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Kouřil K, Wickens C, Meier B, Alom S, Gräsvik J, Whitby RJ, Levitt MH. NMR of molecular endofullerenes dissolved in a nematic liquid crystal. Phys Chem Chem Phys 2017; 19:11793-11801. [DOI: 10.1039/c7cp00906b] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
We report the NMR of the molecular endofullerenes H2@C60, H2O@C60 and HF@C60 dissolved in the nematic liquid crystal N-(4-methoxybenzylidene)-4-butylaniline (MBBA).
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Affiliation(s)
- Karel Kouřil
- School of Chemistry
- University of Southampton
- SO17 1BJ Southampton
- UK
| | | | - Benno Meier
- School of Chemistry
- University of Southampton
- SO17 1BJ Southampton
- UK
| | - Shamim Alom
- School of Chemistry
- University of Southampton
- SO17 1BJ Southampton
- UK
| | - John Gräsvik
- School of Chemistry
- University of Southampton
- SO17 1BJ Southampton
- UK
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ConcistrÈ M, Johannessen OG, Carignani E, Geppi M, Levitt MH. Magic-angle spinning NMR of cold samples. Acc Chem Res 2013; 46:1914-22. [PMID: 23488538 DOI: 10.1021/ar300323c] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Magic-angle-spinning solid-state NMR provides site-resolved structural and chemical information about molecules that complements many other physical techniques. Recent technical advances have made it possible to perform magic-angle-spinning NMR experiments at low temperatures, allowing researchers to trap reaction intermediates and to perform site-resolved studies of low-temperature physical phenomena such as quantum rotations, quantum tunneling, ortho-para conversion between spin isomers, and superconductivity. In examining biological molecules, the improved sensitivity provided by cryogenic NMR facilitates the study of protein assembly or membrane proteins. The combination of low-temperatures with dynamic nuclear polarization has the potential to boost sensitivity even further. Many research groups, including ours, have addressed the technical challenges and developed hardware for magic-angle-spinning of samples cooled down to a few tens of degrees Kelvin. In this Account, we briefly describe these hardware developments and review several recent activities of our group which involve low-temperature magic-angle-spinning NMR. Low-temperature operation allows us to trap intermediates that cannot be studied under ambient conditions by NMR because of their short lifetime. We have used low-temperature NMR to study the electronic structure of bathorhodopsin, the primary photoproduct of the light-sensitive membrane protein, rhodopsin. This project used a custom-built NMR probe that allows low-temperature NMR in the presence of illumination (the image shows the illuminated spinner module). We have also used this technique to study the behavior of molecules within a restricted environment. Small-molecule endofullerenes are interesting molecular systems in which molecular rotors are confined to a well-insulated, well-defined, and highly symmetric environment. We discuss how cryogenic solid state NMR can give information on the dynamics of ortho-water confined in a fullerene cage. Molecular motions are often connected with fundamental chemical properties; therefore, an understanding of molecular dynamics can be important in fields ranging from material science to biochemistry. We present the case of ibuprofen sodium salt which exhibits different degrees of conformational freedom in different parts of the same molecule, leading to a range of line broadening and line narrowing phenomena as a function of temperature.
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Affiliation(s)
- Maria ConcistrÈ
- School of Chemistry, Southampton University, Southampton SO17 1BJ, United Kingdom
| | - Ole G. Johannessen
- School of Chemistry, Southampton University, Southampton SO17 1BJ, United Kingdom
| | - Elisa Carignani
- Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via Risorgimento 35, 56126, Pisa, Italy
| | - Marco Geppi
- Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via Risorgimento 35, 56126, Pisa, Italy
| | - Malcolm H. Levitt
- School of Chemistry, Southampton University, Southampton SO17 1BJ, United Kingdom
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Mamone S, Concistrè M, Heinmaa I, Carravetta M, Kuprov I, Wall G, Denning M, Lei X, Chen JYC, Li Y, Murata Y, Turro NJ, Levitt MH. Nuclear magnetic resonance of hydrogen molecules trapped inside C70 fullerene cages. Chemphyschem 2013; 14:3121-30. [PMID: 23788291 PMCID: PMC4068279 DOI: 10.1002/cphc.201300269] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2013] [Indexed: 11/29/2022]
Abstract
We present a solid-state NMR study of H2 molecules confined inside the cavity of C70 fullerene cages over a wide range of temperatures (300 K to 4 K). The proton NMR spectra are consistent with a model in which the dipole-dipole coupling between the ortho-H2 protons is averaged over the rotational/translational states of the confined quantum rotor, with an additional chemical shift anisotropy δ(H)(CSA)=10.1 ppm induced by the carbon cage. The magnitude of the chemical shift anisotropy is consistent with DFT estimates of the chemical shielding tensor field within the cage. The experimental NMR data indicate that the ground state of endohedral ortho-H2 in C70 is doubly degenerate and polarized transverse to the principal axis of the cage. The NMR spectra indicate significant magnetic alignment of the C70 long axes along the magnetic field, at temperatures below ~10 K.
