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Beckmann PA, Ford J, Malachowski WP, McGhie AR, Moore CE, Rheingold AL, Sloan GJ, Szewczyk ST. Proton Spin-Lattice Relaxation in Organic Molecular Solids: Polymorphism and the Dependence on Sample Preparation. Chemphyschem 2018; 19:2423-2436. [PMID: 29956438 DOI: 10.1002/cphc.201800237] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2018] [Indexed: 11/07/2022]
Abstract
We report solid-state nuclear magnetic resonance 1 H spin-lattice relaxation, single-crystal X-ray diffraction, powder X-ray diffraction, field emission scanning electron microscopy, and differential scanning calorimetry in solid samples of 2-ethylanthracene (EA) and 2-ethylanthraquinone (EAQ) that have been physically purified in different ways from the same commercial starting compounds. The solid-state 1 H spin-lattice relaxation is always non-exponential at high temperatures as expected when CH3 rotation is responsible for the relaxation. The 1 H spin-lattice relaxation experiments are very sensitive to the "several-molecule" (clusters) structure of these van der Waals molecular solids. In the three differently prepared samples of EAQ, the relaxation also becomes very non-exponential at low temperatures. This is very unusual and the decay of the nuclear magnetization can be fitted with both a stretched exponential and a double exponential. This unusual result correlates with the powder X-ray diffractometry results and suggests that the anomalous relaxation is due to crystallites of two (or more) different polymorphs (concomitant polymorphism).
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Affiliation(s)
- Peter A Beckmann
- Department of Physics, Bryn Mawr College, Bryn Mawr, Pennsylvania, USA
| | - Jamie Ford
- Nanoscale Characterization Facility Singh Center for Nanotechnology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | | | - Andrew R McGhie
- Laboratory for Research on the Structure of Matter, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Curtis E Moore
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California, USA
| | - Arnold L Rheingold
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California, USA
| | - Gilbert J Sloan
- Laboratory for Research on the Structure of Matter, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Steven T Szewczyk
- Department of Materials Science and Engineering School of Engineering and Applied Science, University of Pennsylvania, Philadelphia, Pennsylvania, USA
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2
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Beckmann PA, Bohen JM, Ford J, Malachowski WP, Mallory CW, Mallory FB, McGhie AR, Rheingold AL, Sloan GJ, Szewczyk ST, Wang X, Wheeler KA. Monitoring a simple hydrolysis process in an organic solid by observing methyl group rotation. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2017; 85-86:1-11. [PMID: 28260612 DOI: 10.1016/j.ssnmr.2017.01.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Revised: 12/26/2016] [Accepted: 01/24/2017] [Indexed: 06/06/2023]
Abstract
We report a variety of experiments and calculations and their interpretations regarding methyl group (CH3) rotation in samples of pure 3-methylglutaric anhydride (1), pure 3-methylglutaric acid (2), and samples where the anhydride is slowly absorbing water from the air and converting to the acid [C6H8O3(1) + H2O → C6H10O4(2)]. The techniques are solid state 1H nuclear magnetic resonance (NMR) spin-lattice relaxation, single-crystal X-ray diffraction, electronic structure calculations in both isolated molecules and in clusters of molecules that mimic the crystal structure, field emission scanning electron microscopy, differential scanning calorimetry, and high resolution 1H NMR spectroscopy. The solid state 1H spin-lattice relaxation experiments allow us to observe the temperature dependence of the parameters that characterize methyl group rotation in both compounds and in mixtures of the two compounds. In the mixtures, both types of methyl groups (that is, molecules of 1 and 2) can be observed independently and simultaneously at low temperatures because the solid state 1H spin-lattice relaxation is appropriately described by a double exponential. We have followed the conversion 1 → 2 over periods of two years. The solid state 1H spin-lattice relaxation experiments in pure samples of 1 and 2 indicate that there is a distribution of NMR activation energies for methyl group rotation in 1 but not in 2 and we are able to explain this in terms of the particle sizes seen in the field emission scanning electron microscopy images.
