An experimental evaluation of nonselective proton spin–lattice relaxation rates: analyses of data for the eight isomeric 2,3,4-tri-O-acetyl-1,6-anhydro-β-D-hexopyranoses

1980 ◽  
Vol 58 (18) ◽  
pp. 1916-1922 ◽  
Author(s):  
Klaus Bock ◽  
Laurance D. Hall ◽  
Christian Pedersen
Keyword(s):  
Lattice Relaxation ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Proton Relaxation ◽  
Relaxation Rates ◽  
Pyranose Ring ◽  
Solvent Concentration ◽  
Relaxation Data ◽  
Spin Lattice ◽  
Single Set

The nonselective spin–lattice relaxation rates (R1-values) have been determined for all of the ring protons of the eight isomers of 2,3,4-tri-O-acetyl-1,6-anhydro-(β-D-hexopyranose as 0.1 molar solutions in benzene-d6. The effects on the proton R1-values of changes in solvent, concentration, temperature, and proton impurities are documented and 13C R1-values are given to show that the first two sets of variations are due to changes in motional correlation times of the molecules. The proton relaxation data can be fitted by regressional analyses to a single set of interproton relaxation contributions, the numerical values of which accord with a 1C4 conformation for the pyranose ring somewhat distorted by the 1,6-anhydro bridge.

Proton Relaxation in Various Copper (II) Complexes and Determination of the Singlet-Triplet Separation

1980 ◽  
Vol 35 (1) ◽  
pp. 92-97 ◽  
Author(s):  
H. D. Jannek ◽  
W. Midler-Warmuth
Keyword(s):  
Copper Complexes ◽  
Lattice Relaxation ◽  
Magnetic Behaviour ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Proton Relaxation ◽  
Relaxation Rates ◽  
Temperature Dependent ◽  
Spin Lattice

Abstract Proton spin-lattice relaxation rates have been measured at 30 MHz as a function of temperature for a large number of dimeric copper complexes with the ligands 8-hydroxyquinoline, pyridine-N-oxide, methyl and dimethyl pyridine-N-oxide, and quinoline-N-oxide. Two carboxylates and adducts of several complexes with various solvents have also been studied. In contrast to some compounds with a normal magnetic behaviour, for most complexes a temperature dependent relaxation has been observed which agrees well with the concept of a weak antiferromagnetic interaction between the two Cu2+ ions. The singlet-triplet separations or exchange integrals have been determined.

Conformation and dynamics in solution of an N-quaternarized benzophenone derivative: a molecule active as UV filter

1991 ◽  
Vol 69 (6) ◽  
pp. 913-918 ◽  
Author(s):  
Cecilia Anselmi ◽  
Marisanna Centini ◽  
Mirella Scotton ◽  
Alessandro Sega
Keyword(s):  
Alkyl Chain ◽  
Lattice Relaxation ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Proton Relaxation ◽  
Relaxation Rates ◽  
Uv Filter ◽  
Spin Lattice ◽  
Nuclear Overhauser Enhancement ◽  
Nuclear Overhauser

The dynamics and conformation of N,N-dimethyl-N-|3-(benzoyl-4-phenoxy)|-N-n-dodecylammonium bromide, 1, have been established in two solvents (CDCl3 and DMSO-d6) by the use of 13C spin-lattice relaxation rates, non-selective and selective proton spin-lattice relaxation rates, and 1H–{1H} nuclear Overhauser enhancement (nOe) experiments. The data obtained are consistent with two main mean conformations for compound 1: a "linear" conformation in CDCl3 and a folded conformation in DMSO-d6 where the alkyl chain forms a loop toward the aromatic moiety. Key words: UV filter, carbon and proton relaxation rates, nuclear Overhauser enhancement experiments, solvent dependent conformations.

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.

An experimental evaluation of simplified procedures for determining the proton spin–lattice relaxation rates of natural products

1980 ◽  
Vol 58 (19) ◽  
pp. 2016-2023 ◽  
Author(s):  
Lawrence D. Colebrook ◽  
Laurance D. Hall
Keyword(s):  
Natural Products ◽  
Lattice Relaxation ◽  
Null Point ◽  
Proton Spin ◽  
Computational Method ◽  
Spin Lattice Relaxation ◽  
Relaxation Rates ◽  
Spin Lattice ◽  
Simplified Procedures

A general discussion is given of the determination of the proton spin–lattice relaxation rates of natural products, with particular emphasis on use of the null-point method which, for the systems studied here, gives identical results with those obtained via the conventional (and relatively time consuming) computational method.

scholarly journals NMR Spin-Lattice Relaxation and Tunnelling of Partially Deuterated Methyl Groups

1991 ◽  
Vol 46 (12) ◽  
pp. 1123-1130 ◽  
Author(s):  
H. Langen ◽  
W. Müller-Warmuth
Keyword(s):  
Lattice Relaxation ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Spin States ◽  
Relaxation Rates ◽  
Spin Lattice ◽  
Conversion Rates ◽  
Temperature Relaxation ◽  
Field Cycling ◽  
Additional Influence

Abstract Proton spin lattice relaxation rates have been measured at 15 and 30 MHz and down to 5 K for the partially deuterated molecular crystals 4-F-toluene, 4-Cl-toluene, and 2,6-Cl2-toluene. The behaviour of these materials is governed by methyl group tunnelling. As compared with the undeuterated compounds, the low temperature relaxation is enhanced and the details depend on the removal of the symmetry coupling between rotator and spin states. The hindering barriers remain unchanged, the A to E conversion rates are faster, and relaxation is dominated by spectral density contributions J(2ωo) and J(2ω0). In one case an additional influence of level-crossing energy transfer on relaxation is observed. Field-cycling spectroscopy reveals steps rather than peaks if the proton spin Zeeman and tunnelling splittings match

scholarly journals A quantum mechanical alternative to the Arrhenius equation in the interpretation of proton spin–lattice relaxation data for the methyl groups in solids

2015 ◽  
Vol 17 (43) ◽  
pp. 28866-28878 ◽  
Author(s):  
Piotr Bernatowicz ◽  
Aleksander Shkurenko ◽  
Agnieszka Osior ◽  
Bohdan Kamieński ◽  
Sławomir Szymański
Keyword(s):  
Nmr Spectroscopy ◽  
Arrhenius Equation ◽  
Lattice Relaxation ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Quantum Mechanical ◽  
Methyl Groups ◽  
Relaxation Data ◽  
Spin Lattice ◽  
Nuclear Spin Lattice Relaxation

The issue of nuclear spin–lattice relaxation in methyl groups in solids has been a recurring problem in NMR spectroscopy.

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