X-ray crystal structure of tribenzylaluminum · diethyl etherate

The crystal structure of tribenzylaluminum · diethyl etherate has been determined by single crystal X-ray diffraction techniques. It crystallizes in the monoclinic system, space group P2₁, with unit cell dimensions of a 8.106(1), b 15.098(2), c 10.037(1) Å, β 111.02(1)°, V 1146.6(3) ų, and Z = 2. The final full matrix least-squares refinement on 1139 data gave R_F 3.8 and R _wF 5.2%. The compound is similar to other organoaluminum adducts yielding a four coordinate aluminum atom with average AlC distances of 1.986 and an AlO distance of 1.901(4) Å which is significantly shorter than the AlO distance observed in other ether adducts. The average CAlC and CAlO angles are 113 and 106°, respectively.     

X-ray Structure of Bis（salicylidene）-p-diaminobenzene

IntroductionThe interactions between molecules involvingaromatic ring systems are of interest because oftheir effects on the structures and aggregation ofimportant biomolecules,on template efficiency in avariety of organic reactions,and on the solid statestructures of a variety oforganic molecules[1] .Con-sistent are the analysis results of more than 2 0 0phenylalanine- phenylalanine interactions in thecrystal structures of various proteins,which leadsto the following conclusions.( 1 ) Direct …     

X-ray structural study of fluorinated β-diketonate complexes of zirconium(IV)

Three novel complexes of zirconium(IV) are prepared and characterized by single crystal X-ray diffraction: zirconium(IV) pivaloyltrifluoroacetonate Zr(ptac)₄, zirconium(IV) trifluoroacetylacetonate Zr(tfac)₄, and zirconium(IV) hexafluoroacetylacetonate Zr(hfac)₄. Crystal data for C₃₂H₄₀F₁₂ZrO₈: a = 19.9842(6) Å, b = 11.8417(3) Å, c = 16.4831(5) Å; β = 95.2880(10)°, monoclinic, space group Cc, Z = 4, d _calc = 1.491 g/cm³, R = 0.061. Crystal data for C₂₀H₁₆F₁₂ZrO₈: a = 21.5063(15) Å, b = 7.9511(5) Å, c = 16.0510(10) Å; β = 113.736(4)°, monoclinic, space group C2/c, Z = 4, d _calc = 1.860 g/cm³, R = 0.047. Crystal data for C₂₀H₄F₂₄ZrO₈: a = 15.3533(13) Å, b = 20.2613(15) Å, c = 19.6984(17) Å; β = 95.828(2)°, monoclinic, space group P2₁/c, Z = 2, d _calc = 2.004 g/cm³, R = 0.078. All the structures are molecular and include isolated mononuclear Zr(β-dik)₄ complex molecules. Coordination environment of zirconium atom is made by eight oxygen atoms of four β-diketonates; the coordination polyhedron is an almost regular square antiprism. The Zr-O distances fall within 2.14–2.23 Å. Complexes in the structures are joined by van der Waals interactions. Using the structural data, the van der Waals energies of crystal lattices of the studied compounds are calculated by the atom-atom potential method.     

Single-crystal X-ray diffraction analysis of arylamine-containing 2,2′-bipyridine derivatives

The structures of six 2,2′-bipyridine derivatives containing aromatic amine moieties, namely N-aryl-4-aryl-1-(pyridin-2-yl)-6,7-dihydro-5H-cyclopenta[c]pyridine-3-amines, were studied by single-crystal X-ray diffraction. The molecular structures and the effect of the substituents of these compounds on the crystal packing are discussed.

     

High resolution Lα X-ray fluorescence spectra of palladium compounds

High-resolution Pd Lα (L₃–M_4,5) X-ray fluorescence spectra of several Pd compounds were measured on a double-crystal X-ray fluorescence spectrometer. It was found that the chemical shifts of Pd Lα₁ line in Pd metal, Pd–Ag alloy, PdCl₂, PdBr₂, PdI₂, Pd(NO₃)₂ and Pd(acac)₂ were relatively small (less than 0.1 eV with metallic Pd as reference). We adopted the charge transfer effect to elucidate this seemingly anomalous experimental result. For divalent Pd, at the moment of the creation of a 2p⁻¹ core hole, one or two electrons were transferred from the ligand to the central Pd atom. Therefore the divalent Pd (II, 4d⁸) may have valence electron configuration similar to metallic Pd (0, 4d¹⁰), and this eventually results in the small chemical shifts.     

X-ray Fluorescence Characterization of Co/Ni–Cr Structures

A procedure was developed for the determination of the elemental composition and thickness of double-layer Co/Ni–Cr films on Polikor by X-ray fluorescence. Correction factors taking into account mutual interferences of elements in the system under study were calculated. The density of the film-forming materials was determined experimentally. The performance characteristics of the procedure were estimated.     

