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X-ray Diffraction Techniques (x-ray + diffraction_techniques)
Kinds of X-ray Diffraction Techniques Selected AbstractsCobalt and Nickel Complexes Bearing Pyrazolyliminophosphorane Ligands: Synthesis, Characterisation and Catalytic Ethylene Oligomerisation BehaviourEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 23 2006Cheng Zhang Abstract Treatment of 1-(2,-azidophenyl)-3,5-dimethylpyrazole (1) with Ph2PR (R = Ph, Me) and (Ph2P)2CH2, respectively, affords the pyrazolyliminophosphoranes 2, 3 and 4. Reaction of 2 or 3 with [NiCl2(dme)] or NiBr2 yields the N,N-chelate nickel complexes 5,8, and with CoCl2 complexes 9 and 10. Reaction of 4 with [NiCl2(dme)], NiBr2 and CoCl2, respectively, affords the N,N,P-chelate complexes 11,13. Compounds 2,4 were characterised by 1H, 13C, 31P NMR and IR spectroscopy and elemental analysis, while complexes 5,13 were characterised by IR spectroscopy and elemental analysis. The structures of complexes 5, 9 and 12 were further characterised by single-crystal X-ray diffraction techniques. Complexes 5,13 are active catalysts for ethylene oligomerisation upon activation with alkylaluminium derivatives(Et2AlCl, MAO or MMAO). These complexes exhibit good to high catalytic activities (up to 3.54,×,106 g,mol,1,h,atm for the nickel complexes and 5.48,×,105 g,mol,1,h,atm for the cobalt complexes). The effects of varying ethylene pressure, temperature and aluminium co-catalyst/Ni or Co ratios with complexes 5, 9, 11 and 12 are reported. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] A Crystalline Phase Transition and Optical Properties in a CoIICuII Oxamato-Bridged Ferrimagnetic ChainEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 24 2005Cynthia L. M. Pereira Abstract The compound [CoCu(opba)(DMSO)3] (1) [opba = ortho -phenylenebis(oxamato)] has been synthesized and characterized. Its crystal structure has been analyzed by X-ray diffraction techniques at 100 and 298 K. A structural phase-transition has been detected at around 150 K. An orthorhombic crystalline system is found at both temperatures, with very similar unit-cell dimensions. At room temperature 1 crystallizes in the Pnam space group (, -1 phase), with a = 7.6712(2), b = 14.8003(3), c = 21.0028(5) Å, and Z = 4, whereas at low temperature it crystallizes in the Pna21 space group (, -1 phase), with a = 7.3530(2), b = 14.5928(4), c = 21.0510(7) Å, and Z = 4. Both crystalline phases consist of linearly ordered bimetallic chains with the [Cu(opba)]2, units tied by CoII ions to form a one-dimensional system. The DMSO molecules in , -1, which are coordinated to either CuII or CoII, are disordered. At low temperature, a small reorganization of the CuII and CoII environments is observed. The origin of this phase transition, which is completely reversible, is the modification of the crystalline packing with the temperature. Linear birefringence measurements were done on single crystals in the 100,300 K temperature range. Around 150 K, the linear birefringence curve shows an inflexion that is interpreted as being related to the conversion of ,-1 into , -1. Both dc and ac magnetic measurements were performed on the polycrystalline sample. The results reveal a one-dimensional ferrimagnetic behavior. Single crystal optical characterization at room temperature shows that 1 presents a very strong dichroism superposed on the linear birefringence. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Energetic materials: variable-temperature crystal structure of ,-NTOJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 2 2003Nadezhda B. Bolotina The crystal structure of the metastable , form of 5-nitro-2,4-dihydro-3H -1,2,4-triazol-3-one (,-NTO, monoclinic, P21/c) has been investigated at five temperatures in the range 100,298,K using single-crystal X-ray diffraction techniques. The second-rank thermal expansion tensor has been determined to describe thermal behavior of the crystal. The most significant thermal expansion is in a plane, which is almost perpendicular to the planes of all the NTO molecules. Perpendicular to the plane of maximal thermal