ESR Investigation of a Stable Trapped Hydrogen Atom in X-ray-Irradiated β-Tricalcium Phosphate at Room Temperature

2005 ◽  
Vol 127 (6) ◽  
pp. 1606-1607 ◽  
Author(s):  
Kouichi Nakashima ◽  
Jun Yamauchi
Keyword(s):  
Hydrogen Atom ◽  
Tricalcium Phosphate ◽  
Room Temperature ◽  
X Ray

Room-Temperature Structure of Ammonia Borane

2007 ◽  
Vol 60 (3) ◽  
pp. 149 ◽  
Author(s):  
Mark E. Bowden ◽  
Graeme J. Gainsford ◽  
Ward T. Robinson
Keyword(s):  
Hydrogen Atom ◽  
Single Crystal ◽  
Room Temperature ◽  
Ammonia Borane ◽  
Temperature Structure ◽  
Orthorhombic Structure ◽  
Tetrahedral Geometry ◽  
New Model ◽  
X Ray ◽  
Diffraction Peaks

Structural determinations of ammonia borane (BH3NH3) have been carried out for the orthorhombic (at 90 K) and tetragonal (at 298 K) modifications using single-crystal X-ray data. The orthorhombic structure (space group Pmn21) agreed with a previously published neutron determination, while the tetragonal structure (I4mm) exhibited halos of hydrogen atom occupancy around both the nitrogen and boron atoms. The bond angles to the regions of hydrogen occupancy are consistent with the expected tetrahedral geometry for –BH3 and –NH3 groups. A new model for tetragonal BH3NH3 was constructed which accounts for the hydrogen disorder in the I4mm structure while introducing only weak new diffraction peaks. These peaks could not be found, however, and it is likely that the hydrogen disorder in tetragonal BH3NH3 arises from either rotations of higher than 3-fold order, or from random orientations of hydrogen-containing groups.

Structural Systematics of 2/4-Nitrophenoxide Complexes of Closed-Shell Metal Ions. IV [Acid Salts] of the 4-Nitrophenoxides of Group 1

1998 ◽  
Vol 51 (8) ◽  
pp. 747 ◽  
Author(s):  
Jack M. Harrowfield ◽  
Raj Pal Sharma ◽  
Brian W. Skelton ◽  
Allan H. White
Keyword(s):  
Hydrogen Atom ◽  
Metal Ions ◽  
Room Temperature ◽  
Closed Shell ◽  
X Ray ◽  
Salt Structure ◽  
Group 1 ◽  
Parent Ligand ◽  
Oxygen Atoms ◽  
Acid Salts

Room-temperature single-crystal X-ray studies are recorded for a number of ‘acid salts’ formed between Group 1 salts of 4-nitrophenol, M(4-np), and the parent ligand 4-npH, variously hydrated. The 1 : 1 salts M(4-np)(4-npH).x H2O are found for all of M = Li, Na, K, Rb and Cs. The lithium adduct (tetrahydrate) is monoclinic, C2/c, a 19·438(4), b 11·207(2), c 7·421(2) Å, β 91·38(2)°, Z = 4, conventional R on |F| being 0·043 for 1369 independent ‘observed’ (I > 3σ(I)) diffractometer reflections. The sodium adduct (dihydrate) is monoclinic, C2, a 2·174(3), b 3·674(2), c 10·358(1) Å, β 117·21(1)°, Z = 2, R 0·035 for No 1092; the potassium adduct (monohydrate) is monoclinic, C 2/c, a 22·10(1), b 3·798(3), c 21·270(6) Å, β 120·97(4)°, Z = 4, R 0·050 for No 1065. The isomorphous rubidium and caesium monohydrates are triclinic, P-1, a ≈ 11·9, b ≈ 10·2,c ≈ 6·3 Å, α ≈ 90, β ≈ 92, γ ≈ 112°, Z = 2, R 0·042, 0·028 for No 2340, 3053 respectively. For M = Rb, a 1 : 3 adduct Rb(4-np).3(4-npH) is also obtained (with an isomorphous thallium counterpart recorded elsewhere): a 12·143(5), b 11·50(1), c 11·36(1) Å, α 114·38(9), β 110·54(6), γ 96·73(6)°, Z = 2, R 0·034 for No 3945. The lithium salt may be represented as [Li(OH2)4]+ (4-npH.4-np)½-. The cation lies disposed about a crystallographic 2 axis; the anion, close to an axis, confronts its rotational image, with the associated hydrogen atom modelled as disordered between them, rather than located on the 2 axis. The sodium salt is a sheet structure, the six-coordinate sodium atoms being disposed on a crystallographic 2 axis and linked up that axis ... Na(µ-O)2Na(µ-O)2Na ... by bridging water molecule oxygen atoms, while symmetry-related trans O-nitrophenoxide moieties are bridged by confronting phenoxide oxygen atoms about an associated hydrogen atom provisionally disposed on a 2 axis also. The potassium salt structure is developed from this array, modelled with disordered potassium atoms, now lying off the 2 axis, 0·922(2) Å apart. In the rubidium/caesium structure, columns of oxygen-bridged metal ions are disposed about c, crosslinked by O-nitro-bonded phenoxide moieties, with confronting phenoxide oxygen atoms about a shared associated hydrogen.

