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Bernatowicz P, Szymanski S. Molecular Zeeman interactions in NMR spectra of methyl groups. J Chem Phys 2022; 157:074312. [DOI: 10.1063/5.0107637] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Methyl groups in organic solids generally behave as uniaxial quantum rotors. The existing NMR theory appears to be complete, capable of describing even the finest details of the temperature-dependent spectra of such objects. However, the once re-ported temperature effects in the carbon spectra of the 13C-labeled methyl group in a single crystal of acetylsalicylic acid have still not been explained. As the temperature decreases, in the quartet corresponding to the rapid motional averaging regime, the inner lines first begin to broaden but then narrow again, so that at 6 K a pattern similar to that at room temperature was observed. In the present work, these puzzling effects are explained quantitatively by invoking the molecular Zeeman (MZ) interaction. Like the spin-rotation (SR) interaction long known to occur in methyl groups, it engages the magnetic moments generated by their torsional motions. How-ever, it has not been considered in NMR spectroscopy until now. This is a surprising situation because in the magnetic fields currently used in NMR spectroscopy, the MZ interaction is orders of magnitude stronger than the (magnetic field independent) SR effects.
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Press W, Nöldeke C. Rotational Tunneling in Molecular Crystals Revisited: Realization of Pocket States. Chem Phys 2022. [DOI: 10.1016/j.chemphys.2022.111625] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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3
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Tsapatsaris N, Kolesov BA, Fischer J, Boldyreva EV, Daemen L, Eckert J, Bordallo HN. Polymorphism of Paracetamol: A New Understanding of Molecular Flexibility through Local Methyl Dynamics. Mol Pharm 2014; 11:1032-41. [DOI: 10.1021/mp400707m] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
| | - Boris A. Kolesov
- Institute of Inorganic Chemistry SB RAS, Novosibirsk 630090, Russia
- REC-008 Novosibirsk State University, ul. Pirogova 2, Novosibirsk 630090, Russia
| | | | - Elena V. Boldyreva
- REC-008 Novosibirsk State University, ul. Pirogova 2, Novosibirsk 630090, Russia
- Institute of Solid-State Chemistry and Mechanochemistry SB RAS, Kutateladze 18, Novosibirsk 630128, Russia
| | - Luke Daemen
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Juergen Eckert
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
- Department
of Chemistry, University of South Florida, Tampa, Florida 33620, United States
| | - Heloisa N. Bordallo
- European Spallation Source ESS AB, P.O. Box 176, Lund 221 00, Sweden
- Niels Bohr Institute, Universitetsparken
5, Copenhagen 2100, Denmark
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Szymański S. Spin-lattice relaxation of the methyl group protons in solids revisited: damped quantum rotation approach. J Chem Phys 2012; 137:034513. [PMID: 22830717 DOI: 10.1063/1.4734251] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Proton spin-lattice relaxation of the methyl group in solids had been one of the most thoroughly addressed theoretical problems in nuclear magnetic resonance (NMR) spectroscopy, considered at different levels of sophistication. For systems with substantial quantum tunneling effects, several quantum mechanical treatments were reported, although in practical applications the quantum models were always augmented with or replaced by the classical jump model. However, the latter has recently proved invalid in the description of NMR line shape effects in variable-temperature spectra of hindered methyl groups, while the competing theory of damped quantum rotation (DQR) was shown to be adequate. In this work, the spin-lattice relaxation issue for the methyl protons is readdressed using the latter theory. The main outcome is that, while the existing formulas for the relaxation rates remain unchanged, the crucial parameter entering them, the correlation time of the relevant random process, need to be reinterpreted. It proves to be the inverse of one of the two quantum-rate constants entering the DQR model, neither of which, when taken separately, can be related to the jump process. It can be identified with one describing the life-time broadening of the tunnel peaks in inelastic neutron scattering (INS) spectra of the methyl groups. Such a relationship between the relaxation and INS effects was reported from another laboratory long ago, but only for the low-temperature limit where thermal population of the excited torsional levels of the methyl group can be neglected. The whole spectrum of cases encountered in practical relaxation studies on protonated methyl groups is addressed for the first time. Preliminary experimental confirmation of this novel approach is reported, based on already published NMR data for a single crystal of methylmalonic acid. The once extensively debated issues of quenching of the coherent tunneling and of the classical limit in the dynamics of the methyl groups are readdressed and presented in a consistent manner.
