苯基或联苯基桥连双环戊二烯基铼羰基化合物的合成、结构及催化性能

两个单桥连的双环戊二烯（C₅Me₄H）E（C₅Me₄H）（E=C₆H₄,（C₆H₄）₂）分别与Re₂（CO）₁₀在均三甲苯中加热回流,得到了2个双核配合物（E）[（η⁵-C₅Me₄）Re（CO）₃]₂（E=C₆H₄（1）,（C₆H₄）₂（2））。通过元素分析、红外光谱、核磁共振氢谱和碳谱对配合物1和2的结构进行了表征,用X射线单晶衍射分析测定了配合物的结构。同时对2个配合物在芳香族化合物Friedel-Crafts酰基化反应中的催化活性进行了研究。     

Highly Efficient Low Melting Mixture Catalyzed Synthesis of 1,8-Dioxo-dodecahydroxanthene Derivatives

A low melting citric acid‐urea mixture was found to be a new and effective promoting medium for the environmentally friendly synthesis of 1,8‐dioxo‐dodecahydroxanthene derivatives by condensation of aromatic aldehydes and cyclic 1,3‐dicarbobonyl compounds. This deep eutectic solvent acts as both the reaction medium and catalyst, furnishing xanthenediones in high to excellent yields.     

Cation···π interactions: QTAIM and NBO studies on the interaction of alkali metal cations with heteroaromatic rings

The cation···π interactions of alkali metal cations (Li⁺, Na⁺, and K⁺) with five-membered heteroaromatic rings [furan(C₄H₄O), thiophene(C₄H₄S), pyrrole(C₄H₅N)] were examined by high level ab initio calculations, to investigate the different roles of C₄H₄O, C₄H₄S, and C₄H₅N as the electron donor, the influential factors that affect these interactions, the nature of this kind of cation···π interaction, and to determine topological and energetical properties to characterize these interactions. The sulfur atom in C₄H₄S plays a certain role in the cation···π interactions except the C–C π bond, which is different from C₄H₄O and C₄H₅N. The size of cation and the character of heteroaromatic ring are two influential factors that affect the cation···π interactions. The studied cation···π interactions can be classified as “closed-shell” and noncovalent interactions. The electron density and its Laplacian at the bond critical points and ring critical points generated upon complexation are useful measurements for the strength of cation···π interactions.     

Crystal structures and thermodynamic properties of lanthanide complexes with 2-chloro-4,5-difluorobenzoate and 1,10-phenanthroline

A series of lanthanide complexes with the 2-chloro-4,5-difluorobenzoate (2-cl-4,5-dfba) and 1,10-phenanthroline (phen), have been synthesized with the formulae of [La(2-cl-4,5-dfba)₃phen]_n·nH₂O (1), [Nd(2-cl-4,5-dfba)₃phenH₂O]₂ (2), [Ln(2-cl-4,5-dfba)₃phen]₂ (Ln = Eu (3), Ho (4)). The complexes are characterized by elemental analysis, infrared and fluorescent spectra and X-ray single-crystal diffraction. The structures of the four complexes are very different. Complex 1 is an infinite 1D chain polymeric structure formed by the asymmetric units with the mirror growth pattern. Each La³⁺ ion is coordinated to four bridging carboxylic groups, two tridentate chelating–bridging carboxylic groups, simultaneous with one phen molecule, giving the coordination number of nine. In the molecular structures of complexes 2 and 3, two Ln³⁺ ions are linked by four carboxyl groups, forming two binuclear molecules. In addition, each Nd³⁺ ion in complex 2 is bonded to one H₂O molecule and one carboxyl group by monodentate mode, one phen molecule by bidentate chelating, and each Eu³⁺ ion is also chelated to one phen molecule and one carboxyl group in complex 3. And in complex 4, the Ho³⁺ ion yields a eight-coordinated distorted square anti-prism coordination geometry. The three-dimensional IR accumulation spectra of gaseous products for complexes 1 to 4 are analyzed and further authenticated the thermal decomposition processes with TG-DTG curves. The heat capacities of complexes 2 to 4 are measured and fitted to a polynomial equation by the least squares method on the basis of the reduced temperature x (x = [T−(T_max + T_min)/2]/[(T_max − T_min)/2]). Then the smoothed molar heat capacities and thermodynamic functions of complexes 2 to 4 are calculated. The fluorescence intensity of complex 3 is markedly improved as well.     

