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Chen C, Goldberga I, Gaveau P, Mittelette S, Špačková J, Mullen C, Petit I, Métro T, Alonso B, Gervais C, Laurencin D. Looking into the dynamics of molecular crystals of ibuprofen and terephthalic acid using 17 O and 2 H nuclear magnetic resonance analyses. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2021; 59:975-990. [PMID: 33615550 PMCID: PMC8518726 DOI: 10.1002/mrc.5141] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Revised: 02/15/2021] [Accepted: 02/18/2021] [Indexed: 05/09/2023]
Abstract
Oxygen-17 and deuterium are two quadrupolar nuclei that are of interest for studying the structure and dynamics of materials by solid-state nuclear magnetic resonance (NMR). Here, 17 O and 2 H NMR analyses of crystalline ibuprofen and terephthalic acid are reported. First, improved 17 O-labelling protocols of these molecules are described using mechanochemistry. Then, dynamics occurring around the carboxylic groups of ibuprofen are studied considering variable temperature 17 O and 2 H NMR data, as well as computational modelling (including molecular dynamics simulations). More specifically, motions related to the concerted double proton jump and the 180° flip of the H-bonded (-COOH)2 unit in the crystal structure were looked into, and it was found that the merging of the C=O and C-OH 17 O resonances at high temperatures cannot be explained by the sole presence of one of these motions. Lastly, preliminary experiments were performed with a 2 H-17 O diplexer connected to the probe. Such configurations can allow, among others, 2 H and 17 O NMR spectra to be recorded at different temperatures without needing to tune or to change probe configurations. Overall, this work offers a few leads which could be of use in future studies of other materials using 17 O and 2 H NMR.
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Affiliation(s)
| | | | | | | | | | | | - Ivan Petit
- Laboratoire de Chimie de la Matière Condensée de Paris (LCMCP), UMR 7574, Sorbonne Université, CNRSParisFrance
| | | | - Bruno Alonso
- ICGM, Univ Montpellier, CNRS, ENSCMMontpellierFrance
| | - Christel Gervais
- Laboratoire de Chimie de la Matière Condensée de Paris (LCMCP), UMR 7574, Sorbonne Université, CNRSParisFrance
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2
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Engel EA, Kapil V, Ceriotti M. Importance of Nuclear Quantum Effects for NMR Crystallography. J Phys Chem Lett 2021; 12:7701-7707. [PMID: 34355903 DOI: 10.1021/acs.jpclett.1c01987] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The resolving power of solid-state nuclear magnetic resonance (NMR) crystallography depends heavily on the accuracy of computational predictions of NMR chemical shieldings of candidate structures, which are usually taken to be local minima in the potential energy. To test the limits of this approximation, we systematically study the importance of finite-temperature and quantum nuclear fluctuations for 1H, 13C, and 15N shieldings in polymorphs of three paradigmatic molecular crystals: benzene, glycine, and succinic acid. The effect of quantum fluctuations is comparable to the typical errors of shielding predictions for static nuclei with respect to experiments, and their inclusion improves the agreement with measurements, translating to more reliable assignment of the NMR spectra to the correct candidate structure. The use of integrated machine-learning models, trained on first-principles energies and shieldings, renders rigorous sampling of nuclear fluctuations affordable, setting a new standard for the calculations underlying NMR structure determinations.
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Affiliation(s)
- Edgar A Engel
- TCM Group, Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - Venkat Kapil
- Laboratory of Computational Science and Modeling, Institut des Matériaux, École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
| | - Michele Ceriotti
- Laboratory of Computational Science and Modeling, Institut des Matériaux, École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
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3
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Szeleszczuk Ł, Pisklak DM, Zielińska-Pisklak M. How does the NMR thermometer work? Application of combined quantum molecular dynamics and GIPAW calculations into the study of lead nitrate. J Comput Chem 2018; 40:811-819. [PMID: 30586162 DOI: 10.1002/jcc.25766] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2018] [Revised: 11/21/2018] [Accepted: 11/21/2018] [Indexed: 11/08/2022]
Abstract
Lead nitrate is an inorganic salt, commonly used for the accurate temperature determination in the solid state NMR spectroscopy, due to the strong temperature dependence of the 207 Pb chemical shift. As the reason for this phenomenon remained unknown, the main purpose of this study was to explain this temperature dependence at the molecular level. To achieve this, combined CASTEP geometry optimization, quantum molecular dynamics at chosen temperatures and GIPAW NMR computations were performed. Due to the previous literature reports on inaccuracy in the calculation of 207 Pb NMR parameters using GIPAW, a large emphasis was put on the optimization of computational method. The application of quantum molecular dynamics provided the simulation of the temperature-dependent vibrational motions and enabled to accurately compute the changes in the value of Pb δiso resulting from them. © 2018 Wiley Periodicals, Inc.