expansion, a modest thermal contraction takes place. Both thermal expansion and contraction of the crystal lattice indicate anharmonicity of the atomic thermal motion. The experimental thermal variation of the unit-cell parameters is in qualitative agreement with that previously obtained from molecular dynamics calculations. Rigid-body analysis of the molecular thermal motion was performed using the libration and translation second-rank tensors. Although the translation part of the thermal motion is not strongly anisotropic, the largest displacements of the NTO molecules are oriented in the plane of maximal thermal expansion of the crystal and have significant anharmonic components. The libration motion is more anisotropic, and the largest libration as well as the largest translation principal axes are directed along the C5,N5 bond in each NTO molecule. [source] X-ray emission spectroscopy with a laser-heated diamond anvil cell: a new experimental probe of the spin state of iron in the Earth's interiorJOURNAL OF SYNCHROTRON RADIATION, Issue 5 2005Jung-Fu Lin Synchrotron-based X-ray emission spectroscopy (XES) is well suited to probing the local electronic structure of 3d transition metals such as Fe and Mn in their host phases. The laser-heated diamond anvil cell technique is uniquely capable of generating ultra-high static pressures and temperatures in excess of 100,GPa and 3000,K. Here X-ray emission spectroscopy and X-ray diffraction have been interfaced with the laser-heated diamond cell for studying the electronic spin states of iron in magnesiowüstite-(Mg0.75,Fe0.25)O and its crystal structure under lower-mantle conditions. X-ray emission spectra of the ferrous iron in a single crystal of magnesiowüstite-(Mg0.75,Fe0.25)O indicate that a high-spin to low-spin transition of ferrous iron occurs at 54 to 67,GPa and 300,K and the ferrous iron remains in the high-spin state up to 47,GPa and 1300,K. This pilot study points to the unique capability of the synchrotron-based XES and X-ray diffraction techniques for addressing the issue of electronic spin transition or crossover in 3d transition metals and compounds under extreme high- P,T conditions. [source] Nanosized PbZrO3 Powder from Oxalate Precursor: Microwave-Aided Synthesis and Thermal CharacterizationJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2009Yuvraj S. Malghe Nanosized lead zirconate (PbZrO3) powder was synthesized from its oxalate precursor, namely lead zirconyl oxalate (LZO). LZO heated in a microwave heating system for 1 h yielded the PbZrO3 at 600°C. The same precursor (LZO), when heated in a resistance-heated furnace at 850°C for 3 h, does not give a pure product. Thermogravimetry, differential thermal analysis, and X-ray diffraction techniques were used to characterize the precursor and optimize the conditions for microwave processing. The particle size of PbZrO3 powder prepared at 600°C using microwave heating was measured using transmission electron microscopy (TEM). The TEM images show that the particles of PbZrO3 are spherical in shape and that the particle size varies between 20 and 22 nm. [source] X-ray characterization of epi-Ge/Pr2O3/Si(111) layer stacks by pole figures and reciprocal space mappingPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2009Peter Zaumseil Abstract An epi-Ge/Pr2O3/Si(111) layer structure prepared by consecutive steps of epitaxial deposition and annealing is used to demonstrate the possibility of a complex characterization by combination of different X-ray diffraction techniques. Especially pole figure measurements, reciprocal space mapping (RSM) and high resolution (HR) ,/2, scans at selected inclined netplanes were successfully used to determine the in-plane lattice orientation of the layers relative to the substrate, the strain state of all layers and the structural perfection of the epi-Ge film. It was found that the major part of the epi-Ge layer has the same type A stacking orientation as the Si substrate, but about 0.6% is of type B. The Pr2O3 buffer layer exhibits type B only. The strain state of oxide and epi-Ge was determined, and a small difference in the lattice