Monitoring of the Pre-Equilibrium Step in the Alkyne Hydration Reaction Catalyzed by Au(III) Complexes: A Computational Study Based on Experimental Evidences

The coordination ability of the [(ppy)Au(IPr)]²⁺ fragment [ppy = 2-phenylpyridine, IPr = 1,3-bis(2,6-di-isopropylphenyl)-imidazol-2-ylidene] towards different anionic and neutral X ligands (X = Cl⁻, BF₄⁻, OTf⁻, H₂O, 2-butyne, 3-hexyne) commonly involved in the crucial pre-equilibrium step of the alkyne hydration reaction is computationally investigated to shed light on unexpected experimental observations on its catalytic activity. Experiment reveals that BF₄⁻ and OTf⁻ have very similar coordination ability towards [(ppy)Au(IPr)]²⁺ and slightly less than water, whereas the alkyne complex could not be observed in solution at least at the NMR sensitivity. Due to the steric hindrance/dispersion interaction balance between X and IPr, the [(ppy)Au(IPr)]²⁺ fragment is computationally found to be much less selective than a model [(ppy)Au(NHC)]²⁺ (NHC = 1,3-dimethylimidazol-2-ylidene) fragment towards the different ligands, in particular OTf⁻ and BF₄⁻, in agreement with experiment. Effect of the ancillary ligand substitution demonstrates that the coordination ability of Au(III) is quantitatively strongly affected by the nature of the ligands (even more than the net charge of the complex) and that all the investigated gold fragments coordinate to alkynes more strongly than H₂O. Remarkably, a stabilization of the water-coordinating species with respect to the alkyne-coordinating one can only be achieved within a microsolvation model, which reconciles theory with experiment. All the results reported here suggest that both the Au(III) fragment coordination ability and its proper computational modelling in the experimental conditions are fundamental issues for the design of efficient catalysts.     

A Review on Coordination Properties of Al(III) and Fe(III) toward Natural Antioxidant Molecules: Experimental and Theoretical Insights

This review focuses on the ability of some natural antioxidant molecules (i.e., hydroxycinnamic acids, coumarin-3-carboxylic acid, quercetin, luteolin and curcumin) to form Al(III)- and Fe(III)-complexes with the aim of evaluating the coordination properties from a combined experimental and theoretical point of view. Despite the contributions of previous studies on the chemical properties and biological activity of these metal complexes involving such natural antioxidants, further detailed relationships between the structure and properties are still required. In this context, the investigation on the coordination properties of Al(III) and Fe(III) toward these natural antioxidant molecules might deserve high interest to design water soluble molecule-based metal carriers that can improve the metal’s intake and/or its removal in living organisms.     

基于NVivo的卓越化学教师课堂教学创新能力评价*——以东芝杯教学技能创新大赛为例

研究采用视频分析法,利用NVivo软件,以东芝杯教学技能创新大赛的化学组选手为对象,从教学理念、教学情境、实验设计和教学手段等4个维度,评价卓越职前化学教师课堂教学的创新能力。结果发现:教学理念新颖,但具体落实尚有不足;情境创设生动,但主题与学生的联系不够紧密;实验设计别致,但在水平上还有提升空间;教学技术手段先进,但还需要深度融合。研究为创新型卓越化学教师的培养提供了启示。     

Preparation of Low-dielectric Permittivity Polyimide Resins with High Surface Activity from Chemically Bonded Hyperbranched Polysiloxane

Thermosetting resin matrix is the key component of advanced wave-transparent composites,where low dielectric constant,excellent processability,high thermal stability,as well as good bonding ability are required for resins.Herein,we prepared a series of phenylethynyl terminated polyimide(PI)resins by grafting amine-functionalized hyperbranched polysiloxane(HBPSi)to PI chains during the in situ polymerization.The effects of HBPSi on the processability of oligomers,molecular packing,thermal stability,dielectric property and bonding ability to reinforce Kevlar fibers of the cured PI/HBPSi composite resins have been examined in detail.The dielectric constants of the cured composite resins were greatly reduced from 3.29 to 2.19 without compromising its processability and thermal stability.Meanwhile,the 10 wt％HBPSi-containing PI resin demonstrated better bonding ability to reinforce fibers with the interfacial shear strength(IFSS)of 37.64 MPa,compared with that of neat PI-6 matrix(27.34 MPa),and better adhesion to metal with the lap shear strength of 10.48 MPa,50％higher than that of neat resin PI-6(6.98 MPa).These resultant PI/HBPSi composite resins exhibit excellent comprehensive properties,indicating their great potential as low-dielectric constant resin matrix in radar radome.     