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Affiliation(s)
- Peter A Beckmann
- Department of Physics, Bryn Mawr College, 101 North Merion Ave., Bryn Mawr, PA 19010-2899, USA.
| | - Joseph M Bohen
- Department of Chemistry, Bryn Mawr College, 101 North Merion Ave., Bryn Mawr, PA 19010-2899, USA
| | - Jamie Ford
- Nanoscale Characterization Facility, Singh Center for Nanotechnology, University of Pennsylvania, 3205 Walnut St., Philadelphia, PA 19104-3405, USA
| | - William P Malachowski
- Department of Chemistry, Bryn Mawr College, 101 North Merion Ave., Bryn Mawr, PA 19010-2899, USA
| | - Clelia W Mallory
- Department of Chemistry, University of Pennsylvania, 231 South 34 Street, Philadelphia, PA 19104-6323, USA
| | - Frank B Mallory
- Department of Chemistry, Bryn Mawr College, 101 North Merion Ave., Bryn Mawr, PA 19010-2899, USA
| | - Andrew R McGhie
- Laboratory for Research on the Structure of Matter, University of Pennsylvania, 3231 Walnut St., Philadelphia, PA 19104-6202, USA
| | - Arnold L Rheingold
- Department of Chemistry and Biochemistry, University of California, San Diego, 5128 Urey Hall, 9500 Gilman Dr., La Jolla, CA 92093-0358, USA
| | - Gilbert J Sloan
- Laboratory for Research on the Structure of Matter, University of Pennsylvania, 3231 Walnut St., Philadelphia, PA 19104-6202, USA
| | - Steven T Szewczyk
- Department of Materials Science and Engineering, School of Engineering and Applied Science, University of Pennsylvania, 3231 Walnut St., Philadelphia, PA 19104-6202, USA
| | - Xianlong Wang
- Key Laboratory for NeuroInformation of Ministry of Education, School of Life Science and Technology, University of Electronic Science and Technology of China, 4 North Jianshe Rd., 22nd Section, Chengdu 610054, China
| | - Kraig A Wheeler
- Department of Chemistry, Eastern Illinois University, 600 Lincoln Ave., Charleston, IL 69120-3099, USA
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Beckmann PA, McGhie AR, Rheingold AL, Sloan GJ, Szewczyk ST. Solid-Solid Phase Transitions and tert-Butyl and Methyl Group Rotation in an Organic Solid: X-ray Diffractometry, Differential Scanning Calorimetry, and Solid-State 1H Nuclear Spin Relaxation. J Phys Chem A 2017; 121:6220-6230. [PMID: 28742961 DOI: 10.1021/acs.jpca.7b06265] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Using solid-state 1H nuclear magnetic resonance (NMR) spin-lattice relaxation experiments, we have investigated the effects of several solid-solid phase transitions on tert-butyl and methyl group rotation in solid 1,3,5-tri-tert-butylbenzene. The goal is to relate the dynamics of the tert-butyl groups and their constituent methyl groups to properties of the solid determined using single-crystal X-ray diffraction and differential scanning calorimetry (DSC). On cooling, the DSC experiments see a first-order, solid-solid phase transition at either 268 or 155 K (but not both) depending on thermal history. The 155 K transition (on cooling) is identified by single-crystal X-ray diffraction to be one from a monoclinic phase (above 155 K), where the tert-butyl groups are disordered (that is, with a rotational 6-fold intermolecular potential dominating), to a triclinic phase (below 155 K), where the tert-butyl groups are ordered (that is, with a rotational 3-fold intermolecular potential dominating). This transition shows very different DSC scans when both a 4.7 mg polycrystalline sample and a 19 mg powder sample are used. The 1H spin-lattice relaxation experiments with a much larger 0.7 g sample are very complicated and, depending on thermal history, can show hysteresis effects over many hours and over very large temperature ranges. In the high-temperature monoclinic phase, the tert-butyl groups rotate with NMR activation energies (closely related to rotational barriers) in the 17-23 kJ mol-1 range, and the constituent methyl groups rotate with NMR activation energies in the 7-12 kJ mol-1 range. In the low-temperature triclinic phase, the rotations of the tert-butyl groups and their methyl groups in the aromatic plane are quenched (on the NMR time scale). The two out-of-plane methyl groups in the tert-butyl groups are rotating with activation energies in the 5-11 kJ mol-1 range.
