Showing papers in "Chemistry: A European Journal in 2009"

Molecular single-bond covalent radii for elements 1-118.

Abstract: A self-consistent system of additive covalent radii, R(AB)=r(A) + r(B), is set up for the entire periodic table, Groups 1-18, Z=1-118. The primary bond lengths, R, are taken from experimental or theoretical data corresponding to chosen group valencies. All r(E) values are obtained from the same fit. Both E-E, E-H, and E-CH 3 data are incorporated for most elements, E. Many E-E' data inside the same group are included. For the late main groups, the system is close to that of Pauling. For other elements it is close to the methyl-based one of Suresh and Koga [J. Phys. Chem. A 2001, 105, 5940] and its predecessors. For the diatomic alkalis MM' and halides XX', separate fits give a very high accuracy. These primary data are then absorbed with the rest. The most notable exclusion are the transition-metal halides and chalcogenides which are regarded as partial multiple bonds. Other anomalies include H 2 and F 2 . The standard deviation for the 410 included data points is 2.8 pm.

Chemical and Structural Properties of Carbonaceous Products Obtained by Hydrothermal Carbonization of Saccharides

Abstract: Carbon-rich-quick scheme: A carbon-rich solid product made up of uniform micrometer-sized spheres of tunable diameter has been synthesized by the hydrothermal carbonization of saccharides. These microspheres possess a core-shell chemical structure based on the different nature of the oxygen functionalities between the core and the outer layer (see figure).A carbon-rich solid product, here denoted as hydrochar, has been synthesized by the hydrothermal carbonization of three different saccharides (glucose, sucrose, and starch) at temperatures ranging from 170 to 240 degrees C. This material is made up of uniform spherical micrometer-sized particles that have a diameter in the 0.4-6 mum range, which can be modulated by modifying the synthesis conditions (i.e., the concentration of the aqueous saccharide solution, the temperature of the hydrothermal treatment, the reaction time, and type of saccharide). The formation of the carbon-rich solid through the hydrothermal carbonization of saccharides is the consequence of dehydration, condensation, or polymerization and aromatization reactions. The microspheres thus obtained possess, from a chemical point of view, a core-shell structure consisting of a highly aromatic nucleus (hydrophobic) and a hydrophilic shell containing a high concentration of reactive oxygen functional groups (i.e., hydroxyl/phenolic, carbonyl, or carboxylic).

Molecular Double-Bond Covalent Radii for Elements Li–E112

Abstract: The previous systems of triple-bond and single-bond self-consistent, additive covalent radii, R(AB)=r(A)+ r(B), are completed with a fit for σ2π2 double-bonds.The primary bond lengths, R, are taken from experimental or theoretical data corresponding to chosen group valencies. All r(E) values are obtained from the same, self-consistent fit. Many of the calculated primary data came from ECH2 and HECH2 models. Homonuclear LEEL, formaldehyde-type Group 14–Group 16 and open-shell, X3 Σ Group-16 dimer data are included. The standard deviation for the 316 included data points is 3 pm.

Controlled synthesis of large-area and patterned electrochemically reduced graphene oxide films

Abstract: Have you seen the film? Coupling a spray-coating technique with a facile, low-cost, efficient and environmentally friendly electrochemical method may realize the controllable synthesis of large-area and patterned electrochemically reduced graphene oxide films on various conductive and insulating substrates with thicknesses ranging from a single monolayer to several microns (see figure).

Applications of Multicomponent Reactions to the Synthesis of Diverse Heterocyclic Scaffolds

Abstract: The sequencing of multicomponent reactions (MCRs) and subsequent cyclization reactions is a powerful stratagem for the rapid synthesis of diverse heterocyclic scaffolds. The optimal MCR is sufficiently flexible that it can be employed to generate adducts bearing a variety of functional groups that may then be selectively paired to enable different cyclization manifolds, thereby leading to a diverse collection of products. The growing interest in diversity-oriented synthesis has led to increased attention to this paradigm for library synthesis, which has inspired many advances in the design and implementation of MCRs for the construction of diverse heterocyclic scaffolds.

