We report a comprehensive variable-temperature solid-state 17 O NMR study of three 17 O-labeled crystalline sulfonic acids: 2-aminoethane-1-sulfonic acid (taurine, T), 3-aminopropane-1-sulfonic acid (homotaurine, HT), and 4-aminobutane-1-sulfonic acid (ABSA − groups in these compounds undergo a 3-fold rotational jump mechanism but also extracted the corresponding jump rates (10 2 −10 5 s −1 ) and the associated activation energies (E a ) for this process (E a =4 8± 7, 42 ± 3, and 45 ± 1 kJ mol −1 for T, HT, and ABSA, respectively). This is the first time that SO 3 − rotational dynamics have been directly probed by solid-state 17 O NMR. Using the experimental activation energies for SO 3 − rotation, we were able to evaluate quantitatively the total hydrogen bond energy that each SO 3 − group is involved in within the crystal lattice. The activation energies also correlate with calculated rotational energy barriers. This work provides a clear illustration of the utility of solid-state 17 O NMR in quantifying dynamic processes occurring in organic solids. Similar studies applied to selectively 17 O-labeled biomolecules would appear to be very feasible.

Oxygen, oxygen, everywhere! Poor sensitivity has hindered the development of solid‐state 17O NMR spectroscopy as a practical technique for the structural elucidation of protein complexes. However, this has now changed and it has been demonstrated that multinuclear 17O, 27Al, 13C NMR parameters can be used to aid structural refinement for a protein‐bound ligand molecule (see picture).

Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n'arrivez pas à les repérer, communiquez avec nous à PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. Questions? Contact the NRC Publications Archive team atPublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. If you wish to email the authors directly, please see the first page of the publication for their contact information. NRC Publications Archive Archives des publications du CNRCThis publication could be one of several versions: author's original, accepted manuscript or the publisher's version. / La version de cette publication peut être l'une des suivantes : la version prépublication de l'auteur, la version acceptée du manuscrit ou la version de l'éditeur. NRC Publications Record / Notice d'Archives des publications de CNRC:http://nparc.cisti-icist.nrc-cnrc.gc.ca/eng/view/object/?id=4daed0b0-5d6e-4f41-9df3-c6915e17e8b5 http://nparc.cisti-icist.nrc-cnrc.gc.ca/fra/voir/objet/?id=4daed0b0-5d6e-4f41-9df3-c6915e17e8b5 Ba SSNMR spectra of several barium-containing systems (barium nitrate, barium carbonate, barium chlorate monohydrate, barium chloride dihydrate, anhydrous barium chloride, and barium hydrogen phosphate) were acquired at two different magnetic field strengths (9.4 and 21.1 T) using frequency-stepped techniques. The recently reported WURST-QCPMG pulse sequence (O'Dell et al. Chem. Phys. Lett. 2008, 464,9 7 -102) is shown to be very useful for rapidly acquiring high signal-to-noise 137 Ba SSNMR spectra. The breadths of the second-order quadrupolar-dominated spectra and experimental times are notably reduced for experiments conducted at 21.1 T. Ba electric field gradient (EFG) parameters extracted from these spectra are correlated to the local environments at the barium sites, via consideration of molecular symmetry and structure, and first principles calculations of 137 Ba EFG tensors performed using CASTEP software. The rapidity with which 137 Ba SSNMR spectra can be acquired using the WURST pulse sequence and/or at ultrahigh magnetic fields and the sensitivity of the 137 Ba EFG tensor parameters to the changes in the barium environment suggest that 137 Ba SSNMR has great potential for structural characterization of a variety of barium-containing materials.

Sauerstoff, Sauerstoff überall! Ihre geringe Empfindlichkeit hat die Entwicklung der Festkörper‐17O‐NMR‐Spektroskopie zu einer nützlichen Technik zur Aufklärung von Proteinkomplexstrukturen verhindert. Doch das hat sich nun geändert, und es wurde gezeigt, dass 17O‐, 27Al‐, 13C‐Mehrkern‐NMR‐Parameter bei der Verfeinerung der Struktur eines proteingebundenen Ligandmoleküls helfen können.

