Ionic liquids (ILs), in particular imidazolium-based ILs, have proven to be suitable media for the generation and stabilisation of soluble metal nanoparticles (NPs). Indeed, transition-metal NPs with ...small sizes, narrow size distribution and different shapes have been prepared by reduction of organometallic compounds with molecular hydrogen, decomposition of transition-metal complexes in the zero-valent state, metal bombardment or simple transfer for previously prepared water- or classical organic solvent-soluble colloids to the ILs. The formation and stabilisation of NPs in these highly hydrogen bonded organised supramolecular fluids occur with the re-organisation of the hydrogen bond network and the generation of nanostructures with polar and non-polar regions, including the NPs. The IL forms a protective layer, which is probably composed of imidazolium aggregates located immediately adjacent to the nanoparticle surface, which provides both steric and electronic protection against aggregation and/or agglomeration. These stable transition-metal NPs immobilised in the ILs have proven to be efficient green catalysts for several reactions in multiphase conditions and also novel materials for chemical sensors. In this critical review, the structural/surface properties of these soluble metal NPs dispersed in ILs and their application in catalysis and as chemical sensors are discussed, with particular attention paid to the stabilisation models proposed to explain the stability and properties of these metal NPs (219 references).
1,3-dialkyl imidazolium salts are one of the most popular and investigated classes of room temperature ionic liquids. Although in various cases the physical-chemical properties and/or the outcome of ...the processes in these liquids significantly differ from those performed in "classical" dipolar organic solvents, they are still regarded as merely homogeneous solvents. In this brief overview it is developed the concept that pure 1,3-dialkylimidazolium ionic liquids are better described as hydrogen-bonded polymeric supramolecules of the type {(DAI)x(X)x-n) n+ (DAI)x-n(X)x) n-}n where DAI is the 1,3-dialkylimidazolium cation and X the anion. This structural pattern is a general trend for the solid phase and is maintained to a great extent in the liquid phase and even in the gas phase. The introduction of other molecules and macromolecules occurs with a disruption of the hydrogen bond network and in some cases can generate nano-structures with polar and non-polar regions where inclusion-type compounds can be formed.
In this series of articles the board members of ChemSusChem discuss recent research articles that they consider of exceptional quality and importance for sustainability. This entry features Prof. ...Jairton Dupont, who discusses how recent works on fine‐tuning of the electronic and steric properties of ruthenium and rhodium complexes and reaction conditions generates efficient homogeneous transition‐metal catalysts for the transformation of CO2 under hydrogen pressure.
CO2 activation: Our board member Jairton Dupont highlights how the fine‐tuning of the electronic and steric properties of ruthenium and rhodium complexes and reaction conditions generates efficient homogeneous transition‐metal catalysts for the transformation of CO2 under hydrogen pressure. The catalysts find use in the methylation of amines, amides, and CH bonds as well as for the hydroformylation, alkoxycarbonylation, and hydrocarboxylation of alkenes.
Imidazolium Salt Ion Pairs in Solution Stassen, Hubert K.; Ludwig, Ralf; Wulf, Alexander ...
Chemistry : a European journal,
June 1, 2015, Letnik:
21, Številka:
23
Journal Article
Recenzirano
The formation, stabilisation and reactivity of contact ion pairs of non‐protic imidazolium ionic liquids (ILs) in solution are conceptualized in light of selected experimental evidence as well ...theoretical calculations reported mainly in the last ten years. Electric conductivity, NMR, ESI‐MS and IR data as well as theoretical calculations support not only the formation of contact ion pairs in solution, but also the presence of larger ionic and neutral aggregates even when dissolved in solvents with relatively high dielectric constants, such as acetonitrile and DMSO. The presence of larger imidazolium supramolecular aggregates is favoured at higher salt concentrations in solvents of low dielectric constant for ILs that contain shorter N‐alkyl side chains associated with anions of low coordination ability. The stability and reactivity of neutral contact species are also dependent on the nature of the anion, imidazolium substituents, and are more abundant in ILs containing strong coordinating anions, in particular those that can form charge transfer complexes with the imidazolium cation. Finally, some ILs display reactivities as contact ion pairs rather than solvent‐separated ions.
A pair of liquids: The formation, stabilisation, and reactivity of contact ion pairs of non‐protic imidazolium ionic liquids dissolved in organic solvents are conceptualized in the light of selected experimental evidence, as well theoretical calculations, reported mainly in the last ten years.
Ionic liquids (ILs), a special group of classical molten salts, are widely used in various fields of science. Historically, researchers have tested ILs out of curiosity or to improve a specific ...property in a particular system in many areas of chemistry or materials science. However, today, ILs are far from being simple chemical curiosities and sit at the center of various green industrial innovation processes, where they play important roles in materials extraction, reactive catalytic supports, spatial devices, and biotransformations. In this Account, we describe a journey into a nanostructured universe to better understand the unique properties of ionic liquids and their modern applications. Because molten salts have been known for centuries and have found limited uses, we try to explain why modern nonaqueous ILs deserve increased interest and curiosity. We discuss the characteristics that distinguish modern nonaqueous ILs and compare them with classical molten salts. One of the main differences between room temperature ILs, especially those based on imidazolium cations, and simple molten salts, is the molecular asymmetry built into at least one of the ions. This asymmetry in modern, nonaqueous ILs opposes the strong charge ordering due to ionic interactions that normally would cause the system to crystallize. In addition, the presence of a cooperative network of hydrogen bonds between the cations and anions induces structural directionality (the entropic effect). Therefore, modern ILs form preorganized structures, mainly through hydrogen bonding, that induce structural directionality. In contrast, classical salts form aggregates only through ionic bonds. In other words, weak interactions order the structures in modern ILs while charges order the structure within classical salts. ILs cannot be regarded as merely homogeneous solvents. In fact, ILs form extended hydrogen-bond networks with polar and nonpolar nano domains and therefore are by definition “supramolecular” fluids. Thus, ILs are better described as hydrogen-bonded polymeric supramolecules of the type (DAI) m (X) m_n ) n+(DAI) m_n (X) x ) n−. This structural pattern is a general trend for both the solid and the liquid phase and is apparently maintained to a large extent even in the gas phase. This structural organization of ILs can be used as entropic drivers (the “IL effect”) for the preparation of well-defined nanoscale structures with extended order, either in the bulk phase or at the gas/vacuum interface.
