1
|
Ahola SK, Ingman P, Laatikainen R, Sinkkonen J, Jokisaari J. 21Ne and 131Xe NMR study of electric field gradients and multinuclear NMR study of the composition of a ferroelectric liquid crystal. J Chem Phys 2018; 149:234901. [PMID: 30579290 DOI: 10.1063/1.5052499] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
This study has two goals. First, the electric field gradient (EFG) present in the liquid-crystalline phases of ferroelectric FELIX-R&D is determined using NMR spectroscopy of noble gases 21Ne and 131Xe. The 21Ne and 131Xe NMR spectra were recorded over a temperature range, which covers all the mesophases of FELIX-R&D: nematic N*, smectic A, and smectic C*. The spin quantum number of both 21Ne and 131Xe is 3/2. Their electric quadrupole moment interacts with the EFG at the nuclear site, which in liquid-crystalline phases results in the NMR spectra of the triplet structure, instead of a singlet detectable in the isotropic phase. The total EFG experienced by the noble gas nuclei consists of two contributions; one arises from the quadrupole moments of the liquid crystal molecules (external contribution) and the other one from the deformation of the electron distribution of the atoms (deformational contribution). The total EFGs determined from the 131Xe and 21Ne quadrupole splittings are very similar in the nematic and smectic A phases but differ in the smectic C* phase, being about twice larger in the 21Ne case which stems from the larger deformation of the xenon electron cloud than that of neon. For the first time, EFG was determined also in the smectic C* phase applying noble gas NMR spectroscopy. Second, the structure of molecules which, as a mixture, compose the used ferroelectric liquid crystal, FELIX-R&D, is determined by applying a number of various NMR methods and sophisticated spectral analysis. In this part, NMR spectra were recorded from FELIX-R&D/CDCl3 solution. The NMR spectral analysis was divided into four subsystems with over 13 000 000 nonzero intensity transitions. It appeared that FELIX-R&D is composed of three phenyl pyrimidine derivatives and a chiral dopant with fluorine in the asymmetric carbon atom.
Collapse
Affiliation(s)
| | - Petri Ingman
- NMR Research Unit, University of Oulu, 90014 Oulu, Finland
| | - Reino Laatikainen
- Department of Pharmacy, University of Eastern Finland, 70211 Kuopio, Finland
| | - Jari Sinkkonen
- Instrument Centre, Department of Chemistry, University of Turku, 20014 Turku, Finland
| | | |
Collapse
|
2
|
Jokisaari J, Zhu J. Xenon NMR of phase biaxiality in liquid crystals. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2014; 52:556-559. [PMID: 24771455 DOI: 10.1002/mrc.4077] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Revised: 03/31/2014] [Accepted: 04/01/2014] [Indexed: 06/03/2023]
Abstract
Biaxial thermotropic nematic liquid crystals would be of great importance in liquid crystal display technology. Less than a decade ago, such liquid crystals were suggested. The biaxiality of the phases was confirmed using (2)H NMR spectroscopy of deuterated probe molecules. The spectra were collected from a sample rotating around an axis perpendicular to the external magnetic field, resulting in a two-dimensional powder pattern. We have proposed an alternate technique that is based on the second order quadrupole shift detectable in (131)Xe NMR spectra of dissolved xenon. The method has many advantages, such as the NMR spectra are taken from a static sample and the (131)Xe quadrupole coupling tensor is extremely sensitive to the symmetry of the phase. In the present study, we report results obtained on a 600-MHz NMR spectrometer. Together with the data of our earlier study, they confirm that the asymmetry parameter of the (131)Xe quadrupole coupling tensor in the nematic phase of a ferroelectric liquid crystal is 0.85 and in the smectic A phase ca 0.62, indicating significant phase biaxiality.
Collapse
|
3
|
Jokisaari JP, Kantola AM, Lounila JA, Ingman LP. Detection of phase biaxiality in liquid crystals by use of the quadrupole shift in 131Xe NMR spectra. PHYSICAL REVIEW LETTERS 2011; 106:017801. [PMID: 21231771 DOI: 10.1103/physrevlett.106.017801] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2010] [Indexed: 05/30/2023]
Abstract
An experimental method to unambiguously distinguish between uniaxial and biaxial liquid crystal phases is introduced. The method is based on the second order quadrupole shift (SOQS) observable in 131Xe NMR spectra of xenon dissolved in liquid crystals. It is shown that besides revealing the biaxiality, the 131Xe SOQS offers a novel method to determine the tilt angle in smectic C phases. As an example, the 131Xe SOQS in a ferroelectric liquid crystal is reported. It yields up a biaxial phase in between isotropic and smectic C phases.