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Affiliation(s)
- S Szymański
- Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warszawa, Poland.
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5
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Ng MCC, Harper JB, Stampfl APJ, Kearley GJ, Rols S, Stride JA. Central-Atom Size Effects on the Methyl Torsions of Group XIV Tetratolyls. Chemistry 2012; 18:13018-24. [DOI: 10.1002/chem.201202105] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2012] [Indexed: 11/06/2022]
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Zhang Y, Tyagi M, Mamontov E, Chen SH. Quasi-elastic neutron scattering studies of the slow dynamics of supercooled and glassy aspirin. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2012; 24:064112. [PMID: 22277723 DOI: 10.1088/0953-8984/24/6/064112] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Aspirin, also known as acetylsalicylic acid (ASA), is not only a wonderful drug, but also a good glass former. Therefore, it serves as an important molecular system to study the near-arrest and arrested phenomena. In this paper, a high-resolution quasi-elastic neutron scattering (QENS) technique is used to investigate the slow dynamics of supercooled liquid and glassy aspirin from 410 down to 350 K. The measured QENS spectra can be analyzed with a stretched exponential model. We find that (i) the stretched exponent β(Q) is independent of the wavevector transfer Q in the measured Q range and (ii) the structural relaxation time τ(Q) follows a power-law dependence on Q. Consequently, the Q-independent structural relaxation time τ(0) can be extracted for each temperature to characterize the slow dynamics of aspirin. The temperature dependence of τ(0) can be fitted with the mode-coupling power law, the Vogel-Fulcher-Tammann equation and a universal equation for fragile glass forming liquids recently proposed by Tokuyama in the measured temperature range. The calculated dynamic response function χ(T)(Q, t) using the experimentally determined self-intermediate scattering function of the hydrogen atoms of aspirin shows direct evidence of the enhanced dynamic fluctuations as the aspirin is increasingly supercooled, in agreement with the fixed-time mean squared displacement ⟨x(2)⟩ and the non-Gaussian parameter α(2) extracted from the elastic scattering.
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Affiliation(s)
- Yang Zhang
- Neutron Scattering Science Division and Joint Institute for Neutron Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
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Schröder F, Winkler B, Bauer J, Haussühl E, Rivera Escoto B, Tristan López F, Avalos Borja M, Richter C, Ferner J. Origin of the low temperature excess heat capacity of isotopically substituted acetylsalicylic acid. Chem Phys Lett 2011. [DOI: 10.1016/j.cplett.2011.08.031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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8
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Nath R, El Goresy T, Geil B, Zimmermann H, Böhmer R. Relaxation in the glass former acetylsalicylic acid studied by deuteron magnetic resonance and dielectric spectroscopy. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2006; 74:021506. [PMID: 17025436 DOI: 10.1103/physreve.74.021506] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2006] [Indexed: 05/12/2023]
Abstract
Supercooled liquid and glassy acetylsalicylic acid was studied using dielectric spectroscopy and deuteron relaxometry in a wide temperature range. The supercooled liquid is characterized by major deviations from thermally activated behavior. In the glass the secondary relaxation exhibits the typical features of a Johari-Goldstein process. Via measurements of spin-lattice relaxation times the selectively deuterated methyl group was used as a sensitive probe of its local environments. There is a large difference in the mean activation energy in the glass with respect to that in crystalline acetylsalicylic acid. This can be understood by taking into account the broad energy barrier distribution in the glass.
