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Core@shell structured bimetallic nanoparticles are currently of immense interest due to their unique electronic, optical and catalytic properties. However, their synthesis is non-trivial. We report a new supramolecular route for the synthesis of core@shell nanoparticles, based on an anion coordination protocol—the first to function by binding the shell metal to the surface of the pre-formed primary metal core before reduction. The resultant gold/palladium and platinum/palladium core@shell nanoparticles have been characterized by aberration-corrected scanning transmission electron microscopy (as well as other techniques), giving striking atomic-resolution images of the core@shell architecture, and the unique catalytic properties of the structured nanoparticles have been demonstrated in a remarkable improvement of the selective production of industrially valuable chloroaniline from chloronitrobenzene. Bimetallic core@shell nanoparticles often have properties that are different from those of single-metal or alloy nanoparticles. Here, a route to such nanoparticles that binds the second metal to the core surface prior to reduction is described. The unique catalytic properties of the nanoparticles are demonstrated in the selective production of chloroaniline.

Metal nanoparticles (NPs) have physicochemical properties which are distinct from both the bulk and molecular metal species, and provide opportunities in fields such as catalysis and sensing. NPs typically require protection of their surface to impede aggregation, but these coatings can also block access to the surface which would be required to take advantage of their unusual properties. Here, we show that alkyl imidazoles can stabilise Pd, Pt, Au, and Ag NPs, and delineate the limits of their synthesis. These ligands provide an intermediate level of surface protection, for which we demonstrate proof‐of‐principle in catalysis and anion binding. Protecting the surface: Imidazole ligands offer a potentially useful intermediate level of stabilisation for metal nanoparticles. We outline the parameters required for synthesis of such nanoparticles and provide two case studies for their application, in catalysis and in sensing.

Ion‐pair recognition has emerged from cation and anion recognition and become a diverse and active field in its own right. The last decade has seen significant advances in receptor design in terms of the types of binding motifs, understanding of cooperativity and increase in complexity from heteroditopic to multitopic receptors. As a result, attention has turned to applying this knowledge to the rational design of ion‐pair receptors for applications in salt solubilisation and extraction, membrane transport and sensing. This Review highlights recent progress and developments in the design and applications of heteroditopic and multitopic receptors for ion‐pair recognition. From Design to Application: In the last decade ion‐pair recognition has evolved from an emerging to an established field. This Review discusses recent developments in the design and applications of heteroditopic and multitopic ion‐pair receptors. Unusual recognition motifs and topologies are highlighted as well as the applications of ion‐pair receptors as salt solubilisation and extraction agents, in membrane transport, sensing and as switchable receptors.

Halogen bonding (XB), the attractive interaction between an electron-deficient halogen atom and a Lewis base, has undergone a dramatic development as an intermolecular force analogous to hydrogen bonding (HB). However, its utilization in the solution phase remains underdeveloped. Furthermore, the design of receptors capable of strong and selective recognition of anions in water remains a significant challenge. Here we demonstrate the superiority of halogen bonding over hydrogen bonding for strong anion binding in water, to the extent that halide recognition by a simple acyclic mono-charged receptor is achievable. Quantification of iodide binding by rotaxane hosts reveals the strong binding by the XB-rotaxane is driven exclusively by favourable enthalpic contributions arising from the halogen-bonding interactions, whereas weaker association with the HB-rotaxanes is entropically driven. These observations demonstrate the unique nature of halogen bonding in water as a strong alternative interaction to the ubiquitous hydrogen bonding in molecular recognition and assembly. The ability to achieve strong molecular recognition in water is a key challenge for supramolecular chemistry. Now, halogen bonding — the attractive interaction between an electron-deficient halogen atom and a Lewis base — has been shown to be superior to hydrogen bonding for strong anion binding in water. Ripple image: © PhotoDisc/Getty Images.

Anion recognition is pertinent to a range of environmental, medicinal and industrial applications. Recent progress in the field has relied on advances in synthetic host design to afford a broad range of potent recognition motifs and novel supramolecular structures capable of effective binding both in solution and at derived molecular films. However, performance in aqueous media remains a critical challenge. Understanding the effects of bulk and local solvent on anion recognition by host scaffolds is imperative if effective and selective detection in real-world media is to be viable. This Review seeks to provide a framework within which these effects can be considered both experimentally and theoretically. We highlight proposed models for solvation effects on anion binding and discuss approaches to retain strong anion binding in highly competitive (polar) solvents. The synthetic design principles for exploiting the aforementioned solvent effects are explored. Anion recognition in competitive, aqueous media remains a critical challenge. Bulk and local solvation models for anion recognition events are herein explored, as well as targeted design approaches to retain strong anion binding in highly polar media.

Two thread-shaped cations, pyridinium nicotinamide and imidazolium, as their chloride and hexafluorophosphate salts, were studied with regards to complexation with hydrogen-bond-donating acyclic and macrocyclic ligands. In the latter case, the cations form pseudorotaxanes templated by the chloride anion but not hexafluorophosphate. This formation is a function of the coupling of ion-pairing between the cation and chloride anion and subsequent recognition of the anion by the macrocyclic diamide, which provides the driving force for interpenetration. We propose that this anion template principle is a general method for the construction of pseudorotaxanes and could be applied to other cationic threads, anions, and macrocyclic species.

Disulfide and dithiocarbamate functionalized porphyrins have been synthesized and used as protecting ligands for gold nanoparticle formation either via ligand substitution reactions or by direct synthesis. These nanoparticles have been shown to recognize anions via changes in the absorbance spectrum of the surface adsorbed porphyrin moieties. Association constants, derived from quantitative titrations, indicate a remarkable surface enhancement effect where the surface bound porphyrins bind anions much more strongly than the free receptor in solution.

. The author examines the impact of the economic crisis on employment, earnings, inequality and poverty in the EU, focusing on Denmark, Germany, Slovakia, Spain and the United Kingdom during the period 2008–10. After reviewing the literature, he analyses recent trends, finding that during this stage of the crisis real wages reacted countercyclically in most countries, thus diverging from the pattern observed in previous recessions. He finds considerable cross‐national variation in the severity and direction of changes in terms of inequality and poverty rates. However, he argues that inequality may widen because of the potential regressive effects of the announced austerity programmes.

A thorough, accessible, and general overview of chemosensors Providing a comprehensive overview of chemosensors—organic molecules designed to bind and sense small molecules or metal ions—and their applications, Chemosensors: Principles, Strategies, and Applications is an accessible one-stop resource for analysts, clinicians, and graduate students studying advanced chemistry and chemosensing. Chemosensors function on a molecular level, generating a signal upon binding. The book reviews their synthesis, design, and applications for detecting biological and organic molecules as well as metal ions. The text highlights applications in drug discovery and catalyses that have not been well covered elsewhere. Covering such topics as molecular recognition, detection methods, design strategies, and important biological issues, the book is broken into four sections that examine intermolecular interactions, strategies in sensor design, detection methods, and case studies in metal, saccharide, and amino acid sensing. An indispensable source of information for chemical and biomedical experts using sensors, Chemosensors includes case studies to make the material both accessible and understandable to chemists of all backgrounds.