scholarly journals Pristine and hydrated fluoroapatite (0001)

2019 ◽  
Vol 75 (5) ◽  
pp. 830-838
Author(s):  
Xavier Torrelles ◽  
Immad M. Nadeem ◽  
Anna Kupka ◽  
Adrián Crespo-Villanueva ◽  
Sandrina Meis ◽  
...  
Keyword(s):  
Water Molecule ◽  
Experimental Analysis ◽  
Surface Coverage ◽  
Adsorbed Water ◽  
Water Molecules ◽  
X Ray Diffraction ◽  
X Ray ◽  
Crystal Truncation Rod ◽  
Before And After ◽  
Dry Conditions

The surface structure of fluoroapatite (0001) (FAp0001) under quasi-dry and humid conditions has been probed with surface X-ray diffraction (SXRD). Lateral and perpendicular atomic relaxations corresponding to the FAp0001 termination before and after H2O exposure and the location of the adsorbed water molecules have been determined from experimental analysis of the crystal truncation rod (CTR) intensities. The surface under dry conditions exhibits a bulk termination with relaxations in the outermost atomic layers. The hydrated surface is formed by a disordered partially occupied H2O layer containing one water molecule (33% surface coverage) adsorbed at each of the three surface Ca atoms, and is coupled with one OH group randomly bonded to each of the three topmost P atoms with a 33% surface coverage.

Crystal Structure of Calcium Picrate Pentahydrate: A New Eight-Coordinate Stereochemistry for [M(bidentate)2(unidentate)4]

1979 ◽  
Vol 32 (2) ◽  
pp. 301 ◽  
Author(s):  
V Diakiw ◽  
TW Hambley ◽  
DL Kepert ◽  
CL Raston ◽  
AH White
Keyword(s):  
Crystal Structure ◽  
Water Molecule ◽  
Single Crystal ◽  
Title Compound ◽  
Lattice Site ◽  
The Other ◽  
Water Molecules ◽  
X Ray Diffraction ◽  
Triangular Face ◽  
X Ray

The crystal structure of the title compound, Ca(C6H2N307)2,5H2O, has been determined by single-crystal X-ray diffraction at 295(1) K and refined by least squares to a residual of 0.049 for 1513 'observed' reflections. Crystals are orthorhombic, Pmab, a 24.169(6), b l0.292(7), c 8.554(2) �, Z 4. The stereochemistry about the calcium has not been observed previously for the system [M(bidentate)2- (unidentate)4]; in the present structure, the calcium is coordinated by a pair of bidentate picrate ligands and the four water molecules in an array in which three of the water molecules occupy a triangular face of a square antiprism, the overall array having m symmetry. The remaining water molecule occupies a lattice site with no close interaction with the other species.

Synthesis, crystal structure, and vibrational spectra of the complex maleic acid•2H2O•18-crown-6

1990 ◽  
Vol 68 (12) ◽  
pp. 2183-2189 ◽  
Author(s):  
Pierre Audet ◽  
Rodrigue Savoie ◽  
Michel Simard
Keyword(s):  
Crystal Structure ◽  
Water Molecule ◽  
Maleic Acid ◽  
Water Molecules ◽  
Infrared And Raman Spectra ◽  
X Ray Diffraction ◽  
Monoclinic System ◽  
X Ray ◽  
O 18 ◽  
Stoichiometric Complex

A stoichiometric complex of formula maleic acid•2H2O•18-crown-6 has been obtained from maleic acid and the macrocyclic polyether 18-crown-6. Crystals of this complex have been shown by X-ray diffraction crystallography to belong to the Cc space group of the monoclinic system. The acid molecules in the adduct are linked to each other through a water molecule, giving infinite [-acid-H2O-]n chains. They are also linked to the crown ether via water molecules. The infrared and Raman spectra of the complex are presented and compared to those of crystalline maleic acid. Keywords: maleic acid/18-crown-6, structure, X-ray, spectra.

Etude structurale par diffraction des RX et spectroscopie IR des hydrates 10 et 8.4 Å de kaolinite

1999 ◽  
Vol 32 (5) ◽  
pp. 968-976 ◽  
Author(s):  
S. Jemai ◽  
A. Ben Haj Amara ◽  
J. Ben Brahim ◽  
A. Plançon
Keyword(s):  
Water Molecule ◽  
Octahedral Site ◽  
Ammonium Fluoride ◽  
Water Molecules ◽  
X Ray Diffraction ◽  
Tetrahedral Sheet ◽  
X Ray ◽  
Octahedral Sites ◽  
Sheet Structure

