Showing papers in "Accounts of Chemical Research in 2018"
TL;DR: Recent progress in innovative strategies to address the aforementioned four challenges in conventional water electrolysis are described and novel strategies for practicable H2 production from water as well as the electrocatalytic upgrading of diverse organic compounds are described.
Abstract: ConspectusElectrocatalytic water splitting driven by renewable energy input to produce clean H2 has been widely viewed as a promising strategy of the future energy portfolio. Currently, the state-of-the-art electrocatalysts for water splitting in acidic solutions are IrO2 or RuO2 for the O2 evolution reaction (OER) and Pt for the H2 evolution reaction (HER). Realization of large-scale H2 production from water splitting requires competent nonprecious electrocatalysts. Despite the advances of decades in this field, several challenges still exist and need to be overcome: (1) Most efforts in the design of nonprecious electrocatalysts have focused on developing HER catalysts for acidic conditions but OER catalysts for alkaline conditions owing to their thermodynamic convenience, potentially resulting in incompatible integration of the two types of catalysts and thus inferior overall performance. (2) In conventional water electrolysis, HER and OER are strictly coupled and therefore H2 and O2 are produced simult...
1,015 citations
TL;DR: This Account showcases the recent contributions to metal-free catalysis in advanced oxidation, including design of nanocarbon catalysts, exploration of intrinsic active sites, and identification of reactive species and reaction pathways, and offers perspectives on carbocatalysis for future environmental applications.
Abstract: ConspectusCatalytic processes have remarkably boosted the rapid industrializations in chemical production, energy conversion, and environmental remediation. As one of the emerging applications of carbocatalysis, metal-free nanocarbons have demonstrated promise as catalysts for green remediation technologies to overcome the poor stability and undesirable metal leaching in metal-based advanced oxidation processes (AOPs). Since our reports of heterogeneous activation of persulfates with low-dimensional nanocarbons, the novel oxidative system has raised tremendous interest for degradation of organic contaminants in wastewater without secondary contamination. In this Account, we showcase our recent contributions to metal-free catalysis in advanced oxidation, including design of nanocarbon catalysts, exploration of intrinsic active sites, and identification of reactive species and reaction pathways, and we offer perspectives on carbocatalysis for future environmental applications.The journey starts with the dis...
872 citations
TL;DR: This Account examines some of the systems-level strategies that have been applied in an effort to tailor flow reactor components to improve electrocatalytic reduction and highlights the challenges associated with precise and controlled water management in gas phase CO2 electrolyzers.
Abstract: ConspectusElectrocatalytic CO2 conversion at near ambient temperatures and pressures offers a potential means of converting waste greenhouse gases into fuels or commodity chemicals (e.g., CO, formic acid, methanol, ethylene, alkanes, and alcohols). This process is particularly compelling when driven by excess renewable electricity because the consequent production of solar fuels would lead to a closing of the carbon cycle. However, such a technology is not currently commercially available. While CO2 electrolysis in H-cells is widely used for screening electrocatalysts, these experiments generally do not effectively report on how CO2 electrocatalysts behave in flow reactors that are more relevant to a scalable CO2 electrolyzer system. Flow reactors also offer more control over reagent delivery, which includes enabling the use of a gaseous CO2 feed to the cathode of the cell. This setup provides a platform for generating much higher current densities (J) by reducing the mass transport issues inherent to the...
602 citations
TL;DR: The work on understanding how a bulk material, with no obvious emissive sites, can emit every color of the visible spectrum is outlined, finding that greater out-of-plane octahedral tilting increases the propensity for the broad emission, enabling synthetic control over thebroad emission.
Abstract: ConspectusWith nearly 20% of global electricity consumed by lighting, more efficient illumination sources can enable massive energy savings. However, effectively creating the high-quality white light required for indoor illumination remains a challenge. To accurately represent color, the illumination source must provide photons with all the energies visible to our eye. Such a broad emission is difficult to achieve from a single material. In commercial white-light sources, one or more light-emitting diodes, coated by one or more phosphors, yield a combined emission that appears white. However, combining emitters leads to changes in the emission color over time due to the unequal degradation rates of the emitters and efficiency losses due to overlapping absorption and emission energies of the different components. A single material that emits broadband white light (a continuous emission spanning 400–700 nm) would obviate these problems.In 2014, we described broadband white-light emission upon near-UV excita...
571 citations
TL;DR: The asymmetric organocatalytic approach to construct axially chiral styrenes through the 1,4-addition of arylalkynals in good chemical yields and enantioselectivities is discovered and the azo group can effectively perform as a directing and activating group for organoc atalytic formal aRYl C-H functionalization via formal nucleophilic aromatic substitution of azobenzene derivatives.
Abstract: ConspectusAxially chiral compounds have received much attention from chemists because of their widespread appearance in natural products, biologically active compounds, and useful chiral ligands in asymmetric catalysis. Because of the importance of this structural motif, the catalytic enantioselective construction of axially chiral scaffolds has been intensively investigated, and great progress has been accomplished. However, the majority of methodologies in this field focus on the use of metal catalysis, whereas approaches involving organocatalysis have started to emerge only recently. This Account describes certain advances in the organocatalytic asymmetric synthesis of axially chiral compounds involving the following strategies: kinetic resolution, desymmetrization, cyclization/addition, direct arylation, and so on. We began our investigation by developing a highly efficient strategy for the kinetic resolution of axially chiral BINAM derivatives involving a chiral Bronsted acid-catalyzed imine formatio...
