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61.
[Rb2(H2O)2][Re3(μ-Cl)3Br7(H2O)2]2 · H2O, a Mixed Halide-Hydrate with the Anionic Dimer {[Re3(μ-Cl)3Br7(H2O)2]2 · H2O}2? [Rb2(H2O)2][Re3(μ-Cl)3Br7(H2O)2]2 · H2O crystallizes as dark redbrown single crystals from an hydrobromic-acid solution of ReCl3 and RbBr at 0°C. An important feature of the crystal structure (monoclinic, C2/c; a = 1494.61(8); b = 835.71(4); c = 3079.96(19) pm; β = 97.801(4)°; Vm = 573.9(4) cm3mol?1; R = 0.060; Rw = 0.038) is the connection of two anions [Re3(μ-Cl)3Br7(H2O)2]? via a water molecule to dimers, {[Re3(μ-Cl)3Br7(H2O)2]2 · H2O}2?. These dimeric units are contained in slabs that are stacked in the [001] direction and held together by Rb+ cations and crystal water. 相似文献
62.
The title compound ist the first example of an adduct between telluric acid and the twenty four membered ring anion of a cyclododecaphosphate. [C(NH2)3]12P12O36 · 12 Te(OH)6 · 24 H2O crystallizes trigonal (rhomboedral: R3) with Z = 3 and the unit-cell dimensions a = 15.854(9), c = 51.26(2) Å in the hexagonal setting. The crystal structure was solved by direct methods and refined to a final R value of 0.031. It is characterized by a succession of three different typs of alternating layers perpendicular to the c direction. This layers are connected only by hydrogen bonds. The individual layers are built up of A: P12O36 anions, guanidinium cations and water of crystallisation, B: hexagonal arranged Te(OH)6 groups and guanidinium cations and C: water of crystallization. 相似文献
63.
New Rhenium Complexes Containing Trichalcogenido and Tetrachalcogenido Chelate Ligands The reactions of Cp*ReCl4 with polychalcogenide salts such as Na2S4 or (NEt4)2Se6 lead initially to the violet trichalcogenido chelate complexes Cp*ReCl2(E3) (E = S ( 3a ), Se ( 3b )) which, due to their functional chloro ligands, can be used as intermediates for further reactions. Upon hydrolysis in moist solvents or aminolysis with tert. butylamine 3a, b are converted into the tetrachalcogenido chelate complexes Cp*Re(O)(E4) (E = S ( 4a ), Se ( 4b )) and Cp*Re(NtBu)(E4) (E = S ( 5a ), Se ( 5b )), respectively. X-Ray structure analyses were carried out for the three mononuclear cyclo-oligoselenido compounds 3b–5b . It appears that the size of the Se2?n chelate ring (n = 3 or 4) essentially depends on steric factors within the coordination sphere of rhenium. 相似文献
64.
Lili Hu Marcus Wolf Michael Grätzel Zhonghong Jiang 《Journal of Sol-Gel Science and Technology》1995,5(3):219-226
The hydrolysis of niobium pentaethoxide precursor in the presence of triethylamine (TEA) is discussed. Three precursors with TEA/Nb(OEt)5 mole ratios of 0.25, 0.4 and 0.8 were prepared. Niobia colloids with different appearance were obtained after autoclaving the above precursors at 250°C during 12 h. The surface roughness and microstructure of niobia films prepared with the colloids by spread coating method are strongly dependent on the TEA/Nb(OEt)5 mole ratio. At a value of 0.4 TEA/Nb(OEt)5 mole ratio, a niobia film with large surface roughness can be achieved. It is opaque and mechanically stable and has differently ordered needle microstructure. The crystalline structure and photoelectrochemical property of niobia film with the largest surface roughness were examined. The effect of CO2 gas bubbling, reflux and addition of 2-methoxyethanol on the hydrolysis of Nb(OEt)5 and the nature of the Nb2O5 films is also discussed. 相似文献
65.
Mercury Compounds with Cyancarbanions. II Synthesis and Crystal Structure of Dimercury(I)-bis(1,1,3,3-tetracyanpropenide) The structure of dimercury(I)-bis(1,1,3,3-tetracyanpropenide), Hg2(tcp)2, has been determined by single-crystal X-ray diffraction methods. The crystals are monoclinic, space group P 21/n. The unit cell dimensions are: a = 9.9193(3) Å, b = 5.6912(6) Å, c = 13.3806(4), β = 92.544(4)° and Z = 2. The mercury atoms in the centrosymmetric cation are three-coordinate with Hg? Hg 2.503, Hg? N 2.207, 2.207, 2.560 Å. tcp behaves as a bidentate ligand forming infinite chains running parallel to the a-axis. 相似文献
66.
67.
