Proton NMR Relaxation in Six-Coordinate Low-Spin Iron(III) Tetraphenylporphyrinates:  Temperature Dependence of Proton Relaxation Rates and Interpretation of NOESY Experiments

1997 ◽  
Vol 101 (49) ◽  
pp. 9207-9216 ◽  
Author(s):  
Konstantin I. Momot ◽  
F. Ann Walker
Keyword(s):  
Temperature Dependence ◽  
Proton Nmr ◽  
Nmr Relaxation ◽  
Proton Relaxation ◽  
Relaxation Rates

Molecular Reorientation of Methanol in Mixtures with Carbon Tetrachloride

1992 ◽  
Vol 47 (7-8) ◽  
pp. 857-864 ◽  
Author(s):  
M. D. Zeidler ◽  
D. S. Gill ◽  
M. D. Zeidler
Keyword(s):  
Carbon Tetrachloride ◽  
Composition Dependence ◽  
Nmr Relaxation ◽  
Dipolar Interaction ◽  
Coupling Constants ◽  
Proton Relaxation ◽  
Relaxation Rates ◽  
Molecular Reorientation ◽  
Quadrupole Coupling ◽  
Interaction Contribution

Abstract Proton and oxygen-17 nmr relaxation rates of CD317OH as well as deuteron nmr relaxation rates of CH3OD were measured in mixtures with carbon tetrachloride at different compositions and temperatures. By varying the 170-content different contributions to the proton relaxation rate could be separated and from the 17O-H dipolar interaction contribution the correlation time τ2OH of the OH bond was determined. Using these correlation times the composition dependence of the deuterium and oxygen-17 quadrupole coupling constants of methanol was derived. A strong variation of the coupling constants over the measured composition range is evident

Molecular Reorientation in Liquid Methanol

1991 ◽  
Vol 46 (1-2) ◽  
pp. 89-94 ◽  
Author(s):  
R. Ludwig ◽  
D. S. Gill ◽  
M. D. Zeidler
Keyword(s):  
Nmr Relaxation ◽  
Quadrupole Coupling Constant ◽  
Dipolar Interaction ◽  
Proton Relaxation ◽  
Coupling Constant ◽  
Relaxation Rates ◽  
Molecular Reorientation ◽  
Quadrupole Coupling ◽  
Relaxation Measurements ◽  
Recent Computer

AbstractOxygen-17 enriched methanol CD317OH was synthesized and 1H as well as 17O nmr relaxation rates were measured in the temperature range 180-310 K. By varying the 17O-content different contributions to the proton relaxation rate could be separated and from the 17O-H dipolar interaction contribution the correlation time of the OH bond was determined. These results are compared to recent computer simulation data. Additional deuteron relaxation measurements on CH3OD yielded the quadrupole coupling constant which increases with falling temperature. The 17O quadrupole coupling constant shows a similar trend with temperature but not as pronounced.

Proton NMR Relaxation Study of Molecular Motions in a Liquid Crystal with a Strong Polar Terminal Group

1993 ◽  
Vol 48 (8-9) ◽  
pp. 851-860 ◽  
Author(s):  
P. J. Sebastião ◽  
A. C. Ribeiro ◽  
H. T. Nguyen ◽  
F. Noack
Keyword(s):  
Theoretical Calculations ◽  
Proton Nmr ◽  
Nmr Relaxation ◽  
Larmor Frequency ◽  
Terminal Group ◽  
Relaxation Dispersion ◽  
Proton Relaxation ◽  
Self Diffusion ◽  
Smectic A ◽  
Field Cycling