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Affiliation(s)
- Peter A Beckmann
- Department of Physics, Bryn Mawr College , 101 North Merion Avenue, Bryn Mawr, Pennsylvania 19010-2899, United States
| | | | - Arnold L Rheingold
- Department of Chemistry and Biochemistry, University of California, San Diago , 5128 Urey Hall, 9500 Gilman Drive, La Jolla, California 92093-0358, United States
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Beckmann PA, Rheingold AL. 1H and 19F spin-lattice relaxation and CH3 or CF3 reorientation in molecular solids containing both H and F atoms. J Chem Phys 2016; 144:154308. [DOI: 10.1063/1.4944981] [Citation(s) in RCA: 6] [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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5
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Beckmann PA, Moore CE, Rheingold AL. Methyl and t-butyl group rotation in a molecular solid: 1H NMR spin-lattice relaxation and X-ray diffraction. Phys Chem Chem Phys 2016; 18:1720-6. [DOI: 10.1039/c5cp04994f] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We report solid state 1H nuclear magnetic resonance spin-lattice relaxation experiments and X-ray diffractometry in 2-t-butyldimethylsilyloxy-6-bromonaphthalene.
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Affiliation(s)
| | - Curtis E. Moore
- Department of Chemistry and Biochemistry
- University of California
- La Jolla
- USA
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6
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Beckmann PA. Nonexponential (1)H spin-lattice relaxation and methyl group rotation in molecular solids. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2015; 71:91-95. [PMID: 26256302 DOI: 10.1016/j.ssnmr.2015.07.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Accepted: 07/14/2015] [Indexed: 06/04/2023]
Abstract
We report a quantitative measure of the nonexponential (1)H spin-lattice relaxation resulting from methyl group (CH3) rotation in six polycrystalline van der Waals solids. We briefly review the subject in general to put the report in context. We then summarize several significant issues to consider when reporting (1)H or (19)F spin-lattice relaxation measurements when the relaxation is resulting from the rotation of a CH3 or CF3 group in a molecular solid.
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Affiliation(s)
- Peter A Beckmann
- Department of Physics, Bryn Mawr College, Bryn Mawr, PA 19010, USA.
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7
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Beckmann PA, Mallory CW, Mallory FB, Rheingold AL, Wang X. Methoxy and Methyl Group Rotation: Solid-State NMR1H Spin-Lattice Relaxation, Electronic Structure Calculations, X-ray Diffractometry, and Scanning Electron Microscopy. Chemphyschem 2015; 16:1509-19. [DOI: 10.1002/cphc.201402716] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2014] [Revised: 02/17/2015] [Indexed: 11/05/2022]
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Wang X, Mallory FB, Mallory CW, Odhner HR, Beckmann PA. Solid state ¹H spin-lattice relaxation and isolated-molecule and cluster electronic structure calculations in organic molecular solids: the relationship between structure and methyl group and t-butyl group rotation. J Chem Phys 2014; 140:194304. [PMID: 24852535 DOI: 10.1063/1.4874157] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We report ab initio density functional theory electronic structure calculations of rotational barriers for t-butyl groups and their constituent methyl groups both in the isolated molecules and in central molecules in clusters built from the X-ray structure in four t-butyl aromatic compounds. The X-ray structures have been reported previously. We also report and interpret the temperature dependence of the solid state (1)H nuclear magnetic resonance spin-lattice relaxation rate at 8.50, 22.5, and 53.0 MHz in one of the four compounds. Such experiments for the other three have been reported previously. We compare the computed barriers for methyl group and t-butyl group rotation in a central target molecule in the cluster with the activation energies determined from fitting the (1)H NMR spin-lattice relaxation data. We formulate a dynamical model for the superposition of t-butyl group rotation and the rotation of the t-butyl group's constituent methyl groups. The four compounds are 2,7-di-t-butylpyrene, 1,4-di-t-butylbenzene, 2,6-di-t-butylnaphthalene, and 3-t-butylchrysene. We comment on the unusual ground state orientation of the t-butyl groups in the crystal of the pyrene and we comment on the unusually high rotational barrier of these t-butyl groups.
