Synthesis and characterization of organophosphoryl polyoxotungstates [RP(O)]2X n+W11O39 (8−n)− (X n+ = P5+, Si4+, Ge4+, Ga3+)

In the presence of n-Bu₄NBr acting as phase-transfer reagent, n-Bu₄N⁺ salts of organophosphoryl polyoxotungstate derivatives [RP(O)]₂X ⁿ⁺W₁₁O₃₉ ^(8–n)– [R = PhCH₂CH₂P(O), X = P, Si; R = C₆H₁₁P(O); X = Ge, Ga] have been prepared and characterized by elemental analysis, i.r., ³¹P- and ¹⁸³W-n.m.r. spectroscopy. According to the elemental analysis and spectroscopic data, the hybrid anions consist of an -[XW₁₁O₃₉] framework on which are grafted two equivalent organophosphoryl groups through P—O—W bridges; these new species still retain the Keggin structure. The six-line ¹⁸³W spectrum indicates that hybrid anions possess C _s symmetry in MeCN.     

烯烃氢甲酰化催化剂活性物种的原位~1H NMR研究

有机磷配位铐或钴联基配合物是生产难或醇的工业催化剂，一般公认金属氢化物是反应的催化活性物种．通常反应活性物种仅存在干反应状态下，其结构表征非常困难，在许多研究中只能关联催化剂母体与其活性的关系［‘1；而未能揭示出催化的本质，给催化剂设计造成很大困难，因而对催化剂活性物种的直接表征受到普遍关注．B。wn问、Morrista］及本文作者研究组＊均采用加压原位红外光谱方法，在烯烃氢甲酸化反应条件下捕捉到HCO（CO）3L存在的信息·但用相同方法在反应条件下，在RhH键特征吸收谱带195O－2200Cm‘内未观测到错氢化物的Rh－…     

Y2O3薄膜处理对3Cr25Ni7N合金的抗高温氧化性能的影响

采用电沉积-热解法在3Cr25Ni7N合金表面制备了Y2O3薄膜,并研究了薄膜处理对合金在1000℃空气中的抗高温氧化性能的影响。氧化动力学曲线、SEM及XRD分析结果表明,Y2O3薄膜处理使合金表面氧化膜以尖晶石结构为主,氧化膜致密,有效地抑制了Cr2O3的挥发反应,且氧化膜与基体的附着性好,因此合金在高温下的抗氧化性能得到提高,这与氧化钇薄膜在较低温度下抗高温氧化性能提高的机制是不同的。在不同温度下,Y2O3薄膜处理均可以有效提高合金的抗高温氧化性能。     

Two new compounds from Zingiber officinale

A new cyclic diarylheptanoid,1,5-epoxy-3-hydroxy-1-(3-methoxy-4,5-dihydroxyphenyl)-7-(4-hydroxyphenyl)-heptane (1),as well as a new monoterpene,10-O-β-D-glucopyranosyl-hydroxy cineole (2) were isolated from the rhizomes of Zingiber officinale. The structures of compounds 1 and 2 were established based on their spectral data.In addition,the antioxidant activities of these compounds were also measured.     

Concise Synthesis and Antimicrobial Activities of New Substituted 5‐Isoxazolpenicillins

The synthesis of a series of new 5‐isoxazolpenicillins is described, which were obtained by coupling substituted isoxazoles with 6‐APA. Concise large‐scale synthesis of 3,5‐disubstituted isoxazoles by 1,3‐dipolar cycloaddition using copper(I) as catalyst was also investigated. Representative compounds were assayed for antimicrobial activities, showing satisfactory antimicrobial activities against Gram‐negative bacteria.     

Radiation effects in the transient hot-wire technique

The transient hot-wire technique is widely used for absolute measurements of the thermal conductivity and thermal diffusivity of fluids. It is well established that fluid radiation effects significantly influence these measurements, especially those for the thermal diffusivity. Corrections for radiation effects are based on the models developed and deviations of the measured data from the ideal line source model. In this paper, the effect of fluid radiation on the measurements of the thermal conductivity of n-pentane is presented. For comparison, the influence of thermal radiation effect on measurement of transparent fluids, such as argon is also shown. The difference between the influence of natural convection and thermal radiation is also demonstrated.     

Tri-component diblock copolymers of poly(ethylene glycol)–poly(ε-caprolactone-<Emphasis Type="Italic">co</Emphasis>-lactide): synthesis,characterization and loading camptothecin

Biodegradable tri-component diblock copolymer was synthesized by bulk copolymerization of ε-caprolactone (CL) and D, L-lactide (LA) in the presence of methoxy poly(ethylene glycol) (MePEG), using stannous octoate as catalyst. Their chemical structure and physical properties were investigated by GPC, NMR, DSC, TGAand XRD. The increase of CL/LA ratio in the diblock copolymer leads to lower T _g, higher decomposition temperature and crystallinity. Nanoparticles formulated from MePEG–poly(CL-co-LA) (PCAE) possess spherical structure, which was characterized by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The DLS results indicate that the particle size increased with the increase of CL/LA ratio and the hydrophobic fragment length in the copolymer. The drug encapsulation efficiency and the drug release behavior in vitro conditions of camptothecin were measured by high performance liquid chromatography (HPLC). The encapsulation efficiency can be achieved as high as 84.4% and the release behavior can be made well-controlled. MePEG–poly(CL-co-LA) nanoparticles might have a great potential as carriers for hydrophobic drugs.     