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Affiliation(s)
- R Nath
- Experimentelle Physik III and Interdisziplinäres Zentrum für Magnetische Resonanz, Universität Dortmund, 44221 Dortmund, Germany
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Ylinen EE, Kankaanpää M, Punkkinen M. Spectral spin diffusion and magnetic dipolar energy in the NMR of 13CH3 compounds. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2006; 29:330-44. [PMID: 16361090 DOI: 10.1016/j.ssnmr.2005.11.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2005] [Revised: 11/03/2005] [Indexed: 05/05/2023]
Abstract
Spin diffusion between 13CH3 groups in solids is studied both theoretically and experimentally. It is shown to be dominated by mutual spin flip-flops of protons belonging to neighbouring methyl groups. Also nonmethyl protons may contribute significantly if present in the sample. The spin-rotational ground state of 13CH3 consists of 16 sublevels. When their populations are used to describe spin diffusion, eight population combinations are shown to be important, two of them corresponding to the 13C-proton and proton-proton intra-methyl magnetic dipolar energies, Dc and Dp, respectively. Spin-diffusion transitions modulate these combinations so that a further reduction to two sets of four combinations is possible, with no coupling between the sets. Coupled differential equations are derived to describe the time dependence of the combinations in each set. They are solved numerically and compared with experimental results on a single crystal of aspirin with 13C-labelled methyl groups at the carbon resonance. The 13C NMR induction signal was observed as a function of time after the preparation either at the carbon resonance (a two-pulse sequence) or at the proton resonance (proton saturation). Usually carbon spectra were computed first and then three of the mentioned population combinations were obtained from the individual spectral components. Some results on the time dependence of Dc were also obtained directly from the amplitude of the out-of-phase induction signal. Theoretical predictions are found to describe semiquantitatively the overall time dependence of these three combinations and especially their variation with different initial conditions, which are discussed in detail. Also the partial transfer of the magnetic dipolar energy between Dc and Dp is nicely explained. Reasons for discrepancies are discussed.
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Affiliation(s)
- E E Ylinen
- Wihuri Physical Laboratory, Department of Physics, University of Turku, FI-20014 Turku, Finland.
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Birczyński A, Lalowicz Z, Łodziana Z. Rotational barriers in ammonium hexachlorometallates as studied by NMR, tunnelling spectroscopy and ab initio calculations. Chem Phys 2004. [DOI: 10.1016/j.chemphys.2003.12.014] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Kankaanpää M, Ylinen EE, Punkkinen M. Spin-lattice relaxation of 13CH3 groups in 13C-enriched aspirin after proton saturation. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2003; 23:224-242. [PMID: 12787905 DOI: 10.1016/s0926-2040(03)00014-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
We studied the spin-lattice relaxation of the 13C magnetisation, M(C), in 13C-enriched single crystal of aspirin (only methyl carbons enriched to 99%) at the carbon resonance frequency of 54.5 MHz. After the carbon saturation the recovery appears exponential except below 30K, where it is biexponential due to the presence of the level crossing omega(t)=omega(C)+omega(H) (the symbols refer, respectively, to the tunnel frequency and the carbon and proton resonance frequencies in angular units). After the saturation of the proton magnetisation, M(H), the description of the M(C) recovery needs three exponentials. The evaluation of the time constants is easiest from the data in this case, since M(C) varies with time in an initial growth-subsequent decrease (or an initial decrease-subsequent growth depending on temperature) manner, instead of the monotonous growth after the carbon saturation. Experimental data agree semiquantitatively with the predictions of our recent model. According to the model the relaxation of M(C) is coupled to M(H) and the tunnel energy TE at temperatures below the minimum of the 13C relaxation time. Sufficiently above this minimum M(C) is coupled to M(H) and the rotational polarization (but not to TE) in agreement with experiment. Also the effect of torsional oscillations of a methyl group on the magnitude of various 13C-related transition rates was considered in detail. In aspirin the rates are reduced roughly by 10% and the reduction should become larger in samples with a larger tunnel splitting. The reduction also changes somewhat the angular dependence of these rates.
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Affiliation(s)
- M Kankaanpää
- Wihuri Physical Laboratory, Department of Physics, Turku University, Turku Yliopisto, FIN-20014, Finland.
