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Artykuły w czasopismach na temat „NMR-GIPAW”

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Data publikacji: 29 marca 2025

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1

Widdifield, Cory M., Frédéric A. Perras i David L. Bryce. "Solid-state185/187Re NMR and GIPAW DFT study of perrhenates and Re2(CO)10: chemical shift anisotropy, NMR crystallography, and a metal–metal bond". Physical Chemistry Chemical Physics 17, nr 15 (2015): 10118–34. http://dx.doi.org/10.1039/c5cp00602c.

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2

Pizzanelli, Silvia, Susanna Monti, Larisa G. Gordeeva, Marina V. Solovyeva, Angelo Freni i Claudia Forte. "A close view of the organic linker in a MOF: structural insights from a combined 1H NMR relaxometry and computational investigation". Physical Chemistry Chemical Physics 22, nr 27 (2020): 15222–30. http://dx.doi.org/10.1039/d0cp01863e.

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Pöppler, Ann-Christin, Emily K. Corlett, Harriet Pearce, Mark P. Seymour, Matthew Reid, Mark G. Montgomery i Steven P. Brown. "Single-crystal X-ray diffraction and NMR crystallography of a 1:1 cocrystal of dithianon and pyrimethanil". Acta Crystallographica Section C Structural Chemistry 73, nr 3 (6.02.2017): 149–56. http://dx.doi.org/10.1107/s2053229617000870.

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A single-crystal X-ray diffraction structure of a 1:1 cocrystal of two fungicides, namely dithianon (DI) and pyrimethanil (PM), is reported [systematic name: 5,10-dioxo-5H,10H-naphtho[2,3-b][1,4]dithiine-2,3-dicarbonitrile–4,6-dimethyl-N-phenylpyrimidin-2-amine (1/1), C14H4N2O2S2·C12H13N2]. Following an NMR crystallography approach, experimental solid-state magic angle spinning (MAS) NMR spectra are presented together with GIPAW (gauge-including projector augmented wave) calculations of NMR chemical shieldings. Specifically, experimental 1H and 13C chemical shifts are determined from two-dimensional 1H–13C MAS NMR correlation spectra recorded with short and longer contact times so as to probe one-bond C—H connectivities and longer-range C...H proximities, whereas H...H proximities are identified in a 1H double-quantum (DQ) MAS NMR spectrum. The performing of separate GIPAW calculations for the full periodic crystal structure and for isolated molecules allows the determination of the change in chemical shift upon going from an isolated molecule to the full crystal structure. For the 1H NMR chemical shifts, changes of 3.6 and 2.0 ppm correspond to intermolecular N—H...O and C—H...O hydrogen bonding, while changes of −2.7 and −1.5 ppm are due to ring current effects associated with C—H...π interactions. Even though there is a close intermolecular S...O distance of 3.10 Å, it is of note that the molecule-to-crystal chemical shifts for the involved sulfur or oxygen nuclei are small.
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4

Ferreira, Ary R., Karsten Reuter i Christoph Scheurer. "DFT simulations of 7Li solid state NMR spectral parameters and Li+ ion migration barriers in Li2ZrO3". RSC Advances 6, nr 47 (2016): 41015–24. http://dx.doi.org/10.1039/c6ra03339c.

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Energy barriers for Li+ migration in Li2ZrO3 as well as GIPAW NMR isotropic spectral parameters for7 Li were computed, aiming to provide guidance for the interpretation and prediction of spectra of more complex systems like materials for LIBs.
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5

Tantardini, Christian, Alexander G. Kvashnin i Davide Ceresoli. "GIPAW Pseudopotentials of d Elements for Solid-State NMR". Materials 15, nr 9 (6.05.2022): 3347. http://dx.doi.org/10.3390/ma15093347.

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Computational methods are increasingly used to support interpreting, assigning and predicting the solid-state nuclear resonance magnetic spectra of materials. Currently, density functional theory is seen to achieve a good balance between efficiency and accuracy in solid-state chemistry. To be specific, density functional theory allows the assignment of signals in nuclear resonance magnetic spectra to specific sites and can help identify overlapped or missing signals from experimental nuclear resonance magnetic spectra. To avoid the difficulties correlated to all-electron calculations, a gauge including the projected augmented wave method was introduced to calculate nuclear resonance magnetic parameters with great success in organic crystals in the last decades. Thus, we developed a gauge including projected augmented pseudopotentials of 21 d elements and tested them on, respectively, oxides or nitrides (semiconductors), calculating chemical shift and quadrupolar coupling constant. This work can be considered the first step to improving the ab initio prediction of nuclear magnetic resonance parameters, and leaves open the possibility for inorganic compounds to constitute an alternative standard compound, with respect to tetramethylsilane, to calculate the chemical shift. Furthermore, this work represents the possibility to obtain results from first-principles calculations, to train a machine-learning model to solve or refine structures using predicted nuclear magnetic resonance spectra.
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6

Papulovskiy, Evgeny, Aleksandr Shubin i Olga Lapina. "Theoretical Modeling Of The Structure Of Surface Niobium Sites Based On Solid-State 93nb Nmr". Siberian Journal of Physics 11, nr 2 (1.06.2016): 77–91. http://dx.doi.org/10.54362/1818-7919-2016-11-2-77-91.

