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Affiliation(s)
- E. Elliott Burnell
- Chemistry Department, University of British Columbia, 2036 Main Mall, Vancouver, British Columbia V6T 1Z1, Canada
| | - Cornelis A. de Lange
- Atomic, Molecular and Laser Physics, Vrije Universiteit, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
| | - W. Leo Meerts
- Atomic, Molecular and Laser Physics, Vrije Universiteit, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
- Institute for Molecules and Materials, Radboud University Nijmegen, Heyendaalseweg 135, NL-6525 AJ Nijmegen, The Netherlands
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Deuteron and proton NMR study of D2, p-dichlorobenzene and 1,3,5-trichlorobenzene in bimesogenic liquid crystals with two nematic phases. Chem Phys Lett 2016. [DOI: 10.1016/j.cplett.2016.07.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Burnell EE, Weber ACJ, Dong RY, Meerts WL, de Lange CA. A model-free temperature-dependent conformational study ofn-pentane in nematic liquid crystals. J Chem Phys 2015; 142:024904. [DOI: 10.1063/1.4904822] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Affiliation(s)
- E. Elliott Burnell
- Chemistry Department, University of British Columbia, 2036 Main Mall, Vancouver, British Columbia V6T 1Z1, Canada
| | - Adrian C. J. Weber
- Chemistry Department, Brandon University, 270-18th Street, Brandon, Manitoba R7A 6A9, Canada
| | - Ronald Y. Dong
- Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, British Columbia V6T 1Z1, Canada
| | - W. Leo Meerts
- Radboud University, Institute for Molecules and Materials, Heyendaalseweg 135, NL-6525 AJ Nijmegen, The Netherlands
- Laser Centre, Vrije Universiteit, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
| | - Cornelis A. de Lange
- Laser Centre, Vrije Universiteit, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
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Celebre G, De Luca G, Di Pietro ME. Experimental assessment of the vibration-reorientation contribution to liquid crystal NMR dipolar couplings: the case of tetramethylallene dissolved in a nematic mesophase. J Phys Chem B 2011; 115:11119-26. [PMID: 21879737 DOI: 10.1021/jp2021598] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In the present paper, the peculiar orientational behavior, studied by liquid crystal NMR (LXNMR) spectroscopy, of the D(2d) symmetry quasi-spherical molecule of tetramethylallene (TMA) dissolved in the nematic solvent I52 is exploited to attempt a quantitative experimental assessment of the correlation between molecular vibrations and overall rotations in weakly oriented molecules. The analysis of the very small D(HH) and (1)D((13)C-H) dipolar couplings, available from the natural abundance LXNMR spectra of TMA at different temperatures, allows for a derivation leading (by making a few approximations) to the quantification of the vibration-reorientation (also called nonrigid) contribution affecting the observed direct (1)D((13)C-H) dipolar coupling. The obtained results show that, under the particular conditions of the studied system (very weak orientational ordering of a highly symmetric molecule), this contribution is particularly important, in order to reproduce the whole value of the "observed" dipolar coupling. This issue is discussed and commented on at length in the work, also, by making reference to the analogy with perfectly symmetric molecules (such as methane and analogues) dissolved in liquid crystalline phases.
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Affiliation(s)
- Giorgio Celebre
- Dipartimento di Chimica, Università della Calabria, v. P. Bucci, I-87036 Rende (CS), Italy.
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Burnell EE, de Lange CA, Capitani D, Angelini G, Ursini O. 3H NMR of the tritiated isotopologues of methane in nematic liquid-crystal solvents. Chem Phys Lett 2010. [DOI: 10.1016/j.cplett.2009.12.087] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Weber ACJ, Yang X, Dong RY, Burnell EE. The smectic effect on solute order parameters rationalized by double Maier-Saupe Kobayashi-McMillan theory. J Chem Phys 2010; 132:034503. [PMID: 20095744 DOI: 10.1063/1.3291486] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
From the dipolar couplings obtained by NMR spectroscopy we have calculated the order parameters of a wide variety of solutes in the nematic and smectic A phases of the liquid crystals 8CB and 8OCB. These measurements are then rationalized with the previously tested two Maier-Saupe Kobayashi-McMillan interaction potential from which smectic order parameters are calculated.
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Affiliation(s)
- Adrian C J Weber
- Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, British Columbia V6T 1Z1, Canada.
