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Chamignon C, Lelli M, Emsley JW, Luckhurst GR, Zimmermann H. Proton-decoupled deuterium NMR study of an asymmetric liquid crystal dimer having two nematic phases. Phys Rev E 2023; 108:024702. [PMID: 37723701 DOI: 10.1103/physreve.108.024702] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2022] [Accepted: 05/08/2023] [Indexed: 09/20/2023]
Abstract
Proton-decoupled deuterium NMR spectra were obtained for an asymmetric liquid crystal dimer 1-(4-cyanobiphenyl-4'-yloxy)-6-(4-cyanobiphenyl-4'-yl)hexane (CB6OCB) containing a single -CD_{2}- group. The sample has two nematic liquid crystal phases: a twist-bend nematic, N_{TB}, at the lowest temperature followed by a uniaxial nematic, N_{U}, on increasing the temperature. Proton decoupling reduces the linewidths of the peaks in the deuterium spectrum from kHz to ∼100Hz, enabling quadrupolar splittings, Δν, to be obtained with enhanced precision as well as the dipolar coupling between deuterium nuclei within the CD_{2} group, hence enhancing the information content.
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Affiliation(s)
- C Chamignon
- Centre de RMN à Très Hauts Champs de Lyon (FRE 2034-CNRS, UCB Lyon 1, ENS Lyon), 5 rue de la Doua, 69100 Villeurbanne, France
| | - M Lelli
- Department of Chemistry "Ugo Schiff", Center for Magnetic Resonance (CERM), University of Florence, Sesto Fiorentino (FI) 50019, Italy
| | - J W Emsley
- School of Chemistry, Faculty of Engineering and Physical Sciences, University of Southampton, Southampton SO17 1BJ, United Kingdom
| | - G R Luckhurst
- School of Chemistry, Faculty of Engineering and Physical Sciences, University of Southampton, Southampton SO17 1BJ, United Kingdom
| | - H Zimmermann
- Department of Biomolecular Mechanisms, Max-Planck-Institut für Medizinische Forschung, D-69120 Heidelberg, Germany
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Imrie CT, Paterson DA, Storey JMD, Chamignon C, Lelli M, Emsley JW, Luckhurst GR. Phase transitions in a high magnetic field of an odd, symmetric liquid crystal dimer having two nematic phases, N_{U} and N_{TB}, studied by NMR spectroscopy. Phys Rev E 2020; 102:042706. [PMID: 33212702 DOI: 10.1103/physreve.102.042706] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Accepted: 07/31/2020] [Indexed: 11/07/2022]
Abstract
Both ^{1}H and ^{13}C NMR spectra have been obtained in a static magnetic field of 23.5 T on a bent-shaped dimer molecule, 1^{''},7^{''}-bis(4-cyanobiphenyl-4'-yl) nonane (CB9CB), which shows the sequence of liquid crystal phases twist-bend nematic, N_{TB}, and uniaxial nematic, N_{U}, before entering the isotropic phase. The ^{1}H spectra are used to locate the temperature at which the sample melts to form a twist-bend nematic, T_{CrN_{TB}}, and then T_{N_{U}I} when the isotropic phase is entered, both in a magnetic field of 23.5 T, and to compare these with those measured at the Earth's field. The differences between these transition temperatures are found to be zero within the error in their measurement, in stark contrast to previous measurements by Salili et al. [Phys. Rev. Lett. 116, 217801 (2016)10.1103/PhysRevLett.116.217801]. In the isotropic phase in the presence of the field the sample exists in a paranematic phase in which the molecules of CB9CB are partially ordered. The ^{1}H and ^{13}C NMR spectra in the paranematic phase are used to measure the critical temperature T* below which this phase is unstable. The spectra are also used to study the structure, molecular orientational order, and distribution of molecular conformations in the paranematic phase.
