一种卡宾配合物的合成及其在Suzuki反应中的应用

合成了一种N-杂环卡宾的钯配合物,可用于高效地催化芳基溴化物和对甲苯磺酸芳酯对芳基硼酸的Suzuki偶联反应.该反应在二氧六环溶剂中以醋酸钾为助剂、空气氛下80℃即可进行,具有收率高、催化剂容易制备等优点.     

有机硅试剂参与过渡金属催化的C-H官能团化反应形成C-C键的研究进展

作为一类重要的有机金属试剂,有机硅试剂在有机合成化学的C—C键形成中得到了广泛应用.综述了近年来有机硅试剂参与的过渡金属催化下C—H官能团化反应形成C—C键的研究进展,重点介绍了Pd催化下C—H官能团化的Hiyama偶联反应.     

Catalysis and inhibition of benzimidazole units on thermal imidization of poly(amic acid) via hydrogen bonding interactions

The effect of benzimidazole units on thermal imidizaiton was studied when they were introduced into the main chain of poly(amic acid)(PAA). The thermal imidization process of PAA-PABZ synthesized by 3,3',4,4'-biphenyltetracarboxylic dianhydride(BPDA) and 2-(4-aminophenyl)-5(6)-aminobenzimidazole(PABZ) was studied by TGA, DSC, DMA, FTIR and in situ FTIR. The results of FTIR and in situ FTIR indicate benzimidazole units act as an "in situ" catalyst to accelerate thermal imidization of PAA to polyimide(PI) when the temperature is lower than 170 °C. FTIR and 1H-NMR results demonstrate that in situ catalysis is caused by the hydrogen bonding interactions between C=N of benzimidazole and ―NH― in ―CONH― of PAA and the semi-ionization of the H in imidazole ring of benzimidazole. However, when the imidization temperature is higher than 170 °C, the thermal imidization process is inhibited. DMA and in situ FTIR results illustrate that the decreased mobility of PI-PABZ macromolecular chains and the reduced reactive ability of anhydride formed during the intramolecular breakdown of polymer chains lead to the inhibition of thermal imidization process.     

Controlled formation of novel supramolecular microbelts or microprisms from aniline and H2PdCl4 driven by coordination and π–π interactions

In this communication, I report the formation of novel supramolecular one-dimensional (1D) structures including microbelts and microprisms by a direct mix of aniline and H₂PdCl₄ aqueous solutions at room temperature. As-formed supramolecular structures were characterised by scanning electron microscopy, X-ray photoelectron spectra and X-ray diffraction techniques. Both coordination and π–π interactions are expected to be responsible for these 1D microstructures. It suggests that the molar ratio of the reactants is crucial to the formation of such 1D structures.     

气相色谱法测定广藿香油中百秋李醇含量

建立了气相色谱仪测定广藿香油中百秋李醇含量的方法。用毛细管色谱柱DB-5MS（30m×O．32mm．0．25μm）,正十八烷为内标,氢火焰离子化检测器进行检测,内标法定量。百秋李醇含量在0．2-2．0mg／mL范围内,百秋李醇峰面积和内标物峰面积之比与百秋李醇质量浓度呈良好的线性关系,相关系数r=0．9997。方法的检出限为1μg／mL,加标回收率为90．0％～100．6％,测定结果的相对标准偏差为1．22％（n=6）。研究表明,本法简便、快速、测定结果准确可靠,精密度优于外标法。     

Sensitive signal-on fluorescent sensing for copper ions based on the polyethyleneimine-capped silver nanoclusters–cysteine system

In this work, we present a label-free sensor for copper ions. This sensor is composed of silver nanoclusters and cysteine. The fluorescence of the silver nanoclusters was quenched by cysteine, which was recovered in the presence of copper ions. This binding of silver nanoclusters to cysteine promoted agglomeration of silver nanoclusters to yield larger non-fluorescent silver nanoparticles. The presence of copper ions resulted in the oxidation of cysteine to form a disulfide compound, leading to recovery of fluorescence of the silver nanoclusters. The fluorescence of the silver nanoclusters in the presence of cysteine increased with increasing concentration of copper ions in the range of 10–200 nM. The detection limit of this sensor for copper ions was 2.3 nM. The silver nanoclusters–cysteine sensor provides a simple, cost-effective, and sensitive platform for the detection of copper ions.     

