Molecular Motions in Halogen-Bridged One-Dimensional Pt Complexes, [PtII(en)2][PtIVX2(en)2](ClO4)4 (X = Cl, Br) Studied by 2H and 1H NMR

2002 ◽  
Vol 57 (6-7) ◽  
pp. 413-418 ◽  
Author(s):  
Noriyoshi Kimura ◽  
Toru Hachisuka ◽  
Yukitaka Nakano ◽  
Ryuichi Ikeda
Keyword(s):  
Relaxation Times ◽  
Lattice Relaxation ◽  
Energy Difference ◽  
Spin Lattice Relaxation ◽  
X Ray Diffraction ◽  
Potential Wells ◽  
One Dimensional ◽  
X Ray ◽  
Spin Lattice ◽  
H Nmr

2H and 1H NMR measurements were performed on crystalline [Pt(en)2][PtX2(en)2](ClO4)4 (X = Cl, Br), where the protonated and partially deuterated ethylenediamines (en’s), NH2(CH2)2NH2, NH2(CD2)2NH2 and ND2(CH2)2ND2 were used as ligands. Measurements of 2H and 1H NMR spin-lattice relaxation times showed the presence of motions of en chelate rings at the temperatures near the phase transitions, whereas broad 2H NMR spectra and the reported X-ray diffraction data showed no marked motions. These results were consistently explained by introducing the en puckering motion between highly asymmetric potential wells with an energy difference of 10 - 13 kJ mol-1. This difference was shown to be much larger than 2 - 5 kJ mol-1, reported for the iodo-complex, [Pt(en)2][PtI2(en)2](ClO4)4

Molecular Reorientation in the Plastic Crystalline Phase of Tris

1979 ◽  
Vol 32 (4) ◽  
pp. 905 ◽  
Author(s):  
RE Wasylishen ◽  
PF Barron ◽  
DM Doddrell
Keyword(s):  
Phase Transition ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Molecular Reorientation ◽  
Liquid Phase Transition ◽  
X Ray ◽  
Spin Lattice

Carbon-13 N.M.R. spectra of tris(hydroxymethyl)aminomethane (Tris) have been measured between 407 and 461 K. Proton-decoupled 13C N.M.R. spectra of solid Tris between 407 K and its melting point are relatively sharp (v� < 30 Hz) indicating rapid overall molecular reorientation in this temperature range. It was not possible to detect a 13C N.M.R, signal for Tris below 407 K. The observed 13C N.M.R. spin-lattice relaxation times appear continuous across the solid ↔ liquid phase transition. From the temperature dependence of T1, a rotational activation energy of 51.6 � 6 kJ mol-1 is calculated, which indicates that the molecules must expend considerable energy in reorienting. The N.M.R. results are discussed in relation to previous differential scanning calorimetry and X-ray diffraction data which indicate that Tris undergoes a solid ↔ solid transition at 407 K.

A study of molecular motion in tetramethylphosphonium halides by proton magnetic resonance

1976 ◽  
Vol 54 (12) ◽  
pp. 1985-1990 ◽  
Author(s):  
T. T. Ang ◽  
B. A. Dunell
Keyword(s):  
Molecular Motion ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
X Ray Diffraction ◽  
Hexagonal Crystal ◽  
Methyl Group ◽  
X Ray ◽  
Spin Lattice ◽  
Second Moments

Spin–lattice relaxation times of tetramethylphosphonium chloride, bromide, and iodide were measured between 100 and 500 K and the two minima in T1 found for each compound have been assigned to methyl group reorientation and whole cation tumbling. The second moments also indicate that the cations are tumbling isotropically at nmr frequencies in the upper half of this temperature range, and suggest that librational oscillation of the whole cation occurs at frequencies at least of the order of 105 s−1 near 150 K. The energy barriers for both methyl group reorientation and isotropic tumbling decrease from chloride to bromide but increase when one goes from bromide to iodide. Powder photograph X-ray diffraction analysis indicates that the chloride and bromide have hexagonal crystal structures (a and c measured), but that the iodide has lower, undetermined symmetry.