Highly Efficient Visible-Light Plasmonic Photocatalyst Ag@AgBr

Abstract: Visible improvements: Owing to the plasmon resonance of silver nanoparticles deposited on the surface of AgBr, the newly-prepared plasmonic photocatalyst Ag§AgBr has a strong absorption in the visible region (see picture) and shows high efficiency in the photodegradation of organic pollutants under visible light.

Controllable synthesis of mesoporous Co3O4 nanostructures with tunable morphology for application in supercapacitors.

Abstract: Flower power: Various mesoporous Co3O4 architectural structures (see figure) have been successfully prepared through a facile binary-solution route and sequential thermal decomposition at atmospheric pressure. The electrochemical experiments showed that the specific capacitance of Co3O4 nanosheets was higher than that of Co3O4 microspheres in a KOH electrolyte. Novel and complex mesoporous 2D and 3D architectures of the oxide semiconductor Co3O4, including nanosheets, nearly monodisperse microspheres that are self-assembled from nanosheets, and copper-coin-like nanosheets, have been synthesized through a facile binary-solution route and sequential thermal decomposition at atmospheric pressure. The influence of different reaction conditions on the morphology of the products has been discussed in detail. The results revealed that the volume ratio of H2O and ethanolamine (EA) play a crucial role in the morphology of the precursor. The thermal decomposition of the corresponding precursor leads to the formation of the mesoporous structure. The products have been characterized by X-ray diffraction techniques, field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), and Raman spectroscopy. The electrochemical properties of the Co3O4 electrodes were investigated by cyclic voltammetry (CV) and galvanostatic charge–discharge measurements. The electrochemical experiments revealed that the specific capacitance of the Co3O4 nanosheets was higher than that of the Co3O4 microspheres in a KOH electrolyte solution (3 m). Furthermore, the Co3O4 nanosheet electrodes exhibited good rate capabilities, and maintained 93 % of the initial capacity at a current density of 5 mA cm−2 in a KOH (3 m) electrolyte solution. The results show that Co3O4 nanosheets might have potential applications as electrode materials for supercapacitors.

Construction of nitrogen-containing heterocycles by C-H bond functionalization.

Abstract: Nitrogen heterocycles are abundant in natural products and pharmaceuticals. An emerging interest among synthetic chemists is to use C-H functionalization to construct the nitrogen-containing core of these heterocycles. The following article will provide a brief overview of this concept with respect to the type of C-H bond functionalized.

Exploring, tuning, and exploiting the basicity of hydrotalcites for applications in heterogeneous catalysis.

Abstract: Hydrotalcites offer unique basic properties that make them very attractive for catalytic applications. It is of primary interest to make use of accurate tools for probing the basicity of hydrotalcite-based catalysts for the purpose of 1) fundamental understanding of base-catalysed processes with hydrotalcites and 2) optimisation of the catalytic performance achieved in reactions of industrial interest. Techniques based on probe molecules, titration techniques and test reactions along with physicochemical characterisation are overviewed in the first part of this review. The aim is to provide the tools for understanding how series of parameters involved in the preparation of hydrotalcite-based catalytic materials can be employed to control and adapt the basic properties of the catalyst towards the basicity demanded by each target chemical reaction. An overview of recent and significant achievements in that perspective is presented in the second part of the paper.

Organocatalytic Asymmetric Aza-Michael Additions

Abstract: The catalytic aza-Michael addition is an important reaction within synthetic organic chemistry, given the significance of the biologically and synthetically interesting products, such as β-amino acids and β-lactams. In the last decade organocatalysis emerged as a powerful tool in asymmetric synthesis and had a large impact on the development of asymmetric and catalytic conjugate additions of nitrogen nucleophiles to Michael acceptors. In this review a first summary of the recent rapid progress of asymmetric organocatalyzed aza-Michael reactions is presented.

Novel zinc porphyrin sensitizers for dye-sensitized solar cells: synthesis and spectral, electrochemical, and photovoltaic properties.

