Order fluctuations in p-methoxybenzylidene p-n-butylaniline (MBBA): A proton NMR study

1976 ◽  
Vol 54 (15) ◽  
pp. 1600-1605 ◽  
Author(s):  
Ronald Y. Dong ◽  
E. Tomchuk ◽  
J. J. Visintainer ◽  
E. Bock
Keyword(s):  
Nematic Phase ◽  
Frequency Dispersion ◽  
Lattice Relaxation ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Hydrodynamic Modes ◽  
Spin Lattice ◽  
Nmr Study ◽  
Order Of Magnitude ◽  
To Come

Proton spin–lattice relaxation has been studied in the nematic phase of MBBA and MBBA-d8 samples. The proton T1 temperature dependence appears to come from the motions of side chains as in p-azoxyanisole. Order of magnitude calculations of T1 based on order fluctuations agree with the ring proton T1. The proton T1 frequency dispersion of MBBA at 18 °C can be explained by order fluctuations plus a frequency dependent B term without any cutoff in the hydrodynamic modes.

Proton NMR Study of Molecular Dynamics in Hydrazinium Perchlorate

1990 ◽  
Vol 45 (2) ◽  
pp. 102-106
Author(s):  
K. Ganesan ◽  
R. Damle ◽  
J. Ramakrishna
Keyword(s):  
Molecular Dynamics ◽  
Relaxation Time ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Temperature Minimum ◽  
Second Moment ◽  
Spin Lattice ◽  
Nmr Study

AbstractThe proton spin-lattice relaxation time T1 (at 5.4, 10 and 15 MHz) and second moment M2 (at 9.8 MHz) have been measured in hydrazinium Perchlorate (N2H5ClO4). The temperature dependence of T, shows two minima. The low temperature T, minimum has been explained in terms of NH3 reorientation about the N-N axis while the high temperature minimum is attributed to the exchange of protons within the NH2 group (180° flip about the H - N - H bisectrix). The activation energies for NH3 and NH: motions are found to be 20.5 kJ mol-1 and 39.8 kJ mol-1 , respectively. The second moment variation with temperature shows two transitions around 120 K and 210 K and has been discussed in terms of NH3/NH2 motions.

The first observed complex of 11-crown-3 ether. X-ray crystal structure and NMR study of (benzo-11-crown-3)2·LiNCS

2002 ◽  
Vol 80 (2) ◽  
pp. 148-154 ◽  
Author(s):  
G W Buchanan ◽  
M Azad ◽  
G PA Yap
Keyword(s):  
Dipolar Coupling ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Lithium Cation ◽  
Spin Lattice ◽  
Nmr Study ◽  
Effective Removal ◽  
Aliphatic Carbon

The title complex crystallizes in the monoclinic P21/c space group, with a = 7.7397(8), b = 18.287(2), c = 17.4726(19) Å, β = 94.008(2)°, and Z = 4. The coordination geometry around the lithium cation is pseudooctahedral. The effects of lithium complexation on the 1H and 13C solution NMR spectra are discussed. In the solid-state 13C NMR spectrum at 300 K, very long aliphatic proton spin lattice relaxation times are observed along with broadening of the aliphatic carbon resonances. These results are attributed to the dipolar washout phenomenon, where the presence of a low amplitude motion of the same frequency as the 1H decoupler, leads to less effective removal of the 1H–13C dipolar coupling. At 330 K, there is some sharpening of the aliphatic resonances since there is less interference between the motion and the decoupling frequency.Key words: crown ether analog, lithium complex.

NMR Study of Molecular Dynamics in a D ho Columnar Mesophase

1998 ◽  
Vol 53 (10-11) ◽  
pp. 823-827 ◽  
Author(s):  
C. Cruz ◽  
P. J. Sebastião ◽  
J. Figueirinhas ◽  
A. C. Ribeiro ◽  
H. T. Nguyen ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Lattice Relaxation ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Self Diffusion ◽  
Spin Lattice ◽  
Nmr Study ◽  
Collective Movements ◽  
Field Cycling ◽  
Nmr Techniques

Abstract In this paper we report the first molecular dynamics study combining fast field-cycling and conven-tional NMR techniques in a thermotropic liquid crystal of discotic molecules exhibiting an ordered columnar hexagonal mesophase. Using the association of these techniques we obtained proton T1 data over a very large domain of Larmor frequencies (ω/2π from 500 Hz to 85 MHz). The proton spin-lattice relaxation results were analysed considering the structure of the mesophase and the types of movements which are expected to influence significantly the relaxation rate, namely local molecu-lar rotational reorientations, inter-columnar self-diffusion and collective movements corresponding to bending and compression of the columns. We verified that these mechanisms dominate the relaxation respectively for high, medium and low Larmor frequencies.

Dispersion of proton spin-lattice relaxation in a cholesteric liquid crystal

1983 ◽  
Vol 44 (10) ◽  
pp. 1179-1184 ◽  
Author(s):  
M. Vilfan ◽  
R. Blinc ◽  
J. Dolinšek ◽  
M. Ipavec ◽  
G. Lahajnar ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Cholesteric Liquid Crystal ◽  
Lattice Relaxation ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Spin Lattice
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