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Affiliation(s)
- Łukasz Szeleszczuk
- Faculty of Pharmacy with the Laboratory Medicine Division, Department of Physical Chemistry, Medical University of Warsaw, Chair of Physical Pharmacy and Bioanalysis, Banacha 1, 02-093, Warsaw, Poland.,Department of Physical Pharmacy and Bioanalysis, Medical University of Warsaw, 02-093, Warsaw, Poland
| | - Dariusz M Pisklak
- Faculty of Pharmacy with the Laboratory Medicine Division, Department of Physical Chemistry, Medical University of Warsaw, Chair of Physical Pharmacy and Bioanalysis, Banacha 1, 02-093, Warsaw, Poland.,Department of Physical Pharmacy and Bioanalysis, Medical University of Warsaw, 02-093, Warsaw, Poland
| | - Monika Zielińska-Pisklak
- Faculty of Pharmacy with the Laboratory Medicine Division, Medical University of Warsaw, Department of Biomaterials Chemistry, Chair of Analytical Chemistry and Biomaterials, 02-093, Warsaw, Poland
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4
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Monserrat B. Electron-phonon coupling from finite differences. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:083001. [PMID: 29328057 DOI: 10.1088/1361-648x/aaa737] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
The interaction between electrons and phonons underlies multiple phenomena in physics, chemistry, and materials science. Examples include superconductivity, electronic transport, and the temperature dependence of optical spectra. A first-principles description of electron-phonon coupling enables the study of the above phenomena with accuracy and material specificity, which can be used to understand experiments and to predict novel effects and functionality. In this topical review, we describe the first-principles calculation of electron-phonon coupling from finite differences. The finite differences approach provides several advantages compared to alternative methods, in particular (i) any underlying electronic structure method can be used, and (ii) terms beyond the lowest order in the electron-phonon interaction can be readily incorporated. But these advantages are associated with a large computational cost that has until recently prevented the widespread adoption of this method. We describe some recent advances, including nondiagonal supercells and thermal lines, that resolve these difficulties, and make the calculation of electron-phonon coupling from finite differences a powerful tool. We review multiple applications of the calculation of electron-phonon coupling from finite differences, including the temperature dependence of optical spectra, superconductivity, charge transport, and the role of defects in semiconductors. These examples illustrate the advantages of finite differences, with cases where semilocal density functional theory is not appropriate for the calculation of electron-phonon coupling and many-body methods such as the GW approximation are required, as well as examples in which higher-order terms in the electron-phonon interaction are essential for an accurate description of the relevant phenomena. We expect that the finite difference approach will play a central role in future studies of the electron-phonon interaction.
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Affiliation(s)
- Bartomeu Monserrat
- Department of Physics and Astronomy, Rutgers University, Piscataway, NJ 08854-8019, United States of America. TCM Group, Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge CB3 0HE, United Kingdom
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5
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Nemausat R, Gervais C, Brouder C, Trcera N, Bordage A, Coelho-Diogo C, Florian P, Rakhmatullin A, Errea I, Paulatto L, Lazzeri M, Cabaret D. Temperature dependence of X-ray absorption and nuclear magnetic resonance spectra: probing quantum vibrations of light elements in oxides. Phys Chem Chem Phys 2017; 19:6246-6256. [DOI: 10.1039/c6cp08393e] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Probing the quantum thermal fluctuations of nuclei in light-element oxides using XANES and NMR spectroscopies.