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In this work niobium oxide clusters on the surface of Al2O3 are modeled using DFT calculations. 93Nb NMR parameters of modeled clusters were computed with the GIPAW method. The niobia system under consideration represents high niobium loading on the surface of the support. The niobium atoms are highly coordinated and linked to the other niobia polyhedra by one or two bonds. The most of the niobium oxide particles has a coordination number of six. The correlations found between 93Nb NMR parameters and coordination environment are discussed.
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7

Scarperi, Andrea, Giovanni Barcaro, Aleksandra Pajzderska, Francesca Martini, Elisa Carignani i Marco Geppi. "Structural Refinement of Carbimazole by NMR Crystallography". Molecules 26, nr 15 (29.07.2021): 4577. http://dx.doi.org/10.3390/molecules26154577.

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The characterization of the three-dimensional structure of solids is of major importance, especially in the pharmaceutical field. In the present work, NMR crystallography methods are applied with the aim to refine the crystal structure of carbimazole, an active pharmaceutical ingredient used for the treatment of hyperthyroidism and Grave’s disease. Starting from previously reported X-ray diffraction data, two refined structures were obtained by geometry optimization methods. Experimental 1H and 13C isotropic chemical shift measured by the suitable 1H and 13C high-resolution solid state NMR techniques were compared with DFT-GIPAW calculated values, allowing the quality of the obtained structure to be experimentally checked. The refined structure was further validated through the analysis of 1H-1H and 1H-13C 2D NMR correlation experiments. The final structure differs from that previously obtained from X-ray diffraction data mostly for the position of hydrogen atoms.
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8

de Wijs, G. A., R. Laskowski, P. Blaha, R. W. A. Havenith, G. Kresse i M. Marsman. "NMR shieldings from density functional perturbation theory: GIPAW versus all-electron calculations". Journal of Chemical Physics 146, nr 6 (14.02.2017): 064115. http://dx.doi.org/10.1063/1.4975122.

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9

Wong, Alan, Mark E. Smith, Victor Terskikh i Gang Wu. "Obtaining accurate chemical shifts for all magnetic nuclei (1H, 13C, 17O, and 27Al) in tris(2,4-pentanedionato-O,O′)aluminium(III) — A solid-state NMR case study". Canadian Journal of Chemistry 89, nr 9 (wrzesień 2011): 1087–94. http://dx.doi.org/10.1139/v11-046.

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We report a complete set of high-resolution solid-state NMR spectra for all magnetic nuclei (1H, 13C, 17O, and 27Al) in the α-form of tris(2,4-pentanedionato-O,O′)aluminium(III), α-Al(acac)3. These high-resolution NMR spectra were obtained by using a host of solid-state NMR techniques: standard cross-polarization under the magic-angle spinning (CPMAS) method for 13C, 1-D homonuclear decoupling using the windowed DUMBO sequence for 1H, double-rotation (DOR) for 17O and 27Al, and multiple-quantum MAS for 27Al. Some experiments were performed at multiple magnetic fields. We show that the isotropic chemical shifts obtained for 1H, 13C, 17O, and 27Al nuclei in α-Al(acac)3 are highly resolved and accurate, regardless of the nature of the targeted nuclear spins (i.e., spin-1/2 or quadrupolar) and, as such, can be treated equally in comparison with computational chemical shifts obtained from a gauge-including projector-augmented wave (GIPAW) plane-wave pseudopotential DFT method.
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10

Greer, Brandon J., Vladimir K. Michaelis, Victor V. Terskikh i Scott Kroeker. "Reconnaissance of diverse structural and electronic environments in germanium halides by solid-state 73Ge NMR and quantum chemical calculations". Canadian Journal of Chemistry 89, nr 9 (wrzesień 2011): 1118–29. http://dx.doi.org/10.1139/v11-052.

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Solid-state 73Ge nuclear magnetic resonance (NMR) is an attractive technique for the characterization of solid germanium-containing materials, but experiments can be exceedingly difficult in practice due to the unfavourable NMR properties of the 73Ge nucleus. Presented herein is a series of solid-state 73Ge NMR experiments on germanium halides (GeX4 and GeX2, where X = I, Br, and Cl) conducted at moderate (9.4 and 11.7 T) and ultrahigh (21.1 T) magnetic fields, intended to characterize the 73Ge NMR response in highly symmetric and asymmetric coordination environments. Quadrupole coupling constants range from 0.16 to 35 MHz. Isotropic chemical shifts for the GeX4 series trend with halide electronegativity, as found for the analogous silicon and tin halides. The indirect spin-spin coupling constant 1J(73Ge, 127I) is estimated from 73Ge MAS NMR to be 35 ± 10 Hz in GeI2, with the reduced coupling constant agreeing with those of other group 14 halides. Quantum chemical calculations using GIPAW DFT are in reasonable accord with experimental quadrupole couplings, but fail for chemical shielding. A preliminary NMR crystallographic study of GeI2 and GeCl2 incorporating 127I and 35Cl NMR spectra has led to plausible conclusions reflecting the structural homology of these compounds, although definitive characterization remains elusive.
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11

Charpentier, Thibault. "The PAW/GIPAW approach for computing NMR parameters: A new dimension added to NMR study of solids". Solid State Nuclear Magnetic Resonance 40, nr 1 (lipiec 2011): 1–20. http://dx.doi.org/10.1016/j.ssnmr.2011.04.006.