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Danilović Z, Burnell EE. Orientational order of near D3h solutes in nematic liquid crystals. J Chem Phys 2009; 130:154506. [DOI: 10.1063/1.3104606] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
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van der Est A, Barker P, Burnell E, de Lange C, Snijders J. N.M.R. of methanes in liquid crystal mixtures. Mol Phys 2006. [DOI: 10.1080/00268978500102241] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Van der Est A, Kok M, Burnell E. Size and shape effects on the orientation of rigid molecules in nematic liquid crystals. Mol Phys 2006. [DOI: 10.1080/00268978700100271] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Affiliation(s)
- A.J. Van der Est
- a Department of Chemistry , University of British Columbia , 2036 Main Mall, Vancouver , B.C. , Canada , V6T 1Y6
| | - M.Y. Kok
- a Department of Chemistry , University of British Columbia , 2036 Main Mall, Vancouver , B.C. , Canada , V6T 1Y6
| | - E.E. Burnell
- a Department of Chemistry , University of British Columbia , 2036 Main Mall, Vancouver , B.C. , Canada , V6T 1Y6
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Ter Beek LC, Zimmerman DS, Burnell EE. The orientation of molecules with internal rotation in nematic phases. Mol Phys 2006. [DOI: 10.1080/00268979300102161] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Affiliation(s)
- Leon C. Ter Beek
- a Department of Chemistry , University of British Columbia , 2036 Main Mall, Vancouver , British Columbia , Canada , V6T 1Z1
| | - Dan S. Zimmerman
- a Department of Chemistry , University of British Columbia , 2036 Main Mall, Vancouver , British Columbia , Canada , V6T 1Z1
| | - E. Elliott Burnell
- a Department of Chemistry , University of British Columbia , 2036 Main Mall, Vancouver , British Columbia , Canada , V6T 1Z1
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Barnhoorn J, De Lange C. Anab initiostudy of molecular hydrogen and its deuterated analogues partially oriented in nematic liquid crystals. Mol Phys 2006. [DOI: 10.1080/00268979400100474] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Affiliation(s)
- J.B.S. Barnhoorn
- a Laboratory for Physical Chemistry , University of Amsterdam , Nieuwe Achtergracht 127, 1018 , WS Amsterdam , The Netherlands
| | - C.A. De Lange
- a Laboratory for Physical Chemistry , University of Amsterdam , Nieuwe Achtergracht 127, 1018 , WS Amsterdam , The Netherlands
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Kandrashkin YE, Asano MS, van der Est A. Light-Induced Electron Spin Polarization in Vanadyl Octaethylporphyrin: I. Characterization of the Excited Quartet State. J Phys Chem A 2006; 110:9607-16. [PMID: 16884194 DOI: 10.1021/jp0620365] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Laser flash induced spin-polarized transient electron paramagnetic resonance (TREPR) spectra for vanadyl octaethylporphyrin in isotropic and partially ordered frozen solutions are presented and compared with corresponding luminescence data. The TREPR spectra show well-resolved hyperfine couplings to the vanadium nucleus and a multiplet polarization pattern with features typical of zero-field splitting (ZFS). The principal values of the vanadium hyperfine coupling tensor evaluated from the spectra are 1/3 of the corresponding values found from steady-state EPR spectra of the ground state. On the basis of these characteristics and numerical simulations, the polarization patterns are assigned to the excited quartet state. The values of the ZFS parameters of the trip-quartet obtained from simulation of the spectra (D = 17.5 mT and E = 1.5 mT) are comparable to those of the triplet state of the zinc and free base octaethyl porphyrin. The lifetime of the spin polarization is found to be temperature dependent and is essentially the same as that of the optical emission. The temperature dependence is rationalized using a model in which the decay to the ground state occurs from both the trip-quartet and trip-doublet, which are in thermal equilibrium even at 15 K. A fit of the model to the observed spin polarization lifetimes yields an energy gap of 47 cm(-1) between the trip-quartet and trip-doublet. It is shown that the spin polarization evolves from a multiplet pattern at early times to a net absorptive pattern at late times following the laser flash. It is proposed that the establishment of thermal equilibrium leads to the evolution of the spin from multiplet to net polarization.