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Affiliation(s)
- Ruidy Nemausat
- Sorbonne Universités
- UPMC Univ Paris 06
- IMPMC
- UMR CNRS 7590
- F-75005 Paris
| | - Christel Gervais
- Sorbonne Universités
- UPMC Univ Paris 06
- LCMCP
- Collège de France
- UMR CNRS 7574
| | - Christian Brouder
- Sorbonne Universités
- UPMC Univ Paris 06
- IMPMC
- UMR CNRS 7590
- F-75005 Paris
| | - Nicolas Trcera
- Synchrotron SOLEIL
- L'Orme des Merisiers
- F-91192 Gif sur Yvette
- France
| | - Amélie Bordage
- ICMMO
- Univ Paris Sud
- Univ Paris-Saclay
- UMR CNRS 8182
- F-91405 Orsay
| | | | | | | | - Ion Errea
- Fisika Aplikatua 1 Saila
- Bilboko Ingeniaritza Eskola
- University of the Basque Country (UPV/EHU)
- 48013 Bilbao
- Spain
| | - Lorenzo Paulatto
- Sorbonne Universités
- UPMC Univ Paris 06
- IMPMC
- UMR CNRS 7590
- F-75005 Paris
| | - Michele Lazzeri
- Sorbonne Universités
- UPMC Univ Paris 06
- IMPMC
- UMR CNRS 7590
- F-75005 Paris
| | - Delphine Cabaret
- Sorbonne Universités
- UPMC Univ Paris 06
- IMPMC
- UMR CNRS 7590
- F-75005 Paris
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6
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Ashbrook SE, McKay D. Combining solid-state NMR spectroscopy with first-principles calculations - a guide to NMR crystallography. Chem Commun (Camb) 2016; 52:7186-204. [PMID: 27117884 DOI: 10.1039/c6cc02542k] [Citation(s) in RCA: 151] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Recent advances in the application of first-principles calculations of NMR parameters to periodic systems have resulted in widespread interest in their use to support experimental measurement. Such calculations often play an important role in the emerging field of "NMR crystallography", where NMR spectroscopy is combined with techniques such as diffraction, to aid structure determination. Here, we discuss the current state-of-the-art for combining experiment and calculation in NMR spectroscopy, considering the basic theory behind the computational approaches and their practical application. We consider the issues associated with geometry optimisation and how the effects of temperature may be included in the calculation. The automated prediction of structural candidates and the treatment of disordered and dynamic solids are discussed. Finally, we consider the areas where further development is needed in this field and its potential future impact.
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Affiliation(s)
- Sharon E Ashbrook
- School of Chemistry, EaStCHEM and Centre of Magnetic Resonance, University of St Andrews, St Andrews, KY16 9ST, UK.
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7
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Dračínský M, Bouř P, Hodgkinson P. Temperature Dependence of NMR Parameters Calculated from Path Integral Molecular Dynamics Simulations. J Chem Theory Comput 2016; 12:968-73. [PMID: 26857802 DOI: 10.1021/acs.jctc.5b01131] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The influence of temperature on NMR chemical shifts and quadrupolar couplings in model molecular organic solids is explored using path integral molecular dynamics (PIMD) and density functional theory (DFT) calculations of shielding and electric field gradient (EFG) tensors. An approach based on convoluting calculated shielding or EFG tensor components with probability distributions of selected bond distances and valence angles obtained from DFT-PIMD simulations at several temperatures is used to calculate the temperature effects. The probability distributions obtained from the quantum PIMD simulations, which includes nuclear quantum effects, are significantly broader and less temperature dependent than those obtained with conventional DFT molecular dynamics or with 1D scans through the potential energy surface. Predicted NMR observables for the model systems were in excellent agreement with experimental data.
