铋配合物[Bi(S2CNC5H10)2(NO3)]·[1，10-Phen]·0.5H2O的合成及晶体结构

The bismuth complex with dithiopiperdylcarbamate [Bi(S₂CNC₅H₁₀)₂(NO₃)]·[1，10-Phen]·0.5H₂O was synthesized. The crystal and molecular structure were determined by X-ray single crystal diffraction. The crystal belongs to monoiclinic with space group C2/c, a=3.140(2) nm, b=1.176 4(9) nm, c=2.021 6(15) nm, β=103.081(12)°, V=5.713(7) nm³, Z=8, F(000)=3064, D_c=1.815 g·cm^-3, μ=6.502mm^-1. The final R₁=0.0332, wR₂=0.040 3. In the complex, the bismuth atom is eight-coordinated in a capped distorted pentagonal bipyramidal geometry. CCDC: 222655.     

Synthesis and thermal decomposition of bismuth peroxotitanate to Bi2Ti2O7

Bi-peroxotitanate was synthesized by a peroxo method and after thermal decomposition Bi₂Ti₂O₇ was obtained. DTA, TG and DSC curves of Bi₂[Ti₂(O₂)₄(OH)₆]5H₂O were recorded and used to determine isothermal conditions suitable for obtaining the intermediate samples corresponding to the phases observed during the thermal decomposition. The samples were identified by quantitative analysis, IR spectroscopy and X-ray analysis. The experimental results were used to propose a mechanism of thermal decomposition of the investigated compound to a nanosized Bi₂Ti₂O₇. The optimum conditions were also determined for obtaining Bi₂Ti₂O₇, which is applicable for piezosensors.     

Thermal analysis study of the effect of molecular weight on constrained amorphous phase in poly(phenylene sulfide)

We report a thermal analysis study of the effect of molecular weight on the amorphous phase structure of poly(phenylene sulfide), PPS, crystallized at temperatures just above the glass transition temperature. Thermal properties of Fortron PPS, having viscosity average molecular weights of 30000 to 91000, were characterized using temperature modulated differential scanning calorimetry (MDSC). We find that while crystallinity varies little with molecular weight, the heat capacity increment at the glass transition decreases as molecular weight decreases. This leads to a smaller liquid-like amorphous phase, and a larger rigid amorphous fraction, in the lower molecular weight PPS. For all molecular weights, constrained fraction decreases as the scan rate decreases.This research is supported by the U. S. Army Research Office through contract DAAH04-96-1-0009. The authors thank Hoechst Celanese for providing different molecular weight Fortron samples and Dr. George Collins for providing sample information. The authors acknowledge the assistance of Elizabeth Oyebode and Leonardo Grimaldi with sample preparation and MDSC work.     

C207联醇催化剂的羰基硫中毒研究

以常压甲醇分解反应为基础实验测定了不同羰基硫含量和不同反应温度下甲醇合成铜基催化剂活性随时间的变化。结果表明，羰基硫含量增加时；失活速率增快；反应温度升高时，失活速率也加快。羰基硫中毒前后催化剂样品的ＸＲＤ谱图证实了起催化作用的活性组分为Ｃｕ＾＋／ＺｎＯ。应用改进的高斯－牛顿法对失活实验数据进行参数估值，获得了Ｃ２０７铜基催化剂羰基硫中毒的失活速率方程。     

Physical Adsorption of H2S Related to the Conservation of Works of Art: The Role of the Pore Structure at Low Relative Pressure

The adsorption isotherms of H₂S in selected adsorbents were determined at 298 K, at relative pressures up to about 0.005, aiming the use of these materials in the removal of that pollutant from the museums atmosphere. The Dubinin-Astakhov equation adjusts very well the experimental results, although one cannot interpret the pre-exponential factor w₀ as the limiting adsorbed amount. The parameter E, related with the adsorption energy, and the parameter n, that can be associated with the surface heterogeneity of the adsorbents, are correlated and the first is also correlated with the adsorbed amounts. It was not found any expectable relationship between the adsorbed amounts and textural parameters of the adsorbents such as the specific surface area or the microporous volume. This points out that the adsorption of H₂S is highly specific. In general, 13X and Y sodium zeolites seem to be the most effective adsorbents, but at lowest tested pressures, near the concentrations found at museums, a pillared clay prepared from a Wyoming montmorillonite seems to be more efficient.     

Bi(OTf)3-catalyzed allylation of epoxides: a facile synthesis of homoallylic alcohols

Epoxides react smoothly with tetraallyltin in the presence of 2 mol% of Bi(OTf)₃ under mild reaction conditions to afford the corresponding homoallylic alcohols in excellent yields with high regioselectivity while aryl aziridines produce exclusively allyl amines in good yields under similar conditions.     

