The applicability of Woessner's equations for the analysis of 13C spin-lattice relaxation data

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.

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

Physical Chemistry Chemical Physics ◽

10.1039/c5cp04924e ◽

2015 ◽

Vol 17 (43) ◽

pp. 28866-28878 ◽

Cited By ~ 4

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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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

Canadian Journal of Chemistry ◽

10.1139/v80-305 ◽

1980 ◽

Vol 58 (18) ◽

pp. 1916-1922 ◽

Cited By ~ 12

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.

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