微波处理和溶胶凝胶法共同改性废胶粉及其与天然橡胶复合材料性能的研究

采用微波处理打断废胶粉(WRP)的三维网状结构用来提高WRP在有机溶剂中的溶胀性,然后采用溶胶凝胶法,将微波改性后的WRP浸入正硅酸乙酯中,通过水解反应和缩合反应,在WRP表面原位生成SiO2网络,从而制得改性废胶粉(MWRP).将制得MWRP与天然橡胶(NR)共混,制备了NR/MWRP复合材料,研究了NR/MWRP复合材料的性能.通过热重分析仪、差示扫描量热仪和力学分析表明微波处理最佳时间是20 s.由于微波处理提高了NR与WRP的相容性,原位生成的SiO2粒子起到了补强作用,所以所制备的NR/MWRP复合材料拥有较好的力学性能;随着Si69的加入,抑制了SiO2粒子聚集,提高了SiO2粒子的分散性,从而进一步提高复合材料的力学性能并降低复合材料的Payne效应;在进行频率扫描时,硫化胶的储存模量随频率的增大而增大;硫化胶的温度扫描结果表明,随着温度的升高,复合材料中SiO2粒子聚集程度加剧并且复合材料出现老化的现象.为了提高复合材料的耐老化性能,N,N-间苯撑双马来酰亚胺(BMI)作为一种防老剂加入复合材料中,BMI利用Diels-Aider反应补偿橡胶在老化过程中所损失的交联键并提高NR与WRP的界面相容性,从而提高复合材料的耐老化性能.     

热力学变化过程方向的完整判据

目前物理化学教科书中的自发过程方向与限度判据,只能对常见自发过程作判断,不能对含有非体积功的各类过程做出判断。笔者从热力学第二定律的理论基础克劳修斯不等式入手,通过自发变化熵判据的演绎过程,找到了3个判据不完整性的原因所在,给出了完整方向性判据的解决方案。应用表明,完整的方向与限度判据可适用于各类热力学变化过程。     

微流控技术制备微胶囊负载钯催化剂

采用微流控技术结合悬浮聚合方法实现了百微米级含膦配体聚苯乙烯微胶囊的可控制备, 微胶囊尺寸在320~420 μm范围内可调, 且单分散性好. 扫描电子显微镜、能量散射光谱和电感耦合等离子发射光谱结果证实了其形貌和组成的均匀性及钯负载的可控性和有效性. 以溴代芳烃与苯硼酸的Suzuki偶联反应为模型反应评价了负载Pd(PPh₃)₄的百微米级微胶囊的催化性能, 发现其性能与文献报道的7~8 μm的同类催化剂微胶囊接近, 且均优于均相催化剂; 该催化剂经简单过滤后, 可实现多次循环使用, 未发现活性物种的流失. 该法实现了连续制备, 因而有助于提高制备的效率和可控性. 另外, 所制百微米级催化剂微胶囊在固定床反应器内具有较高催化剂浓度和机械性能, 且优于浆态床中使用的微米级催化剂微胶囊.     

离子液体催化CO2与环氧化物合成环状碳酸酯

综述了离子液体催化CO2与环氧化物的环加成反应制备环状碳酸酯的研究进展。目前报道的离子液体主要包括咪唑盐、季铵盐、季鏻盐等。对比了传统离子液体与功能化离子液体对CO2环加成反应的催化活性、选择性以及催化作用机制。与传统的离子液体相比,功能化离子液体的羟基或羧基等官能团与卤素离子等Lewis碱之间存在协同效应,使得其对CO2与环氧化物的环加成反应具有更好的催化活性;将功能化离子液体固载于无机材料(SiO2,SBA-15,MCM-41等)或聚合物所得的多相催化剂不仅保持了官能团与阴离子之间的协同效应,而且载体与离子液体活性组分之间也显示出协同效应,使得该类催化剂具有很好的催化活性,稳定性好,可以多次重复使用,具有较好的工业化前景,是值得深入研发的一类催化材料。此外,离子液体对于手性环状碳酸酯的合成也具有较好的催化活性和立体选择性。