Two hydrated kaolinites, characterized by 10 and 8.4 Å basal distances, were synthesized by treating the kaolinite KGa-1 with dimethyl sulfoxide (DMSO) and ammonium fluoride (NH4F). The X-ray diffraction study was based on a comparison between the experimental and calculated profiles. This study was conducted in two steps: firstly, the study of the 00lreflections enabled the determination of the stacking mode alongc*, the number of water molecules and their positions along the normal to the plane of the sheet structure; secondly, the study of thehkbands, withhand/ork≠ 0, enabled the determination of the stacking mode and the positions of the water molecules in the (a,b) plane. The 10 Å hydrated kaolinite is characterized by two water molecules per Al2Si2O5(OH)4unit, situated at 3 and 3.4 Å from the hydroxyl surface, over the octahedral sites. Two adjacent layers are translated with respect to each other, withT11= −0.38a− 0.37b+ 10n. The 8.4 Å hydrated kaolinite is characterized by one water molecule per Al2Si2O5(OH)4unit, situated at 2.4 Å from the hydroxyl surface and inserted between the vacant octahedral site and the ditrigonal cavity of the tetrahedral sheet. The corresponding interlayer shift isT11= −0.355a+ 0.35b+ 8.4n.

The hydrolytic water molecule in trypsin, revealed by time-resolved Laue crystallography

Science ◽  
1993 ◽  
Vol 259 (5095) ◽  
pp. 669-673 ◽  
Author(s):  
PT Singer ◽  
A Smalas ◽  
RP Carty ◽  
WF Mangel ◽  
RM Sweet
Keyword(s):  
Water Molecule ◽  
Three Dimensional ◽  
Initial Step ◽  
X Ray Diffraction ◽  
Time Resolved ◽  
X Ray ◽  
Density Maps ◽  
Before And After ◽  
Ph Jump ◽  
Hydrolysis Of

Crystals of bovine trypsin were acylated at the reactive residue, serine 195, to form the transiently stable p-guanidinobenzoate. Hydrolysis of this species was triggered in the crystals by a jump in pH. The hydrolysis was monitored by three-dimensional Laue crystallography, resulting in three x-ray diffraction structures, all from the same crystal and each representing approximately 5 seconds of x-ray exposure. The structures were analyzed at a nominal resolution of 1.8 angstroms and were of sufficient quality to reproduce subtle features in the electron-density maps for each of the structures. Comparison of the structures before and after the pH jump reveals that a water molecule has positioned itself to attack the acyl group in the initial step of the hydrolysis of this transient intermediate.

scholarly journals SYNTHESIS AND STRUCTURE OF 4-(9-HYDROXY-1,4,7-TRIOXYNONYL)PHTHALONITRILE

2017 ◽  
Vol 60 (3) ◽  
pp. 15
Author(s):  
Alexandra S. Kuznetsova ◽  
Maksim V. Dmitriev ◽  
Alexander V. Zav’yalov ◽  
Oscar I. Koifman ◽  
Mikhail K. Islyaikin
Keyword(s):  
Water Molecule ◽  
Ethyl Acetate ◽  
Theoretical Calculations ◽  
Triethylene Glycol ◽  
Solvent Evaporation ◽  
Water Molecules ◽  
X Ray Diffraction ◽  
Intermolecular Hydrogen Bonds ◽  
Reduced Pressure ◽  
X Ray

4-(9-Hydroxy-1,4,7-trioxynonyl)phthalonitrile was prepared by reaction of 4-nitrophthalonitrile with triethylene glycol in dry DMSO in the presence of fresh-calcined fine milled K2CO3 at 60 °C for 12 hours. The reaction mixture was poured into cold distilled water and extracted by CH2Cl2. Then the crude product obtained after solvent evaporation was purified by column chromatography on silica gel using elution mixture of ethyl acetate : hexane (1:3) and after that end product was dried at reduced pressure at 80 oC for 4 h. The product was characterized by IR and 1Н NMR spectroscopies, mass-spectrometry, elemental analysis and X-ray diffraction data. In MALDI-TOF spectrum, two signals located at 299 [M+Na]+  and 315 [M+К]+ Da were detected. Conformity between the calculated isotopic distributions and those derived from experimental data proves these assignments. A colorless monocrystal suitable for X-Ray measurements was grown up by low temperature solvent evaporation from a solution of 4-(9-hydroxy-1,4,7-trioxynonyl)phthalonitrile in ethyl acetate. X-ray studying showed that this compound is a monohydrate of 4-(9-hydroxy-1,4,7-trioxynonil)phthalonitrile with a water molecule located in lateral chain. Four molecules of 4-(9-hydroxy-1,4,7-trioxynonil)phthalonitrile and four water molecules were founded to be located in one unit cell with formatting eight intermolecular hydrogen bonds. Hence triethylene glycol fragment forms a chelate-like cavity which is able to hold a water molecule or a cation of alkali metal. It was found that its structure is very similar to that optimized at DFT/B3LYP/6-31G(d,p) level. The some bond lengths of theoretical calculations are found to be greater than experiment data because of close intermolecular interactions in solid state.Forcitation:Kuznetsova A.S., Dmitriev M.V., Zav’yalov A.V., Koifman O.I., Islyaikin M.K. Synthesis and structure of 4-(9-hydroxy-1,4,7-trioxynonyl)phthalonitrile. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 3. P. 15-21.