Synthese, Kristallstruktur und Eigenschaften von 1,1,3,3,3-Pentaaminol- 1-thio-1 λ5,3λ5-diphosphaz-2-en (NH2)2P(S)N=P(NH2)3 / Synthesis, Crystal Structure, and Properties of 1,1,3,3,3-Pentaam 1-thio-1 λ5,3λ5-diphosphaz-2-en (NH2)2P(S)N=P(NH2)3

1997 ◽  
Vol 52 (4) ◽  
pp. 490-495 ◽  
Author(s):  
Stefan Horstmann ◽  
Wolfgang Schnick
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Hydrogen Atom ◽  
Room Temperature ◽  
Acetonitrile Solution ◽  
Structure And Properties ◽  
X Ray ◽  
Hydrogen Bonding Interactions ◽  
Ray Methods

Abstract (NH2)2P(S)N=P(NH2)3 has been prepared by a two step synthesis. Suitable single crystals were obtained from an acetonitrile solution in a temperature gradient between 60 °C and room temperature. The crystal structure of (NH2)2P(S)N=P(NH2)3 has been determined by single crystal X-ray methods (P21/c, a = 998.27(9) b = 762.78(8), c = 1007.70(15) pm, β = 107.340(7)°, Z = 4). In the crystal structure each hydrogen atom is subject to a hydrogen bond. Four N-H -N hydrogen bonding interactions per molecule build up a framework connecting two molecules in eight-membered rings. Each sulfur atom shows six distances N-H···S in the range of weak hydrogen bonding interactions.

Electron Microscopy of Human Gallstones

1971 ◽  
Vol 29 ◽  
pp. 296-297
Author(s):  
C. Wolpers ◽  
R. Blaschke
Keyword(s):  
Electron Microscopy ◽  
Room Temperature ◽  
Bile Pigment ◽  
X Ray Diffraction ◽  
Triclinic Crystal System ◽  
X Ray ◽  
Follow Up Study ◽  
Infra Red ◽  
Main Components

Scanning microscopy was used to study the surface of human gallstones and the surface of fractures. The specimens were obtained by operation, washed with water, dried at room temperature and shadowcasted with carbon and aluminum. Most of the specimens belong to patients from a series of X-ray follow-up study, examined during the last twenty years. So it was possible to evaluate approximately the age of these gallstones and to get information on the intensity of growing and solving.Cholesterol, a group of bile pigment substances and different salts of calcium, are the main components of human gallstones. By X-ray diffraction technique, infra-red spectroscopy and by chemical analysis it was demonstrated that all three components can be found in any gallstone. In the presence of water cholesterol crystallizes in pane-like plates of the triclinic crystal system.