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Affiliation(s)
- Salvatore Mamone
- School of Chemistry, Southampton University, Southampton SO17 1BJ (United Kingdom).
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Levitt MH. Spectroscopy of light-molecule endofullerenes. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2013; 371:20120429. [PMID: 23918717 DOI: 10.1098/rsta.2012.0429] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Molecular endofullerenes are supramolecular systems consisting of fullerene cages encapsulating small molecules. Although most early examples consist of encapsulated metal clusters, recently developed synthetic routes have provided endofullerenes with non-metallic guest molecules in high purity and macroscopic quantities. The encapsulated light molecule behaves as a confined quantum rotor, displaying rotational quantization as well as translational quantization, and a rich coupling between the translational and rotational degrees of freedom. Furthermore, many encapsulated molecules display spin isomerism. Spectroscopies such as inelastic neutron scattering, nuclear magnetic resonance and infrared spectroscopy may be used to obtain information on the quantized energy level structure and spin isomerism of the guest molecules. It is also possible to study the influence of the guest molecules on the cages, and to explore the communication between the guest molecules and the molecular environment outside the cage.
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Affiliation(s)
- Malcolm H Levitt
- School of Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, UK.
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Levitt MH, Horsewill AJ. Nanolaboratories: physics and chemistry of small-molecule endofullerenes. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2013; 371:20130124. [PMID: 23918720 PMCID: PMC3730579 DOI: 10.1098/rsta.2013.0124] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
This Theo Murphy Meeting Issue contains papers presented at a Discussion Meeting held at the Kavli Centre of the Royal Society in March 2012. The meeting brought together a wide variety of scientists working on different aspects of small-molecule endofullerenes--those intriguing chemical systems in which small molecules such as H₂ or H₂O are encapsulated in tiny carbon cages.
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Affiliation(s)
- Malcolm H Levitt
- School of Chemistry, University of Southampton, Southampton SO17 1BJ, UK.
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Rõõm T, Peedu L, Ge M, Hüvonen D, Nagel U, Ye S, Xu M, Bačić Z, Mamone S, Levitt MH, Carravetta M, Chen JYC, Lei X, Turro NJ, Murata Y, Komatsu K. Infrared spectroscopy of small-molecule endofullerenes. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2013; 371:20110631. [PMID: 23918713 DOI: 10.1098/rsta.2011.0631] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Hydrogen is one of the few molecules that has been incarcerated in the molecular cage of C₆₀ to form the endohedral supramolecular complex H₂@C₆₀. In this confinement, hydrogen acquires new properties. Its translation motion, within the C₆₀ cavity, becomes quantized, is correlated with its rotation and breaks inversion symmetry that induces infrared (IR) activity of H₂. We apply IR spectroscopy to study the dynamics of hydrogen isotopologues H₂, D₂ and HD incarcerated in C₆₀. The translation and rotation modes appear as side bands to the hydrogen vibration mode in the mid-IR part of the absorption spectrum. Because of the large mass difference of hydrogen and C₆₀ and the high symmetry of C₆₀ the problem is almost identical to a vibrating rotor moving in a three-dimensional spherical potential. We derive potential, rotation, vibration and dipole moment parameters from the analysis of the IR absorption spectra. Our results were used to derive the parameters of a pairwise additive five-dimensional potential energy surface for H₂@C₆₀. The same parameters were used to predict H₂ energies inside C₇₀. We compare the predicted energies and the low-temperature IR absorption spectra of H₂@C₇₀.
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Affiliation(s)
- T Rõõm
- National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, 12618 Tallinn, Estonia.
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Ye S, Xu M, FitzGerald S, Tchernyshyov K, Bačić Z. H2 in solid C60: Coupled translation-rotation eigenstates in the octahedral interstitial site from quantum five-dimensional calculations. J Chem Phys 2013; 138:244707. [DOI: 10.1063/1.4811220] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Quantum rotation of ortho and para-water encapsulated in a fullerene cage. Proc Natl Acad Sci U S A 2012; 109:12894-8. [PMID: 22837402 DOI: 10.1073/pnas.1210790109] [Citation(s) in RCA: 121] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Inelastic neutron scattering, far-infrared spectroscopy, and cryogenic nuclear magnetic resonance are used to investigate the quantized rotation and ortho-para conversion of single water molecules trapped inside closed fullerene cages. The existence of metastable ortho-water molecules is demonstrated, and the interconversion of ortho-and para-water spin isomers is tracked in real time. Our investigation reveals that the ground state of encapsulated ortho water has a lifted degeneracy, associated with symmetry-breaking of the water environment.
