The 100 most-cited articles in Chemistry - A European Journal, 2017

Reaction prediction and retrosynthesis are the cornerstones of organic chemistry. Rule-based expert systems have been the most widespread approach to computationally solve these two related challenges to date. However, reaction rules often fail because they ignore the molecular context, which leads to reactivity conflicts. Herein, we report that deep neural networks can learn to resolve reactivity conflicts and to prioritize the most suitable transformation rules. We show that by training our model on 3.5 million reactions taken from the collective published knowledge of the entire discipline of chemistry, our model exhibits a top10-accuracy of 95 % in retrosynthesis and 97 % for reaction prediction on a validation set of almost 1 million reactions.

Abstract The relevance of the ‐CF2H moiety has attracted considerable attention from organic synthetic and medicinal chemistry communities, because this group can act as a more lipophilic isostere of the carbinol, thiol, hydroxamic acid, or amide groups. Being weakly acidic, the CF2H moiety can establish hydrogen‐bonding interactions to improve the binding selectivity of biologically active compounds. Therefore, the hydroxyl, amino, and thio substituents of lead structures are routinely replaced by a CF2H motif in drug discovery, with great benefits in the pharmacological activity of drugs and drug candidates and agrochemicals. Consequently, the late‐stage introduction of CF2H is a sought‐after strategy in designing bioactive compounds. Secondly, but nonetheless relevant and meaningful, is the study of synthetic pathways to introduce a CF2−Y moiety (Y≠H, F) into organic substrates because compounds that contain a CF2−Y functionality have also found vast applications in medicinal chemistry and in other areas, such as that of fungicides, insecticides, etc., and thus, this…

Abstract Photoredox chemistry with metal complexes as sensitizers and catalysts frequently relies on precious elements such as ruthenium or iridium. Over the past 5 years, important progress towards the use of complexes made from earth‐abundant elements in photoredox catalysis has been made. This review summarizes the advances made with photoactive Cr III , Fe II , Cu I , Zn II , Zr IV , Mo 0 , and U VI complexes in the context of synthetic organic photoredox chemistry using visible light as an energy input. Mechanistic considerations are combined with discussions of reaction types and scopes. Perspectives for the future of the field are discussed against the background of recent significant developments of new photoactive metal complexes made from earth‐abundant elements.

Using porous materials to cope with environmental issues is promising but remains a challenge especially for removing the radioactive vapor wastes in fission because of harsh adsorption conditions. Here we report a new, stable covalent organic framework (COF) as a porous platform for removing iodine vapor-a major radioactive fission waste. The three-dimensional COF consists of a diamond topology knotted by adamantane units, creates ordered one-dimensional pores and are highly porous. The COF enables the removal of iodine vapor via charge transfer complex formation with the pore walls to achieve exceptional capacity. Moreover, the 3D COF is "soft" to trigger structural fitting to iodine while retaining connectivity and enables cycle use for many times while retaining high uptake capacity. These results set a new benchmark for fission waste removal and suggest the great potential of COFs as a designable porous material for challenging world-threatening pollution issues.

Organic materials have recently gained considerable attention for electronic applications, improving performance and sustainability to current technologies. Commercialized metal-based systems are generally expensive, toxic and difficult to recycle, however organic materials offer promising solutions. Viologens, N,N' di-quaternized bipyridyl salts, are a well-studied species exhibiting three reversible redox states, possessing valuable electrochromic and electron-accepting properties. These properties can be fine-tuned through synthesis by altering the nitrogen substituents and various counteranions. Currently, viologens have become of great interest as functional materials in a wide array of applications; a few to name include electrochromic devices, molecular machines, and organic batteries. This review highlights representative recent work and advances towards utilizing viologens in practical applications that currently compete with metal-based technologies. Additionally, modified viologens that can be further fine-tuned will be discussed.

Abstract Electrocatalytic water splitting is a promising approach for clean and sustainable hydrogen production. Its large‐scale application relies on the availability of low cost and efficient electrocatalysts. Earth‐abundant transition‐metal carbides, especially molybdenum carbides (MoxC), are regarded as potential candidates to replace state‐of‐art but expensive platinum‐group electrocatalysts. In this Review, we summarize recent progress in MoxC electrocatalysts for hydrogen evolution reaction (HER). Nanostructure engineering on the design and preparation of highly efficient electrocatalysts based on MoxC is presented, followed by the comparison and discussion of HER performance on MoxC‐based electrocatalysts. Finally, we offer a perspective on the future development of MoxC‐based electrocatalysts towards HER.

Melanin is the main pigment responsible for the color of human skin, hair and eye. Its biosynthesis requires three melanogenic enzymes, tyrosinase (TYR), and the tyrosinase-related proteins TYRP1 and TYRP2. The difficulty of isolating pure and homogeneous proteins from endogenous sources has hampered their study, and resulted in many contradictory findings regarding their physiological functions. In this review, we summarize recent advances on the structure and function of TYR and TYRPs by virtue of the crystal structure of human TYRP1, which is the first available structure of a mammalian melanogenic enzyme. This structure, combined with tyrosinase structures from other lower eukaryotes and mutagenesis studies of key active site residues, sheds light on the mechanism of TYR and TYRPs. Furthermore, a TYRP1-based homology model of TYR provides a high-quality platform to map and analyze albinism-related mutations, as well as the design of specific antimelanogenic compounds. Finally, we provide perspectives for future structure/function studies of TYR and TYRPs.

Functionalised macrocycles and medium-sized rings have applications in a number of scientific fields, ranging from medicinal chemistry and supramolecular chemistry, to catalysis and nanotechnology. However, their value in these areas can be undermined by a simple, but important limitation: large ring systems are very often difficult to make. Traditional end-to-end cyclisation reactions of long linear precursors are typically unpredictable and impractical processes, mainly due to unfavourable enthalpic and entropic factors. Most published methods to make large rings focus on minimising the damage inflicted by performing the difficult cyclisation step; in contrast, ring-expansion reactions enable it to be avoided altogether. In this Review article, it is highlighted how "growing" rings from existing cyclic systems via ring expansion can expedite the efficient, practical and scalable synthesis of macrocycles and medium-sized rings.

Abstract Inorganic perovskite quantum dots as optoelectronic materials have attracted enormous attention in light‐harvesting and emitting devices. However, photocatalytic conversion based on inorganic perovskite halides has not been reported. Here, we have synthesized colloidal quantum dots (QDs, 3–12 nm) of cesium lead halide perovskites (CsPbBr3) as a new type of photocatalytic material. The band gap energies and photoluminescence (PL) spectra are tunable over the visible spectral region according to quantum size effects on an atomic scale. The increased carrier lifetime revealed by time‐resolved PL spectra, indicates the efficient electron‐hole separation and transfer. As expected, the CsPbBr3 QDs with high selectivity of greater than 99 % achieve an efficient yield of 20.9 μmol g−1 towards solar CO2 reduction. This work has opened a new avenue for inorganic colloidal perovskite materials as efficient photocatalysts to convert CO2 into valuable fuels.

The main limitation of aqueous supercapacitors (SCs) lies in their narrow operating voltages, especially when compared with organic SCs. Fundamental understanding of factors relevant to the operating voltage helps providing guidance for the assembly of high-voltage aqueous SCs. In this regard, this concept analyzes the deciding factors for the operating voltage of aqueous SCs. Strategies applied to expand the operating voltage are summarized and discussed from the aspects of electrolyte, electrode, and asymmetric structure. Dynamic factors associated with water electrolysis and maximally using the available potential ranges of electrodes are particularly emphasized. Finally, other promising approaches that have not been explored and their challenges are also elaborated, hoping to provide more insights for the design of high-voltage aqueous SCs.

Mercury pollution threatens the environment and human health across the globe. This neurotoxic substance is encountered in artisanal gold mining, coal combustion, oil and gas refining, waste incineration, chloralkali plant operation, metallurgy, and areas of agriculture in which mercury-rich fungicides are used. Thousands of tonnes of mercury are emitted annually through these activities. With the Minamata Convention on Mercury entering force this year, increasing regulation of mercury pollution is imminent. It is therefore critical to provide inexpensive and scalable mercury sorbents. The research herein addresses this need by introducing low-cost mercury sorbents made solely from sulfur and unsaturated cooking oils. A porous version of the polymer was prepared by simply synthesising the polymer in the presence of a sodium chloride porogen. The resulting material is a rubber that captures liquid mercury metal, mercury vapour, inorganic mercury bound to organic matter, and highly toxic alkylmercury compounds. Mercury removal from air, water and soil was demonstrated. Because sulfur…

Photoredox catalysis is a versatile approach for the construction of challenging covalent bonds under mild reaction conditions, commonly using photoredox catalysts (PCs) derived from precious metals. As such, there is need to develop organic analogues as sustainable replacements. Although several organic PCs have been introduced, there remains a lack of strongly reducing, visible-light organic PCs. Herein, we establish the critical photophysical and electrochemical characteristics of both a dihydrophenazine and a phenoxazine system that enables their success as strongly reducing, visible-light PCs for trifluoromethylation reactions and dual photoredox/nickel-catalyzed C-N and C-S cross-coupling reactions, both of which have been historically exclusive to precious metal PCs.

Abstract Recently, a polar, rod‐like liquid‐crystalline material was reported to exhibit two distinct nematic mesophases (termed N and N X ) separated by a weakly first‐order transition. Herein, we present our initial studies into the structure–property relationships that underpin the occurrence of the lower‐temperature nematic phase, and report several new materials that exhibit this same transformation. We have prepared material with significantly enhanced temperature ranges, allowing us to perform a detailed study of both the upper‐ and lower‐temperature nematic phases by using small‐angle X‐ray scattering. We observed a continuous change in d spacing rather than a sharp change at the phase transition, a result consistent with a transition between two nematic phases, structures of which are presumably degenerate.