Opening images of synaptic vesicles and calcium localization by means of microwave fixation method

1990 ◽  
Vol 48 (2) ◽  
pp. 182-183
Author(s):  
Vinci Mizuhira ◽  
Hiroshi Hasegawa
Keyword(s):  
Synaptic Vesicles ◽  
Room Temperature ◽  
Osmium Tetroxide ◽  
Sampling Procedure ◽  
Fixation Method ◽  
Potassium Oxalate ◽  
X Ray ◽  
Cacodylate Buffer ◽  
Ultrathin Sections ◽  
Microwave Fixation

Microwave irradiation (MWI) was applied to 0.3 to 1 cm3 blocks of rat central nervous system at 2.45 GHz/500W for about 20 sec in a fixative, at room temperature. Fixative composed of 2% paraformaldehyde, 0.5% glutaraldehyde in 0.1 M cacodylate buffer at pH 7.4, also contained 2 mM of CaCl2 , 1 mM of MgCl2, and 0.1% of tannic acid for conventional observation; and fuether 30-90 mM of potassium oxalate containing fixative was applied for the detection of calcium ion localization in cells. Tissue blocks were left in the same fixative for 30 to 180 min after MWI at room temperature, then proceeded to the sampling procedure, after postfixed with osmium tetroxide, embedded in Epon. Ultrathin sections were double stained with an useal manner. Oxalate treated sections were devided in two, stained and unstained one. The later oxalate treated unstained sections were analyzed with electron probe X-ray microanalyzer, the EDAX-PU-9800, at 40 KV accelerating voltage for 100 to 200 sec with point or selected area analyzing methods.

Evidence for ordered Fe3Ni

1987 ◽  
Vol 45 ◽  
pp. 216-217
Author(s):  
K.B. Reuter ◽  
D.B. Williams ◽  
J.I. Goldstein
Keyword(s):  
Experimental Data ◽  
Martensitic Transformation ◽  
Electron Diffraction ◽  
Room Temperature ◽  
Direct Evidence ◽  
Transformation Product ◽  
Iron Meteorites ◽  
X Ray ◽  
Ni Content ◽  
Temperature Transformation

In the Fe-Ni system, although ordered FeNi and ordered Ni3Fe are experimentally well established, direct evidence for ordered Fe3Ni is unconvincing. Little experimental data for Fe3Ni exists because diffusion is sluggish at temperatures below 400°C and because alloys containing less than 29 wt% Ni undergo a martensitic transformation at room temperature. Fe-Ni phases in iron meteorites were examined in this study because iron meteorites have cooled at slow rates of about 10°C/106 years, allowing phase transformations below 400°C to occur. One low temperature transformation product, called clear taenite 2 (CT2), was of particular interest because it contains less than 30 wtZ Ni and is not martensitic. Because CT2 is only a few microns in size, the structure and Ni content were determined through electron diffraction and x-ray microanalysis. A Philips EM400T operated at 120 kV, equipped with a Tracor Northern 2000 multichannel analyzer, was used.

Electron Microscope study of commensurate-incommensurate phase transition in BaZnGeO4

1990 ◽  
Vol 48 (4) ◽  
pp. 172-173
Author(s):  
Naoki Yamamoto ◽  
Makoto Kikuchi ◽  
Tooru Atake ◽  
Akihiro Hamano ◽  
Yasutoshi Saito
Keyword(s):  
Phase Transition ◽  
Electron Microscope Study ◽  
Room Temperature ◽  
Hexagonal Lattice ◽  
Ferroelectric Materials ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Periodic Arrays ◽  
Modulation Wave Vector

BaZnGeO4 undergoes many phase transitions from I to V phase. The highest temperature phase I has a BaAl2O4 type structure with a hexagonal lattice. Recent X-ray diffraction study showed that the incommensurate (IC) lattice modulation appears along the c axis in the III and IV phases with a period of about 4c, and a commensurate (C) phase with a modulated period of 4c exists between the III and IV phases in the narrow temperature region (—58°C to —47°C on cooling), called the III' phase. The modulations in the IC phases are considered displacive type, but the detailed structures have not been studied. It is also not clear whether the modulation changes into periodic arrays of discommensurations (DC’s) near the III-III' and IV-V phase transition temperature as found in the ferroelectric materials such as Rb2ZnCl4.At room temperature (III phase) satellite reflections were seen around the fundamental reflections in a diffraction pattern (Fig.1) and they aligned along a certain direction deviated from the c* direction, which indicates that the modulation wave vector q tilts from the c* axis. The tilt angle is about 2 degree at room temperature and depends on temperature.