Catalysis of Multi‐walled Carbon Nanotubes Supported PdxCoy Nanoparticles Prepared by a Pyrolysis Method Using Ionic Liquids as the Solvent toward Ethanol Oxidation Reaction

Multi‐walled carbon nanotubes (MWCNTs) decorated with Pd_xCo_y (the nominal atomic ratios of Pd to Co were 3:1, 3:1.5, 3:2, 3:3, respectively) nanoparticles (denoted as Pd_xCo_y/MWCNTs ) were fabricated by a simple pyrolysis process, in which room temperature ionic liquids (RTILs) of butyl‐3‐methylimidazolium hexafluorophosphate (denoted as [BMIM]PF₆) was used as the solvent. X‐ray diffraction (XRD) and transmission electron microscopy (TEM) were all used to characterize the Pd_xCo_y/MWCNTs catalysts, showing that the Pd_xCo_y particles were dispersed on the surface of the MWCNTs with an average particle size of ～25.0 nm. The electro‐catalytic activity of the Pd_xCo_y/MWCNTs catalysts toward ethanol oxidation reaction (EOR) was examined by cyclic voltammetry (CV). It was revealed that the onset potential was ～90 mV lower and the peak current was about four times higher for ethanol oxidation for Pd₃Co_1.5/MWCNTs compared to those of Pd₃Co₁/MWCNTs. The possible catalysis mechanisms of the Pd₃Co_1.5/MWCNTs toward EOR were also discussed.     

矩阵赋$\beta$-范空间中泛函方程的稳定性

文中我们定义了矩阵赋$\beta$-范空间,并在此空间中证明了可加二次方程和Pexider型方程的稳定性.     

纳米粉体CeO_2∶Eu~(3+)的溶胶-凝胶绿色合成及其发光性质

采用溶胶-凝胶法,以硝酸铈为原料,加入适量淀粉为分散剂,并通过氨水来调节溶液p H值,合成稀土Eu~(3+)掺杂的CeO_2红色纳米粉体。通过X射线衍射仪、场发射扫描电子显微镜、荧光分光光度计等手段研究不同煅烧温度对粉体结构、形貌、发光及显色性能的影响。结果表明,所得样品为立方晶系的萤石结构,空间群为Fm3m,颗粒呈近似球形,粒径范围在10~60 nm之间。随着煅烧温度的升高,CeO2晶粒尺寸逐渐增大,荧光粉的红色发光也逐渐增强。经800℃烧结后,近紫外(370 nm)和蓝光区(468 nm)的光都能对粉体有效地激发,这有利于其在固态照明中的应用。在溶胶-凝胶制备过程中,采用淀粉作分散剂,具有工艺简单、绿色环保的优点,有利于纳米氧化铈粉体的大规模制备。     

化学学科核心素养导向的教学实践改革思考*——基于2019版AP化学课程标准的分析

《普通高中化学课程标准(2017年版)》的颁布,开启了我国化学学科核心素养导向的教学实践的新时代。美国高中阶段实施的2019版AP化学课程凸显科学实践的课程目标,以4个化学大概念为依据选择、组织课程内容,倡导教、学、评一体化的教学策略,开展以学生为中心的引导性探究实验,设计多样化的评价任务。对比我国现行化学教学实践中缺少大规模教、学、评一体化平台,科学解释和论证能力目标外显不足,教师难以建立化学知识与学科观念素养间联系的现状,提出聚焦课程目标建设过程性评价体系,深度挖掘教学内容背后的科学解释和科学论证能力要求,深入理解知识承载的认识功能和价值等思考。     

三组分串联反应一锅合成多环稠合的1,5-苯并二氮杂䓬化合物

以取代的邻苯二胺、1,3-环戊二酮或1,3-环己二酮(5,5-二甲基-1,3-环己二酮)、2,3-二羰基化合物为原料,无水乙醇为溶剂,对甲苯磺酸为催化剂,经2~5 h串联反应一锅合成43种新颖的1,5-苯并二氮杂?化合物,产率最高可达95%.该反应序列首先通过两次的亲核加成-脱水反应过程,形成分子内亚胺和烯胺结构的活性中间体,然后再经分子内的碳碳偶联环合-质子转移等过程,生成多环稠合的1,5-苯并二氮杂?目标化合物,实现了在一个反应体系中形成一个二氮杂七元环和四个新化学键(两个C—N,一个C=C,一个C—C).该方法操作简单,反应便捷,对环境友好,产率高,为1,5-苯并二氮杂?化合物的合成提供绿色环保,高效简便的合成思路.