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KANKAANPÄÄ M, PUNKKINEN M, YLINEN EE. Spin-lattice relaxation in13CH3compounds: application to13C enriched aspirin. Mol Phys 2002. [DOI: 10.1080/00268970210123955] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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13
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Szymański S, Olejniczak Z, Detken A, Haeberlen U. Iterative lineshape analysis of quadrupolar echo spectra of a damped CD(3) quantum rotor: preliminary evidence of a novel mechanism of stochastic spin exchange. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2001; 148:277-288. [PMID: 11237633 DOI: 10.1006/jmre.2000.2252] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
It is demonstrated that the wealth of information about damped quantum rotation of CD(3) groups, contained in quadrupolar echo spectra, can be fully explored in a broad temperature range using a method of iterative analysis of the spectral lineshapes. The recently reported lineshape equation which, apart from the quantum tunneling and the dissipative Alexander--Binsch terms, contains an additional dissipative term having no classical analog is shown to be capable of describing even subtle details of the spectra of a crystal of acetylsalicylic acid--CD(3) oriented specifically in the magnetic field. Preliminary evidence of the occurrence of this novel dissipative mechanism in the system studied is reported. The results obtained seem to suggest that there is no "classical limit" in the dissipative behavior of this system.
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Affiliation(s)
- S Szymański
- Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland.
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Johnson MR, Kearley GJ. Quantitative atom-atom potentials from rotational tunneling: their extraction and their use. Annu Rev Phys Chem 2000; 51:297-321. [PMID: 11031284 DOI: 10.1146/annurev.physchem.51.1.297] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Rotational tunneling of small molecular groups has been the subject of considerable theoretical and experimental activity for several decades. Much of this activity has been driven by the promise of exploiting the extreme sensitivity of quantum tunneling to interatomic potentials, but until recently, there was no straightforward means by which quantitative information about these potentials could be extracted. This review explains how a quantitative method, suitable for general application, was developed. It then goes on to show how this has been used to understand tunneling systems for which no previous satisfactory explanation had been found. The application of the methodology, and its results, to other disciplines is discussed.
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Affiliation(s)
- M R Johnson
- Institut Laue Langevin, BP 156, 38042 Grenoble, Cedex 09, France.
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Neumann MA, Johnson MR, Radaelli PG, Trommsdorff HP, Parker SF. Rotational dynamics of methyl groups in durene: A crystallographic, spectroscopic, and molecular mechanics investigation. J Chem Phys 1999. [DOI: 10.1063/1.478137] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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17
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Detken A, Zimmermann H. Reorientational tunneling of partially deuterated methyl groups: A single-crystal deuteron NMR study of aspirin-CH2D. J Chem Phys 1998. [DOI: 10.1063/1.475995] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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18
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Neumann M, Johnson M, Aibout A, Horsewill A. Measured and calculated rotational tunnelling dynamics in methyl acetate. Chem Phys 1998. [DOI: 10.1016/s0301-0104(98)00039-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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19
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Schiebel P, Kearley GJ, Johnson MR. Translational/rotational coupling of the hindered CH3 quantum-rotor in lithium acetate dihydrate. J Chem Phys 1998. [DOI: 10.1063/1.475622] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Prager M, Heidemann A. Rotational Tunneling and Neutron Spectroscopy: A Compilation. Chem Rev 1997; 97:2933-2966. [PMID: 11851482 DOI: 10.1021/cr9500848] [Citation(s) in RCA: 209] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- M. Prager
- Institut Laue-Langevin, B.P. 156, F-38042 Grenoble, France
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Neumann M, Johnson MR. Methyl group tunneling—A quantitative probe of atom–atom potentials. J Chem Phys 1997. [DOI: 10.1063/1.474527] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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22
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The origin and temperature dependence of the single particle, methyl-group rotational potential in acetic acid. Chem Phys 1997. [DOI: 10.1016/s0301-0104(96)00367-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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