Search results for "X-Ray"
showing 10 items of 4234 documents
Synthesis and crystal structure of Na1+xV4P4O17(OH) (x ≈ 1.44)
1990
Abstract Hydrothermal synthesis starting from Na0.46VOPO4 · 1.58H2O leads to a new mixed-valence sodium vanadium phosphate: Na2.44V4P4O17(OH) (orthorhombic, space group Pnma; Z = 4; a = 13.723(5) A, b = 6.314(2) A, c = 16.139(4) A; R = 0.032 for 2659 reflections). In this phase, the interconnection of three complex types of infinite chains, built from VO6 octahedra and PO4 tetrahedra, sometimes edgeshared, defines tunnels partly occupied by a portion of the sodium atoms.
Synthesis and x-ray crystal structure of dimethyltin(IV) dithiocyanate bihydrate adduct with a crown ether
1985
Me 2 Sn(NCS) 2 (OH 2 ) 2 . 18-crown-6 cristallise dans P2 1 /n avec Z=2; affinement jusqu'a R=0,058
2,2'-BIPYRIMIDINEOXALATOCOPPER(II) COMPLEXES - FROM THE MONONUCLEAR COMPLEX TO THE 2D SHEET-LIKE POLYMER
1993
Über polystannane
1987
Abstract The three compounds Ph4Sn2(X3CCO2)2 were synthesized from Ph2SnH2 and X3CCOOH (X = H, Cl) or by cleavage of two phenyl groups in Ph6Sn2 with Stoichiometric amounts of X3CCOOH (X = Cl, F). The crystal structures (R = 0.041, 0.030, 0.058) show that the Ph4Sn2 units are bridged by two isobidentate acetates resulting in five-coordinated tin atoms. Five crystallographically independent centrosymmetric molecules form three distinct conformers. Bonding parameters (compared with Ph6Sn2): distances d(SnSn) 269, 271, 272, 277 pm; NMR couplings (CDCl3 solution) 1J(SnSn) 16870, 9443, 12915, 4480 Hz; stretching vibrations ν(SnSn) 152, 155, 157, 159 cm−. The ion pairs [Ph4Sn2]2+ [(X3CCO2)2]2−…
The structure of a dinuclear silver(I) complex: Ag2[S2C2(CN)2] [P(C6H5)3]4
1986
Abstract The crystal structure of the dimeric Ag maleonitriledithiolate complex, Ag2[S2C2(CN)2] [P(C6- H5)3]4 (1), has been performed. Complex 1 crystallizes in the space group P21/c with a = 12.2898(77), b = 23.8325(91), c = 23.1790(118) A, β = 101.315(43)° and Z = 4. Refinement using 3253 reflections with Fo2>3σ(Fo2) yielded R = 0.0662, Rw= 0.0669. The most interesting aspect of the structure is the strong bridging interaction of the chelating maleonitriledithiolate ligand with the second Ag center, where a Ag-S distance of 2.478 A is observed. The residual bonding capability of the sulfur atoms in the chelating anion [Ag(S2C2(CN)2)(PPh3)2]− for [Ag(PPh3)2]+ is demonstrated.
Morphology and local organization of water-containing (1R,2S)-Dodecyl(2-hydroxy-1-methyl-2-phenylethyl)dimethylammonium bromide reverse micelles disp…
2014
The structure of (1R,2S)-dodecyl(2-hydroxy-1-methyl-2-phenylethyl)dimethylammonium bromide (DMEB) reverse micelles, at various water-to-surfactant molar ratio (R-w, R-w = [water]/[DMEB]) and DMEB concentrations, has been investigated by small angle X-ray scattering (SAXS) and extended X-ray absorption fine structure spectroscopy (EXAFS). SAXS data of dry reverse micelles are consistent with a model of spherical hydrophilic core surrounded by DMEB alkyl chains whose polydispersity decreases significantly with surfactant concentration. By adding water, a sphere to cylinder transition occurs leading to a one-dimensional growth of reverse micellar cores with R-w and surfactant concentration. Th…
Copper(II) complexes of 3-aminopropanols. Synthesis and structure of (3-aminopropanolato)formatocopper(II)
1987
Abstract The crystal and molecular structure of the title compound has been determined from single-crystal X-ray data and refined to a final R value of 0.030 for 971 reflections. The compound crystallizes in the monoclinic space group P21/c with two dimeric molecules in a cell of dimensions a=856.9(1), b= 887.7(1), c=837.0(1) pm and β=99.55(1)°. The blue crystals of Cu(ap)(HCOO) (ap=3-aminopropanolato ion) are made of centrosymmetric dialkoxy bridged dimers (Cu…Cu 296.4(1) pm). The dimers are polymerized along the c axis into chains via two NHO hydrogen bonds (Cu…Cu 547.9(1) pm). These chains are joined together along the b axis by CuOCOCu bridges and NHO hydrogen bonds (Cu…Cu 462.2(1) pm…
Cation and Anion Coordination Chemistry of Palladium(II) with Polyazacycloalkanes. Thermodynamic and Structural Studies
1992
The interaction of PdCI2 4 - with the macrocyclic ligands of the series [3k]aneNk has been studied both in solution and in the solid state. [18]aneN6 and [21]aneN7 form both mono- and binuclear Pd2+ complexes, whose stability constants have been determined in 0.5 mol dm-3 NaCI at 298.15 K. [21]aneN7 also forms, in solution, a trinuclear species in which an amino group deprotonates to bridge two Pd2+ ions, as observed in the solid state. The crystal structure of the complexes [Pd2([18]aneN6)Cl2][CIO4]2 and [Pd3[21]aneN7)CI3][CIO4]2 ⋅ H2O have been solved by single crystal X-ray analysis. C12H30N6CI4O8Pd2: monoclinic, space group C2/m, a = 10.876(2), b = 18.117(2), c = 7.043(2) A, s = 113.78(…
Human neuroglobin: crystals and preliminary X-ray diffraction analysis
2002
Neuroglobin, a recently discovered member of the haemoglobin superfamily, is primarily expressed in the brain of humans and other vertebrates, where it has been proposed to enhance O(2) supply in response to hypoxia or ischaemia, protecting the neuron from hypoxic injury. Neuroglobin is the first example of a vertebrate haemoglobin in which a hexacoordinate haem geometry has been detected. A triple mutant (replacing three Cys residues) of human neuroglobin (151 amino acids) has been expressed in Escherichia coli, purified and crystallized in two crystal forms, the best of which diffracts to 1.95 A resolution using synchrotron radiation. The crystals belong to space group P2(1), with unit-ce…
Concave π-prismand hydrocarbon [2.2.2]cyclophanes and their crystalline Ag-triflate complexes
1999
New small concave hydrocarbon cyclophanes were prepared via the well-known HD-2SO2-method. The cyclophanes obtained are isomers of the very well-known [2.2.2]p,p,p-cyclophane, C24H24, a π-prismand efficiently complexing Ag+-ion. X-ray crystal structure determinations showed the bis-sulfide 7 (1,10-dithia[3.3.2]m,p,p-cyclophane) to be helically chiral and that the conformation of the parent hydrocarbon cyclophane 13 ([2.2.2]m,p,p-cyclophane) does not change dramatically upon complexation with the Ag+-ion. The 16- and 17-membered [2.2.2]m,m,p- and [2.2.2]m,p,p-cyclophane (15 and 16) also act as π-prismands and form surprisingly similar crystalline 1:1 Ag-triflate complexes (π-prismates) as th…