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Affiliation(s)
- C T Imrie
- Department of Chemistry, School of Natural and Computing Sciences, University of Aberdeen, Aberdeen AB24 3FX, United Kingdom
| | - D A Paterson
- Department of Chemistry, School of Natural and Computing Sciences, University of Aberdeen, Aberdeen AB24 3FX, United Kingdom
| | - J M D Storey
- Department of Chemistry, School of Natural and Computing Sciences, University of Aberdeen, Aberdeen AB24 3FX, United Kingdom
| | - C Chamignon
- Centre de RMN à Très Hauts Champs de Lyon (FRE 2034-CNRS, UCB Lyon 1, ENS Lyon), 5 rue de la Doua, 69100 Villeurbanne, France
| | - M Lelli
- Department of Chemistry "Ugo Schiff," Center for Magnetic Resonance, University of Florence, Sesto Fiorentino (FI) 50019, Italy
| | - J W Emsley
- School of Chemistry, Faculty of Engineering and Physical Sciences, University of Southampton, Southampton SO17 1BJ, United Kingdom
| | - G R Luckhurst
- School of Chemistry, Faculty of Engineering and Physical Sciences, University of Southampton, Southampton SO17 1BJ, United Kingdom
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Emsley JW, Lelli M, Luckhurst GR, Zimmermann H. Publisher's Note: ^{13}C NMR study of the director distribution adopted by the modulated nematic phases formed by liquid-crystal dimers with odd numbers of atoms in their spacers [Phys. Rev. E 96, 062702 (2017)]. Phys Rev E 2018; 97:029903. [PMID: 29548113 DOI: 10.1103/physreve.97.029903] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2018] [Indexed: 06/08/2023]
Abstract
This corrects the article DOI: 10.1103/PhysRevE.96.062702.
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Emsley JW, Lelli M, Luckhurst GR, Zimmermann H. ^{13}C NMR study of the director distribution adopted by the modulated nematic phases formed by liquid-crystal dimers with odd numbers of atoms in their spacers. Phys Rev E 2017; 96:062702. [PMID: 29347294 DOI: 10.1103/physreve.96.062702] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Indexed: 11/07/2022]
Abstract
The orientational order of the molecules in the bent mesogen CB6OCB has been studied throughout the range of temperature stability of both the N_{U} and N_{TB} liquid-crystal phases by ^{13}C NMR spectroscopy. These spectra provide local order parameters for the para axes of both of the nonequivalent cyanobiphenyl groups and show how they change on entering the twist-bend nematic phase. A key feature of the order parameters is a weak, but clear maximum in the temperature variation of the order parameter prior to the N_{TB} phase. This suggests that the directors in both the N_{U} and N_{TB} phases are tilted with respect to the magnetic field of the spectrometer. Significantly the conformational states of the spacer are comparable in both phases, although the low temperature nematic is chiral but not that at high temperature. It is proposed that the higher temperature, tilted phase could be the splay-bend nematic phase.
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Affiliation(s)
- J W Emsley
- Chemistry, University of Southampton, Highfield, Southampton, SO17 1BJ, United Kingdom
| | - M Lelli
- Department of Chemistry, Center for Magnetic Resonance, University of Florence, Sesto Fiorentino (FI) 50019, Italy
| | - G R Luckhurst
- Chemistry, University of Southampton, Highfield, Southampton, SO17 1BJ, United Kingdom
| | - H Zimmermann
- Max-Planck-Institut für Medizinische Forschung, Department of Biomolecular Mechanisms, D-69120 Heidelberg, Germany
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Emsley JW. Biaxial nematic liquid crystals: theory, simulation and experiment, edited by Geoffrey R. Luckhurst and Timothy J. Sluckin, Chichester, John Wiley & Sons, 2015, 383 p., £120 ($160, 135 Euro) hardback, ISBN 9780470871959. Liquid Crystals Today 2017. [DOI: 10.1080/1358314x.2017.1401268] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- J. W. Emsley
- Department of Chemistry, University of Southampton, Southampton, UK
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Emsley JW, Lelli M, Joy H, Tamba MG, Mehl GH. Similarities and differences between molecular order in the nematic and twist-bend nematic phases of a symmetric liquid crystal dimer. Phys Chem Chem Phys 2016; 18:9419-30. [DOI: 10.1039/c5cp07304a] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Carbon-13 chemical shift anisotropies reveal an unusual temperature dependence of the order parameters, Szz, for the difluoroterphenyl groups in the normal nematic, N and the twist-bend nematic, NTB, phases.