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Affiliation(s)
- Martin Dračínský
- Institute of Organic Chemistry and Biochemistry , Flemingovo nám. 2, 16610 Prague, Czech Republic
| | - Petr Bouř
- Institute of Organic Chemistry and Biochemistry , Flemingovo nám. 2, 16610 Prague, Czech Republic
| | - Paul Hodgkinson
- Department of Chemistry, Durham University , South Road, DH1 3LE Durham, United Kingdom
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8
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Chan-Huot M, Wimperis S, Gervais C, Bodenhausen G, Duma L. Deuterium MAS NMR Studies of Dynamics on Multiple Timescales: Histidine and Oxalic Acid. Chemphyschem 2014; 16:204-15. [DOI: 10.1002/cphc.201402506] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2014] [Indexed: 11/11/2022]
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9
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Monserrat B, Needs RJ, Pickard CJ. Temperature effects in first-principles solid state calculations of the chemical shielding tensor made simple. J Chem Phys 2014; 141:134113. [DOI: 10.1063/1.4897261] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Bartomeu Monserrat
- TCM Group, Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - Richard J. Needs
- TCM Group, Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - Chris J. Pickard
- Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom
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10
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Torres V, Lopez JM, Langer U, Buntkowsky G, Vieth HM, Elguero J, Limbach HH. Kinetics of Coupled Double Proton and Deuteron Transfer in Hydrogen-Bonded Ribbons of Crystalline Pyrazole-4-carboxylic Acid. ACTA ACUST UNITED AC 2012. [DOI: 10.1524/zpch.2012.0305] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Abstract
The proton tautomerism of pyrazole-4-carboxylic acid (PCA) has been studied by a combination of 15N CPMAS and 2H NMR spectroscopy and relaxometry. Down to 250 K, PCA forms a hydrogen bonded ribbon where adjacent carboxylic and pyrazole groups are linked by an OH···N and an O···HN hydrogen bond, forming either the tautomeric state A or B. Down to about 250 K, the tautomerism is fast on the NMR timescale and degenerate, corresponding to a phase exhibiting dynamic proton disorder. At lower temperatures, a transition to an ordered phase is observed with localized protons, assigned to an all-syn conformation adopting the sequence of tautomeric states ..ABABA.. The longitudinal 15N relaxation times T
1 of PCA-15N2 have been measured at 9.12 MHz (2.1 T). Because of the low field, a chemical shift anisotropy mechanism could be neglected, and the data were analyzed in terms of a dipolar 1H-15N relaxation mechanism, yielding the rate constants k
HH. The rate constants k
HD and k
DD were obtained from the measurement and analysis of the 2H T
1 values of PCA-15N1-d0.9 and PCA-15N1-d0.1 measured at 46.03 MHz. Within the margin of error, no kinetic isotope effects could be detected, in contrast to previous results reported for the very fast tautomerism of solid benzoic acid dimers and the much slower tautomerism of solid 3,5-diphenyl-4-brompyrazole (DPBrP) dimers. The Arrhenius curves of all three systems were simulated using the Bell–Limbach tunneling model. Evidence for a major heavy atom motion for the tautomerism of PCA is obtained, associated with small angle reorientation of PCA molecules around the molecular axis. The observed proton order-disorder transition and the mechanism of the observed rate process are discussed in terms of a coupling of adjacent tautomeric states.
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Affiliation(s)
- Verónica Torres
- Freie Universität Berlin, Institut für Chemie und Biochemie, Berlin, Deutschland
| | - Juan-Miguel Lopez
- Freie Universität Berlin, Institut für Chemie und Biochemie, Berlin, Deutschland
| | - Uwe Langer
- Freie Universität Berlin, Institut für Chemie und Biochemie, Berlin, Deutschland
| | - Gerd Buntkowsky
- Technische Universität Darmstadt, Eduard-Zintl-Institut für Anorganische und, Darmstadt, Deutschland
| | - Hans-Martin Vieth
- Freie Universität Berlin, Institut für Experimentalphysik, Berlin, Deutschland
| | - José Elguero
- CSIC, Instituto de Quimica Medica, Madrid, Spanien
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11
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Seliger J, Žagar V. Unusual Electron Charge Density in Carboxylic Acid. 17O Quadrupole Coupling in cis-Cyclobutane-1,2-dicarboxylic Acid. J Phys Chem A 2012; 116:7139-46. [DOI: 10.1021/jp301802v] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Janez Seliger
- Jozef Stefan Institute, Jamova 39, 1000
Ljubljana, Slovenia
- Faculty
of Mathematics and Physics, University of Ljubljana, Jadranska 19, 1000 Ljubljana, Slovenia
- EN-FIST Centre of Excellence, Dunajska 156, 1000 Ljubljana, Slovenia
| | - Veselko Žagar
- Jozef Stefan Institute, Jamova 39, 1000
Ljubljana, Slovenia
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12
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Dračínský M, Bouř P. Vibrational averaging of the chemical shift in crystalline α-glycine. J Comput Chem 2012; 33:1080-9. [PMID: 22410968 DOI: 10.1002/jcc.22940] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2011] [Revised: 01/04/2012] [Accepted: 01/04/2012] [Indexed: 11/06/2022]
Abstract
Averaging of the chemical shift over the molecular motion improves the simulated data and provides additional information about the temperature dependence and system dynamics. However, crystal modeling is difficult due to the limited precision of the plane-wave density functional theory (DFT) methods and approximate vibrational schemes. On the glycine example, we investigate how the averaging can be achieved within the periodic boundary conditions at the DFT level. The nuclear motion is modeled with the vibrational configuration interaction, with other simplified quantum anharmonic schemes, and the classical Born-Oppenheimer molecular dynamics (BOMD). The results confirm a large vibrational contribution to the isotropic shielding values. Both the first and second derivatives of the shielding were found important for the quantum averaging. The first derivatives influence the shielding mostly due to the anharmonic character of the CH and NH stretching modes, whereas second derivatives produce most vibrational corrections associated with the lower-frequency vibrational modes. Temperature excitations of the lowest-frequency vibrational states and the expansion of the crystal cell both determine the temperature dependence of nuclear magnetic resonance parameters. The vibrational quantum approach as well as classical BOMD schemes provided temperature dependencies of the chemical shifts that are consistent with the previous experimental data.
