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Progress in Chemistry 2012, No.0203 Previous issue Next issue

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Molecular-Recognition and Thermo-Responsive Composite Smart Polymeric Materials
Xie Rui, Yang Mei, Cheng Changjing, Jiang Jing, Chu Liangyin
2012, 24 (0203): 195-202 |
Published: 24 March 2012
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Abstract
Development of dual-stimuli-responsive and multi-stimuli-responsive smart polymeric materials becomes more and more important. The recent progresses in molecular-recognition and thermo-responsive composite smart linear polymers, smart microspheres and smart membranes based on poly(N-isopropylacrylamide) (PNIPAM) and β-cyclodextrin (β-CD) are reviewed in detail. The different kinds of smart materials are prepared by the same reaction mechanism, namely polymerization of N-isopropylacrylamide (NIPAM) with glycidyl methacrylate (GMA) into poly(N-isopropylacrylamide-co-glycidyl methacrylate) (PNG) polymer at first, followed by introduction of modified mono-6-deoxy-6-ethylenediamino-β-cyclodextrin (ECD) or mono-6-deoxy-6-hexanediamino-β-cyclodextrin (HCD) onto PNG polymer by virtue of reaction between primary amino groups and epoxy groups. The effects of preparation conditions, the molar ratio of NIPAM to GMA, grafting yields, the types and concentrations of guest molecules on the thermo-responsibility and molecular-recognition characteristics of different composite smart polymeric materials are discussed. Moreover, the applications of composite smart polymeric membranes in affinity separation, controlled release and chiral separation are also discussed. The significance and future of molecular-recognition and thermo-responsive composite polymeric materials are commented. Contents
1 Introduction
2 Molecular-recognition and thermo-responsive compo-site smart polymeric materials based on poly- (N-isopropylacrylamide) and β-cyclodextrin
2.1 Composite smart linear polymers
2.2 Composite smart microspheres
2.3 Composite smart membranes
3 Conclusions and Outlook
Review
Diversity of Active Intermediates in Homogeneous Catalytic Oxidations
Wang Yujuan, Xu Jie, Yin Guochuan
2012, 24 (0203): 203-211 |
Published: 24 March 2012
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Abstract
Transition metal ions play significant roles in versatile biological and chemical oxidations. In addition to the generally believed metal oxo functional groups(Mn+ O), the metal hydroxo (Mn+-OH)and hydroperoxide functional groups (Mn+-OOH) have also been proposed to serve as the key active intermediates in versatile oxidation processes. However, the reasons why natural redox metalloenzymes make use of a metal oxo or hydroxo group to serve as their active intermediates in specific cases are not fully understood. In addition, certain organic compounds such as benzoquinone and organic N-oxide have also been reported to serve as catalyst in many chemical oxidation reactions, meanwhile, similar organic compounds like NADH and Coenzyme Q have been long believed to play the key roles in versatile biological metabolisms. Apparently, clarifying the oxidative relationships of these active intermediates would help to understand the enzymes' selections on them, thus promote understanding of their mechanisms and help the rational design of medicines, also it would benefit the design of selective oxidation catalysts. Herein, these active intermediates occurring in biological and chemical oxidation events are summarized in this paper. Their oxidative properties and related mechanisms have been discussed in text. Meanwhile, based on the available publications, the oxidative similarities and differences of the metal oxo with its corresponding hydroxo functional groups have also been briefly discussed. Contents
1 Introduction
2 Traditional theories in catalytic oxidations
3 New discoveries for the active metal intermediates in oxidations
4 The redox active organic intermediates in oxidations
5 The reactivity relationships of the metal oxo and its corresponding hydroxo moieties
6 Perspective
Oxidative Kinetic Resolution of Secondary Alcohols
Zhang Yuecheng, Zhao Shanshan, Mi Guorui, Zhao Jiquan
2012, 24 (0203): 212-224 |
Published: 24 March 2012
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Abstract
Optically active alcohols are extremely important starting materials and key intermediates for the synthesis of pharmaceutically and biologically active compounds. They can be obtained by oxidative kinetic resolution of racemic alcohols. In this review the recent progress in the oxidative kinetic resolution of secondary alcohols is discussed according to the kind of the oxidants and chiral catalysts. In addition, the mechanisms of some methods for the resolution of secondary alcohols are also discussed. The oxidative kinetic resolution of secondary alcohols using (-)-sparteine-Pd(Ⅱ), sparteine analogues-Pd(Ⅱ), N-heterocyclic carbine(NHC)-Pd(Ⅱ), chiral difunctional-Ir complexes and chiral (ON)-Ru(salen) complexes as catalyst systems respectively, and molecular oxygen as terminal oxidant are fully discussed. Besides, the resolution of secondary alcohols with chiral salen-Mn(Ⅲ) complex as catalyst and (diacetoxyiodo)benzene as terminal oxidant, and by the means of asymmetric transfer hydrogenation are also discussed. It is found that (-)-sparteine-Pd(Ⅱ)-O2 is the best among all the systems employed in the oxidative kinetic resolution of secondary alcohols. The novel system with high performance in the oxidative kinetic resolution of secondary alcohols need to be developed. Contents
1 Introduction
2 Using molecular oxygen as oxidant