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Affiliation(s)
- Xianlong Wang
- Key Laboratory for NeuroInformation of Ministry of Education, School of Life Science and Technology, University of Electronic Science and Technology of China, 4 North Jianshe Rd., 2nd Section, Chengdu 610054, China
| | - Frank B Mallory
- Department of Chemistry, Bryn Mawr College, 101 North Merion Ave., Bryn Mawr, Pennsylvania 19010-2899, USA
| | - Clelia W Mallory
- Department of Chemistry, Bryn Mawr College, 101 North Merion Ave., Bryn Mawr, Pennsylvania 19010-2899, USA
| | - Hosanna R Odhner
- Department of Physics, Bryn Mawr College, 101 North Merion Ave., Bryn Mawr, Pennsylvania 19010-2899, USA
| | - Peter A Beckmann
- Department of Physics, Bryn Mawr College, 101 North Merion Ave., Bryn Mawr, Pennsylvania 19010-2899, USA
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Vugmeyster L, Ostrovsky D. Restricted diffusion of methyl groups in proteins revealed by deuteron NMR: manifestation of intra-well dynamics. J Chem Phys 2014; 140:075101. [PMID: 24559369 DOI: 10.1063/1.4865412] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The three-site hops of methyl groups are usually used as an approximation of the mechanistic description of motions responsible for the longitudinal NMR relaxation. Distinguishing between three-site hops and a more realistic mechanism of diffusion in a potential requires extended experimental and computational analysis. In order to achieve this goal, in this work the restricted diffusion is decomposed into two independent modes, namely, the jumps between potential wells and intra-well fluctuations, assuming time scale separation between these modes. This approach allows us to explain the rise in the theoretical value of T1 minimum for the restricted diffusion mechanism compared with the three-site hops mechanism via rescaling the three-site hops correlation function by the order parameter of intra-well motions. The main result of the paper is that, in general, intra-well dynamics can be visible in NMR even in the limit of large barrier heights in contrast to the common view that this limit converges to the three-site hops mechanism. Based on a previously collected detailed set of deuteron NMR relaxation and spectral data in the villin headpiece subdomain protein over a wide temperature range of 300-31 K, we are then able to conclude that the mechanism of diffusion in the threefold potential is likely to be the main source of the dynamics in this system.