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Affiliation(s)
- J. W. Emsley
- Department of Chemistry
- University of Southampton
- Southampton SO17 1BJ
- UK
| | - M. Lelli
- Institut des Sciences Analytiques
- Centre RMN à Très Hauts Champs (CRMN)
- 69100 Villeurbanne
- France
| | - H. Joy
- Department of Chemistry
- University of Hull
- Hull HU6 7RX
- UK
| | - M.-G. Tamba
- Department of Chemistry
- University of Hull
- Hull HU6 7RX
- UK
| | - G. H. Mehl
- Department of Chemistry
- University of Hull
- Hull HU6 7RX
- UK
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Heist LM, Poon CD, Samulski ET, Photinos DJ, Jokisaari J, Vaara J, Emsley JW, Mamone S, Lelli M. Benzene at 1GHz. Magnetic field-induced fine structure. J Magn Reson 2015; 258:17-24. [PMID: 26160011 DOI: 10.1016/j.jmr.2015.06.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2015] [Revised: 06/05/2015] [Accepted: 06/11/2015] [Indexed: 06/04/2023]
Abstract
The deuterium NMR spectrum of benzene-d6 in a high field spectrometer (1GHz protons) exhibits a magnetic field-induced deuterium quadrupolar splitting Δν. The magnitude of Δν observed for the central resonance is smaller than that observed for the (13)C satellite doublets Δν'. This difference, Δ(Δν)=Δν'-Δν, is due to unresolved fine structure contributions to the respective resonances. We determine the origins of and simulate this difference, and report pulse sequences that exploit the connectivity of the peaks in the (13)C and (2)H spectra to determine the relative signs of the indirect coupling, JCD, and Δν. The positive sign found for Δν is consonant with the magnetic field biasing of an isolated benzene molecule-the magnetic energy of the aromatic ring is lowest for configurations where the C6 axis is normal to the field. In the neat liquid the magnitude of Δν is decreased by the pair correlations in this prototypical molecular liquid.
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Affiliation(s)
- L M Heist
- Department of Chemistry, University of North Carolina, Chapel Hill, NC 27599-3290, USA
| | - C-D Poon
- Department of Chemistry, University of North Carolina, Chapel Hill, NC 27599-3290, USA
| | - E T Samulski
- Department of Chemistry, University of North Carolina, Chapel Hill, NC 27599-3290, USA.
| | - D J Photinos
- Department of Materials Science, University of Patras, Patras 26504, Greece
| | - J Jokisaari
- NMR Research Group, University of Oulu, 90014 Oulu, Finland
| | - J Vaara
- NMR Research Group, University of Oulu, 90014 Oulu, Finland
| | - J W Emsley
- Department of Chemistry, University of Southampton, Southampton SO17 1BJ, UK
| | - S Mamone
- Department of Chemistry, University of Southampton, Southampton SO17 1BJ, UK
| | - M Lelli
- Centre de RMN à Très Hauts Champs, Institut de Sciences Analytiques (CNRS/ENS Lyon/UCB Lyon 1), Université de Lyon, 69100 Villeurbanne, France
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Emsley JW, De Luca G, Lesage A, Longeri M, Mallory FB, Mallory CW. The indirect through-space F–F coupling in peri-difluoronaphthalene: is it anisotropic? Phys Chem Chem Phys 2008; 10:6534-43. [DOI: 10.1039/b809422e] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Emsley JW, Longeri M, Merlet D, Pileio G, Suryaprakash N. An investigation of the structure and bond rotational potential of some fluorinated ethanes by NMR spectroscopy of solutions in nematic liquid crystalline solvents. J Magn Reson 2006; 180:245-55. [PMID: 16554180 DOI: 10.1016/j.jmr.2006.03.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2006] [Revised: 02/24/2006] [Accepted: 03/01/2006] [Indexed: 05/07/2023]
Abstract
NMR spectra of 1,2-dibromo-1,1-difluoroethane and 1-bromo-2-iodo-tetrafluoroethane dissolved in nematic liquid crystalline solvents have been analysed to yield the magnitudes and signs of the scalar couplings, J(ij), and total anisotropic couplings, T(ij), between all the (1)H, (19)F, and (13)C nuclei, except for those between two (13)C nuclei. The values obtained for T(ij) in principle contain a contribution from J(ij)(aniso), the component along the static applied magnetic field of the anisotropic part of the electron-mediated spin-spin coupling. Neglecting this contribution allows partially averaged dipolar couplings, D(ij), to be extracted from the T(ij), and these were used to determine the structure, orientational order, and the conformational distribution generated by rotation about the C-C bond. The values obtained are compared with the results of calculations by ab initio and density functional methods. The differences found are no greater than those obtained for similar compounds which do not contain fluorine, so that there is no definitive evidence for significant contributions from J(CF)(aniso) or J(FF)(aniso) in the two compounds studied.
