Proton NMR Study of Molecular Motions in the Solid Phase of a Smectic A Liquid Crystal

1975 ◽  
Vol 53 (17) ◽  
pp. 1646-1650 ◽  
Author(s):  
Ronald Y. Dong ◽  
M. Wiszniewska ◽  
E. Tomchuk ◽  
E. Bock
Keyword(s):  
Activation Energy ◽  
Liquid Crystal ◽  
Molecular Motion ◽  
Solid Phase ◽  
Methyl Groups ◽  
Molecular Motions ◽  
Kcal Mole ◽  
Self Diffusion ◽  
Smectic A ◽  
Nmr Study

Proton T1, T1ρ, and T1D were studied in the solid phase of diethylazoxybenzoate from 105 K to the melting point. The activation energies for the threefold reorientation of methyl groups and for the molecular self-diffusion were determined to be about 3.3 and 11 kcal/mole respectively. Between 170 and 240 K, a new slow molecular motion with an estimated activation energy of 3.7 kcal/mole was detected via the T1ρ data.

TEMPERATURE COEFFICIENTS FOR SELF-DIFFUSION IN SOLUTION

1954 ◽  
Vol 32 (2) ◽  
pp. 71-78 ◽  
Author(s):  
C. J. Krauss ◽  
J. W. T. Spinks
Keyword(s):  
Activation Energy ◽  
Aqueous Solutions ◽  
Infinite Dilution ◽  
Kcal Mole ◽  
Self Diffusion ◽  
Temperature Coefficients ◽  
Sodium Dihydrogen

Coefficients of self-diffusion have been measured for aqueous solutions of sodium dihydrogen phosphates from 1 molar to 10−4 molar and at temperatures of 15, 25, 35, and 45 °C. The activation energy of self-diffusion has been calculated for various concentrations. It decreases from 5.4 kcal./mole at 0.9 M to 4.3 kcal./mole. at infinite dilution.

Molecular Motion in Solid Tetrapropylammonium Bromide and Iodide

1992 ◽  
Vol 47 (11) ◽  
pp. 1115-1118 ◽  
Author(s):  
S. Lewicki ◽  
B. Szafranska ◽  
Z. Pajak
Keyword(s):  
Molecular Motion ◽  
Solid Phase ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Methyl Groups ◽  
Methyl Group ◽  
Spin Lattice ◽  
Tetrapropylammonium Bromide ◽  
Solid Phase Transition

Abstract The proton NMR second moment and spin-lattice relaxation time for tetrapropylammonium bromide and iodide have been measured over a wide temperature range. A solid-solid phase transition related to the onset of cation tumbling was found for both salts and confirmed by DTA. In the low temperature phases methyl group reorientation was evidenced. For iodide a dynamic nonequivalence of the methyl groups and the onset of ethyl groups motion was also discovered

H NMR Study of Ionic Motions in High Temperature Solid Phases of (CH3NH3)2ZnCl4

2000 ◽  
Vol 55 (3-4) ◽  
pp. 412-414 ◽  
Author(s):  
Hiroyuki Ishida
Keyword(s):  
Activation Energy ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
The Self ◽  
Spin Lattice Relaxation ◽  
Temperature Phase ◽  
Self Diffusion ◽  
Spin Lattice ◽  
H Nmr ◽  
Nmr Study

Abstract The reorientation of the tetrahedral complex anion ZnCl42- and the self-diffusion of the cation in (CH3NH3)2ZnCl4 were studied by 1H NMR spin-lattice relaxation time (1H T1) experiments. In the second highest-temperature phase, the temperature dependence of 1H T1 observed at 8.5 MHz could be explained by a magnetic dipolar-electric quadrupolar cross relaxation between 1H and chlorine nuclei, and the activation energy of the anion motion was determined to be 105 kJ mol -1 . In the highest-temperature phase, the activation energy of the self-diffusion of the cation was determined to be 58 kJ mol -1 from the temperature and frequency dependence of 1H T1

Pulsed-field-gradient stimulated-spin-echo NMR study of anisotropic self-diffusion in smectic Ad liquid crystal CBOOA

1993 ◽  
Vol 212 (3-4) ◽  
pp. 277-282 ◽  
Author(s):  
Seiichi Miyajima ◽  
A.F. McDowell ◽  
R.M. Cotts
Keyword(s):  
Liquid Crystal ◽  
Field Gradient ◽  
Spin Echo ◽  
Pulsed Field ◽  
Self Diffusion ◽  
Nmr Study

13C NMR Observation of Molecular Motions at the Smectic-A-Smectic-C (Smectic-C*) Transition in a Recemic (Chiral) Smectic Liquid Crystal

1990 ◽  
Vol 29 (Part 2, No. 7) ◽  
pp. L1153-L1156 ◽  
Author(s):  
Atsushi Yoshizawa ◽  
Hiroshi Kikuzaki ◽  
Toshihiro Hirai ◽  
Mamoru Yamane
Keyword(s):  
Liquid Crystal ◽  
13C Nmr ◽  
Molecular Motions ◽  
Smectic A ◽  
Smectic C ◽  
Smectic Liquid Crystal