Abstract Electrocatalysts are critically important for a secure energy future, as they facilitate the conversion between electrical and chemical energy. Molecular catalysts offer precise control of structure that enables understanding of structure–reactivity relationships, which can be difficult to achieve with heterogeneous catalysts. Molecular electrocatalysts can be immobilized on surfaces by covalent bonds or through non‐covalent interactions. Advantages of surface immobilization include the need for less catalyst, avoidance of bimolecular decomposition pathways, and easier determination of catalyst lifetime. This Minireview highlights surface immobilization of molecular electrocatalysts for reduction of O 2 , oxidation of H 2 O, production of H 2 , and reduction of CO 2 .

Abstract Nitrene radical complexes are reactive intermediates with discrete spin density at the nitrogen‐atom of the nitrene moiety. These species have become important intermediates for organic synthesis, being invoked in a broad range of C−H functionalization and aziridination reactions. Nitrene radical complexes have intriguing electronic structures, and are best described as one‐electron reduced Fischer type nitrenes. They can be generated by intramolecular single electron transfer to the “redox non‐innocent” nitrene moiety at the metal. Nitrene radicals generated at open‐shell cobalt(II) have thus far received most attention in terms of spectroscopic characterization, reactivity screening, catalytic nitrene‐transfer reactions and (computational and experimental) mechanistic studies, but some interesting iron and precious metal catalysts have also been employed in related reactions involving nitrene radicals. In some cases, redox‐active ligands are used to facilitate intramolecular single electron transfer from the complex to the nitrene moiety. Organic azides are among the most…

With the aim of developing renewable energy based processes, researchers are paying increasing interest to light induced organic transformations. Metal-organic frameworks (MOFs), a class of micro-/mesoporous hybrid materials, are recently emerging as a new type of photoactive materials for organic syntheses due to their unique structural characteristics. In this Review, we summarized the recent applications of MOFs as photocatalysts for light induced organic transformations, including (1) oxidation of alcohols, amines, alkene, alkanes and sulfides; (2) hydroxylation of aromatic compounds like benzene; (3) activation of the C-H bonds to construct new C-C or C-X bonds; (4) atom-transfer radical polymerization (ATRP). This Review starts with general background information of using MOFs in photocatalysis, followed by a description of light induced organic transformations promoted by photoactive inorganic nodes and photocatalytic active ligands in MOFs, respectively. Thereafter, the use of MOFs as multifunctional catalysts for light induced organic transformations via an efficient merge…

A novel lutidine-based manganese PNP-pincer complex has been synthesized for the selective N-methylation of aromatic amines with methanol. Using borrowing hydrogen methodology, a selection of differently functionalized aniline derivatives is selectively methylated in good yields.

Ar reaction, breaking a C-X single bond and forming a new C-X or C-C bond though ipso substitution. Its vast scope, in terms of nucleophile, leaving group, and ring-size of the transition state, make it a powerful tool for arene functionalization, as it can be employed strategically to switch easily-forged bonds with more difficult connections that would be challenging to realize in the intermolecular mode. The reaction has received significantly renewed attention in recent years, as advances in areas such as arene C-X bond formation and radical generation have been harnessed for new arene syntheses through Smiles chemistry. In addition, new reaction modes have been discovered, such as the Clayden rearrangement of lithiated ureas, creating innovative applications for Smiles rearrangements in asymmetric arylation. This Minireview will discuss advances in these areas in the recent literature, covering both two-electron, polar Smiles rearrangements along with single-electron radical transformations.

Non-precious-metal-catalyzed reactions are of increasing importance in chemistry due to the outstanding ecological and economic properties of these metals. In the subfield of metal-catalyzed direct C-H functionalization reactions, recent years have shown an increasing number of publications dedicated to this topic. Nickel, cobalt, and last but not least iron, have started to enter a field which was long dominated by precious metals such as palladium, rhodium, ruthenium, and iridium. The present review article summarizes the development of iron-, nickel-, and cobalt-catalyzed C-H functionalization reactions until the end of 2016, and discusses the scope and limitations of these transformations.

Abstract Aromatic rings are found in a wide variety of products, including pharmaceuticals, agrochemicals, and functional materials. Diaryliodonium salts are new reagents used to transfer aryl groups under both metal‐free and metal‐catalyzed reactions and thereby synthesize arene‐containing compounds. This minireview focuses on recent studies in selective aryl transfer reactions from unsymmetrical diaryliodonium salts under metal‐free conditions. Reactions reported from 2007 to 2017, which represents a period of significant growth in diaryliodonium salt chemistry, are presented and organized by the type of reactive intermediate formed in the reaction. Specifically, reactions involving λ3‐iodane, λ3‐iodane radical anions, aryl radicals, and arynes are discussed. Chemoselectivity trends in aryl transfer are compared and contrasted across reaction intermediates and translation to potential auxiliaries are posited.

Abstract Three‐dimensional metal carbide MXene/reduced graphene oxide hybrid nanosheets are prepared and applied as a cathode host material for lithium–sulfur batteries. The composite cathodes are obtained through a facile and effective two‐step liquid‐phase impregnation method. Owing to the unique 3 D layer structure and functional 2 D surfaces of MXene and reduced graphene oxide nanosheets for effective trapping of sulfur and lithium polysulfides, the MXene/reduced graphene oxide/sulfur composite cathodes deliver a high initial capacity of 1144.2 mAh g−1 at 0.5 C and a high level of capacity retention of 878.4 mAh g−1 after 300 cycles. It is demonstrated that hybrid metal carbide MXene/reduced graphene oxide nanosheets could be a promising cathode host material for lithium–sulfur batteries.

For the planning of an organic synthesis route, the disconnection approach guided by retrosynthetic analysis of possible intermediates and the chemical reactions involved, back to ready available starting materials, is well established. In contrast, such concepts just get developed for biocatalytic routes. In this Review we highlight functional group interconversions catalyzed by enzymes. The article is organized rather by chemical bonds formed-exemplified for C-N, C-O- and C-C-bonds-and not by enzyme classes, covering a broad range of reactions to incorporate the desired functionality in the target molecule. Furthermore, the successful use of biocatalysts, also in combination with chemical steps, is exemplified for the synthesis of various drugs and advanced pharmaceutical intermediates such as Crispine A, Sitagliptin and Atorvastatin. This Review also provides some basic guidelines to choose the most appropriate enzyme for a targeted reaction keeping in mind aspects like commercial availability, cofactor-requirement, solvent tolerance, use of isolated enzymes or whole cell…

While thioesters are common intermediates in biochemical processes, they are much less appreciated in organic synthesis, also compared to other carboxylic acid derivatives. However, their chemistry and reactivity is intriguing and diversified, reaching much further than the acyl substitution and aldol chemistry. Herein, we focus on metal-catalyzed reactions for the synthesis of thioesters as well as their transformations. Reactions such as thiocarbonylation, cross-coupling, decarbonylation, allylic substitution or dual photoredox/metal catalysis are discussed. On one hand, new atom economic methods allow for convenient synthesis of thioesters from well available starting materials. On the other hand, various synthetically important compounds can by synthesized due to the multifaceted reactivity of thioesters that we aimed to depict.

Abstract An iridium photoredox catalyst in combination with either a stoichiometric amount of Brønsted acid or a catalytic amount of Lewis acid is capable of catalyzing regioselective alkylation of N‐heteroarenes with N‐(acyloxy)phthalimides at room temperature under irradiation. A broad range of N‐heteroarenes can be alkylated using a variety of secondary, tertiary, and quaternary carboxylates. Mechanistic studies suggest that an IrII/IrIII redox catalytic cycle is responsible for the observed reactivity.

Abstract Two‐dimensional atomically thick materials, reduced graphene oxide (RGO), and layered molybdenum disulfide (MoS2) have been investigated as potential novel energy storage materials because of their distinct physicochemical properties. These materials suffer, however, from rapid capacity decay and low rate capability. This study describes a facile, binder‐free approach to fabricate large‐scale, 3D network structured MoS2@carbon nanotube (CNT)/RGO composites for application in flexible supercapacitor devices. The as‐obtained composites possess a hierarchical porosity, and an interconnected framework. The electrochemical supercapacitive measurements of the MoS2@CNT/RGO electrode show a high specific capacitance of 129 mF cm−2 at 0.1 mA cm−2. The symmetric supercapacitor devices based on the as‐obtained composites exhibit a long lifetime (94.7 % capacitance retention after 10 000 cycles), and a high electrochemical performance (29.7 mF cm−2). The present experimental findings will lead to scalable, binder‐free synthesis of MoS2@CNT/RGO hybrid electrodes, with enhanced,…

Multi-catalytic cascade reactions bear a great potential to minimize downstream and purification steps, leading to a drastic reduction of the produced waste. In many examples, the compatibility of chemo- and biocatalytic steps could be easily achieved. Problems associated with the incompatibility of the catalysts and their reactions, however, are very frequent. Cascade-like reactions can hardly occur in this way. One possible solution to combine, in principle, incompatible chemo- and biocatalytic reactions is the defined control of the microenvironment by compartmentalization or scaffolding. Current methods for the control of the microenvironment of biocatalysts go far beyond classical enzyme immobilization and are thus believed to be very promising tools to overcome incompatibility issues and to facilitate the synthetic application of cascade reactions. In this Minireview, we will summarize recent synthetic examples of (chemo)enzymatic cascade reactions and outline promising methods for their spatial control either by using bio-derived or synthetic systems.

Abstract Based on the structure of the nitrogenase FeMo cofactor (FeMoco), it is reported that Fe deposited on MoS 2 2D sheets exhibits high selectivity towards the spontaneous fixation of N 2 against chemisorption of CO 2 and H 2 O. DFT predictions also indicate the ability of this material to convert N 2 into NH 3 with a maximum energy input of 1.02 eV as an activation barrier for the first proton–electron pair transfer.