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Affiliation(s)
- Liliya Vugmeyster
- Department of Chemistry, University of Alaska Anchorage, Anchorage, Alaska 99508, USA
| | - Dmitry Ostrovsky
- Department of Mathematics, University of Alaska Anchorage, Anchorage, Alaska 99508, USA
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Beckmann PA, Conn KG, Mallory CW, Mallory FB, Rheingold AL, Rotkina L, Wang X. Distributions of methyl group rotational barriers in polycrystalline organic solids. J Chem Phys 2013; 139:204501. [DOI: 10.1063/1.4830411] [Citation(s) in RCA: 11] [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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11
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Fahey DP, Dougherty WG, Kassel WS, Wang X, Beckmann PA. Nonexponential Solid State 1H and 19F Spin–Lattice Relaxation, Single-crystal X-ray Diffraction, and Isolated-Molecule and Cluster Electronic Structure Calculations in an Organic Solid: Coupled Methyl Group Rotation and Methoxy Group Libration in 4,4′-Dimethoxyoctafluorobiphenyl. J Phys Chem A 2012; 116:11946-56. [DOI: 10.1021/jp3075892] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Donald P. Fahey
- Department of Physics, Bryn Mawr College, 101 North Merion Avenue, Bryn Mawr,
Pennsylvania 19010-2899, United States
| | - William G. Dougherty
- Department of Chemistry, Villanova University, 800 Lancaster Avenue, Villanova,
Pennsylvania 19085-1597, United States
| | - W. Scott Kassel
- Department of Chemistry, Villanova University, 800 Lancaster Avenue, Villanova,
Pennsylvania 19085-1597, United States
| | - Xianlong Wang
- School of Life Science and Technology, University of Electronic Science and Technology of China, 4 North Jianshe Road, Second Section, Chengdu, China 610054
| | - Peter A. Beckmann
- Department of Physics, Bryn Mawr College, 101 North Merion Avenue, Bryn Mawr,
Pennsylvania 19010-2899, United States
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12
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Beckmann PA, Schneider E. Methyl group rotation,1H spin-lattice relaxation in an organic solid, and the analysis of nonexponential relaxation. J Chem Phys 2012; 136:054508. [DOI: 10.1063/1.3677183] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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13
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Popa LC, Rheingold AL, Beckmann PA. A proton spin-lattice relaxation rate study of methyl and t-butyl group reorientation in the solid state. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2010; 38:31-35. [PMID: 20605083 DOI: 10.1016/j.ssnmr.2010.06.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2010] [Revised: 06/08/2010] [Accepted: 06/10/2010] [Indexed: 05/29/2023]
Abstract
We have measured the solid state nuclear magnetic resonance (NMR) 1H spin-lattice relaxation rate from 93 to 340 K at NMR frequencies of 8.5 and 53 MHz in 5-t-butyl-4-hydroxy-2-methylphenyl sulfide. We have also determined the molecular and crystal structures from X-ray diffraction experiments. The relaxation is caused by methyl and t-butyl group rotation modulating the spin-spin interactions and we relate the NMR dynamical parameters to the structure. A successful fit of the data requires that the 2-methyl groups are rotating fast (on the NMR time scale) even at the lowest temperatures employed. The rotational barrier for the two out-of-plane methyl groups in the t-butyl groups is 14.3+/-2.7 kJ mol(-1) and the rotational barrier for the t-butyl groups and their in-plane methyl groups is 24.0+/-4.6 kJ mol(-1). The uncertainties account for the uncertainties associated with the relationship between the observed NMR activation energy and a model-independent barrier, as well as the experimental uncertainties.
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Affiliation(s)
- Laura C Popa
- Department of Physics, Bryn Mawr College, 101 North Merion Ave., Bryn Mawr, PA 19010-2899, USA
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Beckmann PA, Dougherty WG, Scott Kassel W. Methyl and t-butyl reorientation in an organic molecular solid. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2009; 36:86-91. [PMID: 19595581 DOI: 10.1016/j.ssnmr.2009.06.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2009] [Revised: 06/04/2009] [Accepted: 06/05/2009] [Indexed: 05/28/2023]
Abstract
We have determined the molecular and crystal structure of 4,5-dibromo-2,7-di-t-butyl-9,9-dimethylxanthene and measured the (1)H spin-lattice relaxation rate from 87 to 270K at NMR frequencies of omega/2pi=8.50, 22.5, and 53.0MHz. All molecules in the crystal see the same intra and intermolecular environment and the repeating unit is half a molecule. We have extended models developed for (1)H spin-lattice relaxation resulting from the reorientation of a t-butyl group and its constituent methyl groups to include these rotors and the 9-methyl groups. The relaxation rate data is well-fitted assuming that the t-butyl groups and all three of their constituent methyl groups, as well as the 9-methyl groups all reorient with an NMR activation energy of 15.8+/-1.6kJmol(-1) corresponding to a barrier of 17.4+/-3.2kJmol(-1). Only intramethyl and intra-t-butyl intermethyl spin-spin interactions need be considered. A unique random-motion Debye (or BPP) spectral density will not fit the data for any reasonable choice of parameters. A distribution of activation energies is required.
