含铋金属氧簇的研究进展

含铋金属氧簇结构的多样性和多功能性使其在诸多领域有着非常广泛的应用。本文总结了已报道的50多个含铋金属氧簇化合物,根据Bi(Ⅲ)在金属氧簇中所充当的作用,可将含铋金属氧簇分成4大类:(1)Bi(Ⅲ)作为中心杂原子;(2)Bi(Ⅲ)作为取代原子;(3)Bi(Ⅲ)作为桥联原子;(4)Bi(Ⅲ)作为终端原子,分别对其合成和结构的发展现状进行总结。同时,介绍了含铋金属氧簇在催化、磁性、光学、药物等方面的应用,并对其前景进行了展望。通过本文可以很好了解含铋金属氧簇的合成、性能及发展,对多金属氧簇的拓展研究有重要意义。     

质谱在多金属氧簇化学中的应用

随着多金属氧簇化学的发展,迫切需要将多金属氧簇的液相反应过程和固相结构有机结合起来,以便更好地指导功能导向性多金属氧簇的设计与合成。传统的分析方法对一些特殊结构的多金属氧簇以及溶液自组装机理的研究具有局限性。随着软电离技术的发展,尤其是电喷雾电离(ESI)和基质辅助激光解吸电离(MALDI)的发明,质谱(MS)技术越来越多应用在简单无机化合物、配合物及金属有机化合物的研究中。多金属氧簇属无机高分子,是一类结构较特殊的无机配合物,多阴离子自身常带多个负电荷。钼、钨等具有较多同位素,可方便通过理论模拟与实际测量同位素分布的对比确定簇离子的准确组成。本文综述了质谱技术在多金属氧簇化学中的应用,如ESI-MS分析多阴离子在溶液中存在形式、监测反应过程、推断自组装机理,并对其在多金属氧簇化学中的应用前景进行了展望。     

可溶液加工的聚(多金属氧簇降冰片烯)和聚(己酸降冰片烯)嵌段和无规共聚物的合成及催化功能的研究

将一种可有机功能化的Wells-Dawson POM与降冰片烯相连接,制备了多金属氧簇降冰片烯单体.再利用活性可控的开环易位聚合方法(ROMP),在Grubbs 3~(rd)催化剂的作用下,合成了聚(多金属氧簇降冰片烯)-聚(己酸降冰片烯)的杂化嵌段和无规共聚物(H-CPs),分别简写为Poly(POM)_m-b-Poly(COOH)_n和Poly(POM)_m-r-Poly(COOH)_n.采用~1H-NMR、~(31)P-NMR和FTIR等方法对共聚物结构进行表征,确认我们成功地合成了由共价键连接这2种单体形成的H-CPs.最后,利用带有光散射和红外探测器的凝胶渗透色谱(SEC)测定聚合物的绝对分子量和分子量分布,证明所得到的H-CPs不仅分子量可控,而且分子量分布系数较窄.最后,研究了H-CPs催化氧化四氢噻吩(THT)成环丁亚砜(THTO)反应,结果表明,相比于聚(多金属氧簇)的均聚物(Poly(POM)),H-CPs的催化活性有所下降,原因是POM催化剂含量较低以及H-CPs在催化介质中溶解性的差异.     

杂多铌氧簇聚物的研究进展

多铌氧簇聚物是多金属氧簇聚物的重要组成部分,具有丰富多样的结构类型,在碱催化、光催化产氢等方面具有广泛的应用前景,吸引了越来越多化学工作者的关注。本文系统地综述了主族元素(ⅢA/ⅣA/ⅤA/ⅥA族)为杂原子的杂多铌氧簇聚物和过渡元素(V/Fe/Cu)为杂原子的杂多铌氧聚合物的研究进展,主要包括化合物的合成策略、结构调控、性质及应用的探索。此外,对当前杂多铌氧簇聚物的发展所面临的挑战进行了总结,并对其后续的发展进行了展望。     

