Spin-lattice relaxation of deuterons and 11B nuclei in NaBD4

Niemelä, L.; Ylinen, E.E.

doi:10.1016/0375-9601(70)90988-6

Cited by 14 publications

(10 citation statements)

References 7 publications

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“…These results are consistent with the Arrhenius behavior of the jump rate −1 (T) for the reorientational motion, typical values of the activation energy being in the range of 110-210 meV. Subsequent NMR studies of the reorientational motion in alkali borohydrides [11][12][13][14][15][16] have extended the temperature and frequency ranges of the measurements and addressed the deuterium-substituted borohydrides and borohydrides of Rb and Cs. Recent studies [14,16,17] have emphasized the importance of probing the frequency dependence of R 1 , in particular, in cases when a certain distribution of the jump rates −1 can be expected.…”

Section: Reorientational Motion Of Bh 4 Groupssupporting

confidence: 73%

“…It can be seen that the strong narrowing of the 11 B NMR line occurs in the same temperature range as that of the 1 H NMR line. This suggests that a common motional process is responsible for the observed narrowing of both 1 H and 11 by Corey et al [15], such a process corresponds to translational motion of complete BH 4 units. The idea that B atoms are involved in the translational motion on the NMR time scale is supported by the observation [15,24] that the 11 B line width drops below the value expected for the B-B contribution to the 'rigid lattice' width.…”

Section: Translational Diffusion Of LI + and (Bh 4 ) − Ions In The Himentioning

confidence: 77%

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Nuclear magnetic resonance studies of atomic motion in borohydrides

Skripov

Soloninin

Babanova

2011

Journal of Alloys and Compounds

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Section: Reorientational Motion Of Bh 4 Groupssupporting

confidence: 73%

Section: Translational Diffusion Of LI + and (Bh 4 ) − Ions In The Himentioning

confidence: 77%

Nuclear magnetic resonance studies of atomic motion in borohydrides

Skripov

Soloninin

Babanova

2011

Journal of Alloys and Compounds

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“…The low frequency results suggest the presence of two components having an individual minimum value, as has been demonstrated previously. 19,24 Discontinuity in the T 1 value is observed at the phase transition between 380 and 400 K. In the HT phase, a T 1 minimum is observed at 19.65 MHz in the temperature range studied.…”

Section: Resultsmentioning

confidence: 77%

“…The tetrahedral BH 4 unit reorients very fast in the room-temperature phase of MBH 4 (M = Li, Na, K, Rb, and Cs). 8,[16][17][18][19][20][21][22]24,25,28,29 A slow hopping motion of lithium ion was suggested in the low-temperature (LT) phase of LiBH 4 . 25 Lithium ion diffuses very fast in the high-temperature (HT) phase of LiBH 4 .…”

Section: Introductionmentioning

confidence: 99%

Reorientational Motion of BH₄ Ions in Alkali Borohydrides MBH₄ (M = Li, Na, K) as Studied by Solid-State NMR