Abstract A new luminescent Zn II ‐MOF with 1D triangular channels along the b axis, namely NUM‐5 , has been successfully assembled and well characterized, which features good stability, especially in aqueous solution. Interestingly, this compound exhibits a fast, sensitive and selective luminescence quenching response towards Cr VI (Cr 2 O 7 2− /CrO 4 2− ) in aqueous solution. The detection limits towards Cr 2 O 7 2− and CrO 4 2− ions are estimated to be 0.7 and 0.3 ppm, respectively, which are among the lowest detection limits reported for the MOF‐based fluorescent probes that can simultaneously detect Cr 2 O 7 2− and CrO 4 2− in aqueous environment. The possible detection mechanism has been discussed in detail. Moreover, it can be easily regenerated after detection experiments, indicative of excellent recyclability. All these results suggest NUM‐5 to be a highly selective and recyclable luminescent sensing material for the quantitative detection of Cr VI anions in aqueous solution.

Abstract Nitrofurans are a group of widely used veterinary antibiotics, which have been banned due to antibiotics pollution. Development of a rapid and effective method for the detection of nitrofuran antibiotics (NFAs) is an important challenge. Herein, we designed a chemical sensor based on a thin‐film composed of the lanthanide metal‐organic framework (Ln‐MOF) {[Eu2(BCA)3(H2O)(DMF)3]⋅0.5DMF⋅H2O}n (Eu‐BCA, in which BCA is 2,2′‐biquinoline‐4,4′‐dicarboxylate) coated on a cost‐effective stainless steel wire mesh (SSWM) by Co3O4 nano‐anchor fixation method. The MOF coatings were well adhered to the SSWM, resulting in a three‐dimensional porous, flexible, and processable sensor. The structure of the as‐prepared MOF thin‐film was confirmed by powder X‐ray diffraction (PXRD), and the surface morphology was examined by scanning electron microscopy (SEM). Significantly, the Eu‐BCA thin‐film was highly selective and sensitive to NFAs, and yet remained unaffected by other common antibiotics that may be present. The limits of detection for nitrofurantoin (NFT) and nitrofurazone (NFZ) are…

Bicyclic peptides have greater conformational rigidity and metabolic stability than linear and monocyclic peptides and are capable of binding to challenging drug targets with antibody-like affinity and specificity. Powerful combinatorial library technologies have recently been developed to rapidly synthesize and screen large bicyclic peptide libraries for ligands against enzymes, receptors, and protein-protein interaction targets. Bicyclic peptides have been developed as potential therapeutics against a wide range of diseases, drug targeting agents, imaging/diagnostic probes, and research tools. In this Minireview, we provide a summary of the recent progresses on the synthesis and applications of bicyclic peptides.

Synthesis of biologically active molecules (whether at laboratory or industrial scale) remains a highly appealing area of modern organic chemistry. Nowadays, the need to access original bioactive scaffolds goes together with the desire to improve synthetic efficiency, while reducing the environmental footprint of chemical activities. Long neglected in the field of total synthesis, enantioselective organocatalysis has recently emerged as an environmentally friendly and indispensable tool for the construction of relevant bioactive molecules. Notably, enantioselective Brønsted acid catalysis has offered new opportunities in terms of both retrosynthetic disconnections and controlling stereoselectivity. The present report attempts to provide an overview of enantioselective total or formal syntheses designed around Brønsted acid-catalyzed transformations. To demonstrate the versatility of the reactions promoted and the diversity of the accessible motifs, this Minireview draws a systematic parallel between methods and retrosynthetic analysis. The manuscript is organized according to the…

Equating (3,-1) critical points (CPs), derived from the topological analysis of the electron densities, to chemical bonds has triggered a lot of confusion in recent years. Part of this confusion stems from calling these CPs "bond" CPs (BCPs). While the origin of this terminology is traceable to the late seventies and beginning of eighties, when it sounded reasonable, new computational studies conducted on molecular electron densities cast serious doubt on the supposed universal equivalence between the chemical bonds and (3,-1) CPs. Herein, recent computational studies are briefly reviewed to demonstrate why (3,-1) CPs are not indicators of chemical bonds. It is discussed why this confusing terminology needs to be changed and reemphasized that (3,-1) CPs should be called "line" critical points (LCPs). The proposed terminology detaches the topological properties of molecular electron densities from any a priori chemical interpretation. Such detachment, if adopted by other authors, will hopefully prevent further misinterpretation of the data emerging from the quantum theory of atoms in…

Metal-organic frameworks (MOFs), as an important kind of porous inorganic-organic hybrid materials with inherent outstanding physicochemistry characteristics, can be widely applied as versatile precursors for the facile preparation of functional MOF-derived materials. However, there are plenty of sophisticated factors during the synthetic process, which is far from reaching the goal of effectively controlling the nature of MOF-derived materials (such as the composition, morphology and surface area). Therefore, it is urgently necessary to develop regular protocols and concepts for controllable syntheses of MOF-derived materials. In this minireview, we mainly summarize and analyze complicated factors in the fabrication of MOF-derived materials according to recently reported literatures, and this provides a new insight into the rational design and syntheses of MOF-derived materials.

Photocatalytic bond activations are generally limited by the photon energy and the efficiency of energy and electron transfer processes. Direct two-photon processes provide sufficient energy but the ultra-short lifetimes of the excited states prohibit chemical reactions. The commercial dye 9,10-dicyanoanthracene enabled photocatalytic aromatic substitutions of non-activated aryl halides. This reaction operates under VIS-irradiation via sequential photonic, electronic, and photonic activation of the simple organic dye. The resultant highly reducing excited photocatalyst anion readily effected C-H, C-C, C-P, C-S, and C-B bond formations. Detailed synthetic, spectroscopic, and theoretical studies support a biphotonic catalytic mechanism.

Abstract The synthesis of novel zinc electrodes has been successfully implemented by using the electroplating method with the aid of inorganic additives in the electroplating solution. The selected inorganic additives are indium sulfate, tin oxide, and boric acid. From X‐ray diffraction results, these synthesized zinc electrodes prefer (002) and/or (103) crystallographic orientations, representing basal morphology and high resistance to dendrite growth. The corrosion rates of these electroplated zinc samples decrease as much as 11 times smaller than the corrosion rate on zinc foil when the zinc materials are in contact with the aqueous electrolyte of a rechargeable hybrid aqueous battery (ReHAB). The ReHABs employing these anodes exhibit up to a threefold decrease in float charge current density after a seven‐day constant‐voltage charging at 2.1 V versus Zn2+/Zn. Furthermore, the capacity retention is up to 15 % higher than the performance of battery containing commercial Zn after 1000 cycles of charge–discharge. The significant advancements are attributed to the careful preparation…

Metallaaromatics can be broadly defined as aromatic compounds in which one of the ring atoms is a transition metal. The metallabenzenes are one important class of these compounds that has undergone extensive study recently. Closely related species such as fused-ring metallabenzenes, heterometallabenzenes, π-coordinated metallabenzenes and metallabenzynes have also attracted considerable attention. Although many metallaaromatics can be considered as metalla-analogues of classic organic aromatic compounds, this is not always the case. Recent seminal studies have shown that metallapentalenes and metallapentalynes, which are metalla-analogues of the anti-aromatic compounds pentalene and pentalyne, are in fact aromatic and highly stable. Very unusual spiro-metallaaromatic compounds have also recently been isolated. In this concepts article, key features of all these intriguing metallaaromatic compounds are discussed with reference to the structural, spectroscopic, reactivity and theoretical studies that have been undertaken. These compounds continue to generate much interest, not only…

In this Review article pioneering work and recent achievements in the emerging research area of on-surface chemistry is discussed. On-surface chemistry, sometimes also called two-dimensional chemistry, shows great potential for bottom-up preparation of defined nanostructures. In contrast to traditional organic synthesis, where reactions are generally conducted in well-defined reaction flasks in solution, on-surface chemistry is performed in the cavity of a scanning probe microscope on a metal crystal under ultrahigh vacuum conditions. The metal first acts as a platform for self-assembly of the organic building blocks and in many cases it also acts as a catalyst for the given chemical transformation. Products and hence success of the reaction are directly analyzed by scanning probe microscopy. This Review provides a general overview of this chemistry highlighting advantages and disadvantages as compared to traditional reaction setups. The second part of the Review then focuses on reactions that have been successfully conducted as on-surface processes. On-surface Ullmann and Glaser…

Ladder polymers are unique in that their backbones consist of fused rings with adjacent rings having two or more atoms in common. The restriction of bond rotations in rigid ladder polymers greatly limits their conformational freedom, leading to many intriguing and unique properties. As a non-traditional type of polymers, rigid ladder polymers are of great fundamental interest and technical importance as advanced materials for applications such as membrane gas separation and organic electronics. Ladder polymers can be divided into non-conjugated (with kinked conformations) and conjugated (with planar conformations) structures. Their synthesis can be broadly classified into two general strategies: direct ladder polymerization, and zipping of a linear precursor polymer. This Concept article outlines the historical development of ladder polymers and the chemical strategies used for their synthesis; highlights the challenges associated with their synthesis and characterization, and presents opportunities and outlooks for this unique and intriguing type of polymers.

Abstract Developing high‐performance solid‐state electrolytes is crucial for the innovation of next‐generation lithium‐sulfur batteries. Herein, a facile method for preparation of a novel gel polymer electrolyte (GPE) based on poly(vinylidene fluoride‐hexafluoropropylene) (PVDF‐HFP) is reported. Furthermore, Li 1.5 Al 0.5 Ti 1.5 (PO 4 ) 3 (LATP) nanoparticles as the active fillers are uniformly embedded into the GPE to form the final PVDF‐HFP/LATP composite gel polymer electrolyte (CPE). Impressively, the obtained CPE demonstrates a high lithium ion transference number of 0.51 and improved electrochemical stability as compared to commercial liquid electrolyte. In addition, the assembled solid‐sate Li−S battery with the composite gel polymer electrolyte membrane presents a high initial capacity of 918 mAh g −1 at 0.05 C, and better cycle performance than the counterparts with liquid electrolyte. Our designed PVDF‐HFP/LATP composite can be a promising electrolyte for next‐generation solid‐state batteries with high cycling stability.