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Affiliation(s)
- Yuri E Kandrashkin
- Department of Chemistry, Brock University, 500 Glenridge Ave., St. Catharines, Ontario, Canada L2S 3A1
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Taggar AS, Campbell CJ, Yethiraj A, Burnell EE. Testing assumptions about solute concentration dependence in liquid crystal NMR. J Phys Chem B 2006; 110:1363-8. [PMID: 16471686 DOI: 10.1021/jp052592j] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The NMR spectra of four solutes, used as probes of liquid crystal orientational order, were analyzed. For each solute, samples were prepared at different solute concentrations, and the concentration dependence was used to extrapolate zero-concentration properties. The mean-field (Maier-Saupe) model when applied to solutes neglects solute-solute interactions and assumes all solutes in a mixed-solute sample see the same average environment. The first assumption is only valid as one approaches zero concentration, while experiments are typically carried out at concentrations between 0 and 10 mol %. The solute concentration dependence has in the past been "scaled out" using an internal solute reference as an orientational standard. We measured the concentration dependence of the orientational order parameter and calculate the corresponding interaction energies based on a mean-field interaction potential for a solute. We find agreement at the 3% level between experiments for different solutes while using (i) the zero-concentration values as solute-dependent orientational references and (ii) scaling to either order parameters or interaction energies; these two scalings gave equivalent but not identical results. We find, too, that errors inherent in the experiment and the calculations will limit attempts to refine the theory to push the comparisons beyond the 2% level.
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Affiliation(s)
- Amandeep S Taggar
- 2036 Main Mall, Chemistry Department, University of British Columbia, Vancouver, British Columbia, V6T 1Z1, Canada
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Burnell EE, de Lange CA, Barnhoorn JBS, Aben I, Levelt PF. Molecules with Large-Amplitude Torsional Motion Partially Oriented in a Nematic Liquid Crystal: Ethane and Isotopomers. J Phys Chem A 2005; 109:11027-36. [PMID: 16331947 DOI: 10.1021/jp052817q] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
An NMR study on ethane and five isotopomers dissolved in the nematic liquid crystal Merck ZLI 1132 is performed. A consistent set of dipolar and quadrupolar couplings is obtained. The dipolar couplings are corrected for harmonic vibrational effects, while the contribution from the torsional motion is incorporated classically. The corrected dipolar couplings cannot be understood in terms of a reasonable molecular structure unless effects of the reorientation-vibration interaction are taken into account. Assuming that the reorientation-vibration contributions that are known for the methyl group in methyl fluoride are transferable to ethane, excellent agreement between observed and calculated dipolar couplings is obtained on the basis of the ethane gas-phase structure. The observed and calculated deuterium quadrupolar couplings show discrepancies supporting the notion that average electric field gradients are important in liquid-crystal solvents. An important consequence of the transferability of the reorientation-vibration correlation is that in other molecules with a methyl group the same procedure as for ethane can be followed. Inclusion of this effect generally removes the need to interpret changes in observed dipolar couplings in terms of elusive chemical effects.
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Affiliation(s)
- E E Burnell
- Chemistry Department, University of British Columbia, 2036 Main Mall, Vancouver, Canada, V6T 1Z1.
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Burnell EE, de Lange CA. NMR as a tool in the investigation of fundamental problems in ordered liquids. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2005; 28:73-90. [PMID: 16260122 DOI: 10.1016/j.ssnmr.2005.09.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2005] [Revised: 08/31/2005] [Indexed: 05/05/2023]
Abstract
An overview is presented of modern NMR techniques and a variety of experimental and theoretical tools employed in the study of solutes dissolved in liquid crystals. The NMR techniques involve multiple quantum and spectral subtraction methods. In addition, various experimental and theoretical tools are discussed, including: the theoretical background of observed order parameters; the use of 'magic mixtures' to separate orientational contributions; the reorientation-vibration interaction; the use of model calculations based on size and shape of the various solutes; and the use of computer simulations. Applications to the benchmark probe molecules hydrogen, methane, ethane, and butane and their isotopomers are treated.
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Affiliation(s)
- E E Burnell
- Chemistry Department, University of British Columbia, 2036 Main Mall, Vancouver, BC, Canada V6T 1Z1.
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Syvitski RT, Burnell EE. Multiple quantum and high-resolution NMR, molecular structure, and order parameters of partially oriented ortho and meta dimethyl-, dichloro-, and chloromethylbenzenes codissolved in nematic liquid crystals. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2000; 144:58-73. [PMID: 10783274 DOI: 10.1006/jmre.1999.2013] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
We develop a strategy for analyzing complex nuclear magnetic resonance (NMR) spectra of several solutes codissolved in liquid-crystal phases. Spectral parameters of solutes m- or o-xylene were estimated by analyzing 2D multiple-quantum NMR spectra using a modified version of a least-squares fitting routine which adjusts chemical shifts, order parameters, structural parameters, and/or dipolar couplings independently. These estimates were used to facilitate analysis of the high-resolution spectra which contain resonances from many solutes. Calculated spectra of m- or o-xylene were subtracted from the experimental high-resolution spectra leaving resonances from the other solutes readily visible. Accurate spectral parameters of all codissolved solutes were determined from the high-resolution spectra. Order parameters and structural parameters (including vibrationally corrected parameters) of m- and o-xylene, m- and o-chlorotoluene, and m- and o-dichlorobenzene were calculated from the dipolar couplings.