Abstract: Novel meso- or beta-derivatized porphyrins with a carboxyl group have been designed and synthesized for use as sensitizers in dye-sensitized solar cells (DSSCs). The position and nature of a bridge connecting the porphyrin ring and carboxylic acid group show significant influences on the spectral, electrochemical, and photovoltaic properties of these sensitizers. Absorption spectra of porphyrins with a phenylethynyl bridge show that both Soret and Q bands are red-shifted with respect to those of porphyrin 6. This phenomenon is more pronounced for porphyrins 3 and 4, which have a pi-conjugated electron-donating group at the meso position opposite the anchoring group. Upon introduction of an ethynylene group at the meso position, the potential at the first oxidation alters only slightly whereas that for the first reduction is significantly shifted to the positive, thus indicating a decreased HOMO-LUMO gap. Quantum-chemical (DFT) results support the spectroelectrochemical data for a delocalization of charge between the porphyrin ring and the amino group in the first oxidative state of diarylamino-substituted porphyrin 5, which exhibits the best photovoltaic performance among all the porphyrins under investigation. From a comparison of the cell performance based on the same TiO(2) films, the devices made of porphyrin 5 coadsorbed with chenodeoxycholic acid (CDCA) on TiO(2) in ratios [5]/[CDCA] = 1:1 and 1:2 have efficiencies of power conversion similar to that of an N3-based DSSC, which makes this green dye a promising candidate for colorful DSSC applications.

Bi2O3 Hierarchical Nanostructures: Controllable Synthesis, Growth Mechanism, and their Application in Photocatalysis

Abstract: By introducing VO(3)(-) into the reaction system, uniform hierarchical nanostructures of Bi(2)O(3) have been successfully synthesized by a template-free aqueous method at 60-80 degrees C for 6 h. The as-prepared hierarchitectures are composed of 2D nanosheets, which intercross with each other. Based on the electron microscope observations, the growth of such hierarchitectures has been proposed as an Ostwald ripening process followed by self-assembly. The nucleation, growth, and self-assembly of Bi(2)O(3) nanosheets could be readily tuned, which brought different morphologies and microstructures to the final products. Pore-size distribution analysis revealed that both mesopores and macropores existed in the product. UV-vis spectroscopy was employed to estimate the band gap energies of the hierarchical nanostructures. The photocatalytic activities of as-prepared Bi(2)O(3) hierarchitectures were 6-10 times higher than that of the commercial sample, which was evaluated by the degradation of RhB dye under visible light irradiation (lambda>420 nm).

Dual amino-functionalised phosphonium ionic liquids for CO2 capture.

Abstract: A series of 20 dual amino-functionalised phosphonium ionic liquids, (3-aminopropyl)tributylphosphonium amino acid salts ([aP(4443)][AA], in which [AA](-) = [Ala](-), [Arg](-), [Asn](-), [Asp](-), [Cys](-), [Gln](-), [Glu](-), [Gly](-), [His](-), [Ile](-), [Leu](-), [Lys](-), [Met](-), [Phe](-), [Pro](-), [Ser](-), [Thr](-), [Trp](-), [Tyr](-) and [Val](-)), has been prepared. Their physicochemical properties, such as density, viscosity, glass transition and thermal decomposition temperatures and conductivity, have been determined. In particular, the [aP(4443)][AA] ionic liquids (ILs) have low glass transition temperatures ranging from -69.7 to -29.6 degrees C and high decomposition temperatures (all above 200 degrees C). The effects of the variation of the structure of [AA](-) on the above physicochemical properties are discussed. Furthermore, the CO(2) absorption of [aP(4443)][Gly], [aP(4443)][Ala], [aP(4443)][Val] and [aP(4443)][Leu], taken as examples, was investigated. It was found that the supported absorption of CO(2) by the [aP(4443)][AA] ILs almost reaches equilibrium within 80 min, the chemical absorption of CO(2) by the [aP(4443)][AA] ILs approaches 1 mol CO(2) per mol ionic liquid (twice that reported before) and the [aP(4443)][AA] ILs can be repeatedly recycled for CO(2) uptake.