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12

Ferreira, Ary R. "DFT-GIPAW 27Al NMR Simulations for Intermetallics: Accuracy Issues and Magnetic Screening Mechanisms". Journal of Physical Chemistry C 123, nr 14 (14.03.2019): 9371–81. http://dx.doi.org/10.1021/acs.jpcc.9b00259.

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13

Hangan, Adriana, Gheorghe Borodi, Xenia Filip, Carmen Tripon, Cristian Morari, Luminita Oprean i Claudiu Filip. "Structure of N-(5-ethyl-[1,3,4]-thiadiazole-2-yl)toluenesulfonamide by combined X-ray powder diffraction, 13C solid-state NMR and molecular modelling". Acta Crystallographica Section B Structural Science 66, nr 6 (10.11.2010): 615–21. http://dx.doi.org/10.1107/s0108768110039327.

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The crystal structure solution of the title compound is determined from microcrystalline powder using a multi-technique approach that combines X-ray powder diffraction (XRPD) data analysis based on direct-space methods with information from 13C solid-state NMR (SSNMR), and molecular modelling using the GIPAW (gauge including projector augmented-wave) method. The space group is Pbca with one molecule in the asymmetric unit. The proposed methodology proves very useful for unambiguously characterizing the supramolecular arrangement adopted by the N-(5-ethyl-[1,3,4]-thiadiazole-2-yl)toluenesulfonamide molecules in the crystal, which consists of extended double strands held together by C—H...π non-covalent interactions.
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14

Brouwer, Darren H., Kevin P. Langendoen i Quentin Ferrant. "Measurement and calculation of 13C chemical shift tensors in α-glucose and α-glucose monohydrate". Canadian Journal of Chemistry 89, nr 7 (lipiec 2011): 737–44. http://dx.doi.org/10.1139/v11-017.

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The 13C chemical shift tensors of two crystalline forms of glucose (α-glucose and α-glucose·H2O) were determined from one-dimensional (1D) and two-dimensional (2D) solid-state nuclear magnetic resonance (NMR) spectroscopy experiments. The experimental values determined from 1D and 2D methods are in very good agreement. Quantum chemical calculations were also carried out using the gauge-including projector augmented wave (GIPAW) method for plane-wave density functional theory (DFT) as implemented in the CAmbridge Serial Total Energy Package (CASTEP). The calculated 13C chemical shifts were found to be in excellent agreement with experimental values for crystal structures that had their hydrogen atoms optimized and after an appropriate calibration was applied to convert calculated chemical shieldings into chemical shifts. The work presented here lays an important foundation for future solid-state NMR and quantum chemical calculation investigations of the various crystalline forms of cellulose.
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15

Mazurek, Anna Helena, Łukasz Szeleszczuk, Kostas Bethanis, Elias Christoforides, Marta Katarzyna Dudek, Monika Zielińska-Pisklak i Dariusz Maciej Pisklak. "17-β-Estradiol—β-Cyclodextrin Complex as Solid: Synthesis, Structural and Physicochemical Characterization". Molecules 28, nr 9 (26.04.2023): 3747. http://dx.doi.org/10.3390/molecules28093747.

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17-β-estradiol (EST) is the most potent form of naturally occurring estrogens; therefore, it has found a wide pharmaceutical application. The major problem associated with the use of EST is its very low water solubility, resulting in poor oral bioavailability. To overcome this drawback, a complexation with cyclodextrins (CD) has been suggested as a solution. In this work, the host–guest inclusion complex between the ß-CD and EST has been prepared using four different methods. The obtained samples have been deeply characterized using 13C CP MAS solid state NMR, PXRD, FT-IR, TGA, DSC, and SEM. Using SCXRD, the crystal structure of the complex has been determined, being to the best of our knowledge the first solved crystal structure of an estrogen/CD complex. The periodic DFT calculations of NMR properties using GIPAW were found to be particularly helpful in the analysis of disorder in the solid state and interpretation of experimental NMR results. This work highlights the importance of a combined ssNMR/SCXRD approach to studying the structure of the inclusion complexes formed by cyclodextrins.
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16

Czernek, Jiří, i Jiří Brus. "Polymorphic Forms of Valinomycin Investigated by NMR Crystallography". International Journal of Molecular Sciences 21, nr 14 (11.07.2020): 4907. http://dx.doi.org/10.3390/ijms21144907.