杂多铌氧簇聚物的研究进展

多铌氧簇聚物是多金属氧簇聚物的重要组成部分,具有丰富多样的结构类型,在碱催化、光催化产氢等方面具有广泛的应用前景,吸引了越来越多化学工作者的关注。本文系统地综述了主族元素(ⅢA/ⅣA/ⅤA/ⅥA族)为杂原子的杂多铌氧簇聚物和过渡元素(V/Fe/Cu)为杂原子的杂多铌氧聚合物的研究进展,主要包括化合物的合成策略、结构调控、性质及应用的探索。此外,对当前杂多铌氧簇聚物的发展所面临的挑战进行了总结,并对其后续的发展进行了展望。     

基于多金属氧簇的手性超分子液晶

以手性诱导为切入点,采用含胆固醇基团的季铵盐表面活性剂静电包覆缺位的Keggin结构多金属氧簇K7PW11O39·12H2O,得到了手性介晶阳离子修饰的多金属氧簇杂化超分子复合物。圆二色谱对该复合物光学活性的表征说明外围的手性表面活性剂可以通过静电相互作用诱导复合物显示出手性。利用差示扫描量热曲线法、偏光显微镜观察和变温X射线衍射详细研究了该复合物的热性质和相行为,结果表明该复合物在较宽的温度范围内具有热致液晶性质,是一种典型的手性近晶A相离子液晶材料。     

氧化还原对Lindqvist型多金属氧簇复合物自组装的动态调控

Dynamic regulation of self-assembly is of vital importance in chemistry, biology and material science thanks to its great potential for development of smart materials and devices. Polyoxometalates (POMs) are a class of functional inorganic nanoclusters, which has become one of the excellent building blocks for supramolecular self-assemblies, especially when covalently or non-covalently modified by organic species. As typical stimuli-responsive functional clusters, the POMs could be photochemically or electrochemically reduced to mixed-valence states, of which the structural integrity remains even after encountering stepwise multi-electron redox process. The intriguing photochromism of the POMs in different states exhibits distinct photophysical properties, which motivates us to exploit the dynamic self-assemblies of POM-based complexes. The divalent Lindqvist-type hexamolybdate cluster [Mo₆O₁₉]^2- is one of the least negative-charged POMs, which is the ideal building blocks to construct novel assembly structures. Based on this motivation, herein, a single chain surfactant-encapsulated polyoxometalate (POM) complex (ODTA)₂[Mo₆O₁₉] was prepared by simple counterion replacement of Lindqvist-type (TBA)₂[Mo₆O₁₉] with octadecyltrimethylammonium (ODTA) in acetonitrile solution. The structure of the POM complex was confirmed by ¹H nuclear magnetic resonance (NMR), Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA) and elemental analysis. The solution of complex (ODTA)₂[Mo₆O₁₉] in the mixed solvents of acetonitrile and isopropanol with the volume ration of 4 to 1 exhibited reversible photochromism upon alternate UV light irradiation and air exposure. Upon UV light irradiation, the light yellow transparent solution of (ODTA)₂[Mo₆O₁₉] turned into blue quickly. The new broad absorption band appearing at ca.751 nm assigned to the Mo^V → Mo^VI intervalence charge-transfer (IVCT) transition, indicated the formation of reduced POM, as revealed by UV-Vis absorption spectra. After exposed to air, the blue solution was bleached. The alternate photochromism could be conducted for multiple cycles. Helical self-assembled morphology of (ODTA)₂[Mo₆O₁₉] was formed in acetonitrile/isopropanol, characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) methods. More interestingly, morphology transformation of the complex from helical strips to spherical assemblies occurred accompanied by photochromism occurrence. The morphology evolution during the photochromism process experienced from shortened helical strips through sea urchin-like aggregates to spherical assemblies. Most significantly, the helical assemblies could be recovered again after air oxidation, implying the reversible morphology transformation driven by redox stimulus. The redox-modulated reversible self-assembly is driven by the variation of electrostatic attraction between organic cations and inorganic anions as well as the electrostatic repulsion between inorganic ionic clusters, proved by X-ray photoelectron spectroscopy (XPS) and ¹H NMR spectra. The results will contribute to better understanding the mechanism of dynamic assemblies and inspire the precise fabrication of advanced smart materials.     