Shyh-Horng Chiou 《中国化学会会志》1989,36(5):435-442
A rapid peptide-bond hydrolysis by means of microwave irradiation is introduced for the facile preparation of protein hydrolysates used for amino acid analysis. The optimal hydrolysis condition has been determined using several enzymes with known amino acid compositions. The effects of hydrolysis time on the recovery of various labile and hydrophobic amino acids are also exemplified in the microwave heating of standard amino acids. The method has been applied to the complete amino acid analysis with a single nonvolatile solvent of methanesulfonic acid with good recovery of tryptophan and half-cystine. It provides a radical expedition of protein and peptide hydrolysis via commercial microwave ovens and specially-designed Teflon-Pyrex tubes, circumventing the tedious procedures using vacuum-sealed pyrex lubes heating at 110°C for more than 24 h. This novel type of microwave chemistry associated with rapid peptide-bond cleavage is of great potential in the automation of the complete process of amino acid analysis starting from the preparation of protein hydrolysates. 相似文献
68.
在芳烃溶剂中用氯化二乙基铝和叠氮化钠反应合成了叠氮化二乙基铝(DEAA),其产率高达87%,比文献值高出17%。在正己烷中没有合成出DEAA,在含30%四氢呋喃(THF)的正己烷中合成出DEAA·THF配合物。在芳烃溶剂中,随着苯环上甲基数目的增加,DEAA的收率增加。测定了氯化二乙基铝、氯化二乙基铝的正己烷溶液、氯化二乙基铝的甲苯溶液的 27Al NMR谱。由 27Al NMR谱数 据确定了氯化二乙基铝在甲苯中解离平衡式,计算了氯化二乙基铝在甲苯中解离平衡的热力学数据。用DEAA与苯甲酸甲酯直接合成了苯甲酰叠氮,并表征了其结构。这是一个新反应,至今无文献报导。用实验证明了在正己烷溶液中,用氯化二乙基铝、叠氮化钠与苯甲酸甲酯合成苯甲酰叠氮,没有经过氯化二乙基铝和叠氮化钠反应生成中间体DEAA的这一步。依据实验事实建立了上述三种反应的反应机理。 相似文献
69.
Pinotti Laura M. Silva Rosineide G. Giordano Roberto C. Giordano Raquel L. C. 《Applied biochemistry and biotechnology》2002,98(1-9):679-686
This article reports studies concerning the production of penicillin G acylase (PGA) by Bacillus megaterium. This enzyme has industrial use in the hydrolysis of penicillin G to obtain 6-aminopenicillanic acid, an essential intermediate
for the production of semisynthetic β-lactam antibiotics. Although most microorganisms produce the enzyme intracellularly,
B. megaterium provides extracellular PGA. The enzyme production by microorganisms involves several steps, resulting in a many operational
variables to be studied. The study of the inoculum is an important step to be accomplished, before addressing other issues
such as culture optimization and downstream processing. In this study, using a standard inoculum as reference, several runs
were performed aiming at the definition of operational conditions in the PGA production. Cell concentration and PGA activity
in the production medium were measured after 24, 48, and 72 h of the beginning of the production phase. This study encompasses
the duration of the inoculum germination phase and the concentration of cells used to startup the germination. Based on these
results, PGA productivity during the production phase was maximized. The selected values for these variables were 1.5 × 107 spores/mL of germination medium, germination during 24 h, and 72 h for the production phase. 相似文献
70.
Preparation and crystal structure of the La2Ni12P5 and isotypic ternary lanthanoid—Nickel phosphides
Yu. B. Kuz'ma V. S. Babizhet'sky S. I. Chykhrij S. V. Oryshchyn V. K. Pecharsky 《无机化学与普通化学杂志》1993,619(3):587-592
The new ternary phosphide La2Ni12P5 has been prepared by direct arc melting of the components as pure metals and red phosphorus. The crystal structure has been determined using X-ray single crystal diffraction data. The compound exhibits a new type of crystal structure, P21/m with lattice parameters a = 10.911(3), b = 3.696(2), c = 13.174(4) Å, β = 108.02(2)°, V = 505,2(6) Å3, Z = 2. Atomic parameters least squares refinement of 116 independent variables (anisotropic approximation for thermal vibrations) employed 1 284 independent Io(hkl); RF = 0.0278 and RW = 0.0287. The crystal structure is characterized by trigonal prismatic arrangement of phosphorus atoms stacking variant of infinite (with phosphorus centered) columns built by metal trigonal prisms ‖ [010]. Two or three such columns are connected through common edges (lanthanum atoms). The compounds RE2Ni12P5 (where RE = Ce, Pr, Nd and Eu) display the same with La2Ni12P5 crystal structure. Lattice parameters of these compounds have been refined using powder diffraction data. 相似文献