Molecular Motion in Solid Tetrabutylammonium Tetrafluoroborate

1991 ◽  
Vol 46 (6) ◽  
pp. 545-550 ◽  
Author(s):  
B. Szafranska ◽  
A. Kozak ◽  
Z. Pająk
Keyword(s):  
Relaxation Times ◽  
Activation Parameters ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Fluorine Nmr ◽  
Spin Lattice ◽  
Relaxation Effects ◽  
Second Moments ◽  
Wide Range ◽  
Tetrabutylammonium Tetrafluoroborate

Abstract Proton and fluorine NMR second moments and spin-lattice relaxation times for polycrystalline tetrabutylammonium tetrafluoroborate have been measured over a wide range of temperatures at several Larmor frequencies. An analysis of cross-relaxation effects results in a determination of activation parameters for anion and cation reorientations. Three solid phases characterized by different ion dynamics are evidence

Molecular Motion in Solid Tetraethyl -and Tetrapropylammonium Tetrafluoroborates

1995 ◽  
Vol 50 (6) ◽  
pp. 584-588 ◽  
Author(s):  
Barbara Szafrańska ◽  
Zdzisław Pająk
Keyword(s):  
Molecular Motion ◽  
Solid Phase ◽  
Complex Cation ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Fluorine Nmr ◽  
Spin Lattice ◽  
Second Moments ◽  
Wide Range

Abstract Proton and fluorine NMR second moments and spin-lattice relaxation times for polycrystalline tetraethyl-and tetrapropylammonium tetrafluoroborates have been measured over a wide range of temperatures. Solid-solid phase transitions were found for both compounds and confirmed by DSC. Methyl group C3 reorientation followed by more complex cation motions was evidenced in the low temperature phases. Overall cation reorientation characterises the high temperature phases of both compounds. Isotropic anion reorientation was found in both salts in both phases.

1H and 19F NMR Study of Cation and Anion Motions in Guanidinium Fluoroantimonates

1995 ◽  
Vol 50 (8) ◽  
pp. 742-748 ◽  
Author(s):  
M. Grottel ◽  
A. Kozak ◽  
Z. Pająk
Keyword(s):  
Solid Phase ◽  
Relaxation Times ◽  
Activation Parameters ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Temperature Phase ◽  
Fluorine Nmr ◽  
Spin Lattice ◽  
Nmr Study ◽  
Guanidinium Cation

Abstract Proton and fluorine NMR linewidths, second moments, and spin-lattice relaxation times of polycrystalline [C(NH2)3]2SbF5 and C(NH2)3SbF6 were studied in a wide temperature range. For the pentafluoroantimonate, C3-reorientation of the guanidinium cation and C4-reorientation of the SbF5 anion were revealed and their activation parameters determined. The dynamical inequivalence of the two guanidinium cations was evidenced. For the hexafluoroantimonate, two solid-solid phase transitions were found. In the low temperature phase the guanidinium cation undergoes C3 reorien­ tation while the SbF6 anion reorients isotropically. The respective activation parameters were derived. At high temperatures new ionic plastic phases were evidenced.

1H and 19 F NMR Study of Cation and Anion Motions in Guanidinium Hexafluorozirconate

1996 ◽  
Vol 51 (9) ◽  
pp. 991-996 ◽  
Author(s):  
M. Grottel ◽  
A. Kozak ◽  
Z. Pająk
Keyword(s):  
Solid Phase ◽  
Relaxation Times ◽  
High Mobility ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Fluorine Nmr ◽  
Spin Lattice ◽  
Nmr Study ◽  
Wide Range ◽  
Deuterated Analogue

Abstract Proton and fluorine NMR second moments and spin-lattice relaxation times of polycrystalline guanidinium hexafluorozirconate and its deuterated analogue were studied in laboratory (60 MHz) and rotating (H1 = 20 G) frames over a wide range of temperature. An analysis of the experimental results enabled us to reveal a dynamical inequivalence of two crystallographically independent cations and an unexpected high mobility of nonspherical anion dimers. A comparison of the ions dynamics in 2:1 complex studied with the guanidinium 1:1 and 3:1 complexes has shown a significant contribution of the hydrogen bonds to the potential barriers hindering the anion reorientations. At low temperatures a proton motion in the hydrogen bond and at 400 K a solid-solid phase transition have been discerned.