constant of type A and B epi-Ge was found. Microtwins lying in inclined {111} planes were unambiguously identified by pole figure measurements as the dominating structural defects in the epi-Ge layer. They cause a characteristic scattering pattern in reciprocal space maps. The proposed combination of X-ray techniques allows a relatively fast, integral and non-destructive analysis of heteroepitaxial semiconductor oxide semiconductor structures. [source] Magnetic properties of Fe76X2B22 (X=Cr,Zr,Nb) amorphous alloysPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2003A. Chrobak Abstract The paper contains experimental results referring to optimization of soft magnetic properties and crystallization in the Fe76X2B22 (X=Cr,Zr,Nb) amorphous alloys. We have used measurement of thermomagnetic balance, magnetic permeability, coercive field and also HREM and X-ray diffraction techniques. It was shown that Zr and Nb alloying additions cause a slowing down of diffusion processes and an increase of the annealing for 1 hour optimization temperature of about 50 and 100 K, respectively. Activation enthalpies of the crystallization process were determined as: 2.0 eV (X=Cr), 2.6 eV (X=Zr) and 4.4 eV (X=Nb). [source] Mullite-type Ga4B2O9: structure and order,disorder phenomenonACTA CRYSTALLOGRAPHICA SECTION B, Issue 2 2010Rihong Cong Ga4B2O9, an aluminium-free mullite-type compound, was prepared by a boric-acid flux method and its structure was determined using powder X-ray diffraction techniques, in combination with transmission electron microscopy, solid-state 11B MAS-NMR and IR spectroscopies. GaO6 octahedra share edges in a trans -manner forming one-dimensional chains along the b direction, and the chains are further cross-linked by GaO5, BO3 and BO4 groups into a three-dimensional mullite-type structure. The disorder of the inter-chain groups results in a small unit cell for Ga4B2O9 compared with that for Al4B2O9, an ordered compound with a superstructure. By deconstructing the structure of Ga4B2O9, we were able to identify the fundamental building units and their linking rules which can be used to reconstruct the ordered and disordered structures. For Ga4B2O9, we found that the structure is intrinsically disordered within the ac plane, but ordered along the b axis. The three-dimensional structure can then be constructed by stacking the disordered ac sheets along the b axis (½b) with a ½a shift. The fundamental building units and exclusivity rules identified in this gallium borate mullite may also be useful for understanding other related mullite phases. The structure analysis applying the proposed method is used to recognize the structural features of Al4B2O9 and Al18B4O33. [source] Structure of Ga2O3(ZnO)6: a member of the homologous series Ga2O3(ZnO)mACTA CRYSTALLOGRAPHICA SECTION B, Issue 5 2008Yuichi Michiue The structure of Ga2O3(ZnO)6 was determined using single-crystal X-ray diffraction techniques in the space group Cmcm. The metal ion sublattice resembles some of the Zn ions in the wurtzite ZnO structure. The oxygen ion sublattice in Ga2O3(ZnO)6 also resembles some of the O ions in ZnO. Structural relationships between Ga2O3(ZnO)6 and ZnO are discussed, illustrating the process for obtaining the centrosymmetric Ga2O3(ZnO)6 structure from the noncentrosymmetric ZnO. Structures of phases in the homologous series Ga2O3(ZnO)m are predicted on the basis of the structural data for Ga2O3(ZnO)6. The structures of even m are constructed by simply extending the structure units seen in Ga2O3(ZnO)6, while those of odd m consist of structure units which are of different types from those used for even m. [source] Structure determination and phase transition behaviour of dimethyl sulfateACTA CRYSTALLOGRAPHICA SECTION B, Issue 2 2006Mark T. F. Telling The crystal structures of phase I and phase II of dimethyl sulfate, (CH3O)2SO2, have been determined using complementary high-resolution neutron powder and single-crystal X-ray diffraction techniques. Below its melting point of 241,K dimethyl sulfate crystallizes in an orthorhombic structure (I) in the space group Fdd2. On cooling below ,175,K the