Coupled Nuclear Spin Relaxation and Internal Rotations in Magnesium Fluosilicate Hexahydrate

Utton, D.B.; Tsang, Tung

doi:10.1063/1.1676834

Cited by 5 publications

(2 citation statements)

References 9 publications

(7 reference statements)

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“…Figure 6 shows the temperature dependences of 'H and 19 F T\. At low temperatures, T\ may be determined by the reorientation of [SiF 6 ] 2~ [10]. Above ca.…”

Section: H 19 F T\ In[mg(d 0) 6 ][Sif 6 ]mentioning

confidence: 98%

“…The modulated structure in phase II has been studied by use of ESR spectroscopy, and a drastic change in the modulation amplitude at 343 K has been reported [2][3][4], Although the investigations have been performed with the diffraction methods, a detailed analysis of the modulated structure in the incommensurate phase has not been done [5][6][7][8]. These phase transitions can be considered to be related to the motions of H 2 0, [Mg(H 2 0) 6 [2,9,10]. Because of the cross relaxation between 1 H and l9 F, information about the motion of H 2 0 has not been obtained from 1 H NMR.…”

Section: Introductionmentioning

confidence: 99%

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Studies of Successive Phase Transitions and Molecular Motions in [Mg(H₂O)₆][SiF₆] by ^1,2H and ¹⁹F NMR

Kimura

Fukase

Mizuno

et al. 1998

Zeitschrift Für Naturforschung A

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The successive phase transitions of [Mg(H?0)6][SiF6] were studied by measuring 2 H NMR spectra. The quadrupole coupling constant e 2 Qq/h and asymmetry parameter 77 changed drastically at each transition temperature. 12 H and 19 F NMR T\ were measured for this compound to study the relation between the molecular motions and the successive phase transitions. The activation energy E a and the pre-exponential factor TO for the reorientation of [SiFö] 2~ were estimated as 28 kJmol" 1 and 6.0x 10~1 4 s, and those of the 180° flip of H 2 0 as 33 kJmol -1 and 4.0x 10" 14 s. These two motions occur rapidly even in phase V. For the reorientation of [Mg(H20)6] 2+ , E a = 62 kJmol -1 and TO = 1.1 x 10 -16 s were obtained from the simulation of : H NMR spectra. The jump rate of this motion is of the order of 10 4 -10 6 s _I in phase II. These results suggest that the successive phase transitions are closely related to the motion of [Mg(H 2 0) 6 ] 2+ .

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“…Figure 6 shows the temperature dependences of 'H and 19 F T\. At low temperatures, T\ may be determined by the reorientation of [SiF 6 ] 2~ [10]. Above ca.…”

Section: H 19 F T\ In[mg(d 0) 6 ][Sif 6 ]mentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Studies of Successive Phase Transitions and Molecular Motions in [Mg(H₂O)₆][SiF₆] by ^1,2H and ¹⁹F NMR

Kimura

Fukase

Mizuno

et al. 1998

Zeitschrift Für Naturforschung A

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¹H and ¹⁹F Nuclear Spin‐Lattice Relaxation in Solid [X(CH₃)₄]₂SiF₆, X = N, P, As and Sb