An Effect of Deuteration on Ion Motions and Hydrogen Bondings in Guanidinium Tetrafluoroborate

1992 ◽  
Vol 47 (7-8) ◽  
pp. 803-806 ◽  
Author(s):  
J. Wąsicki ◽  
M. Grottel ◽  
A. Kozak ◽  
Z. Pająk
Keyword(s):  
Relaxation Time ◽  
Activation Parameters ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Systems ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
Relaxation Effects ◽  
Wide Range ◽  
Hydrogen Bondings

Abstract The fluorine spin-lattice relaxation time as well as NMR second moment for perdeuterated guanidinium tetrafluoroborate were studied over a wide range of temperature. An analytical solution of a set of coupled differential equations describing the time variation of nuclear magnetisations for four unlike spin systems was applied to analyse all cross-relaxation effects in the compound. Activation parameters EFa = 19.3 kJ/mole and τFU= 9 • 10"14 s for the isotropic anion reorientation were derived. A coupling of rotational modes of cation and anion was found. Significant lowering of the melting point explained by a weakening of the hydrogen bonds involves diminishing of the ion activation energies due to the large positive isotope effect

Cation and Anion Reorientation at Phase Transition in Pyridinium Tetrafluoroborate

1990 ◽  
Vol 45 (1) ◽  
pp. 33-36 ◽  
Author(s):  
J. Wąsicki ◽  
Z. Pająk ◽  
A. Kozak
Keyword(s):  
Phase Transition ◽  
Relaxation Times ◽  
Activation Parameters ◽  
Lattice Relaxation ◽  
High Temperature Phase ◽  
Spin Lattice Relaxation ◽  
Temperature Phase ◽  
Spin Lattice ◽  
Relaxation Effects ◽  
Temperature Dependences

AbstractTemperature dependences of 1H and 19F second moment and spin-lattice relaxation times for polycrystalline pyridinium tetrafluoroborate were measured. A phase transition was discovered at 202 K. A model of cation reorientation between inequivalent (low-temperature phase) and equivalent (high-temperature phase) equilibrium positions is proposed. Whether the anion reorients isotropically or about a symmetry axis cannot be decided. An analysis of cross-relaxation effects yielded activation parameters for cation and anion reorientation. The rotational correlation times for both ions converge just at the phase transition reaching the value of 10-10s.

NMR Study of Cation Motion in Guanidinium Iodoplumbates

1997 ◽  
Vol 52 (11) ◽  
pp. 783-788 ◽  
Author(s):  
M. Grottel ◽  
M. Szafrański ◽  
Z. Pająk
Keyword(s):  
Solid Phase ◽  
Relaxation Times ◽  
High Mobility ◽  
Activation Parameters ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
Second Moments ◽  
Nmr Study ◽  
New Phase

Abstract Proton NMR second moments and spin-lattice relaxation times of polycrystalline C(NH2)3PbI3 and [C(NH2)3]2PbI4 were studied in a wide temperature range. The order-disorder character of the existing solid-solid phase transitions was confirmed and for tetraiodoplumbate a new phase transition at 170 K was discovered. For both compounds a dynamical inequivalence and unusual high mobility of the guanidinium cations were revealed. For the reorientations discovered (NH2 group flipping, C3 in-plane reorientation and a tumbling) the activation parameters were determined.

Application of Adiabatic Rapid Passage Nuclear Magnetic Resonance Techniques to the Study of Molecular Motions in Solids

1974 ◽  
Vol 52 (2) ◽  
pp. 191-197 ◽  
Author(s):  
J. A. Ripmeester ◽  
B. A. Dunell
Keyword(s):  
Molecular Motion ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Adiabatic Rapid Passage ◽  
Spin Lattice ◽  
Second Moments ◽  
New Information ◽  
Rotating Frame Relaxation ◽  
Rapid Passage

The adiabatic rapid passage (ARP) technique was applied to the study of molecular motion in solids. Second moments and spin–lattice relaxation times for solid furan and benzene were derived using ARP methods from 77 °K to the respective melting points. Unusual variations of the ARP signal height and shape with temperature were observed for these solids. These effects were interpreted as being due to the presence of short rotating frame relaxation times. New information regarding molecular motion in solid furan, as well as acetic acid-d1, was obtained. Also some quantitative statements have been made regarding the conditions required to observe an ARP signal in the solid state.