115 In solid-state NMR (SSNMR) spectroscopy is applied to characterise a variety of low oxidation-state indium(I) compounds. 115 In static wideline SSNMR spectra of several In(I) complexes were acquired with moderate and ultra-high field NMR spectrometers (9.4 and 21.1 T, respectively). 115 In MAS NMR spectra were obtained with moderate and ultra-fast (> 60 kHz) spinning speeds at 21.1 T. In certain cases, variable-temperature (VT) 115 In SSNMR experiments were performed to study dynamic behaviour and phase transitions. The indium electric field gradient (EFG) and chemical shift (CS) tensor parameters were determined from the experimental spectra. With the aid of first principles calculations, the tensor parameters and orientations are correlated to the structure and symmetry of the local indium environments. In addition, calculations aid in proposing structural models for samples where single crystal X-ray structures could not be obtained. The rapidity with which high quality 115 In SSNMR spectra can be acquired at 21.1 T and the sensitivity of the 115 In NMR parameters to the indium environment suggest that 115 In SSNMR is a powerful probe of the local chemical environments of indium sites. This work demonstrates that 115 In NMR can be applied to a wide range of important materials for the purpose of increasing our understanding of structures and dynamics at the molecular/atomic level, especially for the characterisation of disordered, microcrystalline and/or multi-valence solids for which crystal structures are unavailable.

Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n'arrivez pas à les repérer, communiquez avec nous à PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. Questions?Contact the NRC Publications Archive team at PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. If you wish to email the authors directly, please see the first page of the publication for their contact information. NRC Publications Archive Archives des publications du CNRCThis publication could be one of several versions: author's original, accepted manuscript or the publisher's version. / La version de cette publication peut être l'une des suivantes : la version prépublication de l'auteur, la version acceptée du manuscrit ou la version de l'éditeur. For the publisher's version, please access the DOI link below./ Pour consulter la version de l'éditeur, utilisez le lien DOI ci-dessous.http://doi.org/10.1021/jz200296gAccess and use of this website and the material on it are subject to the Terms and Conditions set forth at Experimental verification of the theory of nuclear quadrupole relaxation in liquids over the entire range of molecular tumbling motion Zhu, Jianfeng; Ye, Eric; Terskikh, Victor; Wu, Gang http://nparc.cisti-icist.nrc-cnrc.gc.ca/fra/droits L'accès à ce site Web et l'utilisation de son contenu sont assujettis aux conditions présentées dans le site

Solid ammine metal borohydrides [M­(BH4) m (NH3) n , AMBs] are promising materials for low temperature, high capacity hydrogen generation. Retention of metal halide co-products, arising from typical mechanochemical synthetic methods, is shown to have negative impacts on dehydrogenation properties of yttrium AMB. Halide-free yttrium and lanthanum AMBs, M­(BH4)3(NH3)4, have been synthesized directly by treatment of MCl3 with 3 equiv of NaBH4 in thf followed by filtration, cooling, and exposure to liquid ammonia. The peak dehydrogenation temperature of the Y analog decreased from previously reported 179 to 160 °C while the ammonia peak temperature increased from 86 to 165 °C. To enhance the dehydrogenation properties and increase the selectivity of gas formation from these AMBs, base-metal nanoparticle catalysts, M′NPs; M′ = Fe, Co, Ni, and Cu) were employed. Preparation of the M′NPs from M′Cl2 and liquid hexylamine–borane allowed for separation of the B–Cl byproducts by subsequent solvent washing. Sonification of the M′NPs in toluene followed by addition of the solid AMB afforded composite AMB–M′NP–BN solids. Thermolysis data indicated a threefold reduction in ammonia release from the Y–Co and fourfold for the La–Fe composite. The purity of the released hydrogen was estimated to be 97.9 mol % for Y–Co and 98.9 mol % for La–Fe.

Twenty-five strontium-containing solids were characterized via (87)Sr NMR spectroscopy at natural abundance and high magnetic field strength (B0 = 21.14 T). Strontium nuclear quadrupole coupling constants in these compounds are sensitive to the strontium site symmetry and range from 0 to 50.5 MHz. An experimental (87)Sr chemical shift scale is proposed, and available data indicate a chemical shift range of approximately 550 ppm, from -200 to +350 ppm relative to Sr(2+)(aq). In general, magnetic shielding increased with strontium coordination number. Experimentally measured chemical shift anisotropy is reported for stationary samples of solid powdered SrCl2·6H2O, SrBr2·6H2O, and SrCO3, with δaniso((87)Sr) values of +28, +26, and -65 ppm, respectively. NMR parameters were calculated using CASTEP, a gauge including projector augmented wave (GIPAW) DFT-based program, which addresses the periodic nature of solids using plane-wave basis sets. Calculated NMR parameters are in good agreement with those measured.