2.1 Sparteine-Pd(Ⅱ) catalyst system
2.2 Sparteine analogues-Pd(Ⅱ) catalyst system
2.3 N-heterocyclic carbine(NHC)-Pd catalyst system
2.4 Chiral difunctional-Ir catalyst system
2.5 Chiral (ON)-Ru(salen) complex catalyst system
3 Salen-Mn(Ⅲ)-(diacetoxyiodo)benzene system
4 Resolution of secondary alcohols by asymmetric transfer hydrogenation
5 Conclusion
Application of Magnetic Ionic Liquids
Chen Biao, Long Quan, Zheng Baozhong
2012, 24 (0203): 225-234 |
Published: 24 March 2012
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Abstract
The unique physicochemical properties of magnetic ionic liquid (MIL) have attracted increasing interest due to their potential applications in various areas. In this paper, recent progress in applications of magnetic ionic liquid has been reviewed and discussed. Magnetic ionic liquid is a kind of ionic liquid which formed by organic cation and inorganic anion. It can be absorbed on the magnet, and has a certain magnetization in the presence of external magnetic field. Magnetic ionic liquid is a green solvent. In addition, magnetic ionic liquid can play as solvent, catalyst and template in organic synthesis, the resulting product is easy to separate and the structure of the product can be adjusted by an external magnetic field. Magnetic ionic liquid can be recycled and reused, and the catalytic activity of magnetic ionic liquid is not significantly reduced. In areas of separation, analysis, preparation of nano-materials,magnetic ionic liquid also have unique advantages. Especially, magnetic carbon nanotubes can be synthesized by using magnetic ionic liquid and carbon nanotubes. Contents
1 Introduction
2 The sorts of magnetic ionic liquids
3 The application of magnetic ionic liquids in catalysis
3.1 Catalyze polymerization reaction
3.2 Catalyze Friedel-Crafts reaction
3.3 Catalyze other reactions
4 The application of magnetic ionic liquids in carbon nanotubes
5 The application of magnetic ionic liquids in other fields
6 Recovery of magnetic ionic liquids
7 Conclusions and prospects
Graphene-Containing Composite Materials for Lithium-Ion Batteries Applications
Zhou Guanwei, He Yushi, Yang Xiaowei, Gao Pengfei, Liao Xiaozhen, Ma Zifeng
2012, 24 (0203): 235-245 |
Published: 24 March 2012
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Abstract
Graphene, a one-atom layer of graphite, possesses unique two dimensional structure and excellent electrical, mechanical, and thermal properties. It is considered as one of the most promising candidates for the future electrode materials for lithium ion batteries. Since the microstructure of the electrode material has great influence on its performance, the synthesis of electrode materials with graphene is widely studied to obtain specific morphologies and microstructures with great electrochemical performance improvements. In this review, we highlight recent advancements in the studies of the graphene-containing materials used in lithium ion batteries. Graphene acts as not only a mechanically stable buffer to accommodate the volume effect during cycling, but also a conductive network to enhance the electric conductivity of the anode composite materials. The graphene-containing anode materials can exhibit better cycling and rate performances. Especially, when forming optimized microstructures, such as sandwich-like blocks or other well-controlled encapsulating structures, the graphene can significantly improve electrochemical properties of anode composite materials. A continuous 3D conductive network formed by graphene in the cathode composite materials can effectively improve the electron and ion transportation. Additionally, graphene used as the conductive additive can achieve better charge/discharge performance with a much lower adding amount than those of commercial carbon-based additives. A prospect for future research developments in this field is proposed at the end of this review. Contents
1 Introduction
2 Preparation of graphene
3 Application of graphene in anodes of lithium-ion batteries
3.1 Electrochemical properties of graphene
3.2 Composite materials based on graphene
4 Application of graphene in cathodes of lithium-ion batteries
5 Application of graphene as conductive additive
6 Conclusions and Outlook
Review
Stabilization of Nanocatalysts in Fuel Cells
Chen Weimin
2012, 24 (0203): 246-252 |
Published: 24 March 2012
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Abstract
Low temperature fuel cells are considered to be promising portable power sources. Pt based noble metal nanocatalysts are widely used as electrocatalysts in low temperature fuel cells. The electrochemical stability of nanocatalysts is of significance for long-term operations of fuel cells. Unfortunately, Pt based nanocatalysts are unstable in fuel cells and tend to lose their activities gradually during long-term discharge processes. The activity losses of nanocatalysts are normally caused by nanoparticle agglomeration, metal dissolution, poisoning, support corrosion, etc. In order to extend the lifetime of fuel cells and save costs, the stability of nanocatalysts under internal environments of fuel cells should be improved. Recently, studies regarding the stabilization of Pt based nanocatalysts attracted much attention and various methods were developed to prevent the degradation of nanocatalysts. In this paper, recent research works about the stabilization of nanocatalysts in low temperature fuel cells are reviewed. Firstly, nanocatalysts are stabilized by support modifications, which include the graphitization of carbon supports, the doping of carbon supports, the surface functionalization of carbon supports and the use of other supports. Secondly, nanocatalysts are stabilized by steric effects, which are related to the surface covering of catalyst nanoparticles, the micro-pore enveloping of catalyst particles, the monolayer self-assembly of polyoxometallate on the catalyst surface and the steric obstruction of catalyst nanoparticles by polymer electrolytes. Thirdly, nanocatalysts are stabilized by synergetic effects, such as the elevation of metal oxidation potentials and the enhancement of the interaction between catalyst components. Finally, an outlook of the future development of the stabilization of nanocatalysts in low temperature fuel cells is provided. Contents