Collapse
Affiliation(s)
- Jukka P Jokisaari
- NMR Research Group, Department of Physics, University of Oulu, Finland.
| | | | | | | |
Collapse
|
4
|
Hanni M, Lantto P, Vaara J. Pairwise additivity in the nuclear magnetic resonance interactions of atomic xenon. Phys Chem Chem Phys 2009; 11:2485-96. [PMID: 19325983 DOI: 10.1039/b821907a] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Nuclear magnetic resonance (NMR) of atomic (129/131)Xe is used as a versatile probe of the structure and dynamics of various host materials, due to the sensitivity of the Xe NMR parameters to intermolecular interactions. The principles governing this sensitivity can be investigated using the prototypic system of interacting Xe atoms. In the pairwise additive approximation (PAA), the binary NMR chemical shift, nuclear quadrupole coupling (NQC), and spin-rotation (SR) curves for the xenon dimer are utilized for fast and efficient evaluation of the corresponding NMR tensors in small xenon clusters Xe(n) (n = 2-12). If accurate, the preparametrized PAA enables the analysis of the NMR properties of xenon clusters, condensed xenon phases, and xenon gas without having to resort to electronic structure calculations of instantaneous configurations for n > 2. The binary parameters for Xe(2) at different internuclear distances were obtained at the nonrelativistic Hartree-Fock level of theory. Quantum-chemical (QC) calculations at the corresponding level were used to obtain the NMR parameters of the Xe(n) (n = 2-12) clusters at the equilibrium geometries. Comparison of PAA and QC data indicates that the direct use of the binary property curves of Xe(2) can be expected to be well-suited for the analysis of Xe NMR in the gaseous phase dominated by binary collisions. For use in condensed phases where many-body effects should be considered, effective binary property functions were fitted using the principal components of QC tensors from Xe(n) clusters. Particularly, the chemical shift in Xe(n) is strikingly well-described by the effective PAA. The coordination number Z of the Xe site is found to be the most important factor determining the chemical shift, with the largest shifts being found for high-symmetry sites with the largest Z. This is rationalized in terms of the density of virtual electronic states available for response to magnetic perturbations.
Collapse
Affiliation(s)
- Matti Hanni
- NMR Research Group, Department of Physical Sciences, University of Oulu, P.O. Box 3000, FIN-90014, University of Oulu, Finland.
| | | | | |
Collapse
|
5
|
Tervonen H, Saunavaara J, Ingman LP, Jokisaari J. 19F Single-Quantum and 19F−33S Heteronuclear Multiple-Quantum Coherence NMR of SF6 in Thermotropic Nematogens and in the Gas Phase. J Phys Chem B 2006; 110:16232-8. [PMID: 16913748 DOI: 10.1021/jp062296m] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
(19)F single-quantum (SQC) and (19)F-(33)S heteronuclear multiple-quantum coherence (HMQC) NMR spectroscopy of sulfur hexafluoride (SF(6)) dissolved in thermotropic liquid crystals (TLCs) were used to investigate the properties of TLCs. On one hand, environmental effects on the NMR parameters of SF(6), (19)F nuclear shielding, (19)F-(33)S spin-spin coupling, secondary isotope effects of sulfur on (19)F shielding, and the self-diffusion coefficient in the direction of the external magnetic field were studied as well. The temperature dependence of the (19)F shielding of SF(6) in TLCs was modeled with a function that takes into account the properties of both TLC and SF(6). It appears that the TLC environment deforms the electronic system of SF(6) so that the (19)F shielding tensor becomes slightly anisotropic, with the anisotropy being from -0.5 to -1.4 ppm, depending upon the TLC solvent. On the contrary, no sign of residual dipolar coupling between (19)F and (33)S was found, meaning that the so-called deformational effects, which arise from the interaction between vibrational and reorientational motions of the molecule, on the geometry of the molecule are insignificant. Diffusion activation energies, E(a), were determined from the temperature dependence of the self-diffusion coefficients. In each TLC, E(a) increases when moving from an isotropic phase to a nematic phase. The spin-spin coupling constant, J((19)F,(33)S), increases by ca. 10 Hz when moving from the gas phase to TLC solutions. The secondary isotope shifts of (19)F shielding are practically independent of TLC solvent and temperature. For the first time, (19)F-(33)S heteronuclear multiple-quantum NMR spectra were recorded for SF(6) in the gas phase and in a liquid-crystalline solution.