Development of X-ray fluorescence analysis in Russia in 1991–2010

A review attempted to examine the results of studies in X-ray fluorescence (XRF) analysis performed by Russian authors for the period from 1991 to the present time is given. This proved to be quite a challenge, since the number of articles published only on the theory and practice of XRF (excluding the development of equipment) exceeded 500. Therefore, the author had to limit himself to a more detailed presentation of only several important achievements. Further information, if necessary, can be found in the cited reviews.     

X-ray photoelectron spectroscopy for detection of the different Si–O bonding states of silicon

X-ray photoelectron spectroscopy (XPS) was used to detect the bonding between a silica particle surface and attached silanes. In addition to the commonly recorded Si 2p spectrum, the Si 1 s level is also accessible when monochromatic Ag Lalpha X-rays are applied. Furthermore, the spectrum of the Si 1 s level shows a fine structure. After spectrum deconvolution, we assigned the fitted spectral peaks to Si-C bonds of the silanes and to the Si-O bonds of the silica network. The recorded Si 1 s spectra were deconvoluted into peaks originating from Si-C bonds and the Si-O-Si silica network. To check the results of spectrum deconvolution, several differently functionalized silanes containing stoichiometric amounts of heteroatoms were applied for silica surface modification. We conclude that spectra deconvolution of the Si 1 s signal is an appropriate means for quantification of surface attached silane molecules.     

X-ray imaging of newly-developed gadolinium compound/silica core–shell particles

A preparation method for gadolinium compound (Gd) nanoparticles coated with silica (Gd/SiO₂) is proposed. Gd nanoparticles were prepared with a homogeneous precipitation method at 80 °C using 1.0 × 10⁻³ M Gd(NO₃)₃ and 0.5 M urea in the presence of 1.0 g/L stabilizer. Among stabilizers examined. Sodium n-dodecyl sulfate (SDS) was suitable as the stabilizer for preparing small Gd nanoparticles, and consequently Gd nanoparticles with a size of 46.2 ± 12.4 nm were prepared using the SDS. Silica-coating of the Gd nanoparticles was performed by a St?ber method at room temperature using 0.013 M TEOS and 2.0 × 10⁻³ M NaOH in water/1-propanol solution in the presence of 1.0 × 10⁻³ M Gd nanoparticles, which resulted in production of Gd/SiO₂ particles with an average size of 64.2 ± 14.4 nm. The Gd/SiO₂ particles were surface-modified with 3-aminopropyltrimethoxysilane and succinic anhydride. It was confirmed by measurement of electrophretic light scattering that amino group or carboxyl group was introduced onto the Gd/SiO₂ particles. The gadolinium concentration of 1.0 × 10⁻³ M in the as-prepared colloid solution was increased up to a gadolinium concentration of 0.4 M by centrifugation. The core–shell structure of Gd/SiO₂ particles was undamaged, and the colloid solution was still colloidally stable, even after the concentrating process. The concentrated Gd/SiO₂ colloid solution showed an X-ray image with contrast as high as a commercial Gd complex contrast agent. Internal organs in a mouse could be imaged injecting the concentrated colloid solution into it.     

L X-ray intensity ratios of some elements in the region of 56≤Z≤83

L X-ray intensity ratios of Ba, La, Ce, Gd, Er, Yb, Ta, Au, Hg, Pb, Bi have been measured. The L shell elctrons are excited by 59.5 keV gamma-rays from ²⁴¹ Am and the L X-rays from samples are measured with a Si(Li) detector. The experimental values are compared with the theoretical values of the pure elements.     

Manganese Kβ X-ray emission spectroscopy as a probe of metal-ligand interactions

A systematic series of high-spin mononuclear Mn(II), Mn(III), and Mn(IV) complexes has been investigated by manganese Kβ X-ray emission spectroscopy (XES). The factors contributing to the Kβ main line and the valence to core region are discussed. The Kβ main lines are dominated by 3p-3d exchange correlation (spin state) effects, shifting to lower energy upon oxidation of Mn(II) to Mn(III) due to the decrease in spin state from S = 5/2 to S = 2, whereas the valence to core region shows greater sensitivity to the chemical environment surrounding the Mn center. A density functional theory (DFT) approach has been used to calculate the valence to core spectra and assess the contributions to the energies and intensities. The valence spectra are dominated by manganese np to 1s electric dipole-allowed transitions and are particularly sensitive to spin state and ligand identity (reflected primarily in the transition energies) as well as oxidation state and metal-ligand bond lengths (reflected primarily in the transition intensities). The ability to use these methods to distinguish different ligand contributions within a heteroleptic coordination sphere is highlighted. The similarities and differences between the current Mn XES study and previous studies of Fe XES investigations are discussed. These findings serve as an important calibration for future applications to manganese active sites in biological and chemical catalysis.     