1 Introduction
2 Stabilization of catalysts by support modifications
2.1 Graphitization of carbon supports
2.2 Doping of carbon supports
2.3 Surface functionalization of carbon supports
2.4 Use of other supports
3 Stabilization of catalysts by steric effects
4 Stabilization of catalysts by synergetic effects
5 Conclusions and outlook
Synthesis of Zeolites by Dry Gel Conversion
Yang Na, Yue Mingbo, Wang Yimeng
2012, 24 (0203): 253-261 |
Published: 24 March 2012
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Abstract
Compared with traditional hydrothermal synthesis (HTS), dry gel conversion (DGC) synthesis of zeolites has the advantages of high yield, less waste, less usage of templates,etc. Firstly, this review summarized the developments in last decade and pivoted on the role of water. In typical DGC synthesis, the gel powder keeps intact with the liquid including liquid water. However, water could also be the vapor or those adsorbed/absorbed in gel powders. Therefore, both the water added and those included in gel powder may affect the nucleation, and growth of zeolite, phase selectivity and transformation, and the properties of obtained zeolite. It is believed that water has been the prerequisite for the transformation of zeolite from initial gel. And the required amount of water differs by structural properties of zeolite. Apart from water, other factors have been seen as contributing roles as well in the synthesis condition. Secondly, the difference between HTS and DGC is discussed. Thirdly, this review provided some insights into the formation mechanism of zeolite in DGC process, where nanoparticles and semi-crystalline intermediates play the role. Finally, this review illustrated the applications of DGC in the synthesis of hierarchical zeolite, zeolite film, zeolite monolith and others. Some advices about DGC used in the synthesis of these relatively new materials are concluded. Contents
1 Introduction
2 Definition of DGC
3 Factors in crystallization by DGC
3.1 Role of water
3.2 Other factors
4 Differences between HTS and DGC
5 Crystal growth and zeolite synthesis mechanism
6 Applications in fabrication of zeolite-like materials
6.1 Synthesis of hierarchical zeolite
6.2 Synthesis of zeolite monolith and other zeolite-like materials
7 Outlook
Preparation of Porous Carbon Materials
Wu Xueyan, Wang Kaixue, Chen Jiesheng
2012, 24 (0203): 262-274 |
Published: 24 March 2012
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Abstract
Porous carbon with large specific surface area, tunable porous structure, high stability and good electron conductivity, has attracted considerable attention due to its promising applications in the fields of catalyst, catalyst support, absorption and electrochemical energy storage. This manuscript reviews recent development in the fabrication of microporous carbon, mesoporous carbon, macroporous carbon and hierarchically porous carbon with both ordered and disordered porous structures. The so-called soft- and hard-template methods are efficient in tuning the porous structures and morphologies of carbon materials. The potential applications of porous carbon materials are also highlighted in this review. Contents
1 Introduction
2 Microporous carbon materials
2.1 Disordered microporous carbon materials
2.2 Ordered microporous carbon materials
3 Mesoporous carbon materials
3.1 Disordered mesoporous carbon materials
3.2 Ordered mesoporous carbon materials
3.3 Morphology control
4 Macroporous carbon materials
5 Hierarchical porous carbon materials
6 Conclusion and outlook
Application of Halloysite Nanotubes
Ma Zhi, Wang Jinye, Gao Xiang, Ding Tong, Qin Yongning
2012, 24 (0203): 275-283 |
Published: 24 March 2012
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Abstract
Halloysite nano-particles have recently become the subject of research attention as a new type of material.Halloysite nanotubes (HNTs) are readily obtainable and are much cheaper than other nano-particles such as carbon nanotubes(CNTs). More importantly, the unique crystal structure of HNTs not only resembles that of CNTs in terms of aspect ratio,but also has a highly ordered structure with aluminol groups bound in the inner surface and silanol groups on the external surface. Consequently HNTs not only have potential as additive for enhancing the mechanical performance of polymers but also make them attractive candidates for a variety of potential applications, including molecular adsorption, molecular encapsulation, storage and transport, catalyst or catalyst support in chemical reactions.This review summarizes the extensive but scattered literature on halloysite nanotubes’ application, from its crystal structure, chemical and characteristic of morphological, to its adsorption, transport and catalysis reactivity, involving the various valuable prospects. Finally, the future trends and prospects in the development of application research of HNTs are highlighted. Contents
1 Introduction