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A dodecadepsipeptide valinomycin (VLM) has been most recently reported to be a potential anti-coronavirus drug that could be efficiently produced on a large scale. It is thus of importance to study solid-phase forms of VLM in order to be able to ensure its polymorphic purity in drug formulations. The previously available solid-state NMR (SSNMR) data are combined with the plane-wave DFT computations in the NMR crystallography framework. Structural/spectroscopical predictions (the PBE functional/GIPAW method) are obtained to characterize four polymorphs of VLM. Interactions which confer a conformational stability to VLM molecules in these crystalline forms are described in detail. The way how various structural factors affect the values of SSNMR parameters is thoroughly analyzed, and several SSNMR markers of the respective VLM polymorphs are identified. The markers are connected to hydrogen bonding effects upon the corresponding (13C/15N/1H) isotropic chemical shifts of (CO, Namid, Hamid, Hα) VLM backbone nuclei. These results are expected to be crucial for polymorph control of VLM and in probing its interactions in dosage forms.
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17

Franco, Federico, Marcello Baricco, Michele R. Chierotti, Roberto Gobetto i Carlo Nervi. "Coupling Solid-State NMR with GIPAW ab Initio Calculations in Metal Hydrides and Borohydrides". Journal of Physical Chemistry C 117, nr 19 (maj 2013): 9991–98. http://dx.doi.org/10.1021/jp3126895.

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18

Widdifield, Cory, Maria Baias, Jean-Nicolas Dumez, Per H. Svensson, Hugh Thompson, Staffan Schantz, Graeme Day i Lyndon Emsley. "Powder Crystallography by Combining NMR and Crystal Structure Predictions". Acta Crystallographica Section A Foundations and Advances 70, a1 (5.08.2014): C136. http://dx.doi.org/10.1107/s2053273314098635.

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State-of-the-art work in the field of NMR crystallography for molecular systems at natural abundance has recently focused on the accurate measurement of 1H chemical shift values. We will show how when coupled with crystal structure prediction (CSP) methods, this protocol is well-suited for solving the crystal structures of small to medium sized organic molecules, including cocaine and the de-novo structure determination of AZD8329.[1,2] As complementary 1D and 2D NMR experiments are needed for the 1H assignment process, other information, such as isotropic 13C chemical shift values (δiso) are measured. Unfortunately, 13C chemical shifts are not generally useful for structure determination. Additional NMR parameters that are sensitive to structure would ensure that the structure determination procedure is robust, and would provide more accurate refinements when studying larger or more challenging systems. Here, we measure 13C chemical shift tensors for a variety of prototypical organic pharmaceuticals and use density functional theory computations under the gauge-including projector augmented-wave (GIPAW) formalism to probe whether these parameters may be discriminatory for unit cell determinations and structure determination (notably when added to the CSP + 1H chemical shifts protocol).
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19

Ponomarev, Ilia, i Peter Kroll. "29Si NMR Chemical Shifts in Crystalline and Amorphous Silicon Nitrides". Materials 11, nr 9 (7.09.2018): 1646. http://dx.doi.org/10.3390/ma11091646.

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We investigate 29Si nuclear magnetic resonance (NMR) chemical shifts, δiso, of silicon nitride. Our goal is to relate the local structure to the NMR signal and, thus, provide the means to extract more information from the experimental 29Si NMR spectra in this family of compounds. We apply structural modeling and the gauge-included projector augmented wave (GIPAW) method within density functional theory (DFT) calculations. Our models comprise known and hypothetical crystalline Si3N4, as well as amorphous Si3N4 structures. We find good agreement with available experimental 29Si NMR data for tetrahedral Si[4] and octahedral Si[6] in crystalline Si3N4, predict the chemical shift of a trigonal-bipyramidal Si[5] to be about −120 ppm, and quantify the impact of Si-N bond lengths on 29Si δiso. We show through computations that experimental 29Si NMR data indicates that silicon dicarbodiimide, Si(NCN)2 exhibits bent Si-N-C units with angles of about 143° in its structure. A detailed investigation of amorphous silicon nitride shows that an observed peak asymmetry relates to the proximity of a fifth N neighbor in non-bonding distance between 2.5 and 2.8 Å to Si. We reveal the impact of both Si-N(H)-Si bond angle and Si-N bond length on 29Si δiso in hydrogenated silicon nitride structure, silicon diimide Si(NH)2.
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20

Siudem, Paweł, Łukasz Szeleszczuk, Agnieszka Zielińska i Katarzyna Paradowska. "13C CPMAS NMR as an Alternative Method to Verify the Quality of Dietary Supplements Containing Curcumin". Molecules 28, nr 8 (13.04.2023): 3442. http://dx.doi.org/10.3390/molecules28083442.

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Turmeric is a traditional Indian spice that has recently become very popular worldwide because it contains a powerful ingredient called curcumin, which has strong anti-inflammatory properties. Hence, dietary supplements containing extracts rich in curcumin have gained great popularity. The main problems related to curcumin-containing dietary supplements are poor water solubility and the fact that they are often faked by using synthetic curcumin instead of the plant extract. In this article, we propose the use of the 13C CPMAS NMR method to control the quality of dietary supplements. The analysis of 13C CPMAS NMR spectra supported by GIPAW computations allowed us to identify a polymorphic form present in dietary supplements (which affected the solubility of curcumin) and to point out a dietary supplement that could be faked by using synthetic curcumin. Further PXRD and HPLC investigations confirmed that the examined supplement contained synthetic curcumin instead of the genuine extract. Our method can be used for routine control, especially because the investigation is performed directly from the capsule/tablet content and does not require any special sample preparation.
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21

Biswal, Mamata, Monique Body, Christophe Legein, Aymeric Sadoc i Florent Boucher. "NbF5 and TaF5: Assignment of 19F NMR resonances and chemical bond analysis from GIPAW calculations". Journal of Solid State Chemistry 207 (listopad 2013): 208–17. http://dx.doi.org/10.1016/j.jssc.2013.09.001.