crystal transforms to a monoclinic structure (II) in the space group I2/a. The molecule is located on a twofold axis (Z, = 1/2) in both structures. The phase transition is of first order with strong hysteresis. The phase transition results in changes to both the intra- and the intermolecular coordination environment. [source] Pressure-induced polymorphism in phenolACTA CRYSTALLOGRAPHICA SECTION B, Issue 6 2002David R. Allan The high-pressure crystal structure of phenol (C6H5OH), including the positions of the H atoms, has been determined using a combination of single-crystal X-ray diffraction techniques and ab initio density-functional calculations. It is found that at a pressure of 0.16,GPa, which is just sufficient to cause crystallization of a sample held at a temperature just above its ambient-pressure melting point (313,K), a previously unobserved monoclinic structure with P21 symmetry is formed. The structure is characterized by the formation of hydrogen-bonded molecular chains, and the molecules within each chain adopt a coplanar arrangement so that they are ordered in an alternating 1-1-1 sequence. Although the crystal structure of the ambient-pressure P1121 phase is also characterized by the formation of molecular chains, the molecules adopt an approximate threefold arrangement. A series of ab initio calculations indicates that the rearrangement of the molecules from helical to coplanar results in an energy difference of only 0.162,eV,molecule,1 (15.6,kJ,mole,1) at 0.16,GPa. The calculations also indicate that there is a slight increase in the dipole moment of the molecules, but, as the high-pressure phase has longer hydrogen-bond distances, it is found that, on average, the hydrogen bonds in the ambient-pressure phase are stronger. [source] (E)-2-[(4-Chlorophenyl)iminomethyl]-5-methoxyphenol and (E)-2-[(2-chlorophenyl)iminomethyl]-5-methoxyphenol: X-ray and DFT-calculated structuresACTA CRYSTALLOGRAPHICA SECTION C, Issue 10 2009ak Ko The crystal structures of the title 4-chlorophenyl, (I), and 2-chlorophenyl, (II), compounds, both C14H12ClNO2, have been determined using X-ray diffraction techniques and the molecular structures have also been optimized at the B3LYP/6-31 G(d,p) level using density functional theory (DFT). The X-ray study shows that the title compounds both have strong intramolecular O,H...N hydrogen bonds and that the crystal networks are primarily determined by weak C,H..., and van der Waals interactions. The strong intramolecular O,H...N hydrogen bond is evidence of the preference for the phenol,imine tautomeric form in the solid state. The IR spectra of the compounds were recorded experimentally and also calculated for comparison. The results from both the experiment and theoretical calculations are compared in this study. [source] Hydrolysis of C,N -chelated diorganotin(IV) chlorides and catalysis of transesterification reactionsAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 7 2009ka Pad, lková Abstract Diorganotin(IV) dichlorides of formula LCNRSnCl2 (where R is nBu or Ph) containing one LCN chelating ligand were hydrolyzed with aqueous sodium hydroxide in benzene. The composition of the products is strongly dependent on the amount of hydroxide. The partially hydrolyzed compounds of composition (LCNRSnCl)2(µ-O) were isolated as crystalline products. A hydrolysis where more than one molar equivalent of NaOH is employed gave only a mixture of unidentifiable products. The structure of (LCNPhSnCl)2(µ-O) was determined by X-ray diffraction techniques in the solid state. In solution there was a mixture of diastereoisomers found, where the tin atoms serve as a stereogenic centers. The catalytic activity of starting dichlorides as well as (LCNPhSnCl)2(µ-O) in various transesterification processes was investigated. The activity is very low in the case of starting dichlorides. When two molar equivalents of NaH are added or (LCNPhSnCl)2(µ-O) is employed in the catalytic experiments, the activity is comparable to the literature data. Copyright © 2009 John Wiley & Sons, Ltd. [source] N,O-chelate aluminum and zinc complexes: synthesis and catalysis in the ring-opening