Collapse
Affiliation(s)
- Henri Tervonen
- NMR Research Group, Department of Physical Sciences, University of Oulu, P.O. Box 3000, FIN-90014 Oulu, Finland
| | | | | | | |
Collapse
|
6
|
Jagadeesh B, Prabhakar A, Ramana Rao MHV, Murty CVS, Pisipati VGKM, Kunwar AC, Bowers CR. Probing the Anisotropic Environment of Thermotropic Liquid Crystals Using 129Xe NMR Spectroscopy. J Phys Chem B 2004. [DOI: 10.1021/jp037745m] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- B. Jagadeesh
- NMR Center and Chemical Engineering Division, Indian Institute of Chemical Technology, Uppal Road, Hyderabad 500 007, India; Department of Physics, Nagarjuna University, Nagarjuna Nagar, India; and Chemistry Department, University of Florida, Gainesville, Florida 32611
| | - A. Prabhakar
- NMR Center and Chemical Engineering Division, Indian Institute of Chemical Technology, Uppal Road, Hyderabad 500 007, India; Department of Physics, Nagarjuna University, Nagarjuna Nagar, India; and Chemistry Department, University of Florida, Gainesville, Florida 32611
| | - M. H. V. Ramana Rao
- NMR Center and Chemical Engineering Division, Indian Institute of Chemical Technology, Uppal Road, Hyderabad 500 007, India; Department of Physics, Nagarjuna University, Nagarjuna Nagar, India; and Chemistry Department, University of Florida, Gainesville, Florida 32611
| | - C. V. S. Murty
- NMR Center and Chemical Engineering Division, Indian Institute of Chemical Technology, Uppal Road, Hyderabad 500 007, India; Department of Physics, Nagarjuna University, Nagarjuna Nagar, India; and Chemistry Department, University of Florida, Gainesville, Florida 32611
| | - V. G. K. M. Pisipati
- NMR Center and Chemical Engineering Division, Indian Institute of Chemical Technology, Uppal Road, Hyderabad 500 007, India; Department of Physics, Nagarjuna University, Nagarjuna Nagar, India; and Chemistry Department, University of Florida, Gainesville, Florida 32611
| | - A. C. Kunwar
- NMR Center and Chemical Engineering Division, Indian Institute of Chemical Technology, Uppal Road, Hyderabad 500 007, India; Department of Physics, Nagarjuna University, Nagarjuna Nagar, India; and Chemistry Department, University of Florida, Gainesville, Florida 32611
| | - C. R. Bowers
- NMR Center and Chemical Engineering Division, Indian Institute of Chemical Technology, Uppal Road, Hyderabad 500 007, India; Department of Physics, Nagarjuna University, Nagarjuna Nagar, India; and Chemistry Department, University of Florida, Gainesville, Florida 32611
| |
Collapse
|
7
|
Cifelli M, Saunavaara J, Jokisaari J, Veracini CA. 129Xe Nuclear Shielding and Diffusion in the A and C* Phases of a Chiral Smectogen. J Phys Chem A 2004. [DOI: 10.1021/jp049788o] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Mario Cifelli
- Department of Chemistry and Industrial Chemistry, University of Pisa, Italy, and NMR Research Group, Department of Physical Sciences, University of Oulu, Finland
| | - Jani Saunavaara
- Department of Chemistry and Industrial Chemistry, University of Pisa, Italy, and NMR Research Group, Department of Physical Sciences, University of Oulu, Finland
| | - Jukka Jokisaari
- Department of Chemistry and Industrial Chemistry, University of Pisa, Italy, and NMR Research Group, Department of Physical Sciences, University of Oulu, Finland
| | - Carlo A. Veracini
- Department of Chemistry and Industrial Chemistry, University of Pisa, Italy, and NMR Research Group, Department of Physical Sciences, University of Oulu, Finland
| |
Collapse
|
8
|
Lai S, Locci E, Saba G, Husu I, Masci G, Crescenzi V, Lai A. Solid-state13C and129Xe NMR study of poly(vinyl alcohol) and poly(vinyl alcohol)/lactosilated chitosan gels. ACTA ACUST UNITED AC 2003. [DOI: 10.1002/pola.10899] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
|
9
|
Mair RW, Rosen MS, Wang R, Cory DG, Walsworth RL. Diffusion NMR methods applied to xenon gas for materials study. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2002; 40:S29-S39. [PMID: 12807139 DOI: 10.1002/mrc.1114] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
We report initial NMR studies of (i) xenon gas diffusion in model heterogeneous porous media and (ii) continuous flow laser-polarized xenon gas. Both areas utilize the pulsed gradient spin-echo (PGSE) techniques in the gas phase, with the aim of obtaining more sophisticated information than just translational self-diffusion coefficients--a brief overview of this area is provided in the Introduction. The heterogeneous or multiple-length scale model porous media consisted of random packs of mixed glass beads of two different sizes. We focus on observing the approach of the time-dependent gas diffusion coefficient, D(t) (an indicator of mean squared displacement), to the long-time asymptote, with the aim of understanding the long-length scale structural information that may be derived from a heterogeneous porous system. We find that D(t) of imbibed xenon gas at short diffusion times is similar for the mixed bead pack and a pack of the smaller sized beads alone, hence reflecting the pore surface area to volume ratio of the smaller bead sample. The approach of D(t) to the long-time limit follows that of a pack of the larger sized beads alone, although the limiting D(t) for the mixed bead pack is lower, reflecting the lower porosity of the sample compared to that of a pack of mono-sized glass beads. The Pade approximation is used to interpolate D(t) data between the short- and long-time limits. Initial studies of continuous flow laser-polarized xenon gas demonstrate velocity-sensitive imaging of much higher flows than can generally be obtained with liquids (20-200 mm s-1). Gas velocity imaging is, however, found to be limited to a resolution of about 1 mm s-1 owing to the high diffusivity of gases compared with liquids. We also present the first gas-phase NMR scattering, or diffusive-diffraction, data, namely flow-enhanced structural features in the echo attenuation data from laser-polarized xenon flowing through a 2 mm glass bead pack.
Collapse
Affiliation(s)
- R W Mair
- Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts 02138, USA.
| | | | | | | | | |
Collapse
|
10
|
|