2 Chemical composition and crystalline structure of halloysite nanotubes
3 Adsorption,storage and transport properties of HNTs
3.1 Transport properties of hydrogen-bonding liquids such as water, methanol and ethanol
3.2 Adsorption storage properties of fuel gas CH4, H2 on HNTs
3.3 HNTs as the support for drugs or bioactive molecules
3.4 HNTs as sorbents for contaminants and pollutants
4 HNTs used as catalyst or catalyst support
4.1 Acid catalyst
4.2 Enzymatic carrier
4.3 The support of the catalyst metal complexes
5 Some other properties of HNTs
6 Outlook
Synthesis and Application of Hierarchically Structured Nano-Alumina
Tang Rui, Li Ping
2012, 24 (0203): 284-293 |
Published: 24 March 2012
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Abstract
Nano-alumina with hierarchical structure has recently attracted extensive attention because of its synergism and coupling effect on micro-nano scales. In the paper, the hierarchical structures of nano-alumina reported in the literature have been divided into four main types including hollow sphere, core-shell, cluster, and array. The progress of their synthesis techniques has been reviewed. Several factors affecting the morphology of nano-alumina particles with hierarchical structure in the course of synthesis have been discussed. It has been recognized in the literature that a majority of effects could be altered if changing the synthesis environment, indicating the complexity of hierarchical structure formation. Nevertheless, there is a general rule for the effect of pH in the hydrothermal process on the morphology of the secondary structure of nano-alumina. Acid condition favors the formation of one dimensional nano-alumina while basic condition helps to form two dimensional nano-alumina. The formation mechanism of the hierarchically structured nano-alumina has briefly been explained. Additionally, the effect of hierarchical morphology on the thermal stability of alumina has been depicted using available results presented in the literature. Some examples of the material applied to the areas of luminescence, adsorption and catalysis have been given in the paper. As viewed from the combination of the rational synthesis and the practical applications of the material with specific properties, the prospects of the research on the hierarchically structured nano-alumina have been outlined in the end of the paper. Contents
1 Introduction
2 Synthesis of hierarchically structured nano-alumina with different morphologies
2.1 Hollow structure
2.2 Core-shell structure
2.3 Cluster structure
2.4 Array structure
2.5 Other structures
3 Synthesis factors and structure formation mechanism
3.1 Factors in morphology forming
3.2 Formation mechanism of hierarchical structure
4 Influence of hierarchical structure on material thermostability
5 Application of hierarchically structured nano-alumina
6 Prospects
Two-Dimensional Titania Nanosheets
Shi Jianwen, Chen Shaohua, Cui Haojie, Fu Minglai
2012, 24 (0203): 294-303 |
Published: 24 March 2012
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Abstract
Titania nanosheets is one kind of novel two-dimensional materials with single layer of 0.7 nm thickness, which endows it many special properties different from bulk titania, such as high anisotropy, single crystal property, colloid and polyelectrolyte properties, large specific surface area, high surface energy, quantum size effects, etc. Potential applications can be expected in photon-to-electron conversion, magnetooptical effects, high permittivity devices, electrochemical energy storage, humidity-sensitive sensors, self-cleaning and photocatalysis fields. In this review, the intrinsic properties of titania nanosheets, such as optical absorption, photoluminescence, photon-to-current conversion, photoinduced hydrophilicity and the difference of crystal transformation temperature, are summarized, and the preparation and assembly methods of titania nanosheets are introduced. Then, these new assembled materials and their properties are reviewed in detail by using thin flakes, nanotubes, hollow microspheres and complex films as representations. Afterwards, the modifications of titania nanosheets by doping with impurity ions are also introduced, and the relations between ions doing and properties of titania nanosheets are discussed from three aspects: extending the absorption edge of light, improving electron transfer rate and enhancing magnetooptical response. Finally, the future research trends of titania nanosheets are also suggested. Contents
1 Introduction
2 The properties of titania nanosheets
2.1 Optical absorption property
2.2 Photoluminescence property
2.3 Photon-to-current conversion property
2.4 Photoinduced hydrophilicity property
2.5 Crystal transformation temperature
3 Preparation of titania nanosheets
4 Assembly of titania nanosheets
5 New materials by assembling titania nanosheets
5.1 Thin flakes
5.2 Nanotubes
5.3 Hollow microspheres
5.4 Complex films
6 Modifications of titania nanosheets by doping
6.1 Extending the absorption edge of light
6.2 Improving electron transfer rate
6.3 Enhancing magnetooptical response
7 Conclusions and outlook
Rare-Earth Upconversion Nanophosphors
Liu Tao, Sun Lining, Liu Zheng, Qiu Yannan, Shi Liyi
2012, 24 (0203): 304-317 |
Published: 24 March 2012
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Abstract