polymerization of ,-caprolactoneAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 1 2009Cheng Zhang Abstract Reaction between 2-(1H -pyrrol-1-yl)benzenamine and 2-hydroxybenzaldehyde or 3,5-di- tert -butyl-2-hydroxybenzaldehyde afforded 2-(4,5-dihydropyrrolo[1,2- a]quinoxalin-4-yl)phenol (HOL1NH, 1a) or 2,4-di- tert -butyl-6-(4,5-dihydropyrrolo[1,2- a]quinoxalin-4-yl)phenol (HOL2NH, 1b). Both 1a and 1b can be converted to 2-(H -pyrrolo[1,2- a]quinoxalin-4-yl)phenol (HOL3N, 2a) and 2,4-di- tert -butyl-6-(H -pyrrolo[1,2- a]quinoxalin-4-yl)phenol (HOL4N, 2b), respectively, by heating 1a and 1b in toluene. Treatment of 1b with an equivalent of AlEt3 afforded [Al(Et2)(OL2NH)] (3). Reaction of 1b with two equivalents of AlR3 (R = Me, Et) gave dinuclear aluminum complexes [(AlR2)2(OL2N)] (R = Me, 4a; R = Et, 4b). Refluxing the toluene solution of 4a and 4b, respectively, generated [Al(R2)(OL4N)] (R = Me, 5a; R = Et, 5b). Complexes 5a and 5b were also obtained either by refluxing a mixture of 1b and two equivalents of AlR3 (R = Me, Et) in toluene or by treatment of 2b with an equivalent of AlR3 (R = Me, Et). Reaction of 2a with an equivalent of AlMe3 afforded [Al(Me2)(OL3N)] (5c). Treatment of 1b with an equivalent of ZnEt2 at room temperature gave [Zn(Et)(OL2NH)] (6), while reaction of 1b with 0.5 equivalent of ZnEt2 at 40 °C afforded [Zn(OL2NH)2] (7). Reaction of 1b with two equivalents of ZnEt2 from room temperature to 60 °C yielded [Zn(Et)(OL4N)] (8). Compound 8 was also obtained either by reaction between 6 and an equivalent of ZnEt2 from room temperature to 60 °C or by treatment of 2b with an equivalent of ZnEt2 at room temperature. Reaction of 2b with 0.5 equivalent of ZnEt2 at room temperature gave [Zn(OL4N)2] (9), which was also formed by heating the toluene solution of 6. All novel compounds were characterized by NMR spectroscopy and elemental analyses. The structures of complexes 3, 5c and 6 were additionally characterized by single-crystal X-ray diffraction techniques. The catalysis of complexes 3, 4a, 5a,c, 6 and 8 toward the ring-opening polymerization of ,-caprolactone was evaluated. Copyright © 2008 John Wiley & Sons, Ltd. [source] 6-(3,4-Difluorobenzoyl)-3-[2-(4-pyridyl)ethyl]-1,3-benzothiazol-2(3H)-oneACTA CRYSTALLOGRAPHICA SECTION C, Issue 10 2004Süheyla Özbey A new type of benzothiazolinone derivative with potential pharmacological activity, viz. 6-(3,4-difluorobenzoyl)-3-[2-(4-pyridyl)ethyl]-1,3-benzothiazol-2(3H)-one, C21H14F2N2O2S, has been prepared and studied by NMR, IR and single-crystal X-ray diffraction techniques. The molecule is not planar, the pyridine and difluorobenzene moieties being located above and below the benzothiazole ring system. The carbonyl O atoms are involved in an intramolecular hydrogen-bond-type interaction. [source] Influence of organotin compounds on phosphatidylserine membranesAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 3 2004José A. Teruel Abstract Organotin compounds are widely distributed toxicants. They are membrane-active molecules with broad biological toxicity. We have studied the interaction of tributyltin and triphenyltin with phosphatidylserine model membranes using differential scanning calorimetry, infrared spectroscopy and X-ray diffraction techniques. Organotin compounds produced a broadening of the gel to the liquid-crystalline phase transition of the phospholipid and a shifting of the phase transition temperature to lower values. Infrared spectroscopy experiments showed that tributyltin exerted a fluidizing effect on the apolar part of the bilayer, and that both tributyl- and triphenyltin interact with the interfacial region of the bilayer, making the carbonyl groups less accessible to water. As seen by X-ray diffraction experiments, organotin compounds were unable to change the bilayer macroscopic organization of the phospholipid, but they were able to reduce the long-range order of the multibilayer system and to disorder the packing of the phospholipid molecules. The observed interaction between organotin compounds and phosphatidylserine membranes promotes physical perturbations that could affect membrane