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Affiliation(s)
- J W Emsley
- Department of Chemistry, Universita della Calabria, Arcavacata di Rende, Italy.
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Emsley JW. Tetraethyl stannane: structure, conformations, and orientational order when dissolved in a nematic liquid crystalline solvent. Phys Chem Chem Phys 2006; 8:3726-31. [PMID: 16896435 DOI: 10.1039/b607062k] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Quantum chemical calculations are used to investigate the structure and the distribution of conformers of tetraethyl stannane, and these are compared with those of tetraethyl methane. The calculations predict that the most abundant conformers in tetraethyl stannane are those with symmetry C1, in contrast to tetraethyl methane, in which the D2d and S4 conformers are dominant. The structural and conformational information on tetraethyl stannane are then used, together with the additive potential model, to explain the finite quadrupolar splittings observed in the deuterium NMR spectrum of tetraethyl stannane dissolved in a nematic liquid crystalline solvent. This analysis emphasizes that to understand the orientational order of a flexible molecule in a liquid crystalline phase it is essential to consider the symmetry of individual conformers rather than that of an average structure.
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Affiliation(s)
- J W Emsley
- School of Chemistry, University of Southampton, Southampton, UKSO17 1BJ
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Celebre G, De Luca G, Emsley JW, Longeri M, Merlet D, Pileio G, Suryaprakash N. Obtaining the structure and bond rotational potential of a substituted ethane by NMR spectroscopy of solutions in nematic liquid-crystalline solvents. J Chem Phys 2005; 123:194907. [PMID: 16321113 DOI: 10.1063/1.2121628] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Partially averaged dipolar couplings (also referred to as residual dipolar couplings) D(ij) can be obtained from the analysis of the NMR spectra of molecules dissolved in liquid-crystalline solvents. Their values for a nonrigid molecule depend upon the bond lengths and angles, the rotational potentials, and the orientational order of the molecules. The molecule studied, 1-chloro-2-bromoethane, is one of the simplest example of a substituted alkane in which the rotational potential has three minimum-energy positions, trans and gauche+/-conformations, and the present investigation explores the problems inherent in deriving the form of the potential and the molecular geometry from the set of partially averaged couplings between the protons, and between protons and (13)C nuclei. The geometrical parameters and the rotational potential obtained are compared with the results from a density-functional theory method.
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Affiliation(s)
- G Celebre
- Department of Chemistry, Universita della Calabria, Arcavacata di Rende, 87036 Rende, Italy
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Bras W, Emsley JW, Levine YK, Luckhurst GR, Seddon JM, Timimi BA. Field-induced alignment of a smectic-Aphase: A time-resolved x-ray diffraction investigation. J Chem Phys 2004; 121:4397-413. [PMID: 15332991 DOI: 10.1063/1.1776116] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The field-induced alignment of a smectic-A phase is, in principle, a complicated process involving the director rotation via the interaction with the field and the layer rotation via the molecular interactions. Time-resolved nuclear magnetic resonance spectroscopy has revealed this complexity in the case of the director alignment, but provides no direct information on the motion of the layers. Here we describe a time-resolved x-ray diffraction experiment using synchrotron radiation to solve the challenging problem of capturing the diffraction pattern on a time scale which is fast in comparison with that for the alignment of the smectic layers. We have investigated the alignment of the smectic-A phase of 4-octyl-4(')-cyanobiphenyl by a magnetic field. The experiment consists of creating a monodomain sample of the smectic-A phase by slow cooling from the nematic phase in a magnetic field with a flux density of 7 T. The sample is then turned quickly through an angle phi(0) about an axis parallel to the x-ray beam direction but orthogonal to the field. A sequence of two-dimensional small angle x-ray diffraction patterns are then collected at short time intervals. Experiments were carried out for different values of phi(0), and at different temperatures. The results show that the alignment behavior changes fundamentally when phi(0) exceeds 45 degrees, and that there is a sharp change in the alignment process when the temperature is less than 3 degrees C below the smectic-A-nematic transition. The results of the x-ray experiments are in broad agreement with the NMR results, but reveal major phenomena concerning the maintenance of the integrity of the smectic-A layer structure during the alignment process.