A Sensitive and Selective Fluorescent Thiol Probe in Water Based on the Conjugate 1,4-Addition of Thiols to α,β-Unsaturated Ketones

Abstract: Compound 1 was designed and synthesized as a new fluorescent thiol probe. Probe 1 was constructed on the basis of the conjugate 1,4-addition of thiols to alpha,beta-unsaturated ketones. Notably, probe 1 has suitable water solubility, which allows the sensing assay to be performed in water. Probe 1 is highly sensitive for thiols with a 211-fold fluorescence dynamic range and a low detection limit of 9.25x10(-7) M. The major features of probe 1 also include a high selectivity for thiols over other relevant biological species, excitation and emission in the visible region, rapid functioning at pH 7.4, and a good linear relationship between the fluorescence signal and the thiol concentration. Accordingly, these desirable characteristics may render probe 1 as potentially useful for biological applications.

The Electrochemistry of Carbon Nanotubes: Fundamentals and Applications

Abstract: Carbon nanotubes (CNTs) are in the forefront of electrochemical research. It has become clear that an understanding of the fundamental reasons for the electrochemical activity of CNTs is essential for further progress in the field. This review provides a critical discussion of the fundamental reasons behind the electrochemical and "electrocatalytic" activity of CNTs as well as on important applications of CNTs for sensing, biosensing, and energy storage systems.

Oxyma: An Efficient Additive for Peptide Synthesis to Replace the Benzotriazole‐Based HOBt and HOAt with a Lower Risk of Explosion[1]

Abstract: Oxyma [ethyl 2-cyano-2-(hydroxyimino)acetate] has been tested as an additive for use in the carbodiimide approach for formation of peptide bonds. Its performance in relation to those of HOBt and HOAt, which have recently been reported to exhibit explosive properties, is reported. Oxyma displayed a remarkable capacity to inhibit racemization, together with impressive coupling efficiency in both automated and manual synthesis, superior to those of HOBt and at least comparable to those of HOAt, and surpassing the latter coupling agent in the more demanding peptide models. Stability assays showed that there was no risk of capping the resin under standard coupling conditions. Finally, calorimetry assays (DSC and ARC) showed decomposition profiles for benzotriazole-based additives that were consistent with their reported explosivities and suggested a lower risk of explosion in the case of Oxyma.

A Three-Enzyme Cascade Reaction through Positional Assembly of Enzymes in a Polymersome Nanoreactor

Abstract: Porous polymersomes based on block copolymers of isocyanopeptides and styrene have been used to anchor enzymes at three different locations, namely, in their lumen (glucose oxidase, GOx), in their bilayer membrane (Candida antarctica lipase B, CalB) and on their surface (horseradish peroxidase, HRP). The surface coupling was achieved by click chemistry between acetylene-functionalised anchors on the surface of the polymersomes and azido functions of HRP, which were introduced by using a direct diazo transfer reaction to lysine residues of the enzyme. To determine the encapsulation and conjugation efficiency of the enzymes, they were decorated with metal-ion labels and analysed by mass spectrometry. This revealed an almost quantitative immobilisation efficiency of HRP on the surface of the polymersomes and a more than statistical incorporation efficiency for CalB in the membrane and for GOx in the aqueous compartment. The enzyme-decorated polymersomes were studied as nanoreactors in which glucose acetate was converted by CalB to glucose, which was oxidised by GOx to gluconolactone in a second step. The hydrogen peroxide produced was used by HRP to oxidise 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) to ABTS.+. Kinetic analysis revealed that the reaction step catalysed by HRP is the fastest in the cascade reaction.