459 citations
TL;DR: The recent advance of AIE dots is summarized and their great potential as theranostic nanolights in biomedical applications is highlighted, with particular interest is AIE photosensitizer dots, which simultaneously show bright fluorescence and high photosensitization, yielding superior performance to commercial photosensitized nanoparticles in image-guided therapy.
Abstract: ConspectusTheranostic nanolights refer to luminescent nanoparticles possessing both imaging and therapeutic functions. Their shape, size, surface functions, and optical properties can be precisely manipulated through integrated efforts of chemistry, materials, and nanotechnology for customized applications. When localized photons are used to activate both imaging and therapeutic functions such as photodynamic or photothermal therapy, these theranostic nanolights increase treatment efficacy with minimized damage to surrounding healthy tissues, which represents a promising noninvasive nanomedicine as compared to conventional theranostic approaches.As one of the most promising theranostic nanolights, organic dots with aggregation-induced emission (AIE dots) are biocompatible nanoparticles with a dense core of AIE fluorogens (AIEgens) and protective shells, whose sizes are in the range of a few to tens of nanometers. Different from conventional fluorophores that suffer from aggregation-caused quenching (ACQ) ...
445 citations
TL;DR: This Account gives an overview of recent attempts toward efficient gas-involving electrocatalytic performances with multiscale principles from the respect of electronic structure, hierarchical morphology, and electrode interface step by step.
Abstract: ConspectusVarious gas-involving energy electrocatalysis, including oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER), has witnessed increasing concerns recently for the sake of clean, renewable, and efficient energy technologies However, these heterogeneous reactions exhibit sluggish kinetics due to multistep electron transfer and only occur at triple-phase boundary regions Up to now, tremendous attention has been attracted to develop cost-effective and high-performance electrocatalysts to boost the electrocatalytic activities as promising alternatives to noble metal counterparts In addition to the prolific achievements in materials science, the advances in interface chemistry are also very critical in consideration of the complex phenomena proceeded at triple-phase boundary regions, such as mass diffusion, electron transfer, and surface reaction Therefore, insightful principles and effective strategies for a comprehensive optimization, ranging fro
410 citations
TL;DR: Two critical aspects of CASP and recent machine learning approaches to both challenges are focused on, including the problem of retrosynthetic planning and anticipating the products of chemical reactions, which can be used to validate proposed reactions in a computer-generated synthesis plan.
Abstract: ConspectusComputer-aided synthesis planning (CASP) is focused on the goal of accelerating the process by which chemists decide how to synthesize small molecule compounds. The ideal CASP program would take a molecular structure as input and output a sorted list of detailed reaction schemes that each connect that target to purchasable starting materials via a series of chemically feasible reaction steps. Early work in this field relied on expert-crafted reaction rules and heuristics to describe possible retrosynthetic disconnections and selectivity rules but suffered from incompleteness, infeasible suggestions, and human bias. With the relatively recent availability of large reaction corpora (such as the United States Patent and Trademark Office (USPTO), Reaxys, and SciFinder databases), consisting of millions of tabulated reaction examples, it is now possible to construct and validate purely data-driven approaches to synthesis planning. As a result, synthesis planning has been opened to machine learning te...
399 citations
TL;DR: The proposed new and inspirational mechanisms based on theoretical studies can successfully explain the previous experimental results; some of the mechanisms have been further confirmed by experimental studies and provided guidance for researchers to design new ESPT chemosensors.
Abstract: ConspectusAs one of the most fundamental processes, excited-state proton transfer (ESPT) plays a major role in both chemical and biological systems. In the past several decades, experimental and theoretical studies on ESPT systems have attracted considerable attention because of their tremendous potential in fluorescent probes, biological imaging, white-light-emitting materials, and organic optoelectronic materials. ESPT is related to fluorescence properties and usually occurs on an ultrafast time scale at or below 100 fs. Consequently, steady-state and femtosecond time-resolved absorption, fluorescence, and vibrational spectra have been used to explore the mechanism of ESPT. However, based on previous experimental studies, direct information, such as transition state geometries, energy barrier, and potential energy surface (PES) of the ESPT reaction, is difficult to obtain. These data are important for unravelling the detailed mechanism of ESPT reaction and can be obtained from state-of-the-art ab initio...
390 citations
TL;DR: This Account covers recent important advances in skin-inspired electronics, from basic material developments to device components and proof-of-concept demonstrations for integrated bioelectronics applications, and highlights examples of skin- inspired electronics for three major applications: prosthetic e-skins, wearable electronics, and implantable electronics.
Abstract: ConspectusFuture electronics will take on more important roles in people’s lives. They need to allow more intimate contact with human beings to enable advanced health monitoring, disease detection, medical therapies, and human–machine interfacing. However, current electronics are rigid, nondegradable and cannot self-repair, while the human body is soft, dynamic, stretchable, biodegradable, and self-healing. Therefore, it is critical to develop a new class of electronic materials that incorporate skinlike properties, including stretchability for conformable integration, minimal discomfort and suppressed invasive reactions; self-healing for long-term durability under harsh mechanical conditions; and biodegradability for reducing environmental impact and obviating the need for secondary device removal for medical implants. These demands have fueled the development of a new generation of electronic