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Affiliation(s)
- Martin Dračínský
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences, Flemingovo náměstí 2, Prague 166 10, Czech Republic.
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13
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Fu W, Sun P. Solid state NMR study of hydrogen bonding, miscibility, and dynamics in multiphase polymer systems. ACTA ACUST UNITED AC 2011. [DOI: 10.1007/s11458-011-0254-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
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14
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Dračínský M, Jansa P, Ahonen K, Buděšínský M. Tautomerism and the Protonation/Deprotonation of Isocytosine in Liquid- and Solid-States Studied by NMR Spectroscopy and Theoretical Calculations. European J Org Chem 2011. [DOI: 10.1002/ejoc.201001534] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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15
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Schmidt J, Hutter J, Spiess HW, Sebastiani D. Beyond Isotropic Tumbling Models: Nuclear Spin Relaxation in Liquids from First Principles. Chemphyschem 2008; 9:2313-6. [DOI: 10.1002/cphc.200800435] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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16
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Declerck R, Pauwels E, Van Speybroeck V, Waroquier M. Molecular Environment and Temperature Dependence of Hyperfine Interactions in Sugar Crystal Radicals from First Principles. J Phys Chem B 2008; 112:1508-14. [DOI: 10.1021/jp076571w] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- R. Declerck
- Center for Molecular Modeling, Ghent University, Proeftuinstraat 86, B-9000 Gent, Belgium
| | - E. Pauwels
- Center for Molecular Modeling, Ghent University, Proeftuinstraat 86, B-9000 Gent, Belgium
| | - V. Van Speybroeck
- Center for Molecular Modeling, Ghent University, Proeftuinstraat 86, B-9000 Gent, Belgium
| | - M. Waroquier
- Center for Molecular Modeling, Ghent University, Proeftuinstraat 86, B-9000 Gent, Belgium
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17
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Lee YJ, Bingöl B, Murakhtina T, Sebastiani D, Meyer WH, Wegner G, Spiess HW. High-Resolution Solid-State NMR Studies of Poly(vinyl phosphonic acid) Proton-Conducting Polymer: Molecular Structure and Proton Dynamics. J Phys Chem B 2007; 111:9711-21. [PMID: 17655348 DOI: 10.1021/jp072112j] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The structure and the local proton mobility of poly(vinyl phosphonic acid) were studied by solid-state NMR under fast magic-angle spinning. At elevated temperatures, the signature of the hydrogen-bonded P-OH protons is observed in 1H magic-angle spinning (MAS) NMR as a single resonance at 10.5 ppm. Both 1H double-quantum NMR and variable-temperature experiments demonstrate that P-OH protons are mobile and thus able to contribute to proton conductivity. Below room temperature, two different types of hydrogen-bonded P-OH resonances are observed at 10.5 and 15 ppm, and 1H double-quantum NMR demonstrates that these protons are immobile on the NMR time scale. By means of first-principles calculations of a model polymer, we have assigned the additional hydrogen-bonded species at lower temperatures to phosphonic acid anhydride and charged anhydride. Also, in the 31P MAS NMR spectrum, two distinct resonances appear, arising from "normal" phosphonic acid and phosphonic acid anhydride. 31P double-quantum NMR experiments reveal that there is no phase segregation between normal and phosphonic acid anhydride and the condensation reaction occurs randomly throughout the system. The formation of acid anhydride leads to a decrease in proton conductivity through two mechanisms, (1) decrease in the number of charge carriers and (2) blockage of charge transport pathways through immobilization of charge carriers together with a hindered reorientation of the anhydride group. Our results provide strong evidence for these mechanisms by demonstrating that the conductivity is greatly influenced by the presence of phosphonic acid anhydride.