Poly(phenylene oxide) modified cyanate resin for self‐healing

Self‐healing cyanate ester resins (CE) were developed by adding low molecular weight poly(phenylene oxide) (PPO) resin, yielding a high performance CE/PPO system via a low‐temperature process. The addition of PPO improved the flexural strength and fracture toughness of the CE matrix without sacrificing thermal properties. CE/PPO formulations with 5, 10, and 15 wt.% PPO showed 43%, 65%, and 105% increase in fracture toughness due to a combination of crack deflection, crack pinning, and matrix cavitation around second‐phase particles. When PPO was introduced into the CE, dielectric properties were either unchanged or declined. During thermal treatment to heal damaged CE, liquid PPO flowed into cracks, and during subsequent cooling, solidified to bond the crack surfaces. The self‐healing efficiency for CE with 15 wt.% PPO after heating to 220°C for 1 h exhibited a recovery of 73% in toughness and 81% in microtensile strength. Copyright © 2014 John Wiley & Sons, Ltd.     

About the Journal

正Chinese Journal of Catalysis is an international journal published monthly by Chinese Chemical Society,Dalian Institute of Chemical Physics,Chinese Academy of Sciences,and Elsevier.The journal publishes original,rigorous,and scholarly contributions in the fields of heterogeneous and homogeneous catalysis in English or in both English and Chinese.The scope of the journal includes:     

案例教学与翻转学习结合提升物理化学教学质量

结合我校应用型人才培养方案和培养目标,通过改革物理化学课堂教学提高学生知识掌握能力和应用能力。在传统课堂的基础上,将案例教学结合在翻转学习的教学过程中,充分提高学生的学习积极性与主动性。以稀溶液的依数性为教学案例,阐述翻转学习与案例教学的实施过程。学生深度参与课堂、融入课堂并互动,师生之间在教学中达到共鸣,实现教学相长,从而提高物理化学教学质量。     

Comparative Study of the Chemical Compositions and Antioxidant Activities of Fresh Juices from Romanian Cucurbitaceae Varieties

Cucurbitaceae is a family of health-promoting plants due to their compounds with beneficial effects. The aim of this study was to analyze, for the first time, the chemical composition, the antioxidant activity and the metal chelating properties of fruit juices obtained from four different species of the Cucurbitaceae family cultivated in Romania, namely Momordica charantia, Cucumis metuliferus, Benincasa hispida and Trichosanthes cucumerina. The samples of juice were analyzed by high-performance liquid chromatography (HPLC) and all the four species displayed high levels of the two triterpenes, oleanolic and ursolic acids, and also in phenolic compounds, including catechin, (−)-epicatechin and gallic acid. The juices demonstrated significant antioxidant activity against the free radical 2,2-diphenyl-1-picrylhydrazyl (ranging from 20 to 95%,), a good iron binding ability (ranging from 7.45 ± 0.28% to 86.95 ± 0.97%) and also promising antioxidant potential against the ABTS radical (ranging from 4.97 to 32.60 μETx/mL juice). Our findings raise interesting questions for further research on Cucurbitaceae fruit juices and, consequently, their very good antioxidant potential suggests these fruits should be further explored for their protective effect against oxidative damage. This is the first time the chemical composition and antioxidant activities of fruit juices from these four Romanian Cucurbitaceae varieties have been investigated.     

一种新型双吡啶悬臂Mn(Ⅱ)配合物的合成、晶体结构及DNA结合能力研究

通过3,3′-((乙烷-1,2-二基双(2-甲基吡啶杂氮二基)双(亚甲基))双(2-羟基-5-甲基苯甲醛)与2-羟基-1,3-丙二胺的缩合反应得到一种具有双吡啶悬臂的双核锰配合物。通过X射线单晶衍射确定了该配合物结构,结果显示其分子式为[Mn₂(C₃₇H₄₃N₆O₆)]·(ClO₄)₂。该配合物属于单斜晶系,P2₁/c空间群,晶胞参数为:a=1.096 50(19) nm, b=1.419 5(3) nm, c=3.109 4(5) nm, β=108.153(5)°。进一步分析表明两个二价锰离子分别与(N_amine)₂(N_imine)₂O₃和(N_imine)₂O₄体系配位,它们与配位原子形成的几何构型分别是十面体和扭曲的八面体。两个中心锰离子距离为0.331 6 nm,由酚氧原子和醋酸根共同桥联。另外,本文也利用伏安法和黏度法对该配合物与小牛胸腺DNA的结合能力进行研究,实验结果表明它们之间的结合方式为弱的插入作用。     

以PBL法进行药学实验基本技能教学的探索与实践*

根据西部少数民族地区院校的客观条件和教学特点,提出用以问题为导向的教学法(PBL)进行药学基本技能实验教学。实践证明,实验组(PBL法)的实践基本技能操作水平和发现、分析并解决问题的能力均显著高于对照组(传统教学法)。该法对提高西部少数民族地区药学本科生的创新能力具有较大意义,对其他地区药学本科生创新能力的培养也有一定的借鉴作用。