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22

Ohkubo, Takahiro, Eiji Tsuchida, Takafumi Takahashi i Yasuhiko Iwadate. "Ab Initio Molecular Dynamics Simulations and GIPAW NMR Calculations of a Lithium Borate Glass Melt". Journal of Physical Chemistry B 120, nr 14 (4.04.2016): 3582–90. http://dx.doi.org/10.1021/acs.jpcb.6b00381.

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23

Marín-Luna, Marta, Ibon Alkorta i José Elguero. "A theoretical NMR study of selected benzazoles: Comparison of GIPAW and GIAO-PCM (DMSO) calculations". Magnetic Resonance in Chemistry 56, nr 3 (29.11.2017): 164–71. http://dx.doi.org/10.1002/mrc.4674.

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24

Ośmiałowski, Borys, Erkki Kolehmainen, Satu Ikonen, Kari Ahonen i Miika Löfman. "NMR crystallography of 2-acylamino-6-[1H]-pyridones: Solid-state NMR, GIPAW computational, and single crystal X-ray diffraction studies". Journal of Molecular Structure 1006, nr 1-3 (grudzień 2011): 678–83. http://dx.doi.org/10.1016/j.molstruc.2011.10.034.

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25

Moustafa, Hadeel, Flemming H. Larsen, Anders Ø. Madsen i Stephan P. A. Sauer. "13C NMR Chemical Shifts of Saccharides in the Solid State: A Density Functional Theory Study". Magnetochemistry 9, nr 8 (26.07.2023): 192. http://dx.doi.org/10.3390/magnetochemistry9080192.

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In this work we present a systematic, theoretical investigation of the 13C NMR chemical shifts for several mono-, di- and trisaccharides in the solid state. The chemical shifts have been calculated using density functional theory (DFT) together with the gauge including the projector augmented wave (GIPAW) method as implemented in the CASTEP program. We studied the changes in the 13C NMR chemical shifts in particular due to the formation of one or two glycosidic linkages and due to crystal water. The largest changes, up to 14 ppm, are observed between the mono- and disaccharides and typically for the glycosidic linkage atoms, but not in all cases. An analysis of the bond angles at the glycosidic linkage and the observed changes in chemical shifts displays no direct correlation between them. Somewhat smaller changes in the range of 2 to 5 ppm are observed when single crystal water molecules are close to some of the atoms. Relating the changes in the chemical shifts of the carbon atoms closest to the crystal water to the distance between them does, however, not lead to a simple relation between them.
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26

Duong, Nghia Tuan, Yoshitaka Aoyama, Katsumi Kawamoto, Toshio Yamazaki i Yusuke Nishiyama. "Structure Solution of Nano-Crystalline Small Molecules Using MicroED and Solid-State NMR Dipolar-Based Experiments". Molecules 26, nr 15 (31.07.2021): 4652. http://dx.doi.org/10.3390/molecules26154652.

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Three-dimensional electron diffraction crystallography (microED) can solve structures of sub-micrometer crystals, which are too small for single crystal X-ray crystallography. However, R factors for the microED-based structures are generally high because of dynamic scattering. That means R factor may not be reliable provided that kinetic analysis is used. Consequently, there remains ambiguity to locate hydrogens and to assign nuclei with close atomic numbers, like carbon, nitrogen, and oxygen. Herein, we employed microED and ssNMR dipolar-based experiments together with spin dynamics numerical simulations. The NMR dipolar-based experiments were 1H-14N phase-modulated rotational-echo saturation-pulse double-resonance (PM-S-RESPDOR) and 1H-1H selective recoupling of proton (SERP) experiments. The former examined the dephasing effect of a specific 1H resonance under multiple 1H-14N dipolar couplings. The latter examined the selective polarization transfer between a 1H-1H pair. The structure was solved by microED and then validated by evaluating the agreement between experimental and calculated dipolar-based NMR results. As the measurements were performed on 1H and 14N, the method can be employed for natural abundance samples. Furthermore, the whole validation procedure was conducted at 293 K unlike widely used chemical shift calculation at 0 K using the GIPAW method. This combined method was demonstrated on monoclinic l-histidine.
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Napiórkowska, Ewa, Łukasz Szeleszczuk, Katarzyna Milcarz i Dariusz Maciej Pisklak. "Density Functional Theory and Density Functional Tight Binding Studies of Thiamine Hydrochloride Hydrates". Molecules 28, nr 22 (9.11.2023): 7497. http://dx.doi.org/10.3390/molecules28227497.