Molecular composite films of MoS2 and styrene

1991 ◽  
Vol 6 (5) ◽  
pp. 1103-1107 ◽  
Author(s):  
W.M.R. Divigalpitiya ◽  
R.F. Frindt ◽  
S.R. Morrison
Keyword(s):  
Electrical Conductivity ◽  
Organic Molecules ◽  
Composite Films ◽  
Water Molecules ◽  
X Ray Diffraction ◽  
X Ray ◽  
Before And After ◽  
Molecular Layers

Novel composite films with a monolayer of organic molecules included between single molecular layers of MoS2 can be prepared with a recently described technique. Styrene-included MoS2, before and after polymerization, is discussed as an example that exhibits interesting properties. The sensitivity to humidity of the styrene-included MoS2 system is monitored in situ with x-ray diffraction where reversible incorporation and removal of water molecules are observed. Films with an anisotropy of electrical conductivity of about 108 are obtained by polymerizing the monomer between the layers.

Infrared Studies of Water in Crystalline Hydrates: LiI.3H2O

1971 ◽  
Vol 49 (3) ◽  
pp. 347-351 ◽  
Author(s):  
George Brink ◽  
Michael Falk
Keyword(s):  
Hydrogen Bond ◽  
Water Molecule ◽  
Water Molecules ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
Infrared Studies ◽  
Librational Motion ◽  
Increasing Temperature ◽  
Crystalline Hydrates

The infrared spectra of undeuterated and partially deuterated LiI.3H2O were recorded between 4000 and 1000 cm−1. The splitting of the fundamentals of isotopically dilute HDO indicates that the water molecules are distorted and form one strong, linear OH … I− hydrogen bond and one weak, non-linear hydrogen bond. The non-equivalence of the two hydrogens of the water molecule disagrees with the space group P63mc − C6υ4 for this hydrate, proposed on the basis of X-ray diffraction studies. It is concluded that the space group, including hydrogens, is one of lower symmetry, P63 − C66. The gradual broadening and convergence of the HDO fundamentals at increasing temperature is explained by increasing librational motion of the water molecules.

Evaluation of Freezing Methods by Low Temperature X-Ray Diffraction

1977 ◽  
Vol 35 ◽  
pp. 330-333
Author(s):  
T. Gulik-Krzywicki ◽  
M.J. Costello
Keyword(s):  
Biological Materials ◽  
Molecular Organization ◽  
X Ray Diffraction ◽  
Glass Capillary ◽  
X Ray ◽  
Rate Dependent ◽  
Before And After ◽  
Freeze Etching ◽  
Diffraction Patterns ◽  
Set Up

Freeze-etching electron microscopy is currently one of the best methods for studying molecular organization of biological materials. Its application, however, is still limited by our imprecise knowledge about the perturbations of the original organization which may occur during quenching and fracturing of the samples and during the replication of fractured surfaces. Although it is well known that the preservation of the molecular organization of biological materials is critically dependent on the rate of freezing of the samples, little information is presently available concerning the nature and the extent of freezing-rate dependent perturbations of the original organizations. In order to obtain this information, we have developed a method based on the comparison of x-ray diffraction patterns of samples before and after freezing, prior to fracturing and replication.Our experimental set-up is shown in Fig. 1. The sample to be quenched is placed on its holder which is then mounted on a small metal holder (O) fixed on a glass capillary (p), whose position is controlled by a micromanipulator.

Structural Study of a new Compound Based on Acid 1,4-Cyclohexanedicarboxylic (1,4-CDC)

2010 ◽  
Vol 6 (1) ◽  
pp. 891-896
Author(s):  
Manel Halouani ◽  
M. Dammak ◽  
N. Audebrand ◽  
L. Ktari
Keyword(s):  
Aqueous Solution ◽  
Water Molecules ◽  
Carboxyl Group ◽  
X Ray Diffraction ◽  
Compound I ◽  
Unit Cell Parameters ◽  
Monoclinic System ◽  
X Ray ◽  
Cell Parameters ◽  
Cyclohexanedicarboxylic Acid

One nickel 1,4-cyclohexanedicarboxylate coordination polymers, Ni2 [(O10C6H4)(COO)2].2H2O  (I), was hydrothermally synthesized from an aqueous solution of Ni (NO3)2.6H2O, (1,4-CDC) (1,4-CDC = 1,4-cyclohexanedicarboxylic acid) and tetramethylammonium nitrate. Compound (I) crystallizes in the monoclinic system with the C2/m space group. The unit cell parameters are a = 20.1160 (16) Å, b = 9.9387 (10) Å, c = 6.3672 (6) Å, β = 97.007 (3) (°), V= 1263.5 (2) (Å3) and Dx= 1.751g/cm3. The refinement converged into R= 0.036 and RW = 0.092. The structure, determined by single crystal X-ray diffraction, consists of two nickel atoms Ni (1) and Ni (2). Lots of ways of which is surrounded by six oxygen atoms, a carboxyl group and two water molecules.

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