Jimura

Hayashi

2012

J. Phys. Chem. C

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Ion dynamics in alkali borohydrides, LiBH 4 , NaBH 4 , and KBH 4 , was studied by solid-state NMR. NMR spectra and spin−lattice relaxation times, T 1 , of 1 H and 11 B were measured and analyzed. The T 1 results of 1 H and 11 B indicated that two types of motions take place in the lowtemperature (LT) phase of LiBH 4 . The second moments of 1 H and 11 B NMR spectra suggested that the sum of the two types of motions resembles isotropic reorientation of the BH 4 unit. The T 1 minimum values of 1 H and 11 B supported that the C 3 rotation takes place at first. The second type of motion might be either C 3 rotation or C 2 rotation. The second moments of NMR spectra and the T 1 minimum values of 1 H and 11 B supported that the BH 4 unit reorients isotropically in NaBH 4 and KBH 4 . INTRODUCTIONBorohydrides, alanates, and amides of alkali and alkaline-earth metals have recently received much attention due to their potentials as hydrogen storage materials and energy carriers for fuel cells. 1,2 Alkali borohydrides MBH 4 consist of alkali cations M + and tetrahedral [BH 4 ] − anions. The crystal structures and dynamics of the ions have been studied for a long time by means of various techniques: X-ray and neutron diffractions, 3−9 neutron scattering, 5,7,10−13 Raman spectroscopy, 4,14,15 nuclear magnetic resonance (NMR), 8,16−29 and theoretical calculations. 7,10,13,30,31 Among the various techniques, NMR is suitable to study ion dynamics. The tetrahedral BH 4 unit reorients very fast in the room-temperature phase of MBH 4 (M = Li, Na, K, Rb, and Cs). 8,[16][17][18][19][20][21][22]24,25,28,29 A slow hopping motion of lithium ion was suggested in the low-temperature (LT) phase of LiBH 4 . 25 Lithium ion diffuses very fast in the high-temperature (HT) phase of LiBH 4 . 23,25,27 Both hydrogen and boron atoms diffuse in the HT phase of LiBH 4 , 25 although a Raman study proposed diffusion of single hydrogen atoms. 15 No H exchange was observed between BH 4 units in molten LiBH 4 . 26 In solid LiBH 4 , intact BH 4 units diffuse instead of hydrogen atoms. 26,27 The spin−lattice relaxation time, T 1 , of nuclear spins can sensitively probe a motion with a rate of the order of Larmor frequency. BH 4 reorientation has frequently been studied by means of T 1 . The plot of T 1 as a function of inverse temperature (1/T) shows a V-shaped curve when the relaxation mechanism is originated from a single mode of motion. Analysis of the temperature dependence of T 1 produces the rate and the mode of motions. The rate of BH 4 reorientation was almost established for MBH 4 (M = Li, Na, K, Rb, and Cs). 8,24,28,29 The minimum values of T 1 as well as the line shapes are closely related with the crystal structure and the

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“…Solid‐state 11 B and 10 B MAS NMR spectra of ( 1 ) and ( 8a ) were also compared in order to illustrate experimentally the effect of C Q on the S/N. Sodium‐borohydride represents an example for highly symmetric boron environment because of its very small quadrupolar coupling constant ( C Q < 7 kHz) according to literature data. In this case, both 11 B and 10 B MAS NMR spectra (Figs (c,d)) were readily observed.…”

Section: Resultsmentioning

confidence: 99%

Background‐free solution boron NMR spectroscopy

Király

2012

Magnetic Reson in Chemistry

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The appearance of background signals arising from the NMR probe and tube is a well-known problem of boron NMR spectroscopy. Background suppression may be achieved by using DEPTH, which increases the signal-to-background (S/B) ratio. Although, the quality of such spectra is often adequate, but in the case of rapid relaxation broadened resonances (T(1) < 1 ms), the residual background signals may still hamper the interpretation of the spectra. It was observed that the background signals are practically invisible in solution (10) B NMR. The unusual isotopic effect on the (S/B) ratio was interpreted as an inherent consequence of the integer versus half-integer spin of (10) B and (11) B, respectively. The practicability of (10/11) B NMR was compared for a selected set of boron compounds covering the typical range of (S/B) ratio. The application of (11) B is more favourable than (10) B as long as it is possible to achieve the desired spectral quality by using DEPTH. Otherwise, the 'background-free' appearance of (10) B NMR spectra makes (10) B a reasonable alternative of (11) B DEPTH. This was found typical for compounds having relaxation broadened resonances. The variable temperature (VT) NMR study of an adduct formation process was also presented here as an example of the advantage of (10) B over (11) B.

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Spin-lattice relaxation of deuterons and 11B nuclei in NaBD4

Cited by 14 publications

References 7 publications

Nuclear magnetic resonance studies of atomic motion in borohydrides

Nuclear magnetic resonance studies of atomic motion in borohydrides

Reorientational Motion of BH₄ Ions in Alkali Borohydrides MBH₄ (M = Li, Na, K) as Studied by Solid-State NMR

Background‐free solution boron NMR spectroscopy

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Spin-lattice relaxation of deuterons and 11B nuclei in NaBD4

Cited by 14 publications

References 7 publications

Nuclear magnetic resonance studies of atomic motion in borohydrides

Nuclear magnetic resonance studies of atomic motion in borohydrides

Reorientational Motion of BH4 Ions in Alkali Borohydrides MBH4 (M = Li, Na, K) as Studied by Solid-State NMR

Background‐free solution boron NMR spectroscopy

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Reorientational Motion of BH₄ Ions in Alkali Borohydrides MBH₄ (M = Li, Na, K) as Studied by Solid-State NMR