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Affiliation(s)
- W Bras
- Netherlands Organisation for Scientific Research (NWO), DUBBLE CRG, European Synchrotron Radiation Facility, Boite Postale 220, F-38043 Grenoble Cedex, France
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Emsley JW, Lesot P, Courtieu J, Merlet D. The effect of a chiral nematic solvent on the orientational order and conformational distribution of a flexible prochiral solute. Phys Chem Chem Phys 2004. [DOI: 10.1039/b411203b] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Celebre G, De Luca G, Emsley JW, Foord EK, Longeri M, Lucchesini F, Pileio G. The conformational distribution in diphenylmethane determined by nuclear magnetic resonance spectroscopy of a sample dissolved in a nematic liquid crystalline solvent. J Chem Phys 2003. [DOI: 10.1063/1.1555631] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Castiglione F, Emsley JW, Hird M, Street JM. The determination of the conformation of the aromatic rings in a lateral fluoro-substituted liquid crystal by 13C NMR spectroscopy. Phys Chem Chem Phys 2002. [DOI: 10.1039/b206271m] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Emsley JW, Horne TJ, Celebre G, Longeri M, Zimmermann H. Conformation of the ethoxy group in 4-ethoxy-4'-cyanobiphenyl. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100199a021] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Emsley JW, Wallington ID, Catalano D, Veracini CA, Celebre G, Longeri M. Comparison of the maximum entropy and additive potential methods for obtaining rotational potentials from the NMR spectra of samples dissolved in liquid crystalline solvents. The case of 4-nitro-1-(.beta.,.beta.,.beta.-trifluoroethoxy)benzene. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100126a030] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Emsley JW, Merlet D, Smith KJ, Suryaprakash N. Selective detection of the proton NMR spectra of molecules containing rare spins at natural abundance in liquid crystalline samples. J Magn Reson 2002; 154:303-310. [PMID: 11846588 DOI: 10.1006/jmre.2001.2491] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
It is shown that the proton NMR spectra of molecules containing rare spins at natural abundance dissolved in a liquid crystalline solvent can be obtained free from the strong lines from the spectrum of the abundant isotopomer by the 2D HSQC NMR experiment. The technique can also give the individual chemical shifts of the rare spins, and, for a molecule containing another abundant nucleus, such as fluorine, the rare spin--(19)F total anisotropic couplings are also obtained. The usefulness of the technique is demonstrated for molecules containing (13)C as the rare spins.
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Affiliation(s)
- J W Emsley
- Department of Chemistry, University of Southampton, Southampton, SO17 1BJ, United Kingdom
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Merlet D, Emsley JW, Jokisaari J, Kaski J. Characterisation of the structure, deuterium quadrupolar tensors, and orientational order of acenaphthene, a rigid, prochiral molecule, from the NMR spectra of samples dissolved in nematic and chiral nematic liquid crystalline solvents. Phys Chem Chem Phys 2001. [DOI: 10.1039/b106069b] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Emsley JW, Long JE, Luckhurst GR, Pedrielli P. Magnetic field induced alignment of the directors of a smectic-A liquid crystal. Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 1999; 60:1831-9. [PMID: 11969970 DOI: 10.1103/physreve.60.1831] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/1998] [Indexed: 04/18/2023]
Abstract
Deuterium NMR is used to monitor the magnetic field induced alignment of the directors in the smectic A phase of 4-octyl-4(')-cyanobiphenyl. The experiments consist of first preparing the sample as a monodomain by cooling slowly from the nematic phase in the magnetic field of the NMR spectrometer. The tube containing the sample is then rotated quickly through an angle theta(+), and the subsequent field induced alignment process followed by recording deuterium spectra over a period of time. The results obtained show that the magnetic field induced alignment of the directors in a smectic-A sample is qualitatively different from that of nematic samples. Results are reported for the pure mesogen containing deuteriums at the alpha chain position, and these are compared with data obtained on the alignment process by monitoring the deuterium spectrum of a small amount of an added solute, p-xylene-d(10).