The advances made in the mechanosynthesis of inorganic and organometallic complexes and the excellent past developments with metal-catalyzed cross-coupling reactions by high-speed ball milling have sufficienly laid the ground work for the merging of C-H functionalization and mechanochemical techniques. In recent years, the fast development of mechanochemical C-H activation have given us examples of metal-catalyzed olefinations, amidations, halogenations, and oxidative couplings, among others. This concept article will describe some of the events that led to the development of mechanochemical C-H activation, the current state-of-the-art, the present challenges of this merge, and some unique scenarios in which mechanochemistry could complement the traditional solution-based approaches.

Abstract Cobalt‐porphyrin‐catalysed intramolecular ring‐closing C−H bond amination enables direct synthesis of various N‐heterocycles from aliphatic azides. Pyrrolidines, oxazolidines, imidazolidines, isoindolines and tetrahydroisoquinoline can be obtained in good to excellent yields in a single reaction step with an air‐ and moisture‐stable catalyst. Kinetic studies of the reaction in combination with DFT calculations reveal a metallo‐radical‐type mechanism involving rate‐limiting azide activation to form the key cobalt(III)‐nitrene radical intermediate. A subsequent low barrier intramolecular hydrogen‐atom transfer from a benzylic C−H bond to the nitrene‐radical intermediate followed by a radical rebound step leads to formation of the desired N‐heterocyclic ring products. Kinetic isotope competition experiments are in agreement with a radical‐type C−H bond‐activation step (intramolecular KIE=7), which occurs after the rate‐limiting azide activation step. The use of di‐ tert ‐butyldicarbonate (Boc 2 O) significantly enhances the reaction rate by preventing competitive binding of…

Abstract The selective detection and separation of target ions or molecules is an intriguing issue. Herein, a novel supramolecular organic framework ( SOF‐ T H BP ) was constructed by bis‐thioacetylhydrazine functionalized pillar[5]arenes. The SOF ‐ T H BP shows a fluorescent response for Fe 3+ , Cr 3+ , Hg 2+ and Cu 2+ ions. The xerogel of SOF ‐ T H BP shows excellent recyclable separation properties for these metal ions and the absorption rates were up to 99.29 %. More interestingly, by rationally introducing these metal ions into the SOF ‐ T H BP , a series of metal‐ion‐coordinated SOFs (MSOFs) such as MSOF‐Fe , MSOF‐Hg and MSOF‐Cu were constructed. These metal ions coordinated MSOFs could selectively sense F − , Br − , and l ‐Cys, respectively. The detection limits of these MSOFs for F − , Br − and l ‐Cys were about 10 −8 m.

Porous redox-active metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) have emerged as electrode materials for energy storage devices. These porous frameworks have different levels of intrinsic properties such as low solubility, high ionic conductivity (porosity) and low electrical conductivity, all of which are critical parameters when utilised as electrode materials. This Minireview focuses on recent developments of using porous MOFs/COFs as redox active electrode materials for energy storage and strategies to improve their electrochemical performance.

Abstract Complexation of copper(II) 2,3,9,10,16,17,23,24‐octahydroxy‐29H,31H‐phthalocyanine (CuPcOH) with copper(II) ions gives a two‐dimensional (2D) metal‐organic framework (MOF). This is the first report of a phthalocyanine‐based MOF. This 2D MOF was obtained as a black powder and showed an electrical conductivity of 1.6×10−6 S cm−1 at 80 °C. When this MOF is used as a cathode of lithium ion battery (LIB), large charge/discharge capacities of 151/128 mAh g−1 were obtained. In addition, it showed a good stability during 200 charge/discharge cycles. The obtained LIB performance mainly originates from the electrically conductive and redox‐active framework of the phthalocyanine‐based 2D MOF and its hierarchical microporous/mesoporous structure.

Pd catalysis provides a convenient method for the generation of zwitterionic intermediates that offer significant opportunities for the synthesis of functionalized heterocycles. The combination of electrophilic π-allyl Pd fragments and C-, N- and O-centered nucleophiles allows these intermediates to react with readily available substrates to furnish a range of high value products with control of chemo-, regio- and stereo-selectivity.

Abstract The electrochemical behavior of fac ‐[Mn(pdbpy)(CO) 3 Br] (pdbpy=4‐phenyl‐6‐(phenyl‐2,6‐diol)‐2,2′‐bipyridine) ( 1 ) in acetonitrile under Ar, and its catalytic performances for CO 2 reduction with added water, 2,2,2‐trifluoroethanol (TFE), and phenol are discussed in detail. Preparative‐scale electrolysis experiments, carried out at −1.5 V versus the standard calomel electrode (SCE) in CO 2 ‐saturated acetonitrile, reveal that the process selectivity is extremely sensitive to the acid strength, producing CO and formate in different faradaic yields. A detailed spectroelectrochemical (IR and UV/Vis) study under Ar and CO 2 atmospheres shows that 1 undergoes fast solvolysis; however, dimer formation in acetonitrile is suppressed, resulting in an atypical reduction mechanism in comparison with other reported Mn I catalysts. Spectroscopic evidence of Mn hydride formation supports the existence of different electrocatalytic CO 2 reduction pathways. Furthermore, a comparative investigation performed on the new fac ‐[Mn(ptbpy)(CO) 3 Br]…

Hydrogen peroxide, which is a green oxidant and fuel, is produced by a two-electron/two-proton reduction of dioxygen, two-electron/two-proton oxidation of water, or a combination of four-electron/four-proton or/and two-electron/two-proton oxidation of water and two-electron/two-proton reduction of dioxygen. There are many reports on electrocatalysts for selective two-electron/two-proton reduction of dioxygen to produce hydrogen peroxide instead of four-electron/four-proton reduction of dioxygen to produce water. As compared with the two-electron/two-proton reduction of dioxygen to produce hydrogen peroxide, fewer catalysts are known for the selective two-electron/two-proton oxidation of water to produce hydrogen peroxide instead of four-electron/four-proton oxidation of water to evolve dioxygen. Thus, solar-driven production of hydrogen peroxide mainly consists of the catalytic four-electron/four-proton oxidation of water and the catalytic two-electron/two-proton reduction of dioxygen. The overall reaction is the solar-driven oxidation of water by dioxygen to produce hydrogen…

Abstract It is highly attractive to develop non‐noble‐metal nanoarray architecture as a 3D‐catalyst electrode for molecular detection due to its large specific surface area and easy accessibility to target molecules. Here, we report the development of a copper‐nitride nanowires array on copper foam (Cu3N NA/CF) as a dual‐functional catalyst electrode for efficient glucose oxidation in alkaline solutions and hydrogen peroxide (H2O2) reduction in neutral solutions. Electrochemical tests indicate that such Cu3N NA/CF possesses superior non‐enzymatic sensing ability toward rapid glucose and H2O2 detection with high selectivity. At 0.40 V, this sensor offers a high sensitivity of 14 180 μA mm cm−2 for glucose detection, with a wide linear range from 1 μm to 2 mm, a low detection limit of 13 nm (S/N=3), and satisfactory stability and reproducibility. Its application in determining glucose in human blood serum is also demonstrated. Amperometric H2O2 sensing can also been realized with a sensitivity of 7600 μA mm cm−2, a linear range from 0.1 μm to 10 mm, and a detection limit of 8.9 nm…

Abstract High‐performance supercapacitors require the design and development of electrode materials with high conductivity and a large electrolyte‐accessible surface area. Here, the use of a conductive NiCoP nanoarray on nickel foam (NiCoP/NF) as a superior pseudocapacitor electrode is demonstrated. This 3D electrode exhibits high areal capacitances of 9.2 and 5.97 F cm−2 at current densities of 2 and 50 mA cm−2, respectively, with good rate capability and cycling stability. The asymmetric supercapacitor (ASC) device assembled using NiCoP/NF as positive electrode and active carbon as negative electrode delivers a high energy density of 1.16 mWh cm−2 at a power density of 1.6 mW cm−2 with 72 % retention of its initial specific capacitance after 2000 cycles at 50 mA cm−2. The practical use is further demonstrated with two such ASC devices in series to light six LED indicators and also to drive an alkaline water electro‐ lyzer using NiCoP/NF as both cathode and anode for hydrogen production.

Abstract The chemistry of graphene and its derivatives is one of the hottest topics of current material science research. The derivatisation of graphene is based on various approaches, and to date functionalization with halogens, hydrogen, various functional groups containing oxygen, sulfur, nitrogen, phosphorus, boron, and several other elements have been reported. Most of these functionalizations are based on sp3 hybridization of carbon atoms in the graphene skeleton, which means the formation of out‐of‐plane covalent bonds. Several elements were also reported for substitutional modification of graphene, where the carbon atoms are substituted with atoms like nitrogen, boron, and several others. From tens of functional groups, for only two of them were reported full functionalization of graphene skeleton and formation of its stoichiometric counterparts, fluorographene and hydrogenated graphene. The functionalization of graphene is crucial for most of its applications including energy storage and conversion devices, electronic and optic applications, composites, and many others.