Rare-earth upconversion nanophosphors (UCNPs) have attracted significant attention benefited from their unique properties, such as strong photostability, narrow emission band, long fluorescent lifetime, high chemical stability, and low potential cytotoxicity, etc. Furthermore, being photoexcitable via continuous near infrared (NIR) radiation renders them superior performances, such as great light penetration depth, absence of photobleaching and photoblinking, lack of tissue autofluorescence, and less harmful to biological specimens. Recently, startling research interests have been ascribed to UCNPs, especially fluoride hosts-based UCNPs which are most efficient known to date, among various even interdisciplinary sciences field. Herein, recent synthesis and surface modification methodologies are outlined and summarized. Then the latest advances on research and applications of UCNPs are highlighted and reviewed, including immunoassay, bioimaging, drug delivery, photodynamic therapy, photothermal therapy, light induced switching, data storage, and solar cells, etc. Contents
1 Introduction
2 Synthesis methods of UCNPs
3 Surface modifications of UCNPs
4 Application progresses of UCNPs
4.1 Biological applications of UCNPs
4.2 Non-biological applications of UCNPs
5 Conclusions and outlook
Heavier Homologues of Transition Metal Carbynes: Syntheses, Structures and Reactivity
Wu Xian
2012, 24 (0203): 318-326 |
Published: 24 March 2012
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Abstract
Transition metal silylynes, germylynes, stannylynes and plumbylynes containing metal-element triple bonds are heavier homologues of transition metal carbynes. Since the discovery of the first transition metal germylyne complex in 1996, the whole series have been synthesized including the successful preparation of a molybdenum silylyne complex in 2010, which could be considered as a milestone in the transition metal chemistry of main group elements. These novel complexes have extended our knowledge of the bonding types between transition metals and main group elements and reveal the rich chemistry of metal-element triple bonds. This review covers the syntheses, structures and reactivity of transition metal germylynes, stannylynes, plumbylynes and silylynes which were reported from 1996 to present. Future developments in this area are discussed. Contents
1 Introduction
2 Syntheses and structures
2.1 Transition metal germylynes
2.2 Transition metal stannylynes
2.3 Transition metal plumbylynes
2.4 Transition metal silylynes
3 Reactivity
3.1 Substitution reactions
3.2 Addition reactions
3.3 Coupling reactions
4 Conclusions and outlook
Applications of Superparamagnetically Separable Nano-Catalysts in Organic Synthesis
Liu Yanhong, Zhou Lincheng, Hui Xinping, Zhao Guanghui, Li Yanfeng
2012, 24 (0203): 327-337 |
Published: 24 March 2012
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Abstract
Superparamagnetic nanoparticles and composite materials, which are highly active, possessing high surface to volume ratios and having high surface energies, can be used as catalysts. Since the small particle size of magnetic nanoparticles, the nano-heterogeneous catalysts can achieve similar or even higher activities compared with the homogeneous catalysts. Moreover, they can be reused after separation from the reaction system by using a magnet and simple regeneration process. The application of magnetic nano-catalysts in organic synthesis has attracted wide attention. Here, we review the preparation and application in organic synthesis of the magnetic nano-catalysts. The preparations, structures and characteristics of magnetic nano-catalysts are summarized. We also present their catalytic effect in relevant organic synthesis and analyze the deactivation of magnetic nano-catalysts in detail. Finally, the remaining problems and the future developing prospects are proposed. Contents
1 Introduction
2 Magnetic core as catalyst
3 Active center directly loaded onto magnetic nano-particles
4 Organic coatings
4.1 Dopamine coating
4.2 Silane coupling agent coating
4.3 Organic ionic compound coating
5 Ploymer coating
6 Silica coating
6.1 Metal and metal oxide nanoparticles supported on magnetic silicon nanoparticles
6.2 Metal complex catalysts supported on magnetic silicon nanoparticles
6.3 Phase transfer catalysts and small molecule catalysts supported on magnetic silicon nanoparticles
6.4 Acid and base catalysts supported on magnetic silicon nanoparticles
7 Carbon coating
8 Other coatings
9 Conclusions and outlook
Regioselective Nucleophilic Ring Opening Reactions of Unsymmetric Thiiranes
Zhou Chan, Xu Jiaxi
2012, 24 (0203): 338-347 |
Published: 24 March 2012
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Abstract
Thiiranes are a class of important intermediates in organic synthesis, as well in pharmaceutical and agrochemical industries as their oxygen analogs oxiranes and nitrogen analogs aziridines. They have been widely applied in the preparation of sulfur-containing compounds, such as diverse thiols and thioethers and so on, via ring opening reaction and isomerization. Nucleophilic ring opening reactions of unsymmetric thiiranes and their regioselectivity with various widely used nucleophiles are reviewed. Generally, nucleophilic ring opening reactions of unsymmetric thiiranes occur on their less substituted carbon atom, controlled by the steric hindrance. 2-Alkenylthiiranes can undergo an SN2' ring opening reaction in some cases via the attack on the β-carbon atom of their alkenyl group. Strong nucleophiles easily lead to desulfurization of thiiranes to afford the corresponding olefins, while the relatively weak nucleophiles readily result in polymerization of thiiranes, affording polythioethers. In the presence of Lewis acid, the electronic effect affects the regioselectivity in ring opening reactions, even as the prominent effect in the reactions. Although aliphatic thiiranes are still attacked predominantly on their less substituted carbon atom with nucleophiles (the steric hindrance control), aromatic thiiranes and 2-alkenylthiiranes are attacked on their more substituted carbon atom with nucleophiles (the electronic effect control). The current review provides a general rule for the regioselectivity of the nucleophilic ring opening reaction of unsymmetric thiiranes. Contents
