capability of <em>in-situ</em> solid-state NMR strategies to monitor the structural evolution of multicomponent solid phases during crystallization from solution.</div></div>","PeriodicalId":21937,"journal":{"name":"Solid state nuclear magnetic resonance","volume":"140 ","pages":"Article 102046"},"PeriodicalIF":2.4,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145061265","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}
Proximities between spin-1/2, e.g. 1H and 13C, and quadrupolar nuclei can be analyzed using HMQC (Heteronuclear Multiple-Quantum Correlation) experiments, in which two continuous-wave irradiations similar to those used in TRAPDOR (TRAnsfer of Population in DOuble-Resonance) experiments are applied on the indirectly detected quadrupolar isotope during the defocusing and refocusing delays. Here, we demonstrate that this sequence, called T-HMQC (T stands for TRAPDOR), can be applied to probe proximities between distinct half-integer spin quadrupolar isotopes. We introduce two novel variants of this sequence to reduce the number of resonances along the indirect dimension. These selective variants employ either (i) an echo-antiecho quadrature detection to only retain the single-quantum (1Q) coherences or (ii) two π-pulses selective of the central-transition (CT) to observe only the 1Q-CT coherences. We analyze how the effects of various experimental parameters, including the synchronization of the TRAPDOR recoupling pulses with the sample rotation, and their radio-frequency (rf) field amplitude and frequency offset, affect the efficiency of 11B-27Al T-HMQC experiments on a magnesium aluminoborate glass. The performances of these T-HMQC sequences are compared to those of the D-HMQC scheme employing the SPI-R3 (Synchronous Phase-Inversion Rotary-Resonance-Recoupling) or REDOR (Rotational-Echo DOuble-Resonance) symmetry-based heteronuclear dipolar recouplings built from CT-selective pulses. We demonstrate that the two TRAPDOR pulses in the T-HMQC sequence must be separated by an integer number of rotor periods and must employ the maximum rf field strength compatible with the probe specifications. Furthermore, as the TRAPDOR pulses distribute the populations equally to all possible coherences, the sensitivity of the T-HMQC selective variants is lower than that of the D-HMQC techniques. To limit this sensitivity decrease and the number of cross-peaks, it is preferable to detect indirectly the quadrupolar nucleus I with the lowest spin number, and in the case of I = 3/2, the resolution along the indirect dimension can be enhanced with respect to a MAS spectrum (for instance, by a factor of 27/7, without taking into account the quadrupolar-induced shift (QIS), through the sole indirect detection of triple-quantum (3Q) coherences). Moreover, owing to the use of a high-power TRAPDOR recoupling, the T-HMQC technique benefits from a wider excitation bandwidth than the D-HMQC methods, which is advantageous for broad NMR spectra, especially at high magnetic fields.
{"title":"Through-space NMR correlations between two different half-integer quadrupolar nuclei using T-HMQC sequences","authors":"Yury G. Kolyagin , Julien Trébosc , Olivier Lafon , Jean-Paul Amoureux","doi":"10.1016/j.ssnmr.2025.102044","DOIUrl":"10.1016/j.ssnmr.2025.102044","url":null,"abstract":"<div><div>Proximities between spin-1/2, e.g. <sup>1</sup>H and <sup>13</sup>C, and quadrupolar nuclei can be analyzed using HMQC (Heteronuclear Multiple-Quantum Correlation) experiments, in which two continuous-wave irradiations similar to those used in TRAPDOR (TRAnsfer of Population in DOuble-Resonance) experiments are applied on the indirectly detected quadrupolar isotope during the defocusing and refocusing delays. Here, we demonstrate that this sequence, called T-HMQC (T stands for TRAPDOR), can be applied to probe proximities between distinct half-integer spin quadrupolar isotopes. We introduce two novel variants of this sequence to reduce the number of resonances along the indirect dimension. These selective variants employ either (i) an echo-antiecho quadrature detection to only retain the single-quantum (1Q) coherences or (ii) two π-pulses selective of the central-transition (CT) to observe only the 1Q-CT coherences. We analyze how the effects of various experimental parameters, including the synchronization of the TRAPDOR recoupling pulses with the sample rotation, and their radio-frequency (rf) field amplitude and frequency offset, affect