Rager

Weiß

1978

Ber Bunsenges Phys Chem

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535Festkiirper / Magnetische Kernresonanz / Phasenumwandlungen / Ramanspektren / Rotation The~pin-Iattice relaxation times T 1 (1 H) and Ttl [9F) in the solid compounds [X(CH3)4]2SiF6' X = N, P, As, and Sb, were studied in the temperature range 125 K~T~460 K at a NMR frequency of 34 MHz. In the low temperature region protons and fluorine nuclei are coupled by dipole-dipole interactions and both spin systems relax mainly through the motions of the methyl groups. The activation energy of the methyl group reorientation, v", decreases with increasing size of the cation. With increasing temperature both T 1 ([ H) and T 1 ( 19 F) are influenced by the reorientation of the cations as a whole. The activation energy v,,1 of the reorientation of [X(CH 3)4] + was determined. From the linewidths of the free induction decays it is concluded that the dynamical behavior of the compounds is mainly determined by the size of the cations. The influence of the anion on T 1 is small causing a slight increase of the activation energy Va compared to v" in [X(CH 3)4]I. From the Raman spectrum of [N(CH3)4]2SiF6 a 90°reorientation mechanism of the cation seems most probable.Die Spin-Gitter-Relaxationszeiten der Protonen und Fluorkerne in den Verbindungen [X(CH3)4]2SiF6' X = N, P, As, Sb, wurden im Bereich 125 K~T~460 K bei 34 MHz studiert. Bei tiefen Temperaturen sind die Protonen und die Fluorkerne durch Dipol-Dipol-Wechselwirkungen gekoppelt und beide Spinsysteme relaxieren hauptsachlich durch die Bewegungen der Methylgruppen. Die Aktivierungsenergie der Methylgruppen-Reorientierung nimmt mit grolser werdendem Kation abo Mit steigender Temperatur bestimmt die Reorientierung des Kations zusatzlich die Spin-Gitter-Relaxation sowohl des Protonen-als auch des Fluorspinsystems. Die Aktivierungsenergie fiir die Reorientierung der Kationen wurde bestimmt. Sie ist nicht eindeutig von der Grofse und Art des Kations abhangig, Messungen der Linienbreite des freien Induktionsabfalles als Funktion der Temperatur bestatigen, daB die dynamischen Vorgange in diesen Verbindungen in erster Linie mit der GroBe des Kations gekoppelt sind. Der EinfluB des Anions auf die Spin-Gitter-Relaxation ist gering und besteht hauptsachlich in einer geringfiigigen Erhohung der Aktivierungsenergie der Methylgruppen-Reorientierung im Vergleich zu den entsprechenden Ergebnissen in den Verbindungen [X(CH 3)4]I. Die Raman-Spektren zeigen ebenfalls eine starke Anhangigkeit von der Art des Kations. Fiir [N(CH 3)4LSiF 6 ist aufgrund des Raman-Spektrums eine 90 0 -R e o r i e n t i e r u n g des Kations wahrscheinlich. Results a 90°t -90°pulse sequence with a Bruker BKR 322 s pulse spectrometer. Temperatures in the range 125 K s T~490 K have been reached at the site of the probes by means of a gas flow cryostat. The temperature was measured at the sample site with an accuracy of ± 1 K with the aid of a thermo couple. Furthermore, the free induction decay (FID) was studied. Additionally, Raman measurements were performed at room temperature with a Coderg Laser Raman spectromete...

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NMR investigation of certain hydrated fluorosilicates

Muthukrishnan

Ramakrishna

1973

The Journal of Chemical Physics

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Proton and fluorine NMR were investigated in the temperature range 90–425 °K in the hexahydrated fluorosilicates of Zn, Cu, Mn, Co, and Ni and in the tetrahydrated CuSiF6 to obtain information about the internal motions in these solids. Second moment transitions were observed at widely different temperatures for the different substances, and these are ascribed to the onset of reorientation of the M(H2O)62+ and SiF62− octahedra. The correlation frequency and the potential barrier hindering the motion were calculated in all the cases. Apart from the narrowing taking place at higher temperatures, the Co salt showed a change in the line structure at 248 °K, where a phase transition was reported from magnetic susceptibility measurements. Studies on the single crystals of ZnSiF6 · 6H2O and NiSiF6 · 6H2O showed that there are three nonequivalent p-p vectors, and after the transition they all become equivalent, with the M(H2O)62+ octahedron reorienting about the fourfold axes.

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Coupled Nuclear Spin Relaxation and Internal Rotations in Magnesium Fluosilicate Hexahydrate

Cited by 5 publications

References 9 publications

Studies of Successive Phase Transitions and Molecular Motions in [Mg(H₂O)₆][SiF₆] by ^1,2H and ¹⁹F NMR

Studies of Successive Phase Transitions and Molecular Motions in [Mg(H₂O)₆][SiF₆] by ^1,2H and ¹⁹F NMR

¹H and ¹⁹F Nuclear Spin‐Lattice Relaxation in Solid [X(CH₃)₄]₂SiF₆, X = N, P, As and Sb

NMR investigation of certain hydrated fluorosilicates

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Coupled Nuclear Spin Relaxation and Internal Rotations in Magnesium Fluosilicate Hexahydrate

Cited by 5 publications

References 9 publications

Studies of Successive Phase Transitions and Molecular Motions in [Mg(H2O)6][SiF6] by 1,2H and 19F NMR

Studies of Successive Phase Transitions and Molecular Motions in [Mg(H2O)6][SiF6] by 1,2H and 19F NMR

1H and 19F Nuclear Spin‐Lattice Relaxation in Solid [X(CH3)4]2SiF6, X = N, P, As and Sb

NMR investigation of certain hydrated fluorosilicates

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Studies of Successive Phase Transitions and Molecular Motions in [Mg(H₂O)₆][SiF₆] by ^1,2H and ¹⁹F NMR

Studies of Successive Phase Transitions and Molecular Motions in [Mg(H₂O)₆][SiF₆] by ^1,2H and ¹⁹F NMR

¹H and ¹⁹F Nuclear Spin‐Lattice Relaxation in Solid [X(CH₃)₄]₂SiF₆, X = N, P, As and Sb