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Affiliation(s)
- Peter A Beckmann
- Department of Physics, Bryn Mawr College, 101 North Merion Ave., Bryn Mawr, PA 19010-2899, USA.
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15
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Beckmann P, Hathorn R, Mallory F. Proton Zeeman relaxation and intramolecular reorientation in solidt-butylbenzene. Mol Phys 2006. [DOI: 10.1080/00268979000100311] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Affiliation(s)
- P.A. Beckmann
- a Department of Physics , Bryn Mawr College , Bryn Mawr , Pennsylvania , 19010 , U.S.A
| | - R.M. Hathorn
- a Department of Physics , Bryn Mawr College , Bryn Mawr , Pennsylvania , 19010 , U.S.A
- b Department of Chemistry , Bryn Mawr College , Bryn Mawr , Pennsylvania , 19010 , U.S.A
- c Department of Chemistry , Northwestern University , Evanstown , Illinois , 60208 , U.S.A
| | - F.B. Mallory
- b Department of Chemistry , Bryn Mawr College , Bryn Mawr , Pennsylvania , 19010 , U.S.A
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16
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Colmenero J, Moreno AJ, Alegría A. Neutron scattering investigations on methyl group dynamics in polymers. Prog Polym Sci 2005. [DOI: 10.1016/j.progpolymsci.2005.08.001] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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17
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Harbridge JR, Eaton SS, Eaton GR. Electron Spin-Lattice Relaxation Processes of Radicals in Irradiated Crystalline Organic Compounds. J Phys Chem A 2003. [DOI: 10.1021/jp021504h] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- James R. Harbridge
- Department of Chemistry and Biochemistry, University of Denver, Denver, Colorado 80208-2436
| | - Sandra S. Eaton
- Department of Chemistry and Biochemistry, University of Denver, Denver, Colorado 80208-2436
| | - Gareth R. Eaton
- Department of Chemistry and Biochemistry, University of Denver, Denver, Colorado 80208-2436
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18
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Clough S, Heidemann A, Paley M. The temperature dependence of methyl tunnelling motion in three acetates. ACTA ACUST UNITED AC 2000. [DOI: 10.1088/0022-3719/14/7/006] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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19
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Beckmann PA, Burbank KS, Clemo KM, Slonaker EN, Averill K, Dybowski C, Figueroa JS, Glatfelter A, Koch S, Liable-Sands LM, Rheingold AL. 1H nuclear magnetic resonance spin-lattice relaxation, 13C magic-angle-spinning nuclear magnetic resonance spectroscopy, differential scanning calorimetry, and x-ray diffraction of two polymorphs of 2,6-di-tert-butylnaphthalene. J Chem Phys 2000. [DOI: 10.1063/1.482000] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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20
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Clough S. Unification of the quantum and classical theories of methyl NMR. SOLID STATE NUCLEAR MAGNETIC RESONANCE 1999; 14:73-79. [PMID: 10437660 DOI: 10.1016/s0926-2040(99)00016-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The existing low and high temperature theories of methyl NMR are not linked because two conditions imposed on state functions in the low temperature theory are not compatible with the classical rotations on which the high temperature theory is based. The conditions do not occur in a geometrical theory of quantum phenomena in which particles and waves have separate roles. When applied to methyl dynamics, this theory covers the whole temperature range.