Palladium compounds containing at least one metal-carbon bond intramolecularly stabilized by at least one donor atom, which are termed palladacycles, are one of the most popular class of ...organopalladum derivatives. The main achievements, potential, and limitations of palladacycles are discussed.
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► Top down approach to generate soluble metal nanoparticles is discussed. ► The main technical aspects involved in sputtering deposition technique are presented. ► Sputtering ...deposition over ionic liquids, silicon oil and vegetable oils. ► The size of metal nanoparticles can be modulated by the sputtering conditions. ► The applications of these soluble metal nanoparticles such as in catalysis are presented.
Nanoparticles (NPs) have recently attracted significant attention from the materials science community due to their promise to play an important role in developing new technologies. Indeed, NPs with small sizes, narrow size distributions and various shapes have been prepared via the reduction of organometallic compounds with molecular hydrogen, the decomposition of transition-metal complexes in the zero-valent state, metal bombardment or the simple transfer of previously prepared NPs from one liquid to another. This review paper will discuss the simple and quick method of sputtering deposition over liquid substrates to generate stable colloidal NPs. Initially, the sputtering phenomena will be presented in more detail, as well as the state-of-the-art in sputter deposition over both solid and liquid substrates. Then, special attention will be paid to sputtering onto ionic liquids (ILs), silicon oil and vegetable oils, and some selected results and the current mechanisms of NP formation will be discussed. Finally, applications of this new approach to synthesizing colloidal NPs will be shown.
A series of imidazolium-based ionic liquids (ILs) were synthesised and used as single component and metal-free homogeneous catalysts to convert a renewable, inexpensive and non-toxic CO sub(2) ...feedstock into useful products. The cycloaddition of carbon dioxide to epoxides to produce cyclic carbonate was evaluated. A detailed investigation was carried out on a variety of factors that affected the reactivity and selectivity, such as the catalyst structures (nature of cation and anion). The effect of reaction parameters (temperature, reaction time, CO sub(2) uptake and catalyst amount) on the catalytic performance was also investigated in detail. High conversions and selectivities could be achieved under mild pressure condition (5 bar) using 1-n-butyl-3-methylimidazolium bromide. A synergetic effect of the acidic and basic sites as well as suitable hydrogen-bonding strength is considered crucial for the reaction to proceed smoothly. This protocol was found to be applicable to a disubstituted epoxide. Furthermore, the straightforward synthesis of cyclic carbonates by direct oxidative carboxylation from olefins was achieved using only 1-n-butyl-3-methylimidazolium bromide as a catalyst.
2,1,3‐Benzothiadiazole (BTD) is one of the most important nuclei used in the chemistry of photoluminescent compounds and applicable for light technology. The understanding of its properties and ...reactions is fundamental for the design and application of these derivatives in molecular organic electronic devices and for other technologies. As a result of their potential as constituents of organic light‐emitting diodes, solar cells, liquid crystals, dyes, photovoltaic cells, and many others, attention has been focused on BTD π‐extended derivatives with potential use in this exciting area. Herein, we describe their syntheses, properties, reactions, and selected examples of applications in light technology using by BTD (small molecules) as the core.
Molecular 2,1,3‐benzothiadiazole (BTD) is an important nucleus used in the chemistry of photoluminescent compounds and applicable for light technology. Its properties and chemical reactivity are fundamental for the design of organic electronic devices. BTD derivatives can be used as constituents of organic light‐emitting diodes, solar cells, liquid crystals, dyes, photovoltaic cells and many others, and these compounds represent an exciting area of study.
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•TiO2: Li nanoparticles were synthesized via an ionic liquid-assisted hydrothermal method.•The doping of Li to anatase TiO2 affects the properties of the resultant product.•TiO2: Li ...nanoparticles were used as a photocatalyst for the degradation of dye.•TiO2: Li nanoparticles were used as sensor, and antibacterial agent.•TiO2: Li were used as reducing agent for the reduction of Cr6+ to Cr3+.
We have proposed a simple one pot synthesis of lithium-doped TiO2 nanoparticles (TiO2:Li) via an ionic liquid-assisted hydrothermal method and their potential use as a photocatalyst for the degradation of organic dye, as well as the reduction of toxic Cr6+ to non toxic Cr3+. The structure of TiO2:Li nanoparticles was examined by XRD, FTIR, XPS, Raman, UV–vis, Photoluminescence spectroscopy and morphology by SEM and TEM. The incorporation of Li into anatase-phase TiO2 affected the optical properties of the resultant TiO2 nanoparticles. The photocatalytic activity of the TiO2:Li nanoparticles was determined by degradation of trypan blue. Degradation studies showed improved photocatalytic activity of TiO2:Li nanoparticles compared to TiO2 nanoparticles and bulk TiO2. TiO2:Li nanoparticles also functioned as a detoxification agent which was confirmed by the reduction of Cr6+ to Cr3+.
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