1 Introduction
2 Ring opening of thiiranes by carbon nucleophiles
2.1 Ring opening by organometallic reagents
2.2 Ring opening by benzyne
2.3 Ring opening by cyanide
3 Ring opening of thiiranes by nucleophiles in the nitrogen group
3.1 Ring opening by nitrogen-containing nucleophiles
3.2 Ring opening by phosphines
4 Ring opening of thiiranes by nucleophiles in the oxygen group
4.1 Ring opening by oxygen-containing nucleophiles
4.2 Ring opening by sulfur-containing nucleophiles
5 Ring opening of thiiranes by halogen nucleophiles
6 Ring opening of thiiranes by transition metal complexes
7 Ring opening of thiiranes by hydride anion
8 Conclusion and outlook
Trost-Type Chiral Semi-Azacrown Ether Ligands in Asymmetric Catalysis
Li Gaowei, Wang Xiaojuan, Zhao Wenxian, Lu Liujie, Liu Guanjun, Wang Mincan
2012, 24 (0203): 348-360 |
Published: 24 March 2012
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Abstract
Bifunctional asymmetric metal-catalysis has attracted a considerable amount attention for organic chemists. This review provides an overview of recent advances on the dinuclear metal catalysts and their applications in asymmetric catalytic reactions, including aldol reaction, Henry reaction, Michael addition reaction, Mannich reaction, Friedel-Crafts alkylation reaction, Nozaki-Hiyama allylation, enantioselective alkynylation, cyanosilylation, desymmetrization and copolymerization, with an emphasis on the clarification of the relationship between either sterical or electronic effects of catalysts and substrates in different catalyst systems, and summarizing the regulation that controls the stereoselectivity and proposed mechanism of the reaction. Contents
1 Introduction
2 The applications of Trost-type chiral semi-azacrown ether ligand in asymmetric catalysis
2.1 Asymmetric aldol reaction
2.2 Asymmetric Mannich-type reaction
2.3 Asymmetric Henry reaction
2.4 Asymmetric Michael addition reaction
2.5 Asymmetric alkynylation of aldehydes
2.6 Cyanosilylation of aldehydes
2.7 Asymmetric Friedel-Crafts alkylation reaction
2.8 Asymmetric desymmetrization
2.9 Copolymerization of cyclohexene oxide with CO2
2.10 Nozaki-Hiyama allylation
3 Conclusion and perspectives
Recent Advances in Oxidative Deoximation
Zhang Guofu, Wen Xin, Wang Yong, Mo Weimin, Ding Chengrong
2012, 24 (0203): 361-369 |
Published: 24 March 2012
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Abstract
Oximes are extensively used as preferred derivatives for protection, purification and characterization of carbonyl compounds as well as a valid alternative pathway to prepare carbonyl compounds. Therefore, there has been a continued interest in the development of procedures like hydrolysis, reduction, oxidation for the effective regeneration of carbonyl compounds. Among them, the oxidative deoximation has attracted much attention currently. In this paper, the recent progress in oxidative deoximation, especially in utilizing hydrogen peroxide and oxygen as the green oxidants, are discussed in detail. Contents
1 Introduction
2 Deoximation with traditional oxidizing agents
2.1 Deoximation using metal salts
2.2 Deoximation using nonmetallic oxidants
3 Deoximation with H2O2
4 Deoximation with O2
5 Conclusions and Outlook
Gelation of Polyacrylonitrile Solution
Wan Ajun, Tan Lianjiang
2012, 24 (0203): 370-376 |
Published: 24 March 2012
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Abstract
Polyacrylonitrile (PAN) is one of the most widely used polymers. PAN solutions using suitable solvents are the precursors for fabrication of PAN fibers, osmotic membranes and other PAN-related materials. The physical and chemical properties of PAN solutions have great effect on the performance of the resultant materials. In this article, the gelation characteristics of polymer solution and the characteristics of polymer gels as well as the characteristics of PAN and PAN gels are introduced. Suitable characterization methods for the gelation of PAN solutions are proposed according to the properties of concentrated polymer solution systems. The recent research findings and latest progress of gelation of PAN solutions are summarized in the following respects: influences of concentration and temperature on gelation behavior of PAN solutions, influences of aging and non-solvent on gelation behavior of PAN solutions, thermoreversibility of gelation of PAN solutions, fractal characteristics of gelation of PAN solutions, and crosslinking mechanism of polyacrylonitrile gels. The gelation behavior of PAN solutions and the state of PAN gels have been found to be greatly affected by external environment and the composition of the gels. Finally the research prospect of the gelation of PAN solutions and PAN gels is expected. Contents
1 Introduction
2 Gelation of polymer solutions
3 Gelation behavior of polyacrylonitrile solutions
3.1 Influences of concentration and temperature on gelation behavior of polyacrylonitrile solutions
3.2 Influences of aging and non-solvent on gelation behavior of polyacrylonitrile solutions
3.3 Thermoreversibility of gelation of polyacrylonitrile solutions
3.4 Fractal characteristics of gelation of polyacrylonitrile solutions
3.5 Crosslinking mechanism of polyacrylonitrile gels
4 Conclusions and outlook
Optoelectronic Properties of Silole-Containing Polymers
