Achievements of multiple-pulse n.m.r

1981 ◽  
Vol 299 (1452) ◽  
pp. 497-504 ◽  
Keyword(s):  
Hydrogen Bonds ◽  
Single Crystals ◽  
Spin Relaxation ◽  
Molecular Motions ◽  
Site Specific ◽  
Multiple Pulse ◽  
Area Of Interest ◽  
Relaxation Measurements ◽  
Powder Samples ◽  
Shielding Tensors

A survey is given of the achievements of multiple-pulse n.m.r. with regard to measurements of shielding tensors of protons. The need to investigate single crystals rather than powder samples is stressed. It is useful to consider separately protons in hydrogen bonds and protons bonded directly to carbon atoms. While for the former group of protons there is now a wealth of experimental shielding data, measurements of shielding tensors of protons from the latter group are still difficult and scarce. Symmetry arguments applied to some available data show that the measurable shielding tensors are substantially influenced by the crystal lattice and do not directly reflect molecular properties. Several implications of this fact are discussed. It is pointed out that continuation of multiple-pulse n.m.r. calls for a new kind of motivation. The study of molecular motions in solids through site-specific spin relaxation measurements may become a new area of interest and activities for multiple-pulse n.m.r.

scholarly journals Dislocation dynamics in alkali halide single crystals investigated by nuclear spin relaxation measurements

1980 ◽  
Vol 41 (C6) ◽  
pp. C6-146-C6-149
Author(s):  
W. H. M. Alsem ◽  
A. W. Sleeswyk ◽  
H. J. Hackelöer ◽  
R. Münter ◽  
H. Tamler ◽  
...  
Keyword(s):  
Single Crystals ◽  
Spin Relaxation ◽  
Nuclear Spin ◽  
Alkali Halide ◽  
Dislocation Dynamics ◽  
Nuclear Spin Relaxation ◽  
Relaxation Measurements

scholarly journals Ring rotation of ferrocene in interlocked molecules in single crystals

2021 ◽  
Author(s):  
Chi-Hsien Wang ◽  
Kai-Jen Chen ◽  
Tsung-Huan Wu ◽  
Hung-Kai Chang ◽  
Yoshitaka Tsuchido ◽  
...  
Keyword(s):  
Crown Ether ◽  
Single Crystals ◽  
Internal Rotation ◽  
Molecular Motions ◽  
Interlocked Molecules ◽  
Ring Rotation

Unique molecular motions, reversible internal rotation of ferrocene and flipping of crown ether are observed in DB30C10 and DB18C6-containing interlocked molecules, respectively.

Superconductivity and Magnetism in the La2 CuO4-Based Compounds

MRS Bulletin ◽  
1989 ◽  
Vol 14 (1) ◽  
pp. 33-36 ◽  
Author(s):  
Z. Fisk ◽  
S-W. Cheong ◽  
D.C. Johnston
Keyword(s):  
Single Crystals ◽  
Magnetic Measurements ◽  
Oxygen Stoichiometry ◽  
Layered Perovskite ◽  
Orthorhombic Distortion ◽  
X Ray ◽  
Bulk Superconductivity ◽  
High Oxygen Pressure ◽  
Powder Samples ◽  
Cation Ratio

La2CuO4, crystallizes in an orthorhombic distortion of the tetragonal K2NiF4 structure, a so-called layered perovskite. The important question here concerns the stoichiometry of La2CuO4 prepared by various techniques. Regarding the La and Cu sites, recent neutron diffraction studies of powders have shown that the La:Cu ratio can vary from 2:1 by ≳1% in various preparations., Single crystals have been grown variously from CuO, PbO and Li2O-B2O3 fluxes. The last two fluxes incorporate some Pb and Li, respectively, into the crystals, but the cation ratio is found to be 2:1 within the accuracy of x-ray refinement.It is also known that the oxygen stoichiometry corresponds to La2CuO4 within ≃ 1%. Extensive and precise magnetic susceptibility (χ) and other studies of powder samples showed, however, that the physical properties are extremely sensitive to < 1% changes in the oxygen content. A clear indication from electric and magnetic measurements is that the oxygen stoichiometry is always that, or richer than that, corresponding to a Mott insulator with an exactly half-filled band. Consistent with this, the stoichiometry is more properly written La2-z CuO4-y with small, positive y and z.Several groups found that bulk superconductivity above 30 K can be produced in La2CuO4 by annealing powders or single crystals at high oxygen pressure. The weight gain in this process corresponds to producing La2CuO4.13, and these authors believe the excess oxygens go in as O-2, based on iodometric titration measurements giving the amount of [Cu-O]⊥ in the sample. Jorgensen et al. found that there is a phase separation below 320 K of La2CuO4 and the O2-loaded phase in oxygen-rich samples; the latter structure is also orthorhombic, but the position of the excess oxygens could not be determined unambiguously.

