Formation of direct metal-metal bonds from 16-electron "pseudo-aromatic" half-sandwich complexes Cp'M[E2C2(B10H10)

Continuous study on preparation of multimetallic clusters is stimulated by their rich coordination chemistry and promising applications in a variety of interesting fields. Although numerous efforts have been devoted to this field, the rational design of homo- and hetero-multimetallic compounds with direct metal-metal bonding supported by 1,2-dicarba-closo-dodecarborane-1,2-dichalcogenolates will still be an important step forward. This tutorial review focuses on the synthetic approach via redox reactions between the pseudo-aromatic half-sandwich oraganometallic carborane precursors and low-valent transition metal reagents. The tailoring of reaction conditions and the structural information from the resulting products are discussed extensively.     

氮气在MCM-41中毛细凝聚的模拟和理论研究

采用巨正则系综 Monte Carlo 方法(GCMC)以及基于扩展基本度量理论和 MBWR 状态方程的密度泛函理论,研究了 77.4 K 时氮气在不同孔径的 MCM-41 分子筛中吸附的密度分布和吸附等温线.提出的平均场权重密度泛函理论,克服了平均场近似预测主体相热力学性质时的偏差,获得的密度分布和吸附等温线与 GCMC 分子模拟结果有着很好的一致性.     

Complexation of decamethylcucurbit[5]uril with alkali metal ions

Four coordination compounds, namely [Na(H₂O)(H₂O)₂⊂C₄₀H₅₀N₂₀O₁₀](C₆H₆O₂)₂Cl·8H₂O (1), [K₂(H₂O)₂(H₂O)⊂C₄₀H₅₀N₂₀O₁₀](C₆H₆O₂)₂Cl₂·7H₂O (2), [Rb₂(H₂O)₂(H₂O)⊂C₄₀H₅₀N₂₀O₁₀](C₆H₆O₂)₂Cl₂·7H₂O (3) and [Cs(H₂O)₂(H₂O⊂C₄₀H₅₀N₂₀O₁₀)](C₆H₆O₂)₂Cl·6H₂O (4), were obtained by the reactions of the corresponding alkali metal salts with decamethylcucurbit[5]uril (Me₁₀Q[5]) in the presence of hydroquinone, and their structures were determined by single-crystal X-ray diffraction. The results revealed that in compounds 1 and 4 each Me₁₀Q[5] ligand coordinates one Na⁺ or Cs⁺ ion to form a molecular bowl structure, while in compounds 2 and 3 each Me₁₀Q[5] ligand coordinates two K⁺ or Rb⁺ ions to form a closed molecular capsule structure, and adjacent molecular capsules bridge each other through water molecules to form 1D coordination polymers. In addition, we found that the coordination distances for the metal ions and the height of the metal ions out-of-portal-plane for the four compounds are in the same order, 1 < 2 < 3 < 4, which is attributed to the fact that the radius of alkali cations is in the order Na⁺ < K⁺ < Rb⁺ < Cs⁺. Although each portal of Q[6] binds with two alkali cations (not including Cs⁺), the Q[6]-based alkali cations complexes display similar structural trends.     

Synthesis,Characterization, and Properties of Tetraphenylethylene-Based Tetrakis-NHC Ligands and Their Metal Complexes

The development of highly emissive dinuclear Ag^I or Au^I complexes [M₂L](PF₆)₂ (L= 2 a , 2 b ; M=Ag, Au) derived from tetraphenylethylene (TPE)-based tetrabenzimidazolin-2-ylidene ligands is reported. The new complexes exhibit a remarkable fluorescence enhancement compared to their parent benzimidazolium salts. The quantum yield (Φ_F) value for salt H₄- 2 a (PF₆)₄ in dilute solution (c=10⁻⁵ m ) was found to be less than 1 %, whereas its metal complexes show Φ_F values up to 55 % at similar solution concentration. This observation can be attributed to the rigidification of the TPE skeleton upon metalation resulting in a restriction of the intramolecular rotation of the phenyl groups. Functionalization of the complexes [M₂ 2 b ](PF₆)₂ (M=Ag, Au) with terminal coumarin groups and subsequent photoirradiation yielded the complexes [M₂ 3 b ](PF₆)₂ (M=Ag, Au) bearing a new type of ligand with an unaffected TPE moiety.     