Abstract The bifunctional aminopyridine ligands H2N‐(CH2)n‐4‐C5H4N (n=0, L1; 1, L2; 2, L3) have been utilized for the preparation of the rhenium complexes [Re(phen)(CO)3(L1–L3)]+ (1–3; phen=phenanthroline). Complexes 2 and 3 with NH2‐coordinated L2 and L3, respectively, were coupled with cycloplatinated motifs {Pt(ppy)Cl} and {Pt(dpyb)}+ (ppy=2‐phenylpyridine, dpyb=dipyridylbenzene) to give the bimetallic species [Re(phen)(CO)3(μ‐L2/L3)Pt(ppy)Cl]+ (4, 6) and [Re(phen)(CO)3(μ‐L2/L3)Pt(dpyb)]2+ (5, 7). In solution, complexes 4 and 6 show 3MLCT {Re}‐based emission at 298 K, which changes to the 3IL(ppy) state at 77 K. The photophysical properties of compounds 5 and 7 display a pronounced concentration dependence, presumably due to the formation of bimolecular aggregates. Analysis of the spectroscopic data, combined with TD‐DFT simulations, suggest that unconventional heteroleptic {Re(phen)}⋅⋅⋅{Pt(dpyb)} π–π stacking operates as the driving force for ground‐state association. The latter, together with intra‐ and intermolecular energy‐transfer processes, determines the appearance of…

Carboranes are a class of carbon-boron molecular clusters with unusual thermal and chemical stabilities. They have been proved as very useful building blocks in supramolecular design, optoelectronics, nanomaterials, boron neutron capture therapy agents and organometallic/coordination chemistry. Thus, the functionalization of o-carboranes has received growing interests. Over the past decades, most of the works in this area have been focused on cage carbon functionalization as the weakly acidic cage C-H proton can be readily deprotonated by strong bases. In sharp contrast, selective cage B-H activation/functionalization among chemically very similar ten B-H vertices is very challenging. Considering the differences in electron density of ten cage B-H bonds in o-carborane and the nature of transition metal complexes, we have tackled this selectivity issue by means of organometallic chemistry. Our strategy is as follows: using electron-rich transition metal catalysts for the functionalization of the most electron-deficient B(3,6)-H vertices (bonded to both cage CH vertices); using…

Chalcogen bonding is a noncovalent interaction based on electrophilic chalcogen substituents, which shares many similarities with the more well-known hydrogen and halogen bonding. Herein, the first application of selenium-based chalcogen bond donors in organocatalysis is described. Cationic bifunctionalized organoselenium compounds activate the carbon-chlorine bond of 1-chloroisochroman in a benchmark reaction. While imidazolium-based derivatives showed no noticeable activation, benzimidazolium backbones yielded potent catalysts. In all cases, syn-isomers were markedly more active, presumably due to bidentate coordination, which was confirmed by DFT calculations. Comparison experiments with the corresponding non-selenated as well as the non-cationic reference compounds clearly indicate that the catalytic activity can be ascribed to chalcogen bonding. The rate acceleration by the catalyst-compared to the non-selenated derivative-was about 10 fold.

Abstract Co9S8 is considered a promising candidate as the anode material in lithium‐ion batteries (LIBs) because of its remarkable electrical conductivity, high theoretical capacity, and low cost. However, the practical application of Co9S8 is greatly restricted because of its poor cycling stability and rate performance, which result mainly from the large volume expansion and dissolution of the polysulfide intermediates during the charge/discharge process. In this report, Co9S8 embedded in N‐rich carbon hollow spheres are successfully designed and synthesized through an in situ pyrolysis and sulfurization process, employing the well‐known ZIF‐67 as the precursor and ethanethiol as the sulfur source. Co9S8 nanoparticles embedded in the N‐rich hollow carbon shell exhibit excellent lithium storage properties at a high charge/discharge rate. A discharge capacity of 784 mAh g−1 is obtained upon battery testing at a current density of 1 C (544 mA g−1). Even upon cycling at a current density of 4 C, the as‐prepared Co9S8/N‐C can still deliver a discharge capacity of 518 mAh g−1. The…

The metal-free catalyst tris(2,4,6-trifluorophenyl)borane has demonstrated its extensive applications in the 1,2-hydroboration of numerous unsaturated reagents, namely alkynes, aldehydes and imines, consisting of a wide array of electron-withdrawing and donating functionalities. A range of over 50 borylated products are reported, with many reactions proceeding with low catalyst loading under ambient conditions. These pinacol boronate esters, in the case of aldehydes and imines, can be readily hydrolyzed to leave the respective alcohol and amine, whereas alkynyl substrates result in vinyl boranes. This is of great synthetic use to the organic chemist.

The utility of Meldrum's activated furan (MAF) for the colorimetric detection of sub ppm levels of amines in solution, on solid supports, and as vapors is reported. MAF is synthesized in one step from inexpensive and commercially available starting materials and exhibits high selectivity for primary and secondary amines in the presence of competing nucleophiles. The reaction between activated furans and amines results in a distinct color change, discernable by the naked eye. UV/Vis absorption spectroscopy was utilized to monitor reactions in solution and determine detection limits. Additionally, solutions of MAF were useful as stains for thin layer chromatography and for monitoring solid-phase synthesis of peptides and peptidomimetics. Finally, MAF was used to detect volatile amines released from fish samples, demonstrating potential for food spoilage applications.

Abstract Rechargeable batteries with organic electrodes are preferred to those with transition‐metal‐containing electrodes for their environmental friendliness, and resource availability, but all such batteries reported to date are based on organic electrolytes, which raise concerns of safety and performance. Here an aqueous‐electrolyte all‐organic rechargeable battery is reported, with a maximum operating voltage of 2.1 V, in which polytriphenylamine (PTPAn) and 1,4,5,8‐naphthalenetetracarboxylic dianhydride (NTCDA)‐derived polyimide (PNTCDA) serve as cathode and anode material, respectively. A key feature of the design is use of a “water‐in‐salt” electrolyte to bind “free” water; this impedes the side reaction of water oxidation, thereby enabling excellent reversibility in aqueous solution. The battery can deliver a maximum energy density of 52.8 Wh kg−1, which is close to most of the all‐organic batteries with organic electrolytes. The battery exhibits a supercapacitor‐like high power of 32 000 W kg−1 and a long cycle life (700 cycles with capacity retention of 85 %), due to the…

Self-healing low molecular weight supramolecular gels (SMGs) represent an emerging class of smart materials, which can closely mimic the complex biological healing process, such as blood clotting, bone repair or wound healing. However, a lack of understanding of the structure-function correlation in the self-assembly process limits their molecular design and subsequent property tuning. The indispensability of a rheological study on supramolecular gels lies in direct transcription of the assembly property to the viscoelastic behavior of the material. This is similarly relevant to healable and non-healable systems. Thus, using rheology as a tool for elucidating structure-function relationships in self-assembled systems has huge potential. This review article will depict a general introduction of rheology in the field of soft matter including SMGs, followed by representative studies with interpretations, and discussion on future challenges. Altogether, this would be an effort, where an in-depth rheological study complemented with a real-time visualization with the help of microscopy,…

Abstract The C−H amination of benzene derivatives was achieved using DDQ as photocatalyst and BocNH2 as the amine source under aerobic conditions and visible light irradiation. Electron‐deficient and electron‐rich benzenes react as substrates with moderate to good product yields. The amine scope of the reaction comprises Boc‐amine, carbamates, pyrazoles, sulfonimides and urea. Preliminary mechanistic investigations indicate arene oxidation by the triplet of DDQ to radical cations with different electrophilicity and a charge transfer complex between the amine and DDQ as intermediate of the reaction.

Natural as well as synthetic antioxidants are constantly being investigated for their efficiency in combatting the effects of oxidative stress, which appears to be the responsible cause of several diseases, including cancer, central nervous system disorders, ischaemia-reperfusion disorders, cardiovascular conditions, and diabetes. Superoxide dismutases (SODs) constitute the ubiquitous antioxidant defences against oxidative stress that underlies numerous pathological conditions. Therefore, the development of therapeutics aimed at either delivering MnSOD more effectively to target tissues in the body in the form of MnSOD gene therapy, or the synthesis of molecules that mimic the activity of superoxide dismutase is constantly being explored. Classes that have been developed as SOD mimetics include the Mn-metalloporphyrins, Mn-cyclic polyamines, Mn-salen complexes, MnPLED derivatives as well as the nitroxides. Thus far, SOD mimetics have shown remarkable efficacy in several animal models suffering from oxidative stress injuries. A promising approach for the future of SOD and SOD mimic…

A catalyst- and supporting electrolyte-free method for electrochemical dehydrogenative C-S bond formation in continuous flow has been developed. A broad range of N-arylthioamides have been converted to the corresponding benzothiazoles in good to excellent yields and with high current efficiencies. This transformation is achieved using only electricity and laboratory grade solvent, avoiding degassing or the use of inert atmosphere. This work highlights three advantages of electrochemistry in flow, which is (i) a supporting electrolyte-free reaction, (ii) an easy scale-up of the reaction without the need for a larger reactor and, (iii) the important and effective impact of having a good mixing of the reaction mixture, which can be achieved effectively with the use of flow systems. This clearly improves the reported methods for the synthesis of benzothiazoles.

Despite the fact that perovskite solar cells (PSCs) have a strong potential as a next-generation photovoltaic technology due to continuous efficiency improvements and the tunable properties, some important obstacles remain before industrialization is feasible. For example, the selection of low-cost or easy-to-prepare materials is essential for back-contacts and hole-transporting layers. Likewise, the choice of conductive substrates, the identification of large-scale manufacturing techniques as well as the development of appropriate aging protocols are key objectives currently under investigation by the international scientific community. This Review analyses the above aspects and highlights the critical points that currently limit the industrial production of PSCs and what strategies are emerging to make these solar cells the leaders in the photovoltaic field.

The bandgap is the most important physical property that determines the potential of semiconductors for photovoltaic (PV) applications. This Minireview discusses the parameters affecting the bandgap of perovskite semiconductors that are being widely studied for PV applications, and the recent progress in the optimization of the bandgaps of these materials. Perspectives are also provided for guiding future research in this area.

The design principles, mechanism of action and performance of europium(III) complexes that serve as strongly emissive and responsive molecular probes in water are critically discussed. Examples of systems designed to assess pH, selected metal ions and anions, including chiral species, as well as selected small molecules and biopolymers are considered, and prospects evaluated for improved performance in more complex biological media such as in bio-fluids and within living cells. Modulation of the emission spectral form, lifetime and degree of circular polarisation can be used to quantify the spectral response and permit calibration.