Single-crystal X-ray diffraction study of α-quartz-type Al1−xGaxPO4

Single crystals in the AlPO₄GaPO₄ system prepared by hydrothermal methods were investigated by electron microprobe analysis and X-ray diffraction. The fine details of the crystal structures, and, in particular, the intertetrahedral bridging angle and the tetrahedral tilt angle, were found to vary in an essentially linear manner with gallium content. The piezoelectric properties of α-quartz homeotypes are known to be correlated to these angles. The present results thus open the possibility to tune the piezoelectric properties of these materials by varying the chemical composition.     

Mössbauer and X-ray Investigation of Clay Minerals Originated from Libya

⁵⁷Fe transmission Mössbauer spectroscopy and X-ray diffractometry were used to study clay mineral samples originated from two different regions (Um-arrazm and Alkawasim) of Libya in order to get information about their mineralogical composition to assess their potential for use in the Libyan oil industry. In the samples originated from Um-arrazm calcite, akaganeite and nontronite while in the samples originated from Alkawasim quartz, akaganeite, montmorillonite, kaolinite, illite, mica and hematite were identified with different ratios by using diffraction method. The differences in the phase composition of iron-containing phases of samples from different localities have reflected in the complex Mössbauer spectra at both 300 K and 80 K. For the samples originated from Um-arrazm the Mössbauer parameters of subspectra were identified as nontronite and akaganeite.     

Synthesis and X-ray crystal structure of 3-deoxy-3-fluoro-β-D-allopyranoside

The synthesis of a novel compound, 3-deoxy-3-fluoro--d-allopyranoside, is described. It involves blocking the 4- and 6-positions of allose to cause fluorination only at the 3-position. This six-step synthesis gave pure crystalline compound in a 5% overall yield. The crystal structure, determined by X-ray diffraction, confirmed the chemical formula and configuration of the product. It showed that the C-F bond isaxial, while the C-(OH) bonds areequatorial. The overall conformation of this fluoroallose is similar to that of allose (Acta Cryst.1984,C40, 1863) (with OH instead of F), but the packing in the two crystals is different in the region of C3, the site of chemical variation.     

Characteristics of AOT Microemulsion Structure: a Small Angle X-ray Scattering Study

The structure of micelles has attracted renewed attention during the past decade years due to the widespread use of microemulsions in technology1 and life science1,2. To obtain information of the micellar structure, using X-ray scattering (SAXS) whose wavelength is close to the size of the micellar aggregates is one of the most direct method3-5 and SAXS has been proved to be very sensitive for the change of micellar composition6,7. SAXS experiments have been carried out to compare the st…     

X-ray structural proof of the stoichiometry of samarium polysulfide SmS1.9≡Sm10S19

The crystal structure of a samarium polysulfide single crystal, which is a phase with a composition SmS_1.9 was determined (Enraf-Nonius CAD-4 automatic diffractometer, λMoK_α, graphite monochromator, an absorption correction applied according to transmission curves and habit data, R_aniso = 0.0467 for 1963 independent I_hkl>2Σ(I) of 7817 I_hkl measured in the range 2.56?6?30.95?). The crystal is tetragonal, space group P4₂/n, a = 8.796(1), c = 15.889(3) å, V = 1229.3(3) å³; for the composition SmS_1.9 and Z = 20, d_calc = 5.707 g/cm³, d_exp = 5.71 ±0.02 g/cm³. It is shown that the crystal is isostructural to polyselenide crystals of analogous composition LnSe_1.9 (Ln = La, Ce, Pr, Nd); the stoichiometric formula of the compound is suggested to be Ln₁₀X₁₉ (Ln = La, Ce, Pr, Nd, Sm; X = S, Se). The crystals are of PbFCl structural type (P4/nmm, a₀, c₀) with the unit cell parameters related as $\bar a = \bar a_0 + 2\bar b_0 ,\bar b = - 2\bar a_0 + \bar b_0 ,\bar c = 2\bar c{}_0or a = b = a_0 \sqrt {5,} c = 2c$ . The phase individuality of the polysulfide is confirmed by the form of the P-T projection corresponding to the P-T-X diagram of the Sm-S system.     

Solid-state electrochemical,X-ray and spectroscopic characterization of substitutional solid solutions of iron–copper hexacyanoferrates

Copper and iron hexacyanoferrate form a continuous series of substitutional solid solutions, which have been studied by solid-state electrochemistry, X-ray powder diffraction, IR and ESR spectroscopy. All methods unambiguously prove the formation of solid solutions. The results show the different capabilities of these techniques to study such systems. Especially in the case of poor crystallinity and strongly magnetically interacting metal ions, voltammetry of immobilized microparticles offers a powerful tool for the determination of the composition and properties of solid solutions.