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Thiamine hydrochloride (THCL), also known as vitamin B1, is an active pharmaceutical ingredient (API), present on the list of essential medicines developed by the WHO, which proves its importance for public health. THCL is highly hygroscopic and can occur in the form of hydrates with varying degrees of hydration, depending on the air humidity. Although experimental characterization of the THCL hydrates has been described in the literature, the questions raised in previously published works suggest that additional research and in-depth analysis of THCL dehydration behavior are still needed. Therefore, the main aim of this study was to characterize, by means of quantum chemical calculations, the behavior of thiamine hydrates and explain the previously obtained results, including changes in the NMR spectra, at the molecular level. To achieve this goal, a series of DFT (CASTEP) and DFTB (DFTB+) calculations under periodic boundary conditions have been performed, including molecular dynamics simulations and GIPAW NMR calculations. The obtained results explain the differences in the relative stability of the studied forms and changes in the spectra observed for the samples of various degrees of hydration. This work highlights the application of periodic DFT calculations in the analysis of various solid forms of APIs.
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28

Czernek, Jiri, Martina Urbanova i Jiri Brus. "NMR Crystallography of the Polymorphs of Metergoline". Crystals 8, nr 10 (25.09.2018): 378. http://dx.doi.org/10.3390/cryst8100378.

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Two polymorphs of the drug compound metergoline (C25H29N3O2) were investigated in detail by solid-state NMR measurements. The results have been analysed by an advanced procedure, which uses experimental input together with the results of quantum chemical calculations that were performed for molecular crystals. In this way, it was possible to assign the total of 40 1H–13C correlation pairs in a highly complex system, namely, in the dynamically disordered polymorph with two independent molecules in the unit cell of a large volume of 4234 Å3. For the simpler polymorph, which exhibits only small-amplitude motions and has just one molecule in the unit cell with a volume of 529.0 Å3, the values of the principal elements of the 13C chemical shift tensors were measured. Additionally, for this polymorph, a set of crystal structure predictions were generated, and the {13C, 1H} isotropic and 13C anisotropic chemical shielding data were computed while using the gauge-including projector augmented-wave approach combined with the “revised Perdew-Burke-Ernzerhof“ exchange-correlation functional (GIPAW-RPBE). The experimental and theoretical results were combined in an application of the newly developed strategy to polymorph discrimination. This research thus opens up new routes towards more accurate characterization of the polymorphism of drug formulations.
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Widdifield, Cory M., i David L. Bryce. "Crystallographic structure refinement with quadrupolar nuclei: a combined solid-state NMR and GIPAW DFT example using MgBr2". Physical Chemistry Chemical Physics 11, nr 33 (2009): 7120. http://dx.doi.org/10.1039/b911448n.

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Gambuzzi, Elisa, Alfonso Pedone, Maria Cristina Menziani, Frédéric Angeli, Pierre Florian i Thibault Charpentier. "Calcium environment in silicate and aluminosilicate glasses probed by 43Ca MQMAS NMR experiments and MD-GIPAW calculations". Solid State Nuclear Magnetic Resonance 68-69 (czerwiec 2015): 31–36. http://dx.doi.org/10.1016/j.ssnmr.2015.04.003.

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31

Webber, Amy L., Lyndon Emsley, Rosa M. Claramunt i Steven P. Brown. "NMR Crystallography of Campho[2,3-c]pyrazole (Z′ = 6): Combining High-Resolution1H-13C Solid-State MAS NMR Spectroscopy and GIPAW Chemical-Shift Calculations". Journal of Physical Chemistry A 114, nr 38 (30.09.2010): 10435–42. http://dx.doi.org/10.1021/jp104901j.

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32

Presti, Davide, Alfonso Pedone i Maria Cristina Menziani. "Unraveling the Polymorphism of [(p-cymene)Ru(κN-INA)Cl2] through Dispersion-Corrected DFT and NMR GIPAW Calculations". Inorganic Chemistry 53, nr 15 (14.07.2014): 7926–35. http://dx.doi.org/10.1021/ic5006743.

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33

Chapman, Rebecca P., Jennifer R. Hiscock, Philip A. Gale i David L. Bryce. "A solid-state 35/37Cl NMR study of a chloride ion receptor and a GIPAW-DFT study of chlorine NMR interaction tensors in organic hydrochlorides". Canadian Journal of Chemistry 89, nr 7 (lipiec 2011): 822–34. http://dx.doi.org/10.1139/v10-177.

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The results of a 35/37Cl solid-state nuclear magnetic resonance (SSNMR) study of the 1-butyl-3-methylimidazolium chloride complex of meso-octamethylcalix[4]pyrrole (1) are reported. Line shapes obtained from magic-angle-spinning and stationary powder samples collected at 9.4 and 21.1 T are analyzed to provide the 35/37Cl quadrupolar tensor and chemical shift (CS) tensor and their relative orientation. The relatively high symmetry of the chloride ion coordination environment is manifested in the small value of the quadrupole coupling constant, CQ(35Cl) = 1.0 MHz. The isotropic chemical shift of 120 ppm (with respect to NaCl(s)) is at the upper edge of the typical range seen for organic hydrochlorides. Consideration of chemical shift anisotropy (span, Ω = 50 ppm) and non-coincidence of the quadrupolar and CS tensors were essential to properly simulate the experimental spectra. The utility of gauge-including projector-augmented wave density functional theory (GIPAW-DFT) calculations of chlorine quadrupolar and CS tensors in organic chlorides was explored by validation against available benchmark experimental data for solid amino acid hydrochlorides. The calculations are shown to systematically overestimate the value of the 35Cl quadrupole coupling constant. Additional calculations on various hydrated and solvated models of 1 are consistent with a structure in which solvent and water of hydration are absent.
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34

