Chiral separation of synthetic vicinal diol compounds by capillary zone electrophoresis with borate buffer and beta-cyclodextrin as buffer additive.

The investigation on capillary electrophoretic enantioseparation of six synthetic compounds containing vicinal diol groups has been undertaken to acquire the optimum conditions using native beta-cyclodextrin (beta-CD) as chiral selector and borate as a background electrolyte. The separation was carried out in an uncoated capillary (58.5 cm x 75 microm i.d., effective length 48.5 cm) and the effects of several important factors were investigated in detail. The results showed that beta-CD as a chiral selector exhibited good enantioselectivity and that the enantioseparation was greatly influenced by the structure of the diols, the borate concentration and the buffer pH. The optimum performance was obtained for the chiral vicinal diols under the conditions of 200 mM borate buffer of pH 9.8 containing 1.7% beta-CD at an applied voltage of 15 kV and a capillary temperature of 20 degrees C. Under the conditions, four diols were baseline separated with fast analysis time and the good theoretical plate numbers (above 10 x 10(4)) and favorable migration-time reproducibilities (RSDs below 3.0%) were obtained. The separation results were satisfactory.     

不对称氢化反应

本文总结了各种手性膦配体以及它们的铑络合物在不对称氢化中的应用,并讨论了不对称氢化的机理和影响不对称诱导的各种因素。     

Single-Molecule single crystals of isotactic polystyrene

Single-molecule single crystals were grown from amorphous droplets of fractionated isotactic polystyrene. The crystals were analyzed by electron microscopy and electron diffraction. The molecular mass distribution could be matched with a statistical analysis of single-molecule particles (amorphous and crystals). Proof was brought that single molecules of isotactic polystyrene do not reach equilibrium dimensions on crystallization, rather assume the lamellar morphology with chain-folded macroconformation, also known from crystallization of polymolecular crystals. © 1994 John Wiley & Sons, Inc.

1 This article is a US Government work and, as such, is in the public domain in the United States of America. US Government contract No. DE-AC05-840R-21400.

     

(NiV13O38)7-的电子结构和催化性质的探讨

使用SCC－DV－Xα方法研究了高钒杂多化合物（NiV13O38）7-的电子结构，并探讨了它的催化性质·结果表明，（NiV13O38）7-是一种比Keggin结构更强的催化剂。分析了该阴离子中的键的强弱关系，认为配位数越少的氧与V形成的键越强．并分析了前线轨道HOMO，LUMO的组成，从而得出它的催化活性中心是Ni，V、一配位端氧，二、三配位桥氧，五配位中心氧的结论。     

A convenient and practical heterogeneous palladium‐catalyzed carbonylative Suzuki coupling of aryl iodides with formic acid as carbon monoxide source

A practical heterogeneous palladium‐catalyzed carbonylative Suzuki coupling of aryl iodides with arylboronic acids under carbon monoxide gas‐free conditions has been developed using a bidentate phosphino‐functionalized magnetic nanoparticle‐immobilized palladium(II) complex as catalyst. Formic acid was utilized as the carbon monoxide source with dicyclohexylcarbodiimide as the activator, and a wide variety of biaryl ketones were generated in moderate to high yields. The new heterogeneous palladium catalyst can be prepared via a simple procedure and can easily be separated from a reaction mixture by simply applying an external magnet and recycled up to 10 times without any loss of activity.     

Natural Soft/Rigid Superlattices as Anodes for High-Performance Lithium-Ion Batteries

Volume expansion and poor conductivity are two major obstacles that hinder the pursuit of the lithium-ion batteries with long cycling life and high power density. Herein, we highlight a misfit compound PbNbS₃ with a soft/rigid superlattice structure, confirmed by scanning tunneling microscopy and electrochemical characterization, as a promising anode material for high performance lithium-ion batteries with optimized capacity, stability, and conductivity. The soft PbS sublayers primarily react with lithium, endowing capacity and preventing decomposition of the superlattice structure, while the rigid NbS₂ sublayers support the skeleton and enhance the migration of electrons and lithium ions, as a result leading to a specific capacity of 710 mAh g⁻¹ at 100 mA g⁻¹, which is 1.6 times of NbS₂ and 3.9 times of PbS. Our finding reveals the competitive strategy of soft/rigid structure in lithium-ion batteries and broadens the horizons of single-phase anode material design.     

Keggin杂多阴离子电子结构和物化性质与中心原子的 关系

使用密度泛函理论中的离散变分方法(DFT-DVM),以(XMo12O40)^n-(X=B,Al,Si,Ge,P,As,S)为例计算了七个Keggin杂多阴离子的电子结构,讨论了中心原子对Keggin阴离子的电子结构、稳定性、氧化还原性和酸性关系。根据计算结果,给出稳定性、氧化还原性强弱顺序,计算给出结果与实验一致。     

界面强度对复合材料细观力学性能的影响

用 界面元来连接纤维与基体,利用界面元的力学特征来模拟纤维与基体的粘结特性,计算了纤维单向周期排列的多层板在横向载荷作用下的应力分布问题,计算结果表明,中间相力学特征的变化对纤维和基体的应力分布有明显的影响。     

Synthesis and application of clindamycin succinate as a novel chiral selector for capillary electrophoresis

A novel chiral selector, clindamycin succinate, was synthesized and first used as a chiral selector in capillary electrophoresis (CE). The chiral resolution ability of this kind of clindamycin derivation was studied by CE using some racemic drugs as model analytes. From the experimental results, it was found that both resolution and selectivity of the selector were dependent on the following parameters: concentration of chiral selectors, pH of the running buffer, temperature of the capillary column, applied voltage and organic modifier used. The results show that the chiral selector possesses high resolution toward some racemic drugs, including ofloxacin, chlorphenamine, tryptophan, propranolol, sotalol and metoprolol. Excellent chiral resolution of these tested drugs was achieved under the optimal conditions of 50 mM clindamycin succinate, 10% MeOH v/v, 50 mM Tris buffer, pH 4.0, at 22 kV and 20 °C within 25 min.