Muon-spin relaxation measurements of geometrically frustrated magnets

2001 ◽  
Vol 79 (11-12) ◽  
pp. 1295-1305 ◽  
Author(s):  
K M Kojima
Keyword(s):  
Spin Relaxation ◽  
Muon Spin ◽  
Muon Spin Relaxation ◽  
Spin Systems ◽  
Frustrated Magnets ◽  
Slow Dynamics ◽  
Kagomé Lattice ◽  
Geometrically Frustrated ◽  
Relaxation Measurements ◽  
Frustrated Spin

Muon-spin relaxation (µSR) has been applied to investigations of slow dynamics and quasi-static features of geometrically frustrated spin systems. We take an example in the Kagome-lattice anti-ferromagnets, and briefly review µSR works on S = 1, 3/2, and 5/2 Kagome compounds. PACS No.: 75.30

Komplexe mit substituierten 2,5-Dihydroxy-p-benzochinonen: EA[C6(NO2)2O4] · H2O (EA = Ca, Sr)/ Complexes with Substituted 2,5-D ihydroxy-p-benzoquinones: EA [C6(NO2)2O4] · 4H2O(EA = Ca, Sr)

1987 ◽  
Vol 42 (8) ◽  
pp. 972-976 ◽  
Author(s):  
Christian Robl
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Water Molecule ◽  
Single Crystals ◽  
Coordination Sphere ◽  
Trigonal Prism ◽  
Water Molecules ◽  
Additional Water ◽  
Oxygen Atoms

AbstractSingle crystals of EA[Q(NO2)2O4] · 4H2O (EA = Ca. Sr) were grown in aqueous silicagel. Ca2+ has CN 8. It is surrounded by 4 oxygen atoms of two bis-chelating [C6(NO2)2O4]2- ions and 4 water molecules, which form a distorted, bi-capped trigonal prism. Sr2+ is coordinated similarly, with an additional water molecule joining the coordination sphere to yield CN 8+1. Corrugated chains extending along [010] and consisting of EA2+ and nitranilate ions are the main feature of the crystal structure. Adjacent chains are interlinked by hydrogen bonds.

Na6[TeMo6O24]·22 H2O – A Layered Heteropoly Compound with the Chain-Like Polycation {Na3(Η2O)1111}n3n+

1993 ◽  
Vol 48 (4) ◽  
pp. 404-408 ◽  
Author(s):  
Christian Robl ◽  
Mona Frost
Keyword(s):  
Aqueous Solution ◽  
Hydrogen Bonds ◽  
Oxygen Atom ◽  
Single Crystals ◽  
Solution Space ◽  
Heteropoly Compound ◽  
Water Molecules ◽  
Space Group ◽  
The Third ◽  
Bonding Mode

Colourless triclinic single crystals of Na6[TeMo6O24] · 22 H2O were grown from aqueous solution (space group P 1, a = 1030.89(9), b = 1056.7(1), c = 1106.32(9) pm, α = 90.120(7), β = 115.220(6), γ = 105.195(7), Ζ = 1, 295 Κ, 336 parameters, 3181 reflections, Rg = 0.0186). There are three crystallographically independent Na+ cations. Two of them are coordinated octahedrally by water molecules only. The third Na+ cation is bound to five H2O and one oxygen atom (O(4)) belonging to the Anderson-Evans type anion [TeMo6O24]6-. The sodium-centered coordination octahedra are linked by common edges exclusively formed by water molecules to yield chain-like polycations {Na3(H2O)11}n,3n+ which are bound by the Na(1)-O(4) contact to the anions situated on crystallographic centers of inversion forming a layer-like arrangement. Further connections between the polycations and the [TeMo6O24]6- anions are established by hydrogen bonds involving all the oxygen atoms of the anion except O(4) as almost equivalent proton acceptors regardless of their bonding mode to Te or Mo.

Strukturen cäsiumhaltiger Fluoride, II1 Die Kristall- und Magnetische Struktur von CsFeF4 / Crystal and Magnetic Structure of CsFeF4

1974 ◽  
Vol 29 (3-4) ◽  
pp. 139-148 ◽  
Author(s):  
D. Babel ◽  
F. Wall ◽  
G. Heger
Keyword(s):  
Neutron Diffraction ◽  
Single Crystals ◽  
Magnetic Structure ◽  
Structure Determination ◽  
Mean Value ◽  
X Ray ◽  
Magnetic Structures ◽  
Powder Samples ◽  
Crystal And Magnetic Structure ◽  
Improved Model

The results of an X-ray structure determination on single crystals of CsFeF4 are reported. The compound crystallizes tetragonally with α = 7.794, c = 6.553 Å, z = 4, in spacegroup P4/nmm-D4h7 and is a hitherto unknown superstructure variant of the TlAlF4-type. Cesium exhibits 12-coordination (mean value Cs-F = 3.25 Å); the FeF6-octahedra are characteristically shortened normal to the FeF4⁻-layers (Fe-F = 1.962/1.861Å). An improved model is proposed and verified for a related structure of RbFeF4, showing the same features. Neutron diffraction studies on powder samples of CsFeF4 show that both compounds are identical as for their magnetic structures.

Sign in / Sign up

Export Citation Format

Share Document