function and may mediate some of their toxic effects. Copyright © 2004 John Wiley & Sons, Ltd. [source] Polymeric potassium diaquahexa-,-cyano-holmium(III)ruthenium(II) dihydrateACTA CRYSTALLOGRAPHICA SECTION C, Issue 9 2003Jason A. Kautz The crystal structure of the title bimetallic cyanide-bridged complex, {K[HoRu(CN)6(H2O)2]·2H2O}n, was determined by means of single-crystal X-ray diffraction techniques. The coordination about the central holmium(III) ion is eightfold in a square-antiprismatic arrangement, while the ruthenium(II) ion is octahedrally coordinated. Channels permeating the crystal lattice contain the potassium cations and two zeolitic water molecules. The HoIII and K atoms lie at sites with mm symmetry and the Ru atom is at a site with 2/m symmetry. [source] Mixed-chalcogenide double-butterfly complex [{(CO)6Fe2SSe}2{,-C(H),C(H)}]ACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2000Kaliyamoorthy Panneerselvam Bubbling acetylene gas slowly through a methanol solution of [(CO)6Fe2{,-SSe}] containing sodium acetate for 48,h at room temperature yields the double-butterfly complex ,-[ethane-1,1,2,2-tetra(selenido/sulfido)]bis[hexacarbonyldiiron(Fe,Fe)], [Fe4(C2H2S2Se2)(CO)12]. The molecular structure was established by single-crystal X-ray diffraction techniques. The structure consists of two Fe2SSe butterfly units linked to each other through a bridging HC,CH group. The molecule has twofold symmetry and the two Fe atoms have distorted octahedral geometries. [source] X-ray Diffraction and Solid-State NMR Studies of a Germanium Binuclear ComplexCHEMISTRY - A EUROPEAN JOURNAL, Issue 2 2006Luís Mafra Abstract A compound formulated as (C4H12N2)[Ge2(pmida)2(OH)2],4,H2O (where pmida4,=N -(phosphonomethyl)iminodiacetate and C4H12N22+=piperazinedium cation), containing the anionic [Ge2(pmida)2(OH)2]2, complex, has been synthesised by the hydrothermal approach and its structure determined by single-crystal X-ray diffraction analysis. Several high-resolution solid-state magic-angle spinning (MAS) NMR techniques, in particular two-dimensional 1H,X(13C,31P) heteronuclear correlation (HETCOR) and 1H,1H homonuclear correlation (HOMCOR) experiments incorporating a frequency-switched Lee,Goldburg (FS-LG) decoupling scheme, have been employed for the first time in such a material. Using these tools in tandem affords an excellent general approach to study the structure of other inorganic,organic hybrids. We assigned the NMR resonances with the help of C,,,H and P,,,H internuclear distances obtained through systematic statistical analyses of the crystallographic data. The compound was further characterised by powder X-ray diffraction techniques, IR and Raman spectroscopy, and by elemental and thermal analyses (thermogravimetric analysis and differential scanning calorimetry). [source] Preferred Conformations of Peptides Containing tert -Leucine, a Sterically Demanding, Lipophilic ,-Amino Acid with a Quaternary Side-Chain C, AtomCHEMISTRY - A EUROPEAN JOURNAL, Issue 8 2005Fernando Formaggio Prof. Abstract Terminally protected homopeptides of tert -leucine, from the dimer to the hexamer, co-oligopeptides of tert -leucine in combination with ,-aminoisobutyric acid or glycine residues up to the hexamer level, and simple dipeptides representing known scaffolds for catalysts in asymmetric organic reactions were prepared by solution methods and fully characterized. The results of conformation analysis, performed by use of FT-IR absorption, NMR, CD, and X-ray diffraction techniques, indicate that this hydrophobic ,-amino acid with tetrasubstitution at the C, atom is structurally versatile. We show that it prefers extended or semiextended conformations, but can also be accommodated in folded structures, provided that these are biased by the presence of helicogenic residues. The current large-scale production of Tle, combined with its conformational preferences unravelled in this work, should make this bulky, hydrophobic, C, -trisubstituted ,-amino acid a regular building block of any strategy seeking to tailor peptides with improved catalytic and pharmacological properties. [source] | ||||||||||