The role of hydrophobicity in the antimicrobial and hemolytic activities of polymethacrylate derivatives

Abstract: We synthesized cationic random amphiphilic copolymers by radical copolymerization of methacrylate monomers with cationic or hydrophobic groups and evaluated their antimicrobial and hemolytic activities. The nature of the hydrophobic groups, and polymer composition and length were systematically varied to investigate how structural parameters affect polymer activity. This allowed us to obtain the optimal composition of polymers suitable to act as non-toxic antimicrobials as well as non-selective polymeric biocides. The antimicrobial activity depends sigmoidally on the mole fraction of hydrophobic groups (f(HB)). The hemolytic activity increases as f(HB) increases and levels off at high values of f(HB), especially for the high-molecular-weight polymers. Plots of HC(50) values versus the number of hydrophobic side chains in a polymer chain for each polymer series showed a good correlation and linear relationship in the log-log plots. We also developed a theoretical model to analyze the hemolytic activity of polymers and demonstrated that the hemolytic activity can be described as a balance of membrane binding of polymers through partitioning of hydrophobic side chains into lipid layers and the hydrophobic collapsing of polymer chains. The study on the membrane binding of dye-labeled polymers to large, unilamellar vesicles showed that the hydrophobicity of polymers enhances their binding to lipid bilayers and induces collapse of the polymer chain in solution, reducing the apparent affinity of polymers for the membranes.

Aura of corroles.

Abstract: Corroles display distinctive structural, spectroscopic, and photophysical properties, as well as some exceptional chemical reactivities that are not shared by other molecules. In addition, low-valent metal complexes are extremely reactive when chelated by corroles and the opposite holds for the high-valent counterparts. One aim of this account is to provide a thorough understanding of the underlying principles that govern these phenomena, while the other goal is to demonstrate how these features may be used advantageously for utilization of corroles and their corresponding metal complexes in applications for which they could display superior performances. The main examples that are emphasized regarding the above respect are catalysis, imaging, and aspects relevant to drug development.

Nanostructured FeS as a Mimic Peroxidase for Biocatalysis and Biosensing

Abstract: Artificial enzyme mimics have attracted considerable interest due to easy denaturation and leakage of enzymes during their storage and immobilization procedure. Herein we describe the design of a novel mimic peroxidase, a nanostructure of sheet- like FeS prepared by a simple micelle- assisted synthetic method. Such a nano- structure has a large specific surface area and high peroxidase-like activity, and was thus further used as a mimic enzyme for the development of biocat- alysts and amperometric biosensors. The sheet-like FeS nanostructure showed typical Michaelis-Menten ki- netics and good affinity to both H2O2 and 3,3',5,5'-tetramethyl benzidine. At pH 7.0 the constructed amperometric sensor showed a linear range for the detection of H2O2 from 0.5 to 150 mm with a correlation coefficient of 0.9998 without any electron transfer mediator. The H2O2 sensor based on the sheet- like FeS showed more sensitive re- sponse than those based on spherical FeS nanostructure, and resulted in a better stability than horseradish perox- idase when they were exposed to solu- tions with different pH values and tem- peratures. These excellent properties made the sheet-like nanostructured FeS powerful tools for a wide range of potential applications as an "artificial peroxidase" as biosensors and biotech-

Room Temperature Dynamic Polymers Based on Diels–Alder Chemistry

Abstract: Dynamers based on reversible Diels-Alder chemistry have been obtained and shown to undergo dynamic exchange at room temperature. Their study in solution by small-angle neutron scattering indicated the formation of long and highly flexible chains. Polydispersed molecules gave T(g) values below room temperature, permitting the generation of a dynamic elastomer upon introduction of a dynamic cross-linking agent. The use of a system with a low equilibrium constant gives access to materials with interesting self-healing properties.

COMU: A Safer and More Effective Replacement for Benzotriazole‐Based Uronium Coupling Reagents

Abstract: We describe a new family of uronium-type coupling reagents that differ in their iminium moieties and leaving groups. The presence of the morpholino group in conjunction with an oxime derivative--especially ethyl 2-cyano-2-(hydroxyimino)acetate (Oxyma)--had a marked influence on the solubilities, stabilities, and reactivities of the reagents. Finally, the new uronium salt derived from Oxyma (COMU) performed extremely well in the presence of only 1 equiv of base, thereby confirming the effect of the hydrogen bond acceptor in the reaction. COMU also showed a less hazardous safety profile than the benzotriazole-based HDMA and HDMB, which exhibited unpredictable autocatalytic decompositions. Furthermore, the Oxyma moiety contained in COMU suggests a lower risk of explosion than in the case of the benzotriazole derivatives.