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Shul’ga YM, Shestakov AF, Martynenko VM, Baskakov SA, Trifonov NY, Anokhin EM, Maksimychev AV. On the state of CH4 molecule in the octahedral void of C60 fullerite. Russ Chem Bull 2011. [DOI: 10.1007/s11172-011-0175-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Mamone S, Chen JYC, Bhattacharyya R, Levitt MH, Lawler RG, Horsewill AJ, Rõõm T, Bačić Z, Turro NJ. Theory and spectroscopy of an incarcerated quantum rotor: The infrared spectroscopy, inelastic neutron scattering and nuclear magnetic resonance of H2@C60 at cryogenic temperature. Coord Chem Rev 2011. [DOI: 10.1016/j.ccr.2010.12.029] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Horsewill AJ, Panesar KS, Rols S, Johnson MR, Murata Y, Komatsu K, Mamone S, Danquigny A, Cuda F, Maltsev S, Grossel MC, Carravetta M, Levitt MH. Quantum translator-rotator: inelastic neutron scattering of dihydrogen molecules trapped inside anisotropic fullerene cages. PHYSICAL REVIEW LETTERS 2009; 102:013001. [PMID: 19257185 DOI: 10.1103/physrevlett.102.013001] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2008] [Indexed: 05/27/2023]
Abstract
We report an inelastic neutron scattering investigation of the quantum dynamics of hydrogen molecules trapped inside anisotropic fullerene cages. Transitions among the manifold of quantized rotational and translational states are directly observed. The spectra recorded as a function of energy and momentum transfer are interpreted in terms of the rotational potential and the cage dimensions. The thermodynamics of orthohydrogen and parahydrogen are investigated through temperature dependence measurements.
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Affiliation(s)
- A J Horsewill
- School of Physics & Astronomy, University of Nottingham, Nottingham, NG7 2RD, United Kingdom
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Carravetta M, Johannessen OG, Levitt MH, Heinmaa I, Stern R, Samoson A, Horsewill AJ, Murata Y, Komatsu K. Cryogenic NMR spectroscopy of endohedral hydrogen-fullerene complexes. J Chem Phys 2007; 124:104507. [PMID: 16542088 DOI: 10.1063/1.2174012] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We have observed 1H NMR spectra of hydrogen molecules trapped inside modified fullerene cages under cryogenic conditions. Experiments on static samples were performed at sample temperatures down to 4.3 K, while magic-angle-spinning (MAS) experiments were performed at temperatures down to 20 K at spinning frequencies of 15 kHz. Both types of NMR spectra show a large increase in the intramolecular 1H-1H dipolar coupling at temperatures below 50 K, revealing thermal selection of a small number of spatial rotational states. The static and MAS spectra were compared to estimate the degree of sample heating in high-speed cryogenic MAS-NMR experiments. The cryogenic MAS-NMR data show that the site resolution of magic-angle-spinning NMR may be combined with the high signal strength of cryogenic operation and that cryogenic phenomena may be studied with chemical site selectivity.
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Affiliation(s)
- M Carravetta
- School of Chemistry, Southampton University, Southampton SO17 1BJ, United Kingdom
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Carravetta M, Danquigny A, Mamone S, Cuda F, Johannessen OG, Heinmaa I, Panesar K, Stern R, Grossel MC, Horsewill AJ, Samoson A, Murata M, Murata Y, Komatsu K, Levitt MH. Solid-state NMR of endohedral hydrogen–fullerene complexes. Phys Chem Chem Phys 2007; 9:4879-94. [PMID: 17912417 DOI: 10.1039/b707075f] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We present an overview of solid-state NMR studies of endohedral H(2)-fullerene complexes, including (1)H and (13)C NMR spectra, (1)H and (13)C spin relaxation studies, and the results of (1)H dipole-dipole recoupling experiments. The available data involves three different endohedral H(2)-fullerene complexes, studied over a wide range of temperatures and applied magnetic fields. The symmetry of the cage influences strongly the motionally-averaged nuclear spin interactions of the endohedral H(2) species, as well as its spin relaxation behaviour. In addition, the non-bonding interactions between fullerene cages are influenced by the presence of endohedral hydrogen molecules. The review also presents several pieces of experimental data which are not yet understood, one example being the structured (1)H NMR lineshapes of endohedral H(2) molecules trapped in highly symmetric cages at cryogenic temperatures. This review demonstrates the richness of NMR phenomena displayed by H(2)-fullerene complexes, especially in the cryogenic regime.
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Affiliation(s)
- M Carravetta
- School of Chemistry, University of Southampton, Southampton, UK.
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