DeVore, Michael A., Christopher A. Klug, Maria R. Kriz, Lindsay E. Roy i Matthew S. Wellons. "Investigations of Uranyl Fluoride Sesquihydrate (UO2F2·1.57H2O): Combining 19F Solid-State MAS NMR Spectroscopy and GIPAW Chemical Shift Calculations". Journal of Physical Chemistry A 122, nr 34 (26.07.2018): 6873–78. http://dx.doi.org/10.1021/acs.jpca.8b04369.

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35

Ludwig, Martin, Daniel Himmel i Harald Hillebrecht. "GIAO versus GIPAW: Comparison of Methods To Calculate 11B NMR Shifts of Icosahedral Closo-Heteroboranes toward Boron-Rich Borides". Journal of Physical Chemistry A 124, nr 11 (30.01.2020): 2173–85. http://dx.doi.org/10.1021/acs.jpca.9b06582.

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36

Szeleszczuk, Łukasz, Dariusz Maciej Pisklak, Monika Zielińska-Pisklak i Iwona Wawer. "Effects of structural differences on the NMR chemical shifts in cinnamic acid derivatives: Comparison of GIAO and GIPAW calculations". Chemical Physics Letters 653 (czerwiec 2016): 35–41. http://dx.doi.org/10.1016/j.cplett.2016.04.075.

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37

Venâncio, Tiago, Lyege Magalhaes Oliveira, Javier Ellena, Nubia Boechat i Steven P. Brown. "Probing intermolecular interactions in a diethylcarbamazine citrate salt by fast MAS 1 H solid-state NMR spectroscopy and GIPAW calculations". Solid State Nuclear Magnetic Resonance 87 (październik 2017): 73–79. http://dx.doi.org/10.1016/j.ssnmr.2017.02.006.

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38

Marín-Luna, Marta, Rosa M. Claramunt, Concepción López, Marta Pérez-Torralba, Dionisia Sanz, Felipe Reviriego, Ibon Alkorta i José Elguero. "A GIPAW versus GIAO-ZORA-SO study of 13C and 15N CPMAS NMR chemical shifts of aromatic and heterocyclic bromo derivatives". Solid State Nuclear Magnetic Resonance 108 (sierpień 2020): 101676. http://dx.doi.org/10.1016/j.ssnmr.2020.101676.

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39

Widdifield, Cory M., i David L. Bryce. "Solid-State127I NMR and GIPAW DFT Study of Metal Iodides and Their Hydrates: Structure, Symmetry, and Higher-Order Quadrupole-Induced Effects". Journal of Physical Chemistry A 114, nr 40 (14.10.2010): 10810–23. http://dx.doi.org/10.1021/jp108237x.

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Szeleszczuk, Łukasz, Dariusz M. Pisklak i Monika Zielińska-Pisklak. "How does the NMR thermometer work? Application of combined quantum molecular dynamics and GIPAW calculations into the study of lead nitrate". Journal of Computational Chemistry 40, nr 6 (26.12.2018): 811–19. http://dx.doi.org/10.1002/jcc.25766.

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41

Szeleszczuk, Łukasz, Tomasz Gubica, Andrzej Zimniak, Dariusz M. Pisklak, Kinga Dąbrowska, Michał K. Cyrański i Marianna Kańska. "The potential for the indirect crystal structure verification of methyl glycosides based on acetates’ parent structures: GIPAW and solid-state NMR approaches". Chemical Physics Letters 686 (październik 2017): 7–11. http://dx.doi.org/10.1016/j.cplett.2017.08.028.

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42

Venâncio, Tiago, Lyege Magalhaes Oliveira, Tomasz Pawlak, Javier Ellena, Nubia Boechat i Steven P. Brown. "The use of variable temperature 13 C solid-state MAS NMR and GIPAW DFT calculations to explore the dynamics of diethylcarbamazine citrate". Magnetic Resonance in Chemistry 57, nr 5 (15.10.2018): 200–210. http://dx.doi.org/10.1002/mrc.4790.

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43

Szell, Patrick M. J., Shaina A. Gabriel, Russell D. D. Gill, Shirley Y. H. Wan, Bulat Gabidullin i David L. Bryce. "13C and 19F solid-state NMR and X-ray crystallographic study of halogen-bonded frameworks featuring nitrogen-containing heterocycles". Acta Crystallographica Section C Structural Chemistry 73, nr 3 (6.02.2017): 157–67. http://dx.doi.org/10.1107/s2053229616015023.