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Affiliation(s)
- S Clough
- Department of Physics, School of Physics and Astronomy, University of Nottingham, UK
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21
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Moore EA, Mortimer M, Wigglesworth C, Williams MA. The energy barrier to reorientational motion of the trifluoromethyl group in lithium trifluoromethanesulphonate and its complex with poly(ethylene oxide): a comparison between modelling and NMR relaxation measurements. Chem Phys Lett 1999. [DOI: 10.1016/s0009-2614(99)00626-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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22
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Beckmann PA, Buser CA, Mallory CW, Mallory FB, Mosher J. Methyl reorientation in solid 3-ethylchrysene and 3-isopropylchrysene. SOLID STATE NUCLEAR MAGNETIC RESONANCE 1998; 12:251-256. [PMID: 9800270 DOI: 10.1016/s0926-2040(98)00049-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
We have measured the proton spin-lattice relaxation rate as a function of temperature in polycrystalline 3-ethylchrysene at nuclear magnetic resonance Larmor frequencies of 53.0 and 22.5 MHz and in polycrystalline 3-isopropylchrysene at 53.0, 22.5 and 8.50 MHz. The syntheses of these new compounds are presented. The relatively large chrysene backbone creates an ideal and unique environment for the alkyl groups such that methyl group rotation is the only motion on the nuclear magnetic resonance Larmor frequency timescale over a large temperature range. The relaxation rate data are interpreted in terms of the simplest possible dynamical model: that of random hopping for the methyl group(s), all of which are equivalent in the solid state. The barriers of 11-12 kJ mol-1 are typical for methyl groups in 'isolated' ethyl and isopropyl groups.
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Affiliation(s)
- P A Beckmann
- Department of Physics, Bryn Mawr College, PA 19010-2899, USA.
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van der Putten D, Diezemann G, Fujara F, Hartmann K, Sillescu H. Methyl group dynamics in α‐crystallized toluene as studied by deuteron spin–lattice relaxation. J Chem Phys 1992. [DOI: 10.1063/1.462130] [Citation(s) in RCA: 32] [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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Fry AM, Beckmann PA, Fry AJ, Fox PC, Isenstadt A. Solid state proton spin relaxation andt‐butyl and methyl group reorientation in 1‐bromo‐2,4,6‐tri‐t‐butylbenzene. J Chem Phys 1991. [DOI: 10.1063/1.461720] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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25
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Beckmann PA, Happersett L, Herzog AV, Tong WM. Solid state proton spin relaxation in ethylbenzenes: Methyl reorientation barriers and molecular structure. J Chem Phys 1991. [DOI: 10.1063/1.461090] [Citation(s) in RCA: 24] [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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26
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Beckmann PA. Thermally activated methyl and t-butyl group reorientation in solids. PHYSICAL REVIEW. B, CONDENSED MATTER 1989; 39:12248-12249. [PMID: 9948058 DOI: 10.1103/physrevb.39.12248] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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27
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Methyl rotation in acetamide: the transition from quantum mechanical tunneling to classical reorientation studied by inelastic neutron scattering. ACTA ACUST UNITED AC 1989. [DOI: 10.1007/bf01323489] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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28
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Conn KG, Beckmann PA, Mallory CW, Mallory FB. Methyl reorientation in methylphenanthrenes. I. Solid state proton spin–lattice relaxation in the 3‐methyl, 9‐methyl, and 3,9‐dimethyl systems. J Chem Phys 1987. [DOI: 10.1063/1.453617] [Citation(s) in RCA: 37] [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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29
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Beckmann PA, Cheung AM, Fisch EE, Fusco FA, Herzog RE, Narasimhan M. Methyl andtert‐butyl reorientation and distributions of activation energies in molecular solids. A nuclear spin‐relaxation study in 2,4‐ and 2,5‐di‐tert‐butylhydroxybenzene. J Chem Phys 1986. [DOI: 10.1063/1.450403] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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30
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Beckmann PA, Fusco FA, O'Neill AE. Proton spin-lattice relaxation and intramolecular reorientation in solids. ACTA ACUST UNITED AC 1984. [DOI: 10.1016/0022-2364(84)90283-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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