液相色谱-串联质谱法测定食品接触材料中28种初级芳香胺的迁移量

建立了液相色谱-串联质谱法(LC-MS/MS)同时测定食品接触材料中28种初级芳香胺(PAAs)迁移量的方法。采用C3色谱柱,以甲醇-水为流动相,梯度洗脱分离,在电喷雾正离子模式下以多反应监测(MRM)方式检测,外标法定量。28种PAAs检出限(LOD,S/N=3)和定量限(LOQ,S/N=10)分别为0.02～0.3μg/kg和0.1～1.0μg/kg;在1.0～1000μg/L浓度范围内线性良好,相关系数大于0.9915;加标浓度在1.0～100μg/kg的回收率为77.8%～105.3%;相对标准偏差(RSD)为4.5%～11.8%。本方法操作简便、快速、准确、灵敏度高,能满足相关测定要求。     

Novel synthesis of graphene foils in mesostructured silica between hexagonal and lamellar phases

The mesostructured silica template between hexagonal and lamellar phases derived from self-assembled tetraethyl-ortho-silicate (TEOS) with uniform adsorption of iron-group metal ions provides an ideal environment for growing highly crystalline graphene foils at a low temperature.     

缓蚀剂在铜表面吸附行为的研究

采用密度泛函理论计算了缓蚀分子苯并三氮唑(BTA)和二巯基噻二唑(DMTD)的全局反应活性和局部反应活性. 采用分子动力学方法模拟了不同含量的BTA和DMTD对其热力学性质的影响. 同时通过腐蚀试验研究了缓蚀剂复配体系的缓蚀效果. 结果表明: 两种缓蚀分子的缓蚀效率关系为BTA小于DMTD, 活性主要集中于N和S原子上, 有多个活性位点, 因此, 缓蚀剂分子平卧式吸附在铜表面; 铜表面吸附单个缓蚀剂分子BTA和DMTD后, 室温下比热容基本相同, 但随缓蚀剂含量的增加, 比热容呈增大趋势. 这为铜箔轧制油缓蚀剂的选择提供理论指导. 通过腐蚀试验研究, 复配体系缓蚀具有很好的缓蚀效果, BTA和DMTD 的复配比例为1:1时最佳. 关键词： 密度泛函理论 分子动力学方法 反应活性 热力学性质     

Analysis of Decomposition for Structure I Methane Hydrate by Molecular Dynamics Simulation

Under multi-nodes of temperatures and pressures, microscopic decomposition mechanisms of structure I methane hydrate in contact with bulk water molecules have been studied through LAMMPS software by molecular dynamics simulation. Simulation system consists of 482 methane molecules in hydrate and 3027 randomly distributed bulk water molecules. Through analyses of simulation results, decomposition number of hydrate cages, density of methane molecules, radial distribution function for oxygen atoms, mean square displacement and coefficient of diffusion of methane molecules have been studied. A significant result shows that structure I methane hydrate decomposes from hydrate-bulk water interface to hydrate interior. As temperature rises and pressure drops, the stabilization of hydrate will weaken, decomposition extent will go deep, and mean square displacement and coefficient of diffusion of methane molecules will increase. The studies can provide important meanings for the microscopic decomposition mechanisms analyses of methane hydrate.     

Enhancement on Hemilabile Phosphine-Amide Palladium and Nickel Catalysts for Ethylene (Co)Polymerization with Polar Monomers Using a Cyclizing Strategy

To address the issue of hemilabile catalyst in olefin polymerization catalysis, a cyclizing strategy was used to construct novel N-bridged phosphine-carbonyl palladium and nickel catalysts, resulting in improvements on ethylene(co)polymerizations. The N-bridged phosphinecarbonyl Pd catalysts(Pd1-Pd5) and Ni catalysts(Ni1-Ni5) bearing five-to eight-membered-ring structures were designed and synthesized.Catalytic performance for ethylene(co)polymerization became better as the size of N-containing bridge increased. The seven-membered-ring bridged catalysts Pd4 and Ni4 exhibited the best performance in terms of catalytic activity, polymer molecular weight and incorporation of acrylates and acrylic acid. The better performance of these catalysts bearing larger-size bridges was tentatively attributed to the methyleneinduced higher electron density around nitrogen, which strenghtens the coordination of carbonyl group to metal center, and also to the steric effect offered by this cyclization. This work provides a new strategy to enhance hemilabile polymerization catalysts.     

近红外原位研究杂多酸引发的环氧-四氢呋南阳离子聚合

用近红外光谱原位跟踪的方法,研究了杂多酸催化的环氧树脂和四氢呋喃的阳离子聚合过程.发现在低环氧树脂含量下,环氧消耗速率在整个聚合过程中维持不变;而在高环氧树脂含量下,环氧消耗速率则随时间有所下降.通过红外光谱在碳氢区域的分峰分析,证明环氧树脂与四氢呋喃发生了共聚反应,二维红外光谱的结果也确证了这一结果.此外,还探讨了环氧转化速率与环氧含量间的关系.