X-ray Investigation (x-ray + investigation)

Distribution by Scientific Domains
Distribution within Chemistry

Selected Abstracts

ChemInform Abstract: X-Ray Investigation of Metastable Crystalline Phases in Co-Deposited Fe,Cr Alloy Nanometer Films.

CHEMINFORM, Issue 18 2002
A. A. Levin
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

ChemInform Abstract: X-Ray Investigations of Sulfur-Containing Fungicides.

CHEMINFORM, Issue 1 2002
Part 4.
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

Highly Stereoselective Synthesis of Novel Multistereogenic Bis - Bifunctional Ligands Based on [2.2]Paracyclophane- 4,7-quinone, their Structure Elucidation and Application in Asymmetric Catalysis

Natalia Vorontsova
Abstract Bis - bifunctional cis -4,7-diarylsubstituted-4,7-dihydroxy-4,7-dihydro[2.2]paracyclophanes 3,6 were synthesized by a highly diastereoselective reaction of ortho -substituted aryllithium reagents with [2.2]paracyclophane-4,7-quinone (1). Enantiomerically pure diols 3,5 were tested as chiral inductors in the enantioselective addition of diethylzinc to benzaldehyde (up to 93.5% ee). Acid dehydration of cis -4,7-di(2-methoxyphenyl)-4,7-dihydroxy-4,7-dihydro[2.2]paracyclophane (3) results in 4,7-dihydro-7,8-di(2-methoxyphenyl)[2.2]paracyclophane-4-one (8) , a planar chiral cyclohexadienone of the [2.2]paracyclophane series with a para -semiquinoid substructure. X-Ray investigations of compounds 3, 4 and 8 were performed. [source]

Raman spectroscopic and X-ray investigation of stressed states in diamond-like carbon films

R. Krawietz
Abstract The non-destructive characterization of intrinsic stress is very important to evaluate the reliability of devices based on diamond-like carbon (DLC) films. Whereas the only requirement for the X-ray diffraction method is a crystalline state of specimen, Raman spectroscopic stress analysis is restricted to materials showing intensive and sharp Raman peaks. On the other hand, Raman spectroscopy offers the possibility to measure stress profiles with lateral resolution of about 1 micron. The results of stress measurements in DLC films using both X-ray diffraction and Raman spectroscopy are found in very good correspondence. Mean stress in carbon films consisting of very small crystallites on silicon substrates has been determined by measuring and fitting the stress profiles in the substrate near artificial vertical film edges. ( 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Reaction of Mercury(0) with the I2 Adduct of Tetraphenyldithioimidodiphosphinic Acid (SPPh2)2NH (HL) , Crystal Structures of [Hg(HL)I2] and HgL2

M. Carla Aragoni
Abstract The complex [Hg(HL)I2] (1) has been synthesised by reacting liquid Hg(0) in Et2O under mild reaction conditions with the I2 adduct of HL, HLI2, while HgL2 (2) has been obtained from the reaction of compound 1 with HL in CH3CN. A single-crystal X-ray investigation of 1 shows four independent molecules in the asymmetric unit, each of which contains an HgII ion coordinated to two iodine atoms and two sulfur atoms of one bidentate neutral ligand in a distorted tetrahedral coordination geometry. Compound 2 consists of two anionic ligands coordinated to an HgII ion, which again displays a distorted tetrahedral coordination sphere. The reaction of 2 with HI (55 wt.-% in water) affords [Hg(HL)2](I)2 (3). Compounds 1, 2, and 3 have been characterised by FT-IR and 31P NMR spectroscopy. Density functional calculations suggest that compound 3 should feature a distorted tetrahedral coordination around the metal centre, with unequal Hg,S bond lengths. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