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Affiliation(s)
- J W Emsley
- Department of Chemistry and Southampton Liquid Crystal Institute, University of Southampton, Southampton SO17 1BJ, United Kingdom
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Carravetta M, Castiglione F, De Luca G, Edgar M, Emsley JW, Farrant RD, Foord EK, Lindon JC, Longeri M, Palke WE, Turner DL. Symmetry and phase-selected NMR spectra of liquid crystalline samples. J Magn Reson 1998; 135:298-309. [PMID: 9878460 DOI: 10.1006/jmre.1998.1574] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
It is demonstrated that the NMR spectra of liquid crystalline samples can be simplified by using multiple quantum filtering. In a system of N spin-12 nuclei, the N or (N-1)-multiple quantum filtered spectra (NQF or (N-1)QF) contain lines which originate only from transitions among the eigenstates belonging to the highest symmetry class of the spin permutation group. In addition the NQF spectra are divided further into two sets of lines which differ in phase by 180 degrees. A method for simulating and analysing multiple quantum filtered spectra is described, with examples from molecules with up to eight interacting spins.
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Affiliation(s)
- M Carravetta
- Department of Chemistry, University of Southampton, Southampton, SO17 1BJ, United Kingdom
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Lesot P, Emsley JW, Ouvrard JM, Curzon E. Simplification of 19F NMR spectra of liquid crystalline samples by multiple-pulse COSY experiments. J Magn Reson 1998; 133:166-172. [PMID: 9654481 DOI: 10.1006/jmre.1998.1452] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
A general method is presented of converting second-order fluorine-19 spectra of liquid crystalline samples into first-order spectra. This is achieved by recording a 19F COSY spectrum with a multiple pulse dipolar reducing sequence (MPS) operating in the t1 period, leading to a F1 projection which is first order. The method is illustrated by recording spectra on a sample of 1,3-dichloro-4-fluorobenzene dissolved in the nematic solvent ZLI 1167. Experiments have been done in which the MPS is either the MREV-8 or Flip-Flop-16 sequence. The first-order F1 projections are analyzed to give reduced total 1H-19F couplings, KCSTHFij and the reduction factors, KCS, are obtained by comparison with the THFij available from an analysis of the ordinary 1D spectrum. The reduction factors are compared with values predicted by average Hamiltonian theory (AHT). The reasons for the differences found between observed and predicted values of KCS have been investigated by performing numerical simulations of the 2D MPS COSY experiments. Copyright 1998 Academic Press.
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Affiliation(s)
- P Lesot
- Department of Chemistry, University of Southampton, Southampton, SO17 1BJ, United Kingdom
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Ciampi E, Emsley JW. Measurement of interproton, nuclear spin dipolar couplings in liquid crystalline samples by combining variable angle sample spinning, isotope dilution, and deuterium decoupling. J Magn Reson 1997; 129:207-211. [PMID: 9441886 DOI: 10.1006/jmre.1997.1260] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The proton NMR spectra of liquid crystalline samples can be simplified by selective, partial deuteration followed by deuterium decoupling. This leaves strong peaks from the protons at the undeuterated sites, but also weak resonances from the coupling of these protons to those at low abundance (2% in the present case) at the deuterated sites. The weak resonances can be separated from the strong by recording spectra while spinning the sample at a series of angles to the magnetic field. Copyright 1997 Academic Press. Copyright 1997Academic Press
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Affiliation(s)
- E Ciampi
- Department of Chemistry, University of Southampton, Southampton, SO17 1BJ, United Kingdom