Liu Zhitian, Hu Zhao, Shen Zhi, Hu Shuangqiang, Wang Zixing, Qi Xin
2012, 24 (0203): 377-384 |
Published: 24 March 2012
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Abstract
Siloles are a group of five-membered silacyclics, which have drawn much attention due to its unique electronic structures, molecule diversity and designability recently. High performance OLED can be made using small silole molecules as emitting materials or electron transfer materials. Silole-containing polymers have also attracted much attention of a number of chemists. Besides the high conductivity, many new properties have been found, such as highly efficient power conversion efficiency in plastic solar cells, fast carrier mobility in field-effect transistors (FET), high efficiency in polymeric light-emitting diodes (PLEDs), etc. Thus siloles are promising optoelectronic functional materials. In this review, the optoelectronic properties of silole-containing polymers are described according to the different structures of their parent compounds. Contents
1 Introduction
2 Substituted silole
2.1 Poly(1,1-silole)s
2.2 Poly(2,5-silole)s
2.3 Poly(3,4-silole)s
3 Dibenzosilole
4 Dithienosilole
5 Bis-silicon-bridged stilbene
6 Conclusion
Thiol-Ene Click Chemistry
Xu Yuanhong, Xiong Xingquan, Cai Lei, Tang Zhongke, Ye Zhangji
2012, 24 (0203): 385-394 |
Published: 24 March 2012
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Abstract
“Click chemistry”, introduced by Sharpless in 2001, becomes a new synthetic method used in areas such as drugs, polymers and materials rapidly because of its high efficiency, high selectivity and reliable characteristics. With the further research on click chemistry, the types of it are increasing continuously and the scope of application is also expanding. Radical-mediated or nucleophile-initiated thiol-ene reaction is a novel kind of click reactions, which shows the characteristics of click chemistry. Starting from the concept, characteristic and types of click chemistry, the mechanism and the wide applications of thiol-ene reaction in preparation of functional polymers and topologic macromolecules, polymeric materials surface modification and biomaterials are emphasized. Furthermore, the latest research based on thiol-ene chemistry is summarized. The prospects of thiol-ene reaction are also discussed. Contents
1 Introduction
2 Thiol-ene click reaction and mechanism
3 Applications of thiol-ene click chemistry
3.1 Synthesis of functional polymers
3.2 Synthesis of topologies polymers
3.3 Surface modification
3.4 Biological fields
3.5 Other fields
4 Conclusions and outlook
Synthesis of Functional Polymer Materials via Thiol-Ene/Yne Click Chemistry
Yang Zhenglong, Chen Qiuyun, Zhou Dan, Bu Yilong
2012, 24 (0203): 395-404 |
Published: 24 March 2012
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Abstract
Click chemistry has drawn considerable attention in less than a decade due to its unique advantages, such as simple reaction conditions, high reaction efficiency, high yield, easy post-treatment and high selectivity for the obtained products. Recently, as a new and efficient click reaction, thiol-ene/yne click chemistry has raised much interest and will probably be the main direction for development in click chemistry. On the other hand, synthesis of high-performance functional polymer materials is one of the hot topics of novel material research. In this review, we introduce the characteristics, advantages and reaction mechanism of thiol-ene/yne click chemistry. Research progresses of thiol-ene/yne click chemistry in functional polymer synthesis are highlighted, with focus on the synthetic route of linear, hyperbranched, cross-linked and other types of functional polymers via this method. The monomer features, product features and potential applications of different types of functional polymer materials synthesized by thiol-ene/yne click reaction are also discussed in detail. Furthermore, the problems in thiol-ene/yne click chemistry that still should be resolved are pointed out, and future applications are prospected. Contents
1 Introduction
2 Thiol-ene/yne click chemistry
2.1 Characteristics and advantages of thiol-ene/ yne click chemistry
2.2 Reaction mechanism of thiol-ene/yne click chemistry
3 Functional polymers synthesized by thiol- ene/yne click chemistry
3.1 Synthesis and application of linear polymers
3.2 Synthesis and application of hyper-branched polymers
3.3 Synthesis and application of cross-linked polymers
3.4 Synthesis and application of other type of polymers
4 Conclusions and outlook
Synthesis and Application of Dendrimers Based on Polyhedral Oligomeric Silsesquioxanes
Yao Min, Wang Jiajun, Gu Xueping, Feng Lianfang
2012, 24 (0203): 405-413 |
Published: 24 March 2012
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Abstract
Dendrimer is one type of macromolecules with well-defined, highly-branched and nano-scaled architectures, composed of three distinct domains: core, branches and terminal groups. Its potential functions and applications are explored based on the unique physical and chemical features due to special molecular architecture. Using polyhedral oligomeric silsesquioxanes (POSS) as the core of dendrimers is an effective and facile way to simplify the tedious repetitive steps of preparation and separation. Since POSS allows eight branches to radiate from a silicon-oxygen rigid cubic core, the dendrimers can be constructed in a well-controlled globular, three-dimensional framework, and large numbers of peripheral groups can be obtained at relatively low generation numbers. As a kind of novel nano-hybrid supermolecules, POSS-based dendrimers have attracted considerable interest in materials science. In this review, we briefly introduce the synthetic approaches of some typical POSS-based dendrimers categorized by the different chemical composition of branching units, and then focus on the potential functions and applications of this nano-hybrid material in the fields of catalysis, gene and drug delivery, liquid crystals, light harvesting and energy transfer. The specific and excellent properties imparted by the incorporation of POSS into dendrimers are also presented. Finally, the advances of POSS-based dendrimers are prospected. Contents