A nuclear magnetic resonance investigation of n -pentane, n -hexane and cyclo pentane

1954 ◽  
Vol 222 (1151) ◽  
pp. 526-541 ◽  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Molecular Motion ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Kcal Mole ◽  
Second Moment ◽  
Spin Lattice ◽  
Second Moments

The nuclear magnetic resonance spectra and spin-lattice relaxation times have been measured for the protons in n -pentane (C 5 H 12 ), n -hexane (C 6 H 14 ) and cyclo pentane (C 5 H 10 ) all in the solid state. The temperature range covered was from 70° K to the melting-points of 143·4° K for n -pentane, 177·8° K for n -hexane and 179·4° K for cyclo pentane. In the case of n -pentane and n -hexane the second moments of the absorption lines were found to be smaller than the computed rigid lattice values over the. whole temperature range. Possible molecular motions which might cause this reduction are discussed. It is suggested that the most probable type of motion is reorientation of the methyl groups at the ends of each molecule about the adjacent C—C bonds. An analysis of the spin-lattice relaxation times shows that this reorientation process is governed by an activation energy of 2·7 kcal/mole for n -pentane and 2·9 kcal/mole for n -hexane, values which support the mechanism postulated. At the lowest temperature the absorption lines had not reached their full widths, even though the reorientation frequencies at these temperatures were considerably less than the line-widths. The experimental second moment for cyclo pentane below about 120° K indicates that the lattice is effectively rigid in this temperature region. The uncertainties in both the experimental and theoretical second moments do not allow a distinction to be drawn between the plane and puckered molecular models. At the temperature of the first transition (122·4° K) the line-width second moment and relaxation time all show a sudden decrease. The low value of second moment at the higher temperatures indicates that considerable molecular motion is occurring, the molecules rotating with spherical symmetry. The change in crystal structure at the temperature of the second transition (138·1° K) is thought to be a direct result of this spherical symmetry. As the temperature increases, the results indicate that more molecular motion must be occurring, and it is thought that the rotating molecules are diffusing through the lattice.

Interrelation Between Molecular Motions and Structure in Solid Trimethylamine-boron-trichloride as Studied by NMR

1992 ◽  
Vol 47 (11) ◽  
pp. 1157-1160
Author(s):  
S. Głowinkowski ◽  
, S. Jurga ◽  
E. Szcześniak
Keyword(s):  
Molecular Structure ◽  
Relaxation Times ◽  
Activation Parameters ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Molecular Motions ◽  
Boron Trichloride ◽  
Second Moment ◽  
Spin Lattice ◽  
Temperature Dependences

AbstractThe temperature dependences of proton second-moment and spin-lattice relaxation times (T1 and T1ρ) have been measured in solid (CH3)3NBCl3. The nature of reorientation processes occurring in the complex has been established and the activation parameters determined. The motions are discussed in relation to the molecular structure of the complex

Ionic Dynamics in LiNO2 Studied by 7Li and 15N Solid NMR

1999 ◽  
Vol 54 (8-9) ◽  
pp. 519-523 ◽  
Author(s):  
Hisashi Honda ◽  
Shin'ich Ishimaru ◽  
Ryuichi Ikeda
Keyword(s):  
Relaxation Times ◽  
Activation Parameters ◽  
Lattice Relaxation ◽  
The Self ◽  
Spin Lattice Relaxation ◽  
Plastic Crystal ◽  
Self Diffusion ◽  
Spin Lattice ◽  
Solid Nmr ◽  
Temperature Dependences

The temperature dependences of 7Li and 15N NMR spin-lattice relaxation times and spectra in LiNO2 were measured in the range 120 K -473 K (m.p.). The 180°-flip motion of NO2-- ions along or perpendicular to the molecular C2 -axis and the self-diffusion of Li+ ions (activation energies of 42 -44 and 100 kJ mol-1 , respectively) were observed in this range. From the comparison of the observed activation parameters with those reported for plastic phases of alkali metal nitrites, a new characteristic of the plastic crystal was obtained.

Sign in / Sign up

Export Citation Format

Share Document