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Halogen bonding is a noncovalent interaction between the electrophilic region of a halogen (σ-hole) and an electron donor. We report a crystallographic and structural analysis of halogen-bonded compounds by applying a combined X-ray diffraction (XRD) and solid-state nuclear magnetic resonance (SSNMR) approach. Single-crystal XRD was first used to characterize the halogen-bonded cocrystals formed between two fluorinated halogen-bond donors (1,4-diiodotetrafluorobenzene and 1,3,5-trifluoro-2,4,6-triiodobenzene) and several nitrogen-containing heterocycles (acridine, 1,10-phenanthroline, 2,3,5,6-tetramethylpyrazine, and hexamethylenetetramine). New structures are reported for the following three cocrystals, all in the P21/c space group: acridine–1,3,5-trifluoro-2,4,6-triiodobenzene (1/1), C6F3I3·C13H9N, 1,10-phenanthroline–1,3,5-trifluoro-2,4,6-triiodobenzene (1/1), C6F3I3·C12H8N2, and 2,3,5,6-tetramethylpyrazine–1,3,5-trifluoro-2,4,6-triiodobenzene (1/1), C6F3I3·C8H12N2. 13C and 19F solid-state magic-angle spinning (MAS) NMR is shown to be a convenient method to characterize the structural features of the halogen-bond donor and acceptor, with chemical shifts attributable to cocrystal formation observed in the spectra of both nuclides. Cross polarization (CP) from 19F to 13C results in improved spectral sensitivity in characterizing the perfluorinated halogen-bond donor when compared to conventional 1H CP. Gauge-including projector-augmented wave density functional theory (GIPAW DFT) calculations of magnetic shielding constants, along with optimization of the XRD structures, provide a final set of structures in best agreement with the experimental 13C and 19F chemical shifts. Data for carbons bonded to iodine remain outliers due to well-known relativistic effects.
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44

Gervais, Christel, Laure Bonhomme-Coury, Francesco Mauri, Florence Babonneau i Christian Bonhomme. "GIPAW (gauge including projected augmented wave) and local dynamics in 13C and 29Si solid state NMR: the study case of silsesquioxanes (RSiO1.5)8". Physical Chemistry Chemical Physics 11, nr 32 (2009): 6953. http://dx.doi.org/10.1039/b907450c.

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Küçükbenli, Emine, Kanchan Sonkar, Neeraj Sinha i Stefano de Gironcoli. "Complete 13C NMR Chemical Shifts Assignment for Cholesterol Crystals by Combined CP-MAS Spectral Editing and ab Initio GIPAW Calculations with Dispersion Forces". Journal of Physical Chemistry A 116, nr 14 (27.03.2012): 3765–69. http://dx.doi.org/10.1021/jp3019974.

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Szeleszczuk, Łukasz, Dariusz Maciej Pisklak i Monika Zielińska-Pisklak. "Does the choice of the crystal structure influence the results of the periodic DFT calculations? A case of glycine alpha polymorph GIPAW NMR parameters computations". Journal of Computational Chemistry 39, nr 14 (5.01.2018): 853–61. http://dx.doi.org/10.1002/jcc.25161.

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Corlett, Emily K., Helen Blade, Leslie P. Hughes, Philip J. Sidebottom, David Walker, Richard I. Walton i Steven P. Brown. "Investigating discrepancies between experimental solid-state NMR and GIPAW calculation: N C–N 13C and OH⋯O 1H chemical shifts in pyridinium fumarates and their cocrystals". Solid State Nuclear Magnetic Resonance 108 (sierpień 2020): 101662. http://dx.doi.org/10.1016/j.ssnmr.2020.101662.

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48

Marín‐Luna, Marta, Pilar Sánchez‐Andrada, Ibon Alkorta, José Elguero, M. Carmen Torralba, Patricia Delgado‐Martínez, Dolores Santa María i Rosa M. Claramunt. "A structural analysis of 2,5‐diaryl‐4 H ‐2,4‐dihydro‐3 H ‐1,2,4‐triazol‐3‐ones: NMR in the solid state, X‐ray crystallography, and GIPAW calculations". Magnetic Resonance in Chemistry 59, nr 4 (25.10.2020): 423–38. http://dx.doi.org/10.1002/mrc.5107.

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Asakura, Tetsuo, Koji Yazawa, Kumiko Horiguchi, Furitsu Suzuki, Yusuke Nishiyama, Katsuyuki Nishimura i Hironori Kaji. "Difference in the structures of alanine tri- and tetra-peptides with antiparallel β-sheet assessed by X-ray diffraction, solid-state NMR and chemical shift calculations by GIPAW". Biopolymers 101, nr 1 (25.10.2013): 13–20. http://dx.doi.org/10.1002/bip.22241.

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Yazawa, Koji, Furitsu Suzuki, Yusuke Nishiyama, Takuya Ohata, Akihiro Aoki, Katsuyuki Nishimura, Hironori Kaji, Tadashi Shimizu i Tetsuo Asakura. "Determination of accurate 1H positions of an alanine tripeptide with anti-parallel and parallel β-sheet structures by high resolution 1H solid state NMR and GIPAW chemical shift calculation". Chemical Communications 48, nr 91 (2012): 11199. http://dx.doi.org/10.1039/c2cc36300c.

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