多金属氧酸盐催化烯烃环氧化研究进展

综述了以过氧化氢为氧源,多金属氧酸盐催化烯烃环氧化的研究进展,尤其是针对基于多金属氧酸盐的反应控制相转移催化体系近年来的研究进展进行了详细阐述.     

基于多金属氧簇的手性超分子液晶

以手性诱导为切入点,采用含胆固醇基团的季铵盐表面活性剂静电包覆缺位的Keggin结构多金属氧簇K₇PW₁₁O₃₉·12H₂O,得到了手性介晶阳离子修饰的多金属氧簇杂化超分子复合物。圆二色谱对该复合物光学活性的表征说明外围的手性表面活性剂可以通过静电相互作用诱导复合物显示出手性。利用差示扫描量热曲线法、偏光显微镜观察和变温X射线衍射详细研究了该复合物的热性质和相行为,结果表明该复合物在较宽的温度范围内具有热致液晶性质,是一种典型的手性近晶A相离子液晶材料。     

多金属氧酸盐催化的液相氧化反应

介绍了多金属氧酸盐的结构和性能, 综述了这类化合物具有的多功能性和可调性,并对它们与环境温和、经济廉价的条件（溶剂,氧化剂等）的良好兼容性等特点进行了概述。多金属氧酸盐可以在原子/分子层次上进行催化剂的设计,在绿色催化和清洁生产等方面具有良好的应用前景。文本总结了多金属氧酸盐在液相清洁催化氧化方面的进展,主要针对以过氧化氢和分子氧为氧化剂的烯烃类化合物的环氧化反应、烷烃和芳香族化合物的氧化反应,并详细探讨了此类氧化反应的反应机理。同时也关注了多金属氧酸盐在仿生催化领域的应用。     

多金属氧酸盐催化苯甲醇的选择性氧化：一个绿色可循环的高效催化氧化体系

以Keggin结构的几类杂多酸和三乙胺（TEA）为原料,通过简单的酸碱反应合成了相应杂多酸的TEA盐。 并以它们作为催化剂,30％H2O2作氧化剂,在不使用长链相转移剂的条件下,研究了它们催化苯甲醇选择氧化制备苯甲醛的反应性能。 结果表明,该类催化剂在苯甲醇的选择氧化反应中具有比相应杂多酸更高的催化活性或选择性。 其中[TEAH]H2PW12O40为最佳催化剂,在适宜的反应条件下,该催化剂上苯甲醇转化率可达99.5％以上,苯甲醛选择性达~100％。 催化剂可以被分离和循环使用多次,活性、选择性基本不变。 用水作溶剂,避免了有机溶剂的使用,是一个高效、绿色的苯甲醛选择氧化体系。     

Surfactant‐Encapsulated Polyoxometalates as Immobilized Supramolecular Catalysts for Highly Efficient and Selective Oxidation Reactions

A type of interesting immobilized supramolecular catalysts based on surfactant‐encapsulated polyoxometalates has been developed for oxidation reactions. Through a sol‐gel process with tetraethyl orthosilicate, hydroxyl‐terminated surfactant‐encapsulated polyoxometalate complexes have been covalently and uniformly bound to a silica matrix with unchanged complex structure. The formed hybrid catalysts possess a defined hydrophobic nano‐environment surrounding the inorganic clusters, which is conducive to compatibility between the polyoxometalate catalytic centres and organic substrates. The supramolecular synergy between substrate adsorption, reaction, and product desorption during the oxidation process has been found to have an obvious influence on the reaction kinetics, with the activity of the catalyst being greatly improved. The supramolecular catalysts performed effectively in the selective oxidation of several different kinds of organic compounds, such as alkenes, alcohols, and sulfides, and the main products were the corresponding epoxides, ketones, sulfoxides, and sulfones. More significantly, the catalyst could be easily recovered by simple filtration, and the catalytic activity was well retained for at least five cycles. Finally, the present strategy has proved to be a general route for the fabrication of supramolecular hybrid catalysts containing common polyoxometalates suitable for various purposes.     