Silver‐Ion‐Mediated DNAzyme Switch for the Ultrasensitive and Selective Colorimetric Detection of Aqueous Ag+ and Cysteine

Abstract: Two states, two applications! An Ag(+)-mediated DNAzyme switch has been designed to detect Ag(+) and cysteine with high sensitivity and selectivity. In the closed state, Ag(+) turns on the switch through the formation of cytosine-Ag(+)-cytosine base pairs, whereas adding cysteine turns off the open switch because it competitively binds to Ag(+). This feature endows the DNAzyme switch with two sensing applications.

Supramolecular Chemistry at Interfaces: Molecular Recognition on Nanopatterned Porous Surfaces

Abstract: Through the illustration of key examples that have recently appeared in the literature, the intention of this review is to provide a perspective of current advances on the molecular recognition at the interfaces aimed at the engineering of multifunctional organic-based materials. The great interest in such systems has been motivated by the need to fabricate smaller and smaller components in order to improve, for example, the information storage capabilities of classical silicon-based devices. Although great progress has been achieved on the exploitation of “top-down” approaches, strong hope is now put on the development of hybrid devices in which the elementary components are replaced with single organic molecules. Nevertheless, the drive towards such devices is restricted by both their stability and difficulties to precisely control and manipulate the structural organisation at the molecular level. To overcome these restrictions, the use of nanotemplated surfaces featuring porous domains in which responsive functional molecules can be precisely accommodated at the single-molecule level is one of the most promising approaches. In the first part of this manuscript, we therefore illustrate the main engineering strategies [1) through non-covalent interactions, 2) surface-confined covalent reactions and 3) assembly of pre-organised cavities such as synthetic macrocycles] currently in use to create two-dimensional (2D) patterned surfaces displaying porous structures at the nanoscale level. Such networks, featuring periodic hollow domains (controllable both in shape and size), are of particular significance as their cavities can be used as receptors for the recognition of remotely controllable functional molecules. In the second part, the confinement of molecular guests within the cavities is discussed, emphasising the selectivity and dynamics of key assemblies, with a particular focus on the biomolecular recognition and post-assembly covalent functionalisation, which could provide the opportunity to fabricate devices currently beyond our reach on an unprecedented precision and efficiency. All the examples will be discussed in terms of structural organisation as studied by scanning tunnelling microscopy (STM) techniques.

Bright, Color‐Tunable Fluorescent Dyes in the Vis/NIR Region: Establishment of New “Tailor‐Made” Multicolor Fluorophores Based on Borondipyrromethene

Abstract: A new series of high-performance fluorophores named Keio Fluors (KFL), which are based on borondipyrromethene (BODIPY), are reported. The KFL dyes cover a wide spectral range from the yellow (547 nm) to the near-infrared (NIR, 738 nm) region, and their emission wavelength could be easily and subtly controlled based on simple molecular modifications only, without losing their optical properties. This “tailor-made” synthetic strategy for tuning the emission wavelength enabled the creation of fourteen KFL dyes with well-controlled emission colors (yellow, orange, red, far-red, and NIR). Moreover, these KFL dyes also retain their excellent optical properties, such as spectral bands sharper than quantum dots, high extinction coefficients (140 000–316 000 M−1 cm−1), and high quantum yields (0.56–0.98), without any critical solvent polarity dependent decrease of their brightness. These advantageous characteristics make the KFL dyes potentially useful as new candidates of fluorescent standard dyes to substitute or to complement existing long-wavelength fluorescent dyes, such as cyanines, oxazines, rhodamines, or other BODIPY dyes.