the efficiency of <sup>11</sup>B-<sup>27</sup>Al T-HMQC experiments on a magnesium aluminoborate glass. The performances of these T-HMQC sequences are compared to those of the D-HMQC scheme employing the SPI-R<sup>3</sup> (Synchronous Phase-Inversion Rotary-Resonance-Recoupling) or REDOR (Rotational-Echo DOuble-Resonance) symmetry-based heteronuclear dipolar recouplings built from CT-selective pulses. We demonstrate that the two TRAPDOR pulses in the T-HMQC sequence must be separated by an integer number of rotor periods and must employ the maximum rf field strength compatible with the probe specifications. Furthermore, as the TRAPDOR pulses distribute the populations equally to all possible coherences, the sensitivity of the T-HMQC selective variants is lower than that of the D-HMQC techniques. To limit this sensitivity decrease and the number of cross-peaks, it is preferable to detect indirectly the quadrupolar nucleus <em>I</em> with the lowest spin number, and in the case of <em>I</em> = 3/2, the resolution along the indirect dimension can be enhanced with respect to a MAS spectrum (for instance, by a factor of 27/7, without taking into account the quadrupolar-induced shift (QIS), through the sole indirect detection of triple-quantum (3Q) coherences). Moreover, owing to the use of a high-power TRAPDOR recoupling, the T-HMQC technique benefits from a wider excitation bandwidth than the D-HMQC methods, which is advantageous for broad NMR spectra, especially at high magnetic fields.</div></div>","PeriodicalId":21937,"journal":{"name":"Solid state nuclear magnetic resonance","volume":"140 ","pages":"Article 102044"},"PeriodicalIF":2.4,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145259306","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}
Pub Date : 2025-12-01Epub Date: 2025-08-22DOI: 10.1016/j.ssnmr.2025.102034
Carl H. Fleischer III , Sean T. Holmes , Xinsong Lin , Robert W. Schurko
Quadrupolar NMR crystallography guided crystal structure prediction (QNMRX-CSP) is a method for determining the crystal structures of organic solids. To date, our two previous QNMRX-CSP studies have relied upon on 35Cl solid-state NMR (SSNMR) spectroscopy, powder X-ray diffraction (PXRD), Monte-Carlo simulated annealing (MC-SA), and dispersion-corrected density functional theory (DFT-D2∗) calculations for the determination of crystal structures for organic HCl salts with known crystal structures, in order to benchmark the method and subject it to blind tests. Herein, we apply QNMRX-CSP for the de novo crystal structure determination of L-alaninamide HCl (L-Ala-NH2), for which no crystal structure has been reported, using 35Cl SSNMR and PXRD data for structural prediction and refinement, along with 13C and 14N SSNMR data for subsequent structural validation. To further validate our structural models, we determined the crystal structure of L-Ala-NH2 using single-crystal X-ray diffraction (SCXRD); however, this structure was not obtained until the completion of the QNMRX-CSP analysis and validation. This study highlights the current capabilities of QNMRX-CSP and underscores the benefits of incorporating multinuclear SSNMR data to enhance de novo crystal structure determination across a wide range of organic solids.
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Dynamic Nuclear Polarization (DNP) has revolutionized the field of solid-state NMR spectroscopy by significantly improving the sensitivity of nuclear magnetic resonance experiments. Conventionally, cross-effect DNP relies on biradicals to transfer polarization from coupled electron spins to nearby nuclear spins and subsequent relay to target nuclei via a spin diffusion mechanism. However, direct transfer of electron spin polarization to distant nuclei remains a significant challenge due to the small magnitude of effective Hamiltonian, limiting applicability of DNP in various contexts. In this work, we investigate a biradical design concept that involves a very strong electron–electron coupling, with a magnitude of hundreds of MHz, which could enable direct polarization transfer from coupled electron spins to nuclear spins over much longer distances, exceeding 2.0 nm. The concept is experimentally supported using a 14.1 T MAS DNP setup for various nuclei. The use of ASYMPOL-POK, a strongly coupled biradical, results in up to a four-fold increase in long-range H DNP enhancement compared to AMUPOL, a commonly used standard polarizing agent in traditional MAS DNP.