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Ciampi E, Emsley JW, Luckhurst GR, Timimi BA, Kothe G, Tittelbach M. The dynamics of field-induced director reorientation for a nematic phase comprised of flexible molecules. J Chem Phys 1997. [DOI: 10.1063/1.474316] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Catalano D, Emsley JW, La Penna G, Veracini CA. A constrained maximum entropy method for the interpretation of experimental data: Application to the derivation of single particle orientation‐conformation distributions from the partially averaged nuclear spin dipolar couplings of n‐alkanes dissolved in a liquid crystalline solvent. J Chem Phys 1996. [DOI: 10.1063/1.472945] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Palke WE, Catalano D, Celebre G, Emsley JW. Molecular dynamics simulation of biphenyl dissolved in a liquid crystalline solvent: A test of theoretical methods of deriving rotational potentials from partially averaged nuclear spin dipolar couplings. J Chem Phys 1996. [DOI: 10.1063/1.472504] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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La Penna G, Foord EK, Emsley JW, Tildesley DJ. The shape dependence of the solute–solvent interactions in a liquid crystalline phase: A computer simulation study. J Chem Phys 1996. [DOI: 10.1063/1.470893] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Emsley JW. A review of: “Liquid Cvystuls Topics in Physical Chemistry”. Liquid Crystals Today 1995. [DOI: 10.1080/13583149508047594] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Alejandre J, Emsley JW, Tildesley DJ, Carlson P. Molecular dynamics simulations of a flexible molecule in a liquid crystalline solvent. J Chem Phys 1994. [DOI: 10.1063/1.468328] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Emsley JW. British Liquid Crystal Society Annual Meeting, Oxford, 6–8 April 1992. Liquid Crystals Today 1992. [DOI: 10.1080/13583149208628600] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Lal M, Klein ML, Zerbi G, Van Beest BWH, Chachaty C, Clarke JHR, Nordio PL, Tiddy GJT, Kremer K, Ryckaert JP, Brereton MG, Michopoulos Y, Samulski ET, Yarwood J, Price SL, Boublik T, Windle AH, Burrows HD, Sellers S, Luckhurst GR, Zannoni C, Emsley JW, Pastor RW, Osguthorpe DJ, Moro GJ, Brown D, Stone AJ, Reynolds CA, Teixeira-Dias JJC, Yu K, Hamley IW, Photinos DJ. General discussion. ACTA ACUST UNITED AC 1992. [DOI: 10.1039/ft9928801775] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Emsley JW, Horne TJ, Celebre G, De Luca G, Longeri M. Angle of twist between the two rings of 4-cyanobiphenyl when dissolved in liquid-crystalline solvents. ACTA ACUST UNITED AC 1992. [DOI: 10.1039/ft9928801679] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Emsley JW, Fung BM, Heaton NJ, Luckhurst GR. The potential of mean torque for flexible mesogenic molecules. Determination of the interaction parameters from carbon–hydrogen dipolar couplings for 4‐n‐alkyl‐4′‐cyanobiphenyls. J Chem Phys 1987. [DOI: 10.1063/1.453047] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Wooten JB, Savitsky GB, Jacobus J, Beyerlein AL, Emsley JW. Isotope effects on order in nematic solutions. Deuterium quadrupole coupling constants for CDH2I. J Chem Phys 1979. [DOI: 10.1063/1.437208] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Skinner JM, Emsley JW, Belcher R, Penketh GE, Clarke JS. Book reviews. Analyst 1975. [DOI: 10.1039/an9750000446] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Emsley JW, Lindon JC, Salman SR. 19F Nuclear magnetic resonance spectrum of pentafluoropyridine partially oriented in a nematic phase. ACTA ACUST UNITED AC 1972. [DOI: 10.1039/f29726801343] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Emsley JW, Lindon JC, Tabony JM, Wilmshurst TH. Simplification of the 1H nuclear magnetic resonance spectra of partially oriented molecules by partial deuteriation and deuterium decoupling. ACTA ACUST UNITED AC 1971. [DOI: 10.1039/c29710001277] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Emsley JW. A semi-empirical self consistent field molecular orbital calculation on pyridine and pyridinium ion including all valence electrons. ACTA ACUST UNITED AC 1968. [DOI: 10.1039/j19680001387] [Citation(s) in RCA: 37] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Emsley JW. Calculation of π-electron densities using the variable electronegativity modification of the semi-empirical self consistent field method. ACTA ACUST UNITED AC 1968. [DOI: 10.1039/j19680002523] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Emsley JW. Semi-empirical calculation including all valence electrons. The effect of fluorine substitution in benzenes and pyridines. ACTA ACUST UNITED AC 1968. [DOI: 10.1039/j19680002735] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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