A Ratiometric Fluorescent Probe for Hypochlorite Based on a Deoximation Reaction

Abstract: The first ratiometric fluorescent probe for hypochlorite has been developed through regulation of the electron-withdrawing ability of the electron acceptor in an intramolecular charge-transfer (ICT) system by a deoximation reaction (see figure; EWG=electron-withdrawing group). In this work, we have successfully provided a novel strategy for the rational design and synthesis of a ratiometric fluorescent probe for hypochlorite. The strategy is based on the deoximation reaction, which has not yet been used in the fluorescent hypochlorite probe design. Interestingly, the probe showed a ratiometric fluorescent response to hypochlorite with the emission intensities ratio (I509/I439) increasing from 0.28 to 2.74. Furthermore, the probe displayed high selectivity for hypochlorite over other species due to the distinct deoximation conditions. The probe developed herein represents the first ratiometric fluorescent probe for hypochlorite.

Bright, NIR‐Emitting Au23 from Au25: Characterization and Applications Including Biolabeling

Abstract: A novel interfacial route has been developed for the synthesis of a bright-red-emitting new subnanocluster, Au(23), by the core etching of a widely explored and more stable cluster, Au(25)SG(18) (in which SG is glutathione thiolate). A slight modification of this procedure results in the formation of two other known subnanoclusters, Au(22) and Au(33). Whereas Au(22) and Au(23) are water soluble and brightly fluorescent with quantum yields of 2.5 and 1.3 %, respectively, Au(33) is organic soluble and less fluorescent, with a quantum yield of 0.1 %. Au(23) exhibits quenching of fluorescence selectively in the presence of Cu(2+) ions and it can therefore be used as a metal-ion sensor. Aqueous- to organic-phase transfer of Au(23) has been carried out with fluorescence enhancement. Solvent dependency on the fluorescence of Au(23) before and after phase transfer has been studied extensively and the quantum yield of the cluster varies with the solvent used. The temperature response of Au(23) emission has been demonstrated. The inherent fluorescence of Au(23) was used for imaging human hepatoma cells by employing the avidin-biotin interaction.

Intermolecular olefin functionalisation involving aryl radicals generated from arenediazonium salts.

Abstract: This minireview is aimed at giving an overview of recent advances in olefin functionalisation reactions involving aryl radicals generated from arenediazonium salts. Based on the well-known Meerwein arylation, in which an aryl and a halogen substituent are coupled to an olefinic substrate, new reaction types have been developed that allow the introduction of a broad spectrum of other atoms and functional groups at the place of the original halogen atom and that are applicable to an extended range of olefinic substrates.

Nanoparticle-Supported and Magnetically Recoverable Ruthenium Hydroxide Catalyst: Efficient Hydration of Nitriles to Amides in Aqueous Medium

Abstract: Magnetic attraction not filtration: A magnetic nanoparticle-supported ruthenium hydroxide catalyst (see figure) was readily prepared from inexpensive starting materials and shown to catalyze the hydration of nitriles with excellent yield in a benign aqueous medium. Catalyst recovery using an external magnetic field, superior activity, and the inherent stability of the catalyst system are additional sustainable attributes of this protocol. No Abstract

Auto-tandem catalysis: a single catalyst activating mechanistically distinct reactions in a single reactor.

Abstract: Domino reactions have received great attention as efficient synthetic methodologies for the construction of structurally complex molecules from simple materials in a single operation. Catalysts in domino reactions have also been well studied. In these reactions, a catalyst activates the substrate(s) only once, and the structure of the product is delineated at that time. Recently, the new concept of "tandem catalysis" in domino reactions, in which catalyst(s) sequentially activate more than two mechanistically distinct reactions, has been proposed. Tandem catalysis is categorized into three subclasses: orthogonal-, auto-, and assisted-tandem catalyses. Auto-tandem catalysis is defined as a process in which one catalyst promotes more than two fundamentally different reactions in a single reactor. An overview of recent and significant achievements in auto-tandem catalysis is presented in this paper.