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Affiliation(s)
- R T Syvitski
- Department of Chemistry, University of British Columbia, Vancouver, British Columbia, Canada.
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Syvitski RT, Burnell EE. NMR and molecular structure of partially oriented mono and para methyl- and chlorobenzenes dissolved in nematic liquid crystals. CAN J CHEM 1999. [DOI: 10.1139/v99-144] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Spectral parameters, order parameters, and structural parameters, including the vibrationally corrected ralpha structure of the partially oriented solutes p-xylene, p-chlorotoluene, p-dichlorobenzene, toluene, and chlorobenzene dissolved in three liquid crystal mixtures, are reported. For samples containing the three solutes p-xylene, p-dichlorobenzene, and 1,3,5-trichlorobenzene, multiple quantum (MQ) nuclear magnetic resonance was used to aid in the analysis of the complex high-resolution spectra of the p-xylene. The high-resolution spectra of 1,3,5-trichlorobenzene and p-dichlorobenzene were easily identified and analyzed once the calculated p-xylene spectrum was subtracted from the experimental one. The methyl groups of p-xylene, p-chlorotoluene, and toluene have similar geometries when the structure is determined from dipolar couplings corrected for harmonic vibrations.Key words: nematic liquid crystal, NMR, molecular structure, order parameter.
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Burnell EE, de Lange CA. Prediction from Molecular Shape of Solute Orientational Order in Liquid Crystals. Chem Rev 1998; 98:2359-2388. [PMID: 11848965 DOI: 10.1021/cr941159v] [Citation(s) in RCA: 129] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- E. E. Burnell
- Laboratory for Physical Chemistry, University of Amsterdam, Nieuwe Achtergracht 127-129, 1018 WS Amsterdam, The Netherlands
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Polson JM, Burnell EE. Conformational equilibrium and orientational ordering:1H‐nuclear magnetic resonance of butane in a nematic liquid crystal. J Chem Phys 1995. [DOI: 10.1063/1.470367] [Citation(s) in RCA: 34] [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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Ter Beek LC, Zimmerman DS, Burnell EE. The conformation of 2,2′-dithiophene in nematic solvents determined by1H-NMR. Mol Phys 1991. [DOI: 10.1080/00268979100102781] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Ingman P, Jokisaari J, Pulkkinen O, Diehl P, Muenster O. 21Ne NMR spectroscopy: temperature dependence of the 21Ne quadrupole coupling and electric field gradient in a liquid crystal. Chem Phys Lett 1991. [DOI: 10.1016/0009-2614(91)80210-o] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Lounila J, Diehl P. Anisotropic solute–solvent interactions in liquid crystals: An analysis of dipolar and quadrupolar couplings of methane in nematic solvents. J Chem Phys 1991. [DOI: 10.1063/1.459952] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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van der Est AJ, Burnell EE, Barnhoorn JBS, de Lange CA, Snijders JG. Acetylene in nematic liquid crystals: A vibrational analysis of the observed dipolar couplings. J Chem Phys 1988. [DOI: 10.1063/1.455700] [Citation(s) in RCA: 16] [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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Burnell E, De Lange C. On the determination of chemical shielding anisotropies of solutes in liquid-crystal mixtures of opposite diamagnetic anisotropies. Chem Phys Lett 1987. [DOI: 10.1016/0009-2614(87)87303-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Plomp L, Loman AC, Bulthuis J. Frequency dependent biexponential14N relaxation of methylisocyanide in nematic liquid crystals. J Chem Phys 1986. [DOI: 10.1063/1.450851] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Beckmann PA, Bloom M, Burnell EE. Deuteron Zeeman relaxation of CD4 in the isotropic liquid, the liquid crystalline, and the solid state of several substances. J Chem Phys 1986. [DOI: 10.1063/1.449901] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Hiltunen Y, Jokisaari J, Pulkkinen A, Väänänen T. An experimental 1H NMR study of the structural deformation of benzene and the dipolar CH splitting of methane in various nematic liquid crystals and in smectic HAB. Chem Phys Lett 1984. [DOI: 10.1016/0009-2614(84)80353-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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