1 Introduction
2 Synthesis of POSS-based dendrimers
2.1 POSS-carbosilane dendrimers
2.2 POSS-polypeptide dendrimers
2.3 POSS-PAMAM dendrimers
2.4 Other POSS-based dendrimers
3 Applications of POSS-based dendrimers
3.1 Catalyst
3.2 Biomaterials
3.3 Liquid crystals
3.4 Luminescent materials
4 Summary and Prospects
Sensitive Vesicle System Based on Supramolecular Cyclodextrin Amphiphiles
Xin Feifei, Zhang Huacheng, Sun Tao, Kong Li, Li Yueming, Hao Aiyou
2012, 24 (0203): 414-422 |
Published: 24 March 2012
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Abstract
Sensitive vesicle system, which is formed by amphiphiles constructed non-covalently has unique responsiveness to external stimuli. Vesicles prepared from “surpamolecular cyclodextrin amphiphiles” (SCA)are one of the most important types. Here, the development of this kind of vesicular system is reviewed. At first, the preparation and applications in pharmaceutical engineering, new smart materials, biological mimics, etc. of this kind of vesicle system classified by the guest molecules are introduced and described. Then the prospects are pointed out based on the current development of the system. Contents
1 Introduction
2 Preparation and applications of the vesicle system based on “Supramolecular cyclodextrin amphiphiles”
2.1 System based on cyclodextrin-ferrocene derivatives
2.2 System based on cyclodextrin-anthraquinone derivatives
2.3 System based on cyclodextrin-azo compounds
2.4 System based on cyclodextrins-amphiphiles
2.5 System based on cyclodextins-polymers
3 Conclusion and outlook
Environmental Photochemistry of Iron Complexes and Their Involvement in Environmental Chemical Processes
Wang Zhaohui, Song Wenjing, Ma Wanhong, Zhao Jincai
2012, 24 (0203): 423-432 |
Published: 24 March 2012
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Abstract
Iron is one of the most abundant metals in the continental crust, while most of dissolved iron is complexed with organic ligands. The irradiated iron complexes in the environment undergo direct photolysis and secondary (photo)chemical reactions, generating Fe(Ⅱ), organic radicals and some reactive oxygen species (ROS). Environmental photochemistry of iron complexes can greatly affect ROS dynamics, organics degradation and redox cycling of other elements. Therefore, it is becoming a hot topic in the international field of environmental sciences research. This review firstly summarizes three types of iron complexes including inorganic Fe complexes, simple organic Fe complexes and macrocyclic organic Fe complexes, and photoreduction mechanisms of iron complexes. Secondly, the potential oxidants of Fe(Ⅱ) in acidic aquatic environment are introduced. The oxidation kinetics, possible reaction mechanism and influencing factors (such as dissolved oxygen concentration, pH, ionic strength, temperature and natural organic matters concentrations) of (photo)chemical oxidation of Fe(Ⅱ) are elucidated. This review also highlights recent findings in the study of environmental processes involving iron photochemistry. Finally, the future prospects in this field are discussed based on the current status. Contents
1 Introduction
2 Princile of environmental photochemistry of iron complexes
2.1 Photoreduction of Fe(Ⅲ)
2.2 (Photo)chemical oxidation of Fe(Ⅱ)
3 Some environmental chemical processes involved in Fe complexes
3.1 Production and decay of reactive oxygen species (ROS)
3.2 Degradation of organic compounds
3.3 Coupling with other metals' redox cycling
4 Conclusions and outlook
Solid Heteropolyacids (HPAs) in Hydrolytic Conversion of Biomass
Zhang Jianming, Zhai Shangru, Huang Dezhi, Zhai Bin, An Qingda
2012, 24 (0203): 433-444 |
Published: 24 March 2012
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Abstract
With global oil production flattening out, attention is being increasingly paid to a kind of renewable clean energy-biomass. Heteropolyacids are important catalysts in the so-called clean technologies. They possess strong acidity, structural flexibility and fairly high thermal stability. It would be preferable to carry out the heteropolyacids-catalyzed reaction in biomass hydrolytic conversion. The performance of heteropolyacids towards hydrolysis of biomass in pure water, organic solvents and biphasic systems exhibit different advantages and limitations. In this paper, we reviewed the latest progress in the hydrolytic conversion of biomass into valuable chemicals using heteropolyacids in different catalytic systems. Highly effective utilization of biomass has positive effects on solving energy problems and achieving sustainable development of energy and chemical industry.Heteropolyacids used as excellent green catalyst will possess extensive application prospect in biomass conversion. Contents
1 Introduction
2 Characteristics and Utilization of Biomass
3 Structure features and current situation of HPAs
3.1 Pure HPAs
3.2 Salts of HPAs
3.3 Supported HPAs
4 Applications of HPAs in hydrolytic conversion of biomass
4.1 Water solvent
4.2 Organic solvents
4.3 Biphasic system
5 Conclusion and outlook