Abstract Alcohols are promising sustainable starting materials because they can be obtained from abundant and indigestible biomass. The substitution of expensive noble metals in catalysis by earth abundant 3d metals, such as Mn, Fe, or Co, (nonprecious or base metals) is a related key concept with respect to sustainability. Here, we report on the first cobalt‐catalyzed alkylation of secondary alcohols with primary alcohols. Easy‐to‐synthesize and easy‐to‐activate PN 5 P‐pincer‐ligand‐stabilized Co complexes developed in our laboratory mediate the reaction most efficiently. The catalysis is applicable to a broad substrate scope and proceeds under relatively mild conditions. We have even demonstrated the coupling of a variety of purely aliphatic alcohols with a base or nonprecious metal catalyst. Mechanistic studies indicate that the reaction follows the borrowing hydrogen or hydrogen autotransfer concept.

Aerogels are attracting increasing attention due to their high thermal insulation ability as well as unique properties such as high porosity, surface area, and transparency. However, low mechanical strengths, originating from their unique porous structure, impede handling, formability, mass production, and extended applications. This minireview focuses on the strengthening of aerogels by several organic-inorganic hybridization strategies. In particular, successful strengthening methodologies, which employ organo-substituted alkoxysilanes as the single precursor for the sol-gel preparations, developed by the authors are highlighted. Moreover, improvements in compressive strength and elasticity lead to monolithic aerogel-like xerogels through ambient pressure drying. Correlations between structures in different length scales (e.g., molecular, network, and pore structure levels) and resultant mechanical properties are discussed for further understandings and better design toward mechanically improved aerogels/xerogels and their applications.

Reactive oxygen species (ROS) are endogenously produced oxidants with various functions ranging from host defense to signaling. These transient species can cause severe damage to the body when their production is dysregulated or when environmental factors elevate their concentrations. To study their effects and prevent oxidative harm, tools capable of monitoring ROS in cells and tissue in a sensitive and selective fashion are required. In this Review, a summary of existing ratiometric probes is provided, together with a critical discussion of selected examples.

This article looks at the chemistry surrounding the concept of inherently chiral calixarenes (ICCs), whose synthesis and application have only recently being realised. One challenge in the area of ICC chemistry is the sheer breadth and scope for installing different aspects of inherent chirality. The aim of this article is not to cover every known method, but rather to give the reader an overview of the main themes that have emerged in this area, including more recent additions to the literature. This overview will also touch on the very limited reports on the applications of ICCs which give a glimpse into the potential these compounds may have in future studies.

Hydrogels have emerged as a highly interdisciplinary topic as they play a significant role for a vast number of applications. They have been studied extensively as materials for contact lenses, wound dressing and as filler material in soft-tissue augmentation, in which classical polymer backbones such as hydroxyethylmethacrylate (HEMA) are typically employed. More recently, polysaccharides have received attention, particularly in the fields of regenerative medicine and tissue engineering, as ideal candidate materials for artificial extracellular matrices (ECM). The polysaccharides of choice are dextran, alginate, chitosan, hyaluronic acid and pullulan and in order to obtain suitable hydrogels from these polysaccharides, controlled chemical functionalization is of critical importance. This short review summarizes recent developments in the chemical derivatization of polysaccharides to pave the way for crosslinking and to decorate individual polysaccharide chains with bioactive ligands. The report covers convergent and divergent protocols for crosslinking, as well strategies for…

Abstract The development of H2 gas sensors is important for H2 production as a fuel. In this work, a ZnO@ZIF‐8 core–shell nanorod film is designed and synthesized as a gas sensor through a facile solution deposition process. This film shows an excellent selective response for H2 over CO. By fine‐tuning the reaction conditions, a ZnO@ZIF‐8 core–shell structure with a thin, fine‐grain, porous ZIF‐8 shell is obtained. Owing to the facile H2 penetration through the ZIF‐8 thin shell (≈110 nm) and the increased oxygen vacancies for the complex film, the ZnO@ZIF‐8 nanorod film shows a higher H2 sensitivity than a raw ZnO nanorod film. More importantly, the ZnO@ZIF‐8 nanorod film shows no response for CO at 200 °C. Because of the fine‐grain confinement of the porous ZIF‐8 shell (<140 nm), the molecular sieving effect is strengthened, which allows the effective separation of H2 over CO. This work provides a promising strategy for the design of high‐performance H2 sensors.

Abstract Molybdenum disulfide (MoS 2 ) nanoflowers consisting of hybridized 1T/2H phases have been synthesized by using a microwave‐assisted hydrothermal (MTH) method. The concentration of the 1T phase, ranging from 40 % to 73 %, is controlled by simply adjusting the ratio of the Mo and S precursors. By using the hybridized 1T/2H MoS 2 as an electrode material, it was demonstrated that the resulting supercapacitor performance is dominated by the 1T phase concentration. It was found that a supercapacitor with 73 % 1T phase exhibits excellent capacitance of 259 F g −1 and great cyclic stability after 1000 cycles. The formation mechanism of the MHT‐synthesized hybridized 1T/2H MoS 2 is also reported. More importantly, the mechanism also explains the observed relationship between the 1T phase concentration and the ratio of the Mo and S precursors.

Abstract Herein, we report a greener protocol for the synthesis of 3‐Se/S‐indoles and imidazo[1,2‐a]pyridines through direct C(sp2)−H bond chalcogenation of heteroarenes with half molar equivalents of different dichalcogenides, using KIO3 as a non‐toxic, easy‐to‐handle catalyst and a stoichiometric amount of glycerol. The reaction features are high yields, based on atom economy, easy performance on gram‐scale, metal‐ and solvent‐free conditions as well as applicability to different types of N‐heteroarenes.

The synthesis of metal oxide nanoparticles in organic solvents, so-called nonaqueous (or nonhydrolytic) processes represent powerful alternatives to aqueous approaches and have become an independent research field. 10 Years ago, when we published our first review on organic reaction pathways in nonaqueous sol-gel approaches, the number of examples was relatively limited. Nowadays, it is almost impossible to provide an exhaustive overview. Here we review the development of the last few years, without neglecting pioneering examples, which help to follow the historical development. The importance of a profound understanding of mechanistic aspects of nanoparticle crystallization and formation mechanisms can't be overestimated, when it comes to the design of rational synthesis concepts under minimization of trial-and-error experiments. The main reason for the progress in mechanistic understanding lies in the availability of characterization tools that make it possible to monitor chemical reactions from the dissolution of the precursor to the nucleation and growth of the nanoparticles, by…

Abstract A new three‐dimensional (3D) framework, [Ni(btzip)(H2btzip)]⋅2 DMF⋅2 H2O (1) (H2btzip=4,6‐bis(triazol‐1‐yl)isophthalic acid) as an acidic heterogeneous catalyst was constructed by the reaction of nickel wire and a triazolyl‐carboxyl linker. Framework 1 possesses intersected 2D channels decorated by free COOH groups and uncoordinated triazolyl N atoms, leading to not only high CO2 and C2H6 adsorption capacity but also significant selective capture for CO2 and C2H6 over CH4 and CO in 273–333 K. Moreover, 1 reveals chemical stability toward water. Grand Canonical Monte Carlo simulations confirmed the multiple CO2‐ and C2H6‐philic sites. As a result of the presence of accessible Brønsted acidic COOH groups in the channels, the activated framework demonstrates highly efficient catalytic activity in the cycloaddition reaction of CO2 with propylene oxide/4‐chloromethyl‐1,3‐dioxolan‐2‐one/3‐butoxy‐1,2‐epoxypropane into cyclic carbonates.

Halogenating enzymes are increasingly attracting attention for biocatalytic C-H functionalization. Despite its importance for synthetic chemistry, selective introduction of halogens using conventional approaches often remains challenging, whereas biocatalysis offers excellent catalyst-controlled selectivity without requiring protecting groups or hazardous reagents. Owing to the high prevalence of halogenated secondary metabolites, a still growing repertoire of halogenases has been identified. Recently, flavin-dependent tryptophan halogenases came into focus for synthetic use. Nevertheless, these enzymes still suffer from severe deficiencies. Herein, current attempts in optimizing tryptophan halogenases have been compiled. Enzyme discovery, structure elucidation and mechanisms are reviewed with focus on biosynthesis of halogenated arenes. Emphasis is also given to random and rational engineering, high-throughput screening and implementation of halogenases into one-pot processes.

Abstract Copper and gold halide and pseudo‐halide complexes stabilised by methyl‐, ethyl‐ and adamantyl‐substituted cyclic (alkyl)(amino)carbene (CAAC) ligands are mostly linear monomers in the solid state, without aurophilic Au⋅⋅⋅Au interactions. (Et2L)CuCl shows the highest photoluminescence quantum yield (PLQY) in the series, 70 %. The photoemissions of Me2L and Et2L copper halide complexes show S1→S0 fluorescence on the ns time scale, in agreement with theory, as well as a long‐lived emission. Monomeric (Me2L)CuNCS is a white emitter, whereas dimeric [(Et2L)Cu(μ‐NCS)]2 shows intense yellow emission with a photoluminescence (PL) quantum yield of 49 %. The reaction of (AdL)MCl (M=Cu or Au) with phenols ArOH (Ar=Ph, 2,6‐F2C6H3, 2,6‐Me2C6H3, 3,5‐tBu2C6H3, 2‐tBu‐5‐MeC6H3, 2‐pyridyl), thiophenol, or aromatic amines H2NAr′′ (Ar′=Ph, 3,5‐(CF3)2C6H3, C6F5, 2‐py) afforded the corresponding phenolato, thiophenolato and amido complexes. Although the emission wavelengths are only marginally affected by the ring substitution pattern, the PL intensities respond sensitively to the presence of…