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Affiliation(s)
- Young Joo Lee
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
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18
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de la Lande A, Fressigné C, Gérard H, Maddaluno J, Parisel O. First-Principles Molecular Dynamics Evaluation of Thermal Effects on the NMR1JLi,C Spin–Spin Coupling. Chemistry 2007; 13:3459-69. [PMID: 17225217 DOI: 10.1002/chem.200601108] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Car-Parrinello (CP) molecular dynamics were applied to sample conformations of various models of organolithium aggregates which are chosen to estimate (1)J(Li,C) NMR coupling constants. The results show that the deviations from the values computed using static (optimized) geometries are small provided no large-amplitude motions occur within the timescale of the simulations. In the case of the vinyllithium dimer, for which rotation of the vinyl chain is observed, this approach allows analysis of the various contributions to the experimentally measured constants. For the trisolvated methyllithium monomer, partial decoordination of solvating dimethyl ether is observed and results in a significant shift of (1)J(Li,C). All these results highlight that a varied physicochemical machinery is hidden behind general empirical formulas, such as the Bauer-Winchester-Schleyer rule used experimentally.
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Affiliation(s)
- Aurélien de la Lande
- Laboratoire de Chimie Théorique, UMR 7616 CNRS, Université P. and M. Curie, Case Courrier 137, 4, place Jussieu, 75252 Paris Cedex 05, France
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19
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Murakhtina T, Heuft J, Meijer EJ, Sebastiani D. First Principles and Experimental 1H NMR Signatures of Solvated Ions: The Case of HCl(aq). Chemphyschem 2006; 7:2578-84. [PMID: 17072940 DOI: 10.1002/cphc.200600385] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
A combined experimental and ab initio study is presented of the 1H NMR chemical shift distribution of aqueous hydrogen chloride solution as a function of acid concentration, based on Car-Parrinello molecular dynamics simulations and fully periodic NMR chemical-shift calculations. The agreement of computed and experimental spectra is very good. From first-principles calculations, we can show that the individual contributions of Eigen and Zundel ions, regular water molecules, and the chlorine solvation shell to the NMR line are very distinct and almost independent of the acid concentration. From the computed instantaneous NMR distributions, it is further possible to characterize the average variation in hydrogen-bond strength of the different complexes.
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Affiliation(s)
- Tatiana Murakhtina
- Max-Planck-Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
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20
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Schmidt J, Hoffmann A, Spiess HW, Sebastiani D. Bulk Chemical Shifts in Hydrogen-Bonded Systems from First-Principles Calculations and Solid-State-NMR. J Phys Chem B 2006; 110:23204-10. [PMID: 17107166 DOI: 10.1021/jp0640732] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We present an analysis of bulk (1)H NMR chemical shifts for a series of biochemically relevant molecular crystals in analogy to the well-known solvent NMR chemical shifts. The term bulk shifts denotes the change in NMR frequency of a gas-phase molecule when it undergoes crystallization. We compute NMR parameters from first-principles electronic structure calculations under full periodic boundary conditions and for isolated molecules and compare them to the corresponding experimental fast magic-angle spinning solid-state NMR spectra. The agreement between computed and experimental lines is generally very good. The main phenomena responsible for bulk shifts are packing effects (hydrogen bonding and pi-stacking) in the condensed phase. By using these NMR bulk shifts in well-ordered crystalline model systems composed of biologically relevant molecules, we can understand the individual spectroscopic signatures of packing effects. These local structural driving forces, hydrogen bonding, pi-stacking, and related phenomena, stand as a model for the forces that govern the assembly of much more complex supramolecular aggregates. We show to which accuracy condensed-phase ab initio calculations can predict structure and structure-property relationships for noncovalent interactions in complex supramolecular systems.
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Affiliation(s)
- J Schmidt
- Max-Planck-Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany
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