X-ray investigation of CdSe nanowires

zgl Kurtulu
Abstract CdSe nanowires (NWs) have been prepared by a solution,liquid,solid (SLS) approach using Bi nanocatalysts. Structural characterization has been performed by X-ray powder diffraction providing an admixture of wurtzite and zinc-blende (ZB) structure units separated by different types of stacking faults. The relative contributions of ZB type stacking units within the NWs were determined to be in the order of 3,6% from a set of ratios of reflection intensities appearing in only wurtzite structure to those appearing in both ZB and wurtzite (W) structure. In addition, the anisotropy of domain size within the NWs was evaluated from the evolution of peak broadening for increasing scattering length. The coherence lengths along the growth direction are found to be changing between 16 and 21,nm, smaller than the results obtained from TEM measurement, while the NW diameters are determined to be between 5 and 8,nm which is in good agreement with TEM inspection. [source]

X-ray investigation of gene-engineered human insulin crystallized from a solution containing polysialic acid

V. I. Timofeev
Attempts to crystallize the noncovalent complex of recombinant human insulin with polysialic acid were carried out under normal and microgravity conditions. Both crystal types belonged to the same space group, I213, with unit-cell parameters a = b = c = 77.365,, , = , = , = 90.00. The reported space group and unit-cell parameters are almost identical to those of cubic insulin reported in the PDB. The results of X-ray studies confirmed that the crystals obtained were cubic insulin crystals and that they contained no polysialic acid or its fragments. Electron-density maps were calculated using X-ray diffraction sets from earth-grown and microgravity-grown crystals and the three-dimensional structure of the insulin molecule was determined and refined. The conformation and secondary-structural elements of the insulin molecule in different crystal forms were compared. [source]

Probing the shapes of chiral bis-(o -naphthalimidobenzoyl) systems using X-ray and circular dichroism methods

Urszula Rychlewska
CD (circular dichroism) and X-ray investigations have been carried out in order to identify the prevalent conformations and define the forces that determine the molecular and supramolecular organization of the alkyl-bridged bichromophoric [NAB, ortho -(1,8-naphthalimido)benzoyl] units, each consisting of the benzoyl substituted in the ortho position with the 1,8-naphthalimide group. The results reveal that NAB bichromophores incorporated into the same molecule exist in a variety of conformation/helicity combinations. The molecular structures are largely stabilized by local 1,3-CH/CO dipole,dipole interactions, while the crystal packing besides dispersive H...H interactions is mostly governed by multiple C,H...O(=C) and C,H..., interactions. The relatively small contribution of ,..., interactions comes from a pairwise off-face stacking between naphthalimide rings or from pairwise carbonyl..., interactions. All these types of intermolecular interactions have been summarized quantitatively by means of a Hirshfeld surface analysis. [source]

Synthesis and structural characteristics of lithocholate triads: steroid-type channels occupied by spacer fragments

Urszula Rychlewska
Reported in this paper are the syntheses and X-ray investigations of C2 symmetrical molecular A,B,A triads consisting of two steroid units (lithocholic acid or its methyl ester) joined together by linkers derived from bifunctional molecules such as terephthalic acid or N,N,-dicarboxypiperazine. Unlike their monomeric analogues, some of these compounds form inclusion complexes. All steroidal triads form crystals that are highly pseudo-centrosymmetric, in which the constituting molecules are held together either exclusively by van der Waals forces or form lattice inclusion complexes, with guest molecules hydrogen bonded to the host. The presence of carboxyl groups promotes the inclusion of pyridine molecules and the formation of the well known carboxylic acid...pyridine hydrogen bonds. Combined with pairwise face-to-face ,-stacking between pyridine rings, these hydrogen-bond interactions lead to the formation of extended supramolecular tapes, analogous to polymers. The co-crystals of pyridine and a lithocholic acid triad undergo a symmetry-lowering phase transition from a P1 cell with Z = 1 to a P1 cell with Z = 2. The two structures are virtually the same, the two independent molecules in the larger cell being related by pseudo-translation. Changes in the type of spacer between two methyl lithocholate units from planar aromatic (terephthalic acid) to highly puckered aliphatic six-membered ring (N,N,-dicarboxypiperazine) bring about inclusion properties and changes in side-chain conformation in a crystal. Although the efficient packing of these highly elongated molecules is hindered, as indicated by low values of crystal density, ranging from 1.16 to 1.19,g,cm,3, several very short C...O and H...H contacts are present in the crystals. [source]