Abstract Hydrogen‐bonded organic frameworks (HOFs) have drawn unprecedented interest because of their high crystallinity as well as facile process for construction, deconstruction, and reassembly arising from reversible bond formation‐dissociation. However, structural fragility and low stability frequently prevent formation of robust HOFs with permanent porosity. Here, we report that hexakis(4‐carboxyphenyl)‐hexaazatriphenylene (CPHAT) forms three dimensionally networked H‐bonded framework CPHAT‐1. Interestingly, the activated framework CPHAT‐1 a retains not only permanent porosity but single‐crystallinity, enabling precise structural characterization and property evaluation on a single crystal. Moreover, CPHAT‐1 a retains its framework up to 339 °C or in hot water and in acidic aqueous solution. These results clearly show that even a simple H‐bonding motif can be applied for the construction of robust HOFs, which creates a pathway to establish a new class of porous organic frameworks. We also characterize its uptake of gases and I2, in addition to a detailed photophysical study…

Abstract Among reported electrode materials, a nanoarray is an attractive architecture for molecular detection because of its large specific surface area and easy accessibility for target molecules. Here, a new Fe3N‐Co2N nanowires array grown on carbon cloth (Fe3N‐Co2N/CC) is reported as a non‐noble‐metal bifunctional catalyst electrode for high‐performance glucose oxidation and H2O2 reduction. As an electrochemical non‐enzymatic sensor for glucose detection, Fe3N‐Co2N/CC shows a fast response time of 8 s, a low detection limit (LOD) of 77 nm (signal/noise=3), and a high sensitivity of 4333.7 μA mm−1 cm−2. As an H2O2 sensor, it shows a LOD of 59 nm (signal/noise=3) and a sensitivity of 2273.8 μA mm−1 cm−2 with a response time of 2 s. In addition, the proposed sensor is stable with high selectivity, specificity, and reproducibility, and its application for real sample analysis has been successfully demonstrated.

Abstract The pentagonal bipyramidal single‐ion magnets (SIMs) are among the most attractive prototypes of high‐performance single‐molecule magnets (SMMs). Here, a fluorescence‐active phosphine oxide ligand CyPh2PO (=cyclohexyl(diphenyl)phosphine oxide) was introduced into [Dy(CyPh2PO)2(H2O)5]Br3⋅2 (CyPh2PO)⋅EtOH⋅3 H2O, and combined dynamic magnetic measurement, optical characterization, ab initio calculation, and magneto‐optical correlation of this high‐performance pseudo‐D5h DyIII SIM with large Ueff (508(2) K) and high magnetic hysteresis temperature (19 K) were performed. This work provides a deeper insight into the rational design of promising molecular magnets.

Abstract Metal organic frameworks (MOFs) are a class of porous organic‐inorganic crystalline materials that have attracted much attention as H2 storage devices and catalytic supports. In this paper, the synthesis of highly‐dispersed Ni nanoparticles (NPs) for the hydrogenation of olefins was achieved by employing Ni‐MOF‐74 as a precursor. Investigations of the structural transformation of Ni species derived from Ni‐MOF‐74 during heat treatment were conducted. The transformation was monitored in detail by a combination of XRD, in situ XAFS, and XPS measurements. Ni NPs prepared from Ni‐MOF‐74 were easily reduced by the generation of reducing gases accompanied by the decomposition of Ni‐MOF‐74 structures during heat treatment at over 300 °C under N2 flow. Ni‐MOF‐74‐300 exhibited the highest activity for the hydrogenation of 1‐octene due to efficient suppression of excess agglomerated Ni species during heat treatment. Moreover, Ni‐MOF‐74‐300 showed not only high activity for the hydrogenation of olefins but also high size‐selectivity because of the selective formation of Ni NPs covered…

Abstract An unprecedented reversible dynamic transformation is reported in a metal‐organic framework involving bond formation, which is accompanied by two important structural changes; achiral to chiral and two‐ to three‐dimensions. Using two bent organic ligands (diimpym=4,6‐di(1H‐imidazol‐1‐yl)pyrimidine; H2npta=5‐nitroisophthalic acid) and CoII(NO3)2⋅6 H2O the coordination polymer Co(diimpym)(npta)⋅CH3OH, (1⋅CH3OH), was obtained solvothermally. Its structure consists of knitted pairs of square layers (44‐sql net) of five‐coordinated Co and disordered methanol, and it crystallized in the achiral Pbca space group at room temperature. It undergoes a single crystal to single crystal (SC‐SC) transformation to a 3D interpenetrated framework (α‐polonium‐type net, pcu) of six‐coordinated Co and ordered methanol in the chiral P212121 space group below 220 K. Most unusual is the dynamic temperature‐dependent shortening of a Co⋅⋅⋅O connection from a non‐bonded 2.640 Å (298 K) to a bonded 2.347 Å distance (100 K) transforming the square pyramidal cobalt polyhedron to a distorted octahedron.…

Abstract We show that by judicious choice of substituents at the 2‐ and 7‐positions of pyrene, the frontier orbital order of pyrene can be modified, giving enhanced control over the nature and properties of the photoexcited states and the redox potentials. Specifically, we introduced a julolidine‐like moiety and Bmes 2 (mes=2,4,6‐Me 3 C 6 H 2 ) as very strong donor (D) and acceptor (A), respectively, giving 2,7‐D‐π‐D‐ and unsymmetric 2,7‐D‐π‐A‐pyrene derivatives, in which the donor destabilizes the HOMO−1 and the acceptor stabilizes the LUMO+1 of the pyrene core. Consequently, for 2,7‐substituted pyrene derivatives, unusual properties are obtained. For example, very large bathochromic shifts were observed for all of our compounds, and unprecedented green light emission occurs for the D/D system. In addition, very high radiative rate constants in solution and in the solid state were recorded for the D‐π‐D‐ and D‐π‐A‐substituted compounds. All compounds show reversible one‐electron oxidations, and Jul 2 Pyr exhibits a second oxidation, with the largest potential splitting (Δ E =440…

C-H/C-C Functionalizations were achieved with the aid of a versatile manganese(I) catalyst. Thus, an organometallic manganese-catalyzed C-H activation set the stage for silver-free C-H/C-C transformations with ample substrate scope and excellent levels of chemo-, site-, and diastereo-selectivities. The robust nature of the manganese(I) catalysis regime was reflected by the first C-H/C-C functionalization on amino acids under racemization-free reaction conditions. Detailed experimental and computational mechanistic studies provided strong evidence for a facile C-H activation and a rate-determining C-C cleavage, with considerable contribution from London dispersion interactions.

Abstract Organic room‐temperature phosphorescence (ORTP), when combined with external stimuli‐responsive capability, is very attractive for sensors and bio‐imaging devices, but remains challenging. Herein, by doping two β‐iminoenamine‐BF 2 derivatives (S‐2CN and S‐2I) into a 4‐iodoaniline (I−Ph−NH 2 ) crystalline matrix, the formation of S‐2CN⋅⋅⋅I−Ph−NH 2 and S‐2I⋅⋅⋅I−Ph−NH 2 halogen bonds leads to bright‐red RTP emissions from these two host–guest doped crystals (hgDCs) with quantum efficiencies up to 13.43 % and 15.96 %, respectively. Upon treatment with HCl, the competition of I−Ph−NH 2 ⋅ HCl formation against S‐2I⋅⋅⋅I−Ph−NH 2 halogen bonding switches off the red RTP from S‐2I/I−Ph−NH 2 hgDCs, whereas the stable halogen‐bonded S‐2CN⋅⋅⋅I−Ph−NH 2 ensures red RTP from S‐2CN/I−Ph−NH 2 hgDCs remains unchanged. A security protection luminescence pattern by using these different HCl‐responsive RTP behaviors was designed.

Abstract Studying inter‐dimensional phase transitions of zeolitic‐imidazolate frameworks (ZIFs) is essential for developing strategies in controlling morphology and properties. Herein, the inter‐dimensional topotactic phase transformations of 3D ZIF‐67 to 2D ZIF‐L are investigated in detail by employing a simple and efficient solvent‐induced growth method. In addition to ZIF‐67 and ZIF‐L, a series of novel core–shell composites of ZIF‐67@ZIF‐L, with unprecedented morphologies, are also obtained and well‐defined. The different behaviors of the amine hydrogen of 2‐MIM in the solvents play a pivotal role for inter‐dimensional phase transformations, and in combination with the concentration of 2‐MIM, the 2D to 3D phase transformations are also revealed. The findings are very beneficial for morphological design of the ZIFs, along with exploration of the corresponding properties. Impressively, Co‐ZIFs exhibit interesting tunable CO2 adsorption behaviors with the phase evolution, which might bring broader understanding for designing CO2 detection and adsorption devices.

Molecular chirality provides a key challenge in host-guest recognition and other related chemical applications such as asymmetric catalysis. For a molecule to act as an efficient enantioselective receptor, it requires multi-point interactions between host and chiral guest, which may be achieved by an appropriate chiral 3D scaffold. As a consequence of their interlocked structure, catenanes and rotaxanes may present such a 3D scaffold, and can be chiral by inclusion of a classical chiral element and/or as a consequence of the mechanical bond. This Minireview presents illustrative examples of chiral [2]catenanes and [2]rotaxanes, and discusses where these molecules have been used in chemical applications such as chiral host-guest recognition and asymmetric catalysis.

Abstract The direct introduction of alkenyl groups into the indole framework avoiding its preliminary functionalization can be carried out using different synthetic strategies. Transition‐metal complexes facilitate the C−H activation of indoles or alkenes allowing an efficient Csp2‐ Csp2 bond formation. The hydroindolation of alkynes catalyzed by the same metal complexes or various acidic promoters can also be pursued for the alkenylation process. Conjugate addition of electron‐poor alkenes and direct condensation of carbonyl derivatives with indoles are also of interest for this purpose. The regiochemical control can be exploited using the intrinsic C‐3 reactivity of the indole ring. The introduction of a suitable directing group at the nitrogen atom allows the preparation of C‐2 alkenylated derivatives by transition metal catalyzed reactions. This review collects the fundamental contributions in this field reported in literature during the last fifteen years.