NUCLEAR MAGNETIC RESONANCE STUDY OF 205Tl IN MULTIPHASE Tl-Ba-Ca-Cu OXIDE SUPERCONDUCTORS

1988 ◽  
Vol 02 (05) ◽  
pp. 1227-1234 ◽  
Author(s):  
L. Mihály ◽  
K. Tompa ◽  
I. Bakonyi ◽  
P. Bánki ◽  
É. Zsoldos ◽  
...  
Keyword(s):  
Room Temperature ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Nuclear Magnetic Resonance Study ◽  
Spin Lattice Relaxation ◽  
Oxide Superconductors ◽  
X Ray Diffraction ◽  
Magnetic Resonance Study ◽  
X Ray ◽  
Spin Lattice

Several batches of T l- Ba - Ca - Cu oxide superconductors have been synthesized and characterized by resistivity, magnetic susceptibility and X-ray diffraction measurements. The 205 T l NMR line snifts (K), the spin-lattice and spin-spin relaxation times have been measured at room temperature. The temperature dependence of the spin-lattice relaxation rate is also reported. The resonance around K = 0.25 % has a composite line shape indicating the presence of two T l sites. The two sites are tentatively assigned to thallium atoms in the (2223) and (2212) T l- Ba - Ca - Cu phases.

Dynamics of Two-Dimensionally Arranged n-Octylammonium Ions Intercalated into Tetrasilicicfluormica

1999 ◽  
Vol 54 (12) ◽  
pp. 755-760
Author(s):  
Miho Yamauchi ◽  
Shin’ichi Ishimaru ◽  
Ryuichi Ikeda
Keyword(s):  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
X Ray Diffraction ◽  
Potential Wells ◽  
Spin Lattice ◽  
Equivalent Potential ◽  
Axis Parallel ◽  
New Type ◽  
Motion Mode

Abstract The dynamic behaviour of n-octylammonium ions intercalated into tetrasilicicfluormica was investigated by measuring 1H and 2H solid state NMR spectra and 1H spin-lattice relaxation times. X-Ray diffraction measurements revealed that the cations are arranged with the long axis parallel to the clay sheet. Uniaxial rotation of cations was found to take place above ca. 200 K among non-equivalent potential wells made by clay sheets. As a new type of 2-D motion mode, whole cationic in-plane tumbling in the 2-D layer seems to be excited above ca. 450 K. The obtained results are compared with those previously reported on saponite of an analogous structure.

Bonded Hydrogen and Trapped H2 in a-Si1−xGex:H Alloys

1989 ◽  
Vol 149 ◽  
Author(s):  
E. J. Vanderheiden ◽  
G. A. Williams ◽  
P. C. Taylor ◽  
F. Finger ◽  
W. Fuhs
Keyword(s):  
Temperature Dependence ◽  
Molecular Hydrogen ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
H Nmr ◽  
Local Environments

ABSTRACT1H NMR has been employed to study the local environments of bonded hydrogen and trapped molecular hydrogen (H2) in a series of a-Si1−xGex:H alloys. There is a monotonic decrease of bonded hydrogen with increasing x from ≈ 10 at. % at x = 0 (a-Si:H) to ≈ 1 at. % at x = 1 (a-Ge:H). The amplitude of the broad 1H NMR line, which is attributed to clustered bonded hydrogen, decreases continuously across the system. The amplitude of the narrow 1H NMR line, which is attributed to bonded hydrogen essentially randomly distributed in the films, decreases as x increases from 0 to ≈ 0.2. From x = 0.2 to x ≈ 0.6 the amplitude of the narrow 1H NMR line is essentially constant, and for x ≥ 0.6 the amplitude decreases once again. The existence of trapped H2 molecules is inferred indirectly by their influence on the temperature dependence of the spin-lattice relaxation times, T1. Through T1, measurements it is determined that the trapped H2 concentration drops precipitously between x = 0.1 and x = 0.2, but is fairly constant for 0.2 ≤ x ≤ 0.6. For a-Si:H (x = 0) the H2 concentration is ≈ 0.1 at. %, while for x ≥ 0.2 the concentration of H2 is ≤ 0.02 at. %.