Abstract Liquid crystalline compounds containing a cyano terminal group often exhibit peculiar molecular organizations of their mesophases. In this work we present proton NMR relaxation studies, performed by means of standard NMR and fast field-cycling NMR techniques, in the nematic (N) and bilayered smectic-A phase (SA2) of 4-pentyl-phenyl 4'-cyanobenzoyloxy-benzoate. The field-cycling measurements were used to clarify the relaxation behaviour in the low Larmor frequency range, where conventional techniques are not applicable. Self-diffusion and rotational reorientations are found to be the essential relaxation mechanisms at MHz frequencies in the smectic mesophase, while the contribution of collective modes appears only at lower frequencies in the kHz range. In the nematic mesophase the order director fluctuations mechanism dominates the relaxation dispersion up to 10 MHz, where the rotational reorientations become important, with minor corrections from the self-diffusion process. The agreement between the experimental findings and model fits could be improved by an additional relaxation mechanism in the kHz regime, ascribed to the interaction between protons and fast relaxing quadrupolar nitrogen 14N nuclei. Though all four processes are present in the nematic and smectic-A2 phases, the overall T1 frequency dependence is quite different in the two cases. This behaviour is discussed in terms of available theoretical calculations of the proton relaxation dispersion in liquid crystals, and it is also compared with data known from other cyano compounds.

scholarly journals Conductivity and Magnetic Properties of the Charge-Transfer Complex from N,N'-Dicyanonaphthoquinonedimimine (DCNNI)and Tetrathiafulvalene (TTF)

1989 ◽  
Vol 44 (9) ◽  
pp. 825-832 ◽  
Author(s):  
H.-P. Werner ◽  
W. Grauf ◽  
J. U. von Schütz ◽  
H. C. Wolf ◽  
H. W. Helberg ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Charge Transfer ◽  
Physical Properties ◽  
Temperature Dependence ◽  
Charge Transfer Complex ◽  
Organic Conductors ◽  
Proton Relaxation ◽  
Relaxation Rates ◽  
Temperature Range ◽  
Donor And Acceptor

Abstract Conductivity (dc and ac), ESR-properties and proton relaxation rates of the charge transfer complex Tetrathiafulvalene N,N′-dicyanonaphthoquinonediimine in the temperature range be­ tween 300 K and 3.8 K are reported. This salt belongs to the unusual group of organic conductors, in which segregated donor and acceptor stacks are associated in a pairwise manner. The physical properties, which are compared with TTF-TCNQ, give evidence of non-stoichiometric charge transfer (ρ ≠ 1). A metal like state can be identified for T> 70 K, as is seen from the weak temper­ ature dependence of the conductivity (σrt ≈ 30 Scm-1) and the susceptibility (Xrt ≈ 7.5 ⋅ 10-4 emu/ mole) and from the Korringa like temperature dependence of the proton relaxation rates. The drop of the susceptibility at Tc ≈ 70 K and the activated temperature dependence of the conductivity for T < 70 K are explained by a metal-to-semiconductor transition.

Protonenspinrelaxation von Benzol an Silikageloberflächen

1968 ◽  
Vol 23 (3) ◽  
pp. 339-347
Author(s):  
D. Michel
Keyword(s):  
Temperature Dependence ◽  
Magnetic Relaxation ◽  
Spin Echo ◽  
Relaxation Times ◽  
Proton Relaxation ◽  
Relaxation Rates ◽  
Proton Proton ◽  
Proton Interaction ◽  
Paramagnetic Impurities ◽  
Hydroxyl Protons

Using spin-echo-techniques the temperature dependence of the proton magnetic relaxation times T1 and T2 of adsorbed benzene has been measured in the interval between +70 °C and —140 °C. Normal benzene C6H6 and mixtures of benzene and C6D6e were adsorbed on two sorts of silicagels which have been described elsewhere 4,9.The effective nuclear magnetic relaxation rates of adsorbed benzene are given by four contributions: the intramolecular proton-proton interaction, the interaction between benzene protons and paramagnetic impurities of the adsorbents, the interaction between benzene protons and hydroxyl protons on the silicagel surface, and the intermolecular interaction between benzene protons. These proton relaxation mechanisms depend differently on the H/D-ratio in C6H6—C6D6 mixtures (see section 4.1).The temperature dependence of the contributions 1/T1 intra and 1/T2 intra due to intramolecular proton-proton interaction suggests an anisotropic rotation of benzene molecules on the gel used. Furthermore, the existence of three different regions for the adsorbed benzene molecules has been inferred (see sections 4.2 and 5).

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