Stimuli-responsive molecules change their properties when exposed to external signals, such as light, and enable the preparation of smart materials. UV light, which often destroys organic materials, is typically required for activating the desired response of photoswitchable compounds, significantly limiting the potential applications of light-operated smart materials. Herein, we present the first metal-organic framework (MOF), which enables reversible modulation of key properties upon irradiation with visible light only. The fluorinated azobenzene side groups in the MOF structure can be reversibly switched between the trans and cis state by green and violet light, avoiding UV light. It was demonstrated that the uptake of guest molecules by these MOF films can be switched in a fully remote-controlled way. The membrane separation of hydrogen/hydrocarbon mixtures was investigated. The light-induced changes of the MOF pore size result in the switching of the permeation and of the selection factor.

Abstract The synthesis and structures of the first Si II ‐donor supported manganese(II) complexes [L1]MnCl 2 , [L2]MnCl 2 , and [L3] 2 MnCl 2 are reported, bearing a pincer‐type bis(NHSi)‐pyridine ligand L1 , bidentate bis(NHSi)‐ferrocene ligand L2 , and two monodentate NHSi ligands L3 (NHSi = N ‐heterocyclic silylene), respectively. They act as unprecedented very active and stereoselective Mn‐based precatalysts (1 mol % loading) in transfer semi‐hydrogenations of alkynes to give the corresponding E ‐olefins using ammonia–borane as a convenient hydrogen source under mild reaction conditions. Complex [L1]MnCl 2 shows the best catalytic performance with quantitative conversion rates and excellent E ‐stereoselectivities (up to 98 %) for different alkyne substrates. Different types of functional groups can be tolerated, except CN, NH 2 , NO 2 , and OH groups at the phenyl group of 1‐phenyl substituted alkynes.

Abstract Highly ordered mesoporous carbon nitrides (MCN) with 3D structure and a high nitrogen content are successfully prepared for the first time using “uncalcined” mesoporous silica template, KIT‐6 and 3‐amino‐1,2,4‐triazole as a single molecular carbon and nitrogen precursor. The prepared MCN with C and N stoichiometry of C 3 N 5 shows unique CN framework and exhibits the CO 2 capture capacity of 5.63 mmol g −1 at 273 K and 30 bar, which is higher than that of MCN with 2D structure and C 3 N 4 stoichiometry.

Abstract Two [Ru(phen)2dppz]2+ derivatives (phen=1,10‐phenantroline, dppz=dipyrido[3,2‐a:2′,3′‐c]phenazine) with different functional groups on the dppz ligand [dppz‐7,8‐(OMe)2 (1), dppz‐7,8‐(OH)2 (2)] have been synthesized, characterized and investigated as photosensitizers (PSs) for photodynamic therapy (PDT) against cancer. Both complexes showed intense red phosphorescence and promising singlet oxygen (1O2) quantum yields of 75 % (1) and 54 % (2) in acetonitrile. Complex 1 (logPo/w=−0.52, 2.4 nmol Ru per mg protein) was found to be more lipophilic, having also a higher cellular uptake efficiency compared to 2 (logPo/w=−0.20, 0.9 nmol Ru per mg protein). Complex 1 localized evenly in HeLa cells whereas 2, was mainly visualized in the cell membrane by confocal microscopy. In the dark, complex 1 (IC50=36.5 μm) was found to be more toxic than complex 2 (IC50 >100 μm) on a HeLa cells monolayer. Importantly, in view of PDT applications, both complexes were found to be non‐toxic in the dark towards multicellular HeLa spheroids (IC50>100 μm). Upon one‐photon irradiation (420 nm, 9.27 J…

Stereoselectivity towards substrates is one of the most important characteristics of enzymes. Amino acids, as cofactors of many enzymes, play important roles in stereochemistry. Herein, chiral nanozymes were constructed by grafting a series of d- or l-amino acids onto the surfaces of ceria (cerium oxide) nanoparticles. We selected the most commonly used drug for combating Parkinson's disease, that is, 3,4-dihydroxyphenylalanine (DOPA) enantiomers, as examples for chiral catalysis. Through detailed kinetic studies of cerium oxide nanoparticles (CeNPs) modified with different eight amino acids, we found that phenylalanine-modified CeNP was optimal for the DOPA oxidation reaction and showed excellent stereoselectivity towards its enantiomers. l-Phenylalanine-modified CeNPs showed higher catalytic ability for oxidation of d-DOPA, while d-phenylalanine-modified CeNPs were more effective towards l-DOPA. Taken together, the results indicated that stereoselective nanozyme can be constructed by grafting nanoparticles with chiral molecules. This work may inspire better design of chiral…

Sustainable, cobalt-catalyst enabled, synthetically significant C-F/C-H functionalizations were achieved with an ample substrate scope at an ambient temperature of 25 °C, thereby delivering perfluoroallylated heteroarenes. Detailed experimental and computational mechanistic studies on the C-F/C-H functionalizations provided strong support for a facile C-F cleavage.

Although several Prussian Blue analogues (PBAs) have been investigated as water oxidation catalysts, the field lacks a comprehensive study that focuses on the design of the ideal PBA for this purpose. Here, members of a series of PBAs with different cyanide precursors have been investigated to study the effect of hexacyanometal groups on their electrocatalytic water oxidation activities. Cyclic voltammetric, chronoamperometric, and chronopotentiometric measurements have revealed a close relationship between the electron density of electroactive cobalt sites and electrocatalytic activity, which has also been confirmed by infrared and XPS studies. Furthermore, pH-dependent cyclic voltammetry and computational studies have been performed to gain insight into the catalytic mechanism and electronic structure of cyanide-based systems to identify possible intermediates and to assign the rate-determining step of the target process.

Abstract Porous FeVO4 is prepared by hydrothermal method and further modified by coating with carbon to obtain FeVO4/C with a hierarchical pore structure. FeVO4/C is used as an anodic electrode in aqueous rechargeable magnesium‐ion batteries. The FeVO4/C material not only has improved electrical conductivity as a result of the carbon coating layer, but also has an increased specific surface area as a result of the hierarchical pore structure, which is beneficial for magnesium‐ion insertion/deinsertion. Therefore, an aqueous rechargeable magnesium‐ion full battery is successfully constructed with FeVO4/C as the anode, Mg‐OMS‐1 (OMS=octahedral molecular sieves) as the cathode, and 1.0 mol L−1 MgSO4 as the electrolyte. The discharge capacity of the Mg‐OMS‐1//FeVO4/C aqueous battery is 58.9 mAh g−1 at a current density of 100 mA g−1; this value is obtained by calculating the total mass of two electrodes and the capacity retention rate of this device is 97.7 % after 100 cycles, with almost 100 % coulombic efficiency, which indicates that the system has a good electrochemical…

Abstract Positron emission tomography (PET) imaging study of fluorine‐18 labeled biomolecules is an emerging and rapidly growing area for preclinical and clinical research. The present review focuses on recent advances in radiochemical methods for incorporating fluorine‐18 into biomolecules via “direct” or “indirect” bioconjugation. Recently developed prosthetic groups and pre‐targeting strategies, as well as representative examples in 18 F‐labeling of biomolecules in PET imaging research studies are highlighted.

Abstract Rational design of a transition metal layered double hydroxide (LDH) and graphene composite is vitally important for designing high‐performance supercapacitor electrodes. Although various methods are performed, the realization of high‐performance is still impeded by the agglomeration of graphene and layered double hydroxide. Here, metal–organic framework derived cobalt–cobalt layered double hydroxide (Co−Co LDH) hollow nanocages, uniformly deposited on graphene nanosheets, are fabricated through facile in situ co‐deposition and thermal ion‐exchange reaction. Electrochemical investigation reveals that Co−Co LDH/15 mg graphene is rather outstanding, which delivers high specific capacitance of 1205 F g −1 , excellent rate capability (60.3 % capacitance retention is obtained after the current density increased 6.67 times), and cycling stability. The excellent performance of electrode is also confirmed by assembling an asymmetric supercapacitor, which delivers high energy density of 49.5 Wh kg −1 as well as the maximum power density of 7000 W kg −1 . The Co−Co LDH/graphene…

The first cobalt-catalyzed amide activation of N-Boc-amides, and their conversion into esters, is reported here. This new methodology presents a very practical process that does not require an inert atmosphere, uses an inexpensive cobalt catalyst, and proceeds under mild reaction conditions. This catalytic system has a broad substrate scope and has been shown to be highly efficient, with catalyst loadings as low as 1 mol %.

The first example for the ruthenium-catalyzed ligand-directed meta-selective C-H mono- and difluoromethylation is developed, affording a variety of new meta-mono- and difluoromethylated 2-phenylpyridines, 2-phenylpyrimidines, and 1-phenylpyrazoles in moderate-to-good yields. This new transformation exhibits broad substrate scope, good functional group tolerance, and high efficiency, and offers a practical approach to synthesize mono- and difluoromethylated arenes. Mechanistic studies indicate that a reaction pathway involving palladium-initiated radical species is involved in the catalytic cycle. The new dual catalytic system consisting of compatible ruthenium(II) and palladium(0) complexes enables the key processes of C-H activation and mono-/difluoromethyl-radical formation to occur and achieves the meta-selective functionalization efficiently. In addition, the present protocol can also be extended to non-fluoromethylation.

In the field of renewable energy, the splitting of water into hydrogen and oxygen fuel gases using water electrolysis is a prominent topic. Traditionally, these catalytic processes have been performed by platinum-group metal catalysts, which are effective at promoting water electrolysis but expensive and rare. The search for an inexpensive and Earth-abundant catalyst has led to the development of 3d-transition-metal phosphides for the hydrogen evolution reaction. These catalysts have shown excellent activity and stability. In this review, we discuss the electronic and crystal structures of bulk and surface of selected Fe, Co, and Ni phosphides, and their relationships to the experimental catalytic activity. The various synthetic protocols towards the state-of-the-art transition metal phosphide electrocatalysts are also discussed.