Single Crystal Growth of High-Pressure Phases of Ice and Salt Hydrate Far Below the Original Melting Point by Mixing Alcohol: Crystal Structure Determination of Magnesium Chloride Heptahydrate

2020 ◽  
Author(s):  
Keishiro Yamashita ◽  
Kazuki Komatsu ◽  
Hiroyuki Kagi
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Crystal Growth ◽  
Single Crystal ◽  
Room Temperature ◽  
Growth Technique ◽  
Salt Hydrate ◽  
X Ray

An crystal-growth technique for single crystal x-ray structure analysis of high-pressure forms of hydrogen-bonded crystals is proposed. We used alcohol mixture (methanol: ethanol = 4:1 in volumetric ratio), which is a widely used pressure transmitting medium, inhibiting the nucleation and growth of unwanted crystals. In this paper, two kinds of single crystals which have not been obtained using a conventional experimental technique were obtained using this technique: ice VI at 1.99 GPa and MgCl<sub>2</sub>·7H<sub>2</sub>O at 2.50 GPa at room temperature. Here we first report the crystal structure of MgCl2·7H2O. This technique simultaneously meets the requirement of hydrostaticity for high-pressure experiments and has feasibility for further in-situ measurements.

Xenon Trioxide Adducts of O-Donor Ligands; [(CH3)2CO]3XeO3, [(CH3)2SO]3(XeO3)2, (C5H5NO)3(XeO3)2, and [(C6H5)3PO]2XeO3

2018 ◽  
Author(s):  
Katherine Marczenko ◽  
James Goettel ◽  
Gary Schrobilgen
Keyword(s):  
Room Temperature ◽  
Triphenylphosphine Oxide ◽  
Donor Ligands ◽  
Mechanical Shock ◽  
X Ray Diffraction ◽  
X Ray ◽  
Oxygen Coordination ◽  
Xenon Trioxide ◽  
Distorted Octahedra ◽  
Coordination Spheres

Oxygen coordination to the Xe(VI) atom of XeO<sub>3</sub> was observed in its adducts with triphenylphosphine oxide, dimethylsulfoxide, pyridine-N-oxide, and acetone. The crystalline adducts were characterized by low-temperature, single-crystal X-ray diffraction and Raman spectroscopy. Unlike solid XeO<sub>3</sub>, which detonates when mechanically or thermally shocked, the solid [(C<sub>6</sub>H<sub>5</sub>)<sub>3</sub>PO]<sub>2</sub>XeO<sub>3</sub>, [(CH<sub>3</sub>)<sub>2</sub>SO]<sub>3</sub>(XeO<sub>3</sub>)<sub>2</sub>,<sub> </sub>and (C<sub>5</sub>H<sub>5</sub>NO)<sub>3</sub>(XeO<sub>3</sub>)<sub>2</sub> adducts are insensitive to mechanical shock, but undergo rapid deflagration when ignited by a flame. Both [(C<sub>6</sub>H<sub>5</sub>)<sub>3</sub>PO]<sub>2</sub>XeO<sub>3 </sub>and (C<sub>5</sub>H<sub>5</sub>NO)<sub>3</sub>(XeO<sub>3</sub>)<sub>2</sub> are air-stable whereas [(CH<sub>3</sub>)<sub>2</sub>SO]<sub>3</sub>(XeO<sub>3</sub>)<sub>2</sub> slowly decomposes over several days and [(CH<sub>3</sub>)<sub>2</sub>CO]<sub>3</sub>XeO<sub>3</sub> undergoes adduct dissociation at room temperature. The xenon coordination sphere of [(C<sub>6</sub>H<sub>5</sub>)<sub>3</sub>PO]<sub>2</sub>XeO<sub>3</sub> is a distorted square pyramid which provides the first example of a five-coordinate XeO<sub>3</sub> adduct. The xenon coordination spheres of the remaining adducts are distorted octahedra comprised of three Xe---O secondary contacts that are approximately trans to the primary Xe–O bonds of XeO<sub>3</sub>. Quantum-chemical calculations were used to assess the Xe---O adduct bonds, which are predominantly electrostatic σ-hole bonds between the nucleophilic oxygen atoms of the bases and the σ-holes of the xenon atoms.

Sign in / Sign up

Export Citation Format

Share Document