基于杂多酸的负载离子液相催化在醇氧化中的应用

采用溶胶-凝胶法制备的离子液体功能化的二氧化硅对于杂多酸是一种可行的载体,三种商用杂多酸成功的负载在离子液体功能化的二氧化硅上作为醇氧化的催化剂.利用FTIR、XRD、XPS对该种负载离子液相催化剂进行了表征.基于磷钨酸的负载离子液相催化剂活性最好,高产率(大部分＞93%)的得到了相应的羰基化合物.且该催化剂经过简单的...     

Asymmetric Synthesis of Chromans Through Bifunctional Enamine-Metal Lewis Acid Catalysis

Cooperative enamine-metal Lewis acid catalysis has emerged as a powerful tool to construct carbon-carbon and carbon-heteroatom bond forming reactions. A concise synthetic method for asymmetric synthesis of chromans from cyclohexanones and salicylaldehydes has been developed to afford tricyclic chromans containing three consecutive stereogenic centers in good yields (up to 87 %) and stereoselectivity (up to 99 % ee and 11 : 1 : 1 dr). This difficult organic transformation was achieved through bifunctional enamine-metal Lewis acid catalysis. It is believed that the strong activation of the salicylaldehydes through chelating to the metal Lewis acid and the bifunctional nature of the catalyst accounts for the high yields and enantioselectivity of the reaction. The absolute configurations of the chroman products were established through X-ray crystallography. DFT calculations were conducted to understand the mechanism and stereoselectivity of this reaction.     

Binary Pd–Polyoxometalates and Isolation of a Ternary Pd–V–Polyoxomolybdate Active Species for Selective Aerobic Oxidation of Alcohols

Binary Pd–polyoxometalates [Pd(dpa)₂]₃[PW₁₂O₄₀]₂ ? 12 DMSO ( 2 ), [Pd(dpa)₂]₃[PMo₁₂O₄₀]₂ ? 12 DMSO ? 2 H₂O ( 3 ), and [Pd(dpa)(DMSO)₂]₂[HPMo₁₀V₂O₄₀] ? 4 DMSO ( 4 ) were synthesized by reaction of [Pd(dpa)(OAc)₂] ? 2 H₂O ( 1 ; dpa=2,2′‐dipyridylamine) with three Keggin‐type polyoxometalates and fully characterized by single‐crystal and powder XRD analyses, IR spectroscopy, and elemental analyses. The synthesis is facile and straightforward, and the complicated ligand‐modification procedure often used in the traditional charge‐transfer method can be omitted. In 2 – 4 , Pd complexes and polyoxometalate anions are coupled through electrostatic interaction. Compound 4 is more active than the other three compounds in the selective aerobic oxidation of alcohols at ambient pressure. Interestingly, during catalytic recycling of compound 4 , unprecedented ternary Pd–V–polyoxometalate [Pd(dpa)₂{VO(DMSO)₅}₂][PMo₁₂O₄₀]₂ ? 4 DMSO ( 5 ), which was captured and characterized by single‐crystal XRD, proved to be the true active species and showed high catalytic activity for the selective aerobic oxidation of aromatic alcohols (98.1–99.8 % conversion, 91.5–99.1 % selectivity). Moreover, on the basis of control experiments and EPR and UV/Vis spectra, a plausible reaction mechanism for the oxidation of alcohols catalyzed by 5 was proposed.     

反应控制相转移催化研究的进展

反应控制相转移催化是近年来发展起来的一类新的催化体系.该催化体系在反应过程中具有均相催化的本征,当反应结束后,催化剂发生相的变化而从反应介质中析出,从而可实现催化剂的分离和循环使用.本文就反应控制相转移催化原理及其在烯烃环氧化、醇氧化、烯烃断键氧化、苯羟基化、硒催化羰基化和酯化反应等方面应用的最新进展进行了综述.     

When Gold Cations Meet Polyoxometalates

Merging gold(I) cations with polyoxometalate anions results in various interclusters and complexes. Herein, the synthesis of these newly emerging gold(I)/polyoxometalate materials is reviewed. The applications of these promising hybrids in organic catalysis are also summarized and evaluated in terms of the advantages and limitations of the catalysts including efficiency, synergistic effects and recyclability.