Syntheses, structures, optical properties, and theoretical calculations of Cs2Bi2ZnS5, Cs2Bi2CdS5, and Cs2Bi2MnS5

Three new compounds, Cs₂Bi₂ZnS₅, Cs₂Bi₂CdS₅, and Cs₂Bi₂MnS₅, have been synthesized from the respective elements and a reactive flux Cs₂S₃ at 973 K. The compounds are isostructural and crystallize in a new structure type in space group Pnma of the orthorhombic system with four formula units in cells of dimensions at 153 K of a=15.763(3), b=4.0965(9), c=18.197(4) Å, V=1175.0(4) Å³ for Cs₂Bi₂ZnS₅; a=15.817(2), b=4.1782(6), c=18.473(3)  Å, V=1220.8(3)  ų for Cs₂Bi₂CdS₅; and a=15.830(2), b=4.1515(5), c=18.372(2) Å, V=1207.4(2) Å³ for Cs₂Bi₂MnS₅. The structure is composed of two-dimensional _∞²[Bi₂MS₅²⁻] (M=Zn, Cd, Mn) layers that stack perpendicular to the [100] axis and are separated by Cs⁺ cations. The layers consist of edge-sharing _∞¹[Bi₂S₆⁶⁻] and _∞¹[MS₃⁴⁻] chains built from BiS₆ octahedral and MS₄ tetrahedral units. Two crystallographically unique Cs atoms are coordinated to S atoms in octahedral and monocapped trigonal prismatic environments. The structure of Cs₂Bi₂MS₅, is related to that of Na₂ZrCu₂S₄ and those of the AMM′Q₃ materials (A=alkali metal, M=rare-earth or Group 4 element, M′= Group 11 or 12 element, Q=chalcogen). First-principles theoretical calculations indicate that Cs₂Bi₂ZnS₅ and Cs₂Bi₂CdS₅ are semiconductors with indirect band gaps of 1.85 and 1.75 eV, respectively. The experimental band gap for Cs₂Bi₂CdS₅ is ≈1.7 eV, as derived from its optical absorption spectrum.     

Thermal and spectral properties of some anhydrous and hydrated rare earth hydrazinecarboxylates

Thermal investigations of two novel coordination compounds, potential precursor of copper sulfides, namely [Cu₂(S₂O₃)₂(NH₃)₄]·₅H2_O and Na₂[Cu₄(S₂O₃)₅(NH₃)₈]·₂H₂O were performed either in solid state (static air atmosphere), as well as in reaction medium. During both decompositions, Cu²⁺ reduction occurs. In solid state decomposition, a mixture containing sulfides and sulfates is observed. In the reaction medium, CuS_y compounds with sulfur content y (0.66<y<1) dependent on thiosulfate concentration are obtained. This revised version was published online in July 2006 with corrections to the Cover Date.     

在N—甲基吡咯烷酮中聚苯硫醚合成的宏观动力学

研究了无水硫化钠与对二氯苯（以Ｎ－甲基吡咯烷酮为溶剂）合成聚苯硫醚反应的宏观动力学，该反应是一个小分子缩合串联自缩聚的过程，通过测定不同反应聚合体系中氯化钠的徨成率和硫化内的转化率，建立了该反应的宏观动力学方程：１／（１－ＰＮａＣｌ＋ＰＮａ２ｓ）＝Ｃ０Ｋｔ＋１；并计算得到２２０、２５０℃的表观反应速率为４．５×１０＾－４和３．０×１０＾－３ｋｇ／（ｍｏｌ．ｓ），表观活化能为１３４ｋＪ／ｍｏｌ。     

Gas-phase Reaction of 2-Chlorothiophene with Hydrogen Sulfide in the Presence of Alcohols

The effect of methanol and ethanol on the route of the gas-phase reaction of 2-chlorothiophene with hydrogen sulfide, leading to 2-thiophenethiol and to bis(2-thienyl) sulfide, has been investigated. It was found that methanol significantly enhances this reaction and increases its selectivity for the thiol at higher temperatures than without the initiator. The optimal conditions were achieved at 570°C in the presence of 10 mole % of methanol when the conversion of the 2-chlorothiophene in the reaction with hydrogen sulfide reaches 98% and the yield of the thiophenethiol (43%) exceeds that of the bis(2-thienyl)sulfide (31%). In the absence of methanol the 2-thiophenethiol is formed only at 510-540°C in just 17% yield, the basic reaction product being the indicated sulfide (52% yield); the conversion of the 2-chlorothiophene does not exceed 54%.