Molecular Motions in (CH3)3XCl, X = Sn and Pb. NMR Investigations and Crystal Structure Study of (CH3)3PbCl and CH3SnBr3

1991 ◽  
Vol 46 (4) ◽  
pp. 337-343 ◽  
Author(s):  
Da Zhang ◽  
Shi-Qi Dou ◽  
Alarich Weiss
Keyword(s):  
Molecular Motion ◽  
Structure Study ◽  
Methyl Groups ◽  
Monoclinic Space Group ◽  
Molecular Motions ◽  
X Ray Diffraction ◽  
Orthorhombic Space Group ◽  
Space Group ◽  
X Ray ◽  
Group D

Abstract The molecular motion in (CH3)3XCl, X = Sn and Pb has been investigated by measurement of the second moment M2(1H) as function of temperature in the range 95 < T,/K<345. The methyl groups in both compounds rotate freely over the whole temperature range studied. In (CH3)3SnCl the C'3-rotation of (CH3)3Sn-group about the Sn CI axis sets in above 273 K. To explain the NMR and INS results, the crystal structures of (CH3)3PbCl and CH3SnBr3 were determined by single X-ray diffraction. (CH3)3PbCl crystallizes in a monoclinic space group C32-C2, a = 1276.7(3) pm, b = 982.3(3) pm, c = 547.0(2) pm, ß = 91.12(1)°; Z = 4, R = 0.035. CH3SnBr3 crystallizes in an orthorhombic space group D162h-Pnma, a = 643.0(3) pm, b= 1005.3(4) pm, c= 1148.0(4) pm; Z = 4, R =0.057

1H NMR Studies on the Cation Motions in Crystalline Cadmium Bromide Complexes [C(NH2)3]Cd2Br5, [(CH3)3NH]3Cd2Br7, and [i-C3H7NH3]CdBr3

2010 ◽  
Vol 65 (4) ◽  
pp. 499-502 ◽  
Author(s):  
Hideta Ishihara ◽  
Keizo Horiuchi ◽  
Yoshihiro Furukawa
Keyword(s):  
Activation Energy ◽  
1H Nmr ◽  
Molecular Motion ◽  
Higher Order ◽  
Methyl Groups ◽  
Nmr Studies ◽  
H Nmr ◽  
Cadmium Bromide

1H NMR T1 measurements of crystalline [C(NH2)3]Cd2Br5 showed a single minimum due to the C3 reorientation of the planar [C(NH2)3]+ ion with an activation energy (Ea) of 35.8 kJ mol−1. In [(CH3)3NH]3Cd2Br7 crystals, two T1 minima appeared which are assigned to the C3 reorientation of methyl groups in the [(CH3)3NH]+ cation with Ea = 13.0 kJ mol−1 and to the C3 reorientation of a whole cation around the molecular C3 axis with Ea = 28.9 kJ mol−1. In [i-C3H7NH3]CdBr3 crystals, a very broad T1 minimum appeared near 160 K which is assigned to the C3 reorientations of two methyl groups with Ea = 11.3 kJ mol−1 and of an NH3 group with Ea = 13.3 kJ mol−1 in the [i-C3H7NH3]+ ion, and another minimum with Ea = 23.5 kJ mol−1 near 300 K assigned to a higher order molecular motion of the cation.

The 18-crown-6.2 chloroacetonitrile complex. X-ray crystal structure and solid phase motions of guest and host as studied by variable temperature 13C CPMAS NMR spectroscopy

1992 ◽  
Vol 70 (4) ◽  
pp. 1033-1041 ◽  
Author(s):  
G. W. Buchanan ◽  
A. Rodrigue ◽  
C. Bensimon ◽  
C. I. Ratcliffe
Keyword(s):  
Activation Energy ◽  
Correlation Time ◽  
Molecular Motion ◽  
Solid Phase ◽  
Variable Temperature ◽  
13C Cpmas Nmr ◽  
X Ray ◽  
Guest Species ◽  
Motional Correlation Time ◽  
13C Cpmas Nmr Spectroscopy

The title complex has two distinct 18-crown-6 moieties of approximate D3d symmetry in the unit cell. The 45.3 MHz 13C CPMAS spectra have two regions of broadening for the crown ether carbons. At high temperatures a dipolar washout mechanism is operative, leading to broadening when molecular motion has a correlation time approximately equal to the inverse of the decoupling field. At lower temperatures broadening occurs when the motional correlation time is equal to the inverse of the chemical shift difference. The activation energy for 18-crown-6 reorientation in this solid is calculated to be ca. 48 kJ/mol. For the chloroacetonitrile, the CH2 carbon also shows dipolar washout, but at a temperature much lower than the 18-crown-6. The activation energy for reorientation for this "guest species" is ca. 42 kJ/mol.

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