276 resultados para CRYSTAL STRUCTURE
Resumo:
Radiation effects on polyamide-1010 specimens having various states of aggregation were studied using wide angle X-ray diffraction, electron spin resonance, calorific and sol measurement techniques. Experimental results indicated that chain crosslinking
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The reaction of lanthanide trichlorides with sodium tetrahydrofurfurylcyclopentadienyl in THF afforded bis(tetrahydrofurfurylcyclopentadienyl)lanthanide chloride complexes (C4H7OCH2C5H4),LnCl (Ln = Nd, Gd, Dy, Yb). All of the complexes were characterized
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X-ray diffraction and electrical and diamagnetic analyses revealed that the 2223 phase was significantly enhanced by high-valence cation (V5+, Nb5+, Ta5+, etc.) doping in BiSrCaCuO samples. The optimum nominal composition was Bi1.6M0.4Sr2Ca2Cu3 O(y)(M =
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Tricyclopentadienyl cerium tetrahydrofuranate (THF) was prepared by the reaction of (NH4)2Ce(NO3)6 with sodium cyclopentadienide(C5H5Na) in THF at molar ratio of 1:6 to give a brown crystal of (eta5-C5H5)3Ce.OC4H8; tricyclopentadienyl erbium tetrahydrofur
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Three series of samples LaMnyCo1-yO3+/-lambda, LaFeyMn1-yO3+/-lambda, and LaFeyCo1-yO3+/-lambda (y = 0.0 to 1.0) with Perovskite structure were prepared by an explosion method different from the generally used ceramic techniques. The variation of crystal
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A lanthanum coordination compound with glycine {[La(Gly)3.2H2O].(ClO4)3}n (Gly = NH+ 3-CH2-COO-) was synthesized and obtained in the form of single crystals. Its X-ray crystal structure has been determined and the IR spectrum has been studied. Crystallo
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A series of neutral eta6-C6Me6 complexes of lanthanide elements Ln(176-C6Me6)(AlCl4)3 . MeC6H5(Ln = Nd, Sm, Gd, Yb) has been prepared directly in good yields from the reaction of LnCl3, AlCl3 and C6Me6 in toluene. The complexes have been characte
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In the presence of 1,10-phenanthroline (phen), lanthanide chlorides LnCl3 reacted with cyclopentadienylsodium to give the novel complexes [Na.3phen]+[Ln(C5H5)3Cl]-.phen (Ln = La, Pr or Nd). In the praseodymium case, crystal structure analysis showed that
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{(C8H8)Dy[mu-OCH2(CH2)2CH=CH2](THF)}2 was prepared by the reaction of (C8H8)DyCl(THF)n with CH2=CH(CH2)2CH2ONa in THF and characterized by spectroscopic, analytical and crystallographic methods. Its crystal structure shows that the complex is a dimer with
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The title complex [Li(THF)4] [(tBuCp)Yb(NPh2)3] was synthesized by the reaction of t-butylcyclopentadienyl ytterbium dichloride with 2 equivalents of LiNPh2 in THF, hexane, and toluene at -78-degrees-C. The complex was characterized by elemental analysis,
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Me4C2(C5H4MgCl)2(THF) (THF = tetrahydrofuran) reacts with anhydrous SmCl3 in THF to give [Me4C2CP2SMCl.THF]2. The molecule is a dimer. Sm1 and Sm2 are bridged unsymmetrically by two chlorine atoms [Sm(1)-CI(1) 2.787(2), Sm(1)-Cl(2) 2.848(2), Sm(2)-Cl(1) 2
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A novel framework material, Zn-2(HPO4)(3).H3NCH2CH2NH3, has been synthesised and its crystal structure determined by single crystal X-ray diffraction.
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The title complex was prepared by reacting Yb(NO3)3 (12-crown-4) with 1, 10-phenanthiroline (hereafter phen) in acetone. It crystallized in the triclinic space group P1BAR with a = 10.095(5), b = 17.415(4), c = 8.710(2) angstrom; alpha = 92.45(2), beta = 115.83(3), gamma = 74.08(3)degrees and D(c), = 1.85 g cm-3; Z = 2. The metal ion in this complex is nine-coordinated to three bidentate nitrate ions, two nitrogen atoms of a phen and a water molecule. The crown ligand is hydrogen bonded to the coordination water molecule. The symmetry change of the crown ether is also discussed.
HOST-GUEST INTERACTIONS OF THIAMINE WITH ANIONS - CRYSTAL-STRUCTURE OF THIAMINE IODIDE SESQUIHYDRATE
Resumo:
The crystal structure of thiamine iodide sesquihydrate has been determined by X-ray diffraction methods as a host-guest model for coenzyme-substrate interactions. The asymmetric unit contains two chemical units. Both the thiamine molecules A and B, which are crystallographically independent, assume the usual F conformation and have a disordered hydroxyethyl side chain. An iodide anion (or a water molecule) bridges the pyrimidine and thiazolium rings of molecule A (or B) by forming a hydrogen bond with the amino group and an electrostatic contact with the thiazolium ring to stabilize the molecular conformation. In the crystal the thiamine molecules self-associate to form a pipe-like polymeric structure, in which four thiamine hosts surround an iodide guest and hold it through C(2)-H...I hydrogen bonds and thiazolium...I electrostatic interactions. Crystal data: C12H17N4OS+.I- . 1.5 H2O, monoclinic, P2(1)/c, a = 12.585(2), b = 25.303(5), c = 12.030(2) angstrom, beta = 115.15(1)degrees, V = 3468(1) angtrom3, Z = 8, D(c) = 1.606 g cm-3, R = 0.045 for 3328 observed reflections.
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A tetrahydrofurfurylcyclopentadienyl sodium tetrahydrofuranate complex was prepared by the reaction of tetrahydrofurfurylcyclopentadiene with metallic sodium in THF. Its crystal structure was determined by X-ray analysis. In the crystal. the tetrahydrofuranate complex C4H7OCH2C5H4Na . THF adopts a puckered chain structure with an eta5-(C4H7OCH2)C5H4 ring connected by a bridging Na(THF) unit. The oxygen in the eta5-(C4H7OCH2)C5H4 ring is coordinated to the sodium atom.