Rb3In(H2O)Si5O13: a novel indium silicate with a CdSO4-topological-type structure

A novel indium silicate, Rb3In(H2O)Si5O13, has been synthesized using a high-temperature, high-pressure hydrothermal method and characterized by single-crystal X-ray diffraction. The structure consists of five-membered rings of corner-sharing SiO4 tetrahedra connected via corner sharing to four adjacent five-membered rings to form a 3D silicate framework that belongs to the CdSO4 topological type. The InO6 octahedron shares five of its corners with five different SiO4 tetrahedra to form a 3D frame-work that delimits two types of channels to accommodate the rubidium cations. The sixth corner of InO6 is coordinated H2O. The structure is related to that of the titanium silicate ETS-10, and these are the only two metal silicates that have the CdSO4-topological-type structure. In addition, the crystal of Rb3In(H2O)Si5O13 shows an intense second harmonic generation signal. Crystal data: H2Rb3InSi5O14, monoclinic, space group Cc (No. 9), a = 9.0697(5) A, b = 11.5456(6) A, c = 13.9266(8) A, beta = 102.300(1) degrees, V = 1424.8(1) A3, and Z = 4.     

Odd/even effect in the chain length on the enthalpy of micellization of gemini surfactants in aqueous solution

The micellization properties of cationic symmetric gemini surfactants, [CmH(2m+1)(CH3)2N(CH2)6N(CH3)2CmH(2m+1)]Br2 (designated as CmC6CmBr2, with m = 7, 8, 9, 10, 11, 12, and 16), has been investigated by isothermal titration microcalorimetry. The critical micelle concentration (CMC) and enthalpy of micellization (DeltaHmic) were determined from calorimetric titration curves. The linear decreasing of log CMC with increasing the length of the hydrophobic chain is consistent with an increase in the hydrophobicity of the alkyl chain. Interestingly, with increasing the length of the alkyl chain, the DeltaHmic values of the surfactants with even numbered alkyl chains vary from endothermic to exothermic, whereas the DeltaHmic values of the surfactants with odd numbered alkyl chains are all endothermic and tend to become more endothermic. The pronounced even/odd effect in DeltaHmic is discussed with respect to the "donor-acceptor" interaction.     

Theoretical prediction of the contact distance dependence of the electron transfer reactivity of the ClO/ClO− coupling system

On the basis of the structures and properties of the ClO/ClO^? system obtained at the density functional theory (DFT) (UB3LYP) level, employing the 6‐311+G(3df) standard basis set, the electron transfer reactivity of this system is investigated. The results indicate that there are five possible stable coupling complexes that correspond to the generous minima on the global potential energy surfaces (PES). The most stable coupling complex is planar EC4, in which there is a O? O linkage with two trans‐Cl atoms. Their stabilization energies are calculated to be 20.57 (EC1: C₁), 20.54 (EC2: C₂, ²B), 20.69 (EC3: C₁), 20.70 (EC4: C_s, ²A′), and 20.69 (EC.5: C_2h, ²B_u) kcal/mol at the B3LYP/6‐311+G(3df) level; with the correction of the basis set superposition error (BSSE), the stability order of these encounter complexes is EC4 > EC.5 > EC3 > EC1 > EC2. Based on the five encounter complexes, five coupling modes are designed for the study of the electron transfer reactivity of this system. The dissociation energy curves at the activated states and the corresponding activation energies of these five coupling modes are obtained and are compared at the B3LYP/6‐311+G(3df) and MP2/6‐311+G* levels. The inapplicability of DFT methods has also been discussed in this article in predicting the energy curves, especially with a long contact distance, in which DFT methods give the abnormal behavior for the dissociations of the complexes caused by the “inverse symmetry breaking” problem. On the basis of the golden rule of the time‐dependent perturbation theory, the electron transfer reactivity and the contact distance dependence of the various electron transfer kinetics parameters (e.g., activation energy, coupling matrix element) have been analyzed at the UMP2(full)/6‐311+G* level. The electron transfer can take place over a range of contact distances, but the most effective coupling distance corresponds to only a small range. The coupling orientation analyses also indicate that the most favorable coupling mode to the electron transfer does not always correspond to the most stable encounter complex mechanism. Some highly energetic coupling modes are more favorable for the electron transfer. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005