Motional behavior of "asperlin" in solution. A 13C spin-lattice relaxation study

1986 ◽  
Vol 64 (3) ◽  
pp. 560-565 ◽  
Author(s):  
Photis Dais ◽  
George Fainos
Keyword(s):  
Lattice Relaxation ◽  
Structural Features ◽  
Spin Lattice Relaxation ◽  
Single Type ◽  
Relaxation Data ◽  
Pyrone Ring ◽  
Spin Lattice ◽  
Internal Motions ◽  
Resonance Spin ◽  
Motional Behavior

l3C nuclear magnetic resonance spin-lattice relaxation times (T1) have been used to probe the motional behavior of 5-acetoxy-5,6-dihydro-6-(1,2-epoxypropyl)-2-pyrone ("asperlin") in dimethyl sulfoxide solution. This molecule offers structural features suited to a study of internal motions, i.e., epoxypropyl and methyl internal motions superimposed on an anisotropic overall reorientation. The rigidity of the pyrone ring and its semiplanar conformation result in an overall ellipsoidal shape, and hence the rotational dynamics of asperlin are adequately approximated by the diffusion of a prolate ellipsoid with the major axis passing through the C(2)—H(2) bond. The description of the internal motion of the epoxypropyl ring is strongly model dependent. Furthermore, the relaxation data for the oxirane ring carbons do not uniquely define a dynamic model. Due to similarities in the activation energies of the overall and internal motions, based on temperature-dependent measurements, it has not been feasible to interpret the relaxation data by a single type of motion. Internal rotation of the epoxymethyl substituent is rationalized by applying the stochastic diffusion model of multiple internal rotations

Motional behavior of 2,3:5,6-di-O-isopropylidene-α-D-mannofuranose in solution. A 13C spin-lattice relaxation study

1983 ◽  
Vol 61 (7) ◽  
pp. 1542-1548 ◽  
Author(s):  
Photis Dais ◽  
Arthur S. Perlin
Keyword(s):  
Temperature Dependence ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Structural Features ◽  
Spin Lattice Relaxation ◽  
Hindered Rotation ◽  
Spin Lattice ◽  
Resonance Spin ◽  
Diffusional Model ◽  
Motional Behavior

13C nuclear magnetic resonance spin-lattice relaxation times (T1) have been used to probe the motional behavior of 2,3:5,6-di-O-isopropylidene-α-D-mannofuranose (1) in dimethyl sulfoxide solution. This system offers structural features well suited to the study of a variety of internal motions, i.e., ring oscillation, ring puckering interconversion, and methyl internal rotation, all of which are superimposed on an isotropic overall reorientation. Among various models examined to evaluate internal rotations, a two-sites jump model was found satisfactory for interpreting the oscillation and puckering motions of the flexible 5,6-O-isopropylidene ring, whereas a diffusional model described hindered rotation of the geminal methyl groups of the rigid 2,3-O-isopropylidene ring from 15° to 80 °C. The activation energy associated with the temperature dependence of the rate of overall molecular tumbling was found to agree with the hydrodynamical prediction of 4.57 kcal/mol associated with the temperature dependence of the ratio (η/T). In addition, an explicit treatment of the relaxation data vs. solution viscosities, as a function of temperature, indicated that 1 reorients under the "slip" boundary conditions.

NMR studies of alkali intercalted carbon nanotubes

2003 ◽  
Vol 772 ◽  
Author(s):  
M. Schmid ◽  
C. Goze-Bac ◽  
M. Mehring ◽  
S. Roth ◽  
P. Bernier
Keyword(s):  
Carbon Nanotubes ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Energy Storage Devices ◽  
Nmr Studies ◽  
Storage Devices ◽  
Spin Lattice ◽  
Relaxation Measurements ◽  
Resonance Spin ◽  
Walled Carbon Nanotubes

AbstractLithium intercalted carbon nanotubes have attracted considerable interest as perspective components for energy storage devices. We performed 13C Nuclear Magnetic Resonance spin lattice relaxation measurements in a temperature range from 4 K up to 300 on alkali intercalated Single Walled Carbon Nanotubes in order to investigate the modifications of the electronic properties. The density of states at the Fermi level were determined for pristine, lithium and cesium intercalated carbon nanotubes and are discussed in terms of intercalation and charge transfer effects.

Anion reorientations and cation diffusion in a carbon-substituted sodium nido-borate Na-7,9-C2B9H12: 1H and 23Na NMR studies

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Alexander V. Skripov ◽  
Olga A. Babanova ◽  
Roman V. Skoryunov ◽  
Alexei V. Soloninin ◽  
Terrence J. Udovic
Keyword(s):  
Lattice Relaxation ◽  
Activation Energies ◽  
Spin Lattice Relaxation ◽  
Relaxation Rates ◽  
Cation Diffusion ◽  
Relaxation Data ◽  
Nmr Studies ◽  
Spin Lattice ◽  
Jump Rate ◽  
Disordered Phase

Abstract Polyhydroborate-based salts of lithium and sodium have attracted much recent interest as promising solid-state electrolytes for energy-related applications. A member of this family, sodium dicarba-nido-undecahydroborate Na-7,9-C2B9H12 exhibits superionic conductivity above its order-disorder phase transition temperature, ∼360 K. To investigate the dynamics of the anions and cations in this compound at the microscopic level, we have measured the 1H and 23Na nuclear magnetic resonance (NMR) spectra and spin-lattice relaxation rates over the temperature range of 148–384 K. It has been found that the transition from the low-T ordered to the high-T disordered phase is accompanied by an abrupt, several-orders-of-magnitude acceleration of both the reorientational jump rate of the complex anions and the diffusive jump rate of Na+ cations. These results support the idea that reorientations of large [C2B9H12]− anions can facilitate cation diffusion and, thus, the ionic conductivity. The apparent activation energies for anion reorientations obtained from the 1H spin-lattice relaxation data are 314 meV for the ordered phase and 272 meV for the disordered phase. The activation energies for Na+ diffusive jumps derived from the 23Na spin-lattice relaxation data are 350 and 268 meV for the ordered and disordered phases, respectively.

Nuclear magnetic resonance spin–lattice relaxation and the rotation of adamantane and hexamethylenetetramine in solution

1977 ◽  
Vol 55 (13) ◽  
pp. 2564-2569 ◽  
Author(s):  
Roderick E. Wasylishen ◽  
Brian A. Pettitt
Keyword(s):  
Variable Temperature ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Hard Sphere Model ◽  
Correlation Times ◽  
Spin Lattice ◽  
H Nmr ◽  
Large Step ◽  
Resonance Spin

Deuterium nmr spin–lattice relaxation times have been measured for dilute solutions of adamantane-d16 in CH2I2, CHBr3, CCl4, CHCl3, and CH2Cl2. The reorientation correlation times, τ2, calculated from the experimental data are used to calculate τJ, the angular momentum correlation times, assuming both the J-diffusion and Hubbard relations. The derived τJ values suggest that adamantane executes small step diffusion in CH2I2 and CHBr3, and large step diffusion in CCl4, CHCl3, and CH2Cl2. The calculated τJ values do not appear to be related to the mean times between collisions calculated using a hard sphere model. Both variable solvent and variable temperature experiments indicate 1 ps/cP for the viscosity dependence of the adamantane reorientation time, about 1/36th the value predicted using the familiar Stokes–Einstein equation.Carbon-13 and 1H nmr T1 data indicate that reorientation of hexamethylenetetramine in H2O (28 ps/cP), CHCl3 (27 ps/cP), and CHBr3 (18 ps/cP) is severely hindered because of inter-molecular hydrogen bonding.

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