Nuclear magnetic resonance spin–lattice relaxation and the rotation of adamantane and hexamethylenetetramine in solution

1977 ◽  
Vol 55 (13) ◽  
pp. 2564-2569 ◽  
Author(s):  
Roderick E. Wasylishen ◽  
Brian A. Pettitt
Keyword(s):  
Variable Temperature ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Hard Sphere Model ◽  
Correlation Times ◽  
Spin Lattice ◽  
H Nmr ◽  
Large Step ◽  
Resonance Spin

Deuterium nmr spin–lattice relaxation times have been measured for dilute solutions of adamantane-d16 in CH2I2, CHBr3, CCl4, CHCl3, and CH2Cl2. The reorientation correlation times, τ2, calculated from the experimental data are used to calculate τJ, the angular momentum correlation times, assuming both the J-diffusion and Hubbard relations. The derived τJ values suggest that adamantane executes small step diffusion in CH2I2 and CHBr3, and large step diffusion in CCl4, CHCl3, and CH2Cl2. The calculated τJ values do not appear to be related to the mean times between collisions calculated using a hard sphere model. Both variable solvent and variable temperature experiments indicate 1 ps/cP for the viscosity dependence of the adamantane reorientation time, about 1/36th the value predicted using the familiar Stokes–Einstein equation.Carbon-13 and 1H nmr T1 data indicate that reorientation of hexamethylenetetramine in H2O (28 ps/cP), CHCl3 (27 ps/cP), and CHBr3 (18 ps/cP) is severely hindered because of inter-molecular hydrogen bonding.

Milli-Kelvin NQR: A Study of the Praseodymium Trihalides

1992 ◽  
Vol 47 (1-2) ◽  
pp. 221-226 ◽  
Author(s):  
Robin L. Armstrong ◽  
Sunyu Su
Keyword(s):  
Relaxation Times ◽  
Lattice Relaxation ◽  
Dilution Refrigerator ◽  
Spin Lattice Relaxation ◽  
Technical Consideration ◽  
One Dimensional ◽  
Spin Lattice ◽  
Quadrupole Resonance

AbstractMilli - Kelvin NQR experiments are often essential for the study of pseudo one-dimensional materials. A brief overview of the special technical consideration for carrying out NQR measurements in a dilution refrigerator is given. Recent halide quadrupole resonance experiments on the pseudo one-dimensional XY crystals PrCl3 and PrBr3 are reviewed including the measurement and interpretation of frequencies, and spin-lattice relaxation times.

Structure and Successive Phase Transitions of RGeBr3 (R = Alkylammonium) Studied by Means of NQR

1996 ◽  
Vol 51 (5-6) ◽  
pp. 686-692 ◽  
Author(s):  
Shusaku Gotou ◽  
Tsutomu Okuda ◽  
Toshirou Takahashi ◽  
Hiromitsu Terao ◽  
Koji Yamada
Keyword(s):  
Phase Transitions ◽  
Crystal Structures ◽  
Conduction Mechanism ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Rietveld Analysis ◽  
Spin Lattice Relaxation ◽  
X Ray Diffraction ◽  
Spin Lattice ◽  
Successive Phase

Abstract A series of tribromogermanate(II) complexes RGeBr3 (R = CH3NH3, (CH3)2NH2, (CH3)4N, C2H5NH3, (C2H5)4N) have been synthesized and characterized by 81Br NQR, AC conductivity, DTA, and X-rax diffraction. These measurements revealed the presence of successive phase transitions in these complexes. The crystal structures of Phases I and II in (NH3)4NGeBr3 were derived from the Rietveld analysis of powder X-ray diffraction. The electric conductivity was considerably high in CH3NH3GeBr3 and (NH3)4NGeBr3. The conduction mechanism is discussed on the basis of 81Br NQR spin-lattice relaxation times and crystal structures.

Solitons, polarons and their dynamics in mixed-valence halogen-bridged MX-chains

2007 ◽  
Vol 366 (1862) ◽  
pp. 93-100 ◽  
Author(s):  
Shinya Takaishi ◽  
Masahiro Yamashita
Keyword(s):  
Mixed Valence ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Relaxation Processes ◽  
Spin Lattice ◽  
H Nmr ◽  
Spin Resonance ◽  
1D Chain ◽  
The One

This article describes the photo-generation processes of elementary excitations such as solitons and polarons, and their dynamics in the one-dimensional (1D) halogen-bridged Pt compound [Pt(en) 2 Br](ClO 4 ) 2 . Spin-solitons were photo-generated via relaxation processes of CT excitons and self-trapped excitons, made evident by photo-induced absorption and photo-induced electron spin resonance spectra. Polarons were not generated from CT excitons. Diffusion of spin-solitons on the 1D chain was studied quantitatively by analysing 1 H NMR spin-lattice relaxation times ( T 1 ).

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