We also discuss the potential of tailored biradicals in scenarios where conventional spin diffusion mechanisms are inefficient or where direct nuclear spin polarization enhancement or sensing through electron spin interactions is desired. Our study presents an avenue for expanding the scope of cross-effect DNP in solid-state NMR spectroscopy of H, 19F and 31P nuclei, commonly found in various biological and material systems.
动态核极化（DNP）通过显著提高核磁共振实验的灵敏度，彻底改变了固态核磁共振波谱学领域。传统上，交叉效应DNP依赖于双基将极化从耦合电子自旋转移到附近的核自旋，然后通过自旋扩散机制传递到目标核。然而，由于有效哈密顿量较小，电子自旋极化直接转移到远核仍然是一个重大挑战，限制了DNP在各种情况下的适用性。在这项工作中，我们研究了一种双基设计概念，它涉及到一个非常强的电子-电子耦合，其量级为数百MHz，可以实现从耦合电子自旋到核自旋的直接极化转移，距离超过2.0 nm。用14.1 T MAS DNP装置对各种核进行了实验支持。与传统MAS DNP中常用的标准极化剂AMUPOL相比，使用强耦合双自由基ASYMPOL-POK，远程1H DNP增强效果可提高4倍。我们还讨论了定制双基在传统自旋扩散机制效率低下或需要通过电子自旋相互作用直接增强核自旋极化或传感的情况下的潜力。我们的研究为扩大交叉效应DNP在各种生物和材料系统中常见的1H， 19F和31P核的固态核磁共振波谱中的范围提供了一条途径。
{"title":"Direct polarization transfer to remote nuclei: Expanding the reach of cross-effect Dynamic Nuclear Polarization","authors":"Amaria Javed , Ribal Jabbour , Waqqas Zia , Asif Equbal","doi":"10.1016/j.ssnmr.2025.102049","DOIUrl":"10.1016/j.ssnmr.2025.102049","url":null,"abstract":"<div><div>Dynamic Nuclear Polarization (DNP) has revolutionized the field of solid-state NMR spectroscopy by significantly improving the sensitivity of nuclear magnetic resonance experiments. Conventionally, cross-effect DNP relies on biradicals to transfer polarization from coupled electron spins to nearby nuclear spins and subsequent relay to target nuclei via a spin diffusion mechanism. However, direct transfer of electron spin polarization to distant nuclei remains a significant challenge due to the small magnitude of effective Hamiltonian, limiting applicability of DNP in various contexts. In this work, we investigate a biradical design concept that involves a very strong electron–electron coupling, with a magnitude of hundreds of MHz, which could enable direct polarization transfer from coupled electron spins to nuclear spins over much longer distances, exceeding 2.0 nm. The concept is experimentally supported using a 14.1 T MAS DNP setup for various nuclei. The use of ASYMPOL-POK, a strongly coupled biradical, results in up to a four-fold increase in long-range <span><math><msup><mrow></mrow><mrow><mn>1</mn></mrow></msup></math></span>H DNP enhancement compared to AMUPOL, a commonly used standard polarizing agent in traditional MAS DNP.</div><div>We also discuss the potential of tailored biradicals in scenarios where conventional spin diffusion mechanisms are inefficient or where direct nuclear spin polarization enhancement or sensing through electron spin interactions is desired. Our study presents an avenue for expanding the scope of cross-effect DNP in solid-state NMR spectroscopy of <span><math><msup><mrow></mrow><mrow><mn>1</mn></mrow></msup></math></span>H, <sup>19</sup>F and <sup>31</sup>P nuclei, commonly found in various biological and material systems.</div></div>","PeriodicalId":21937,"journal":{"name":"Solid state nuclear magnetic resonance","volume":"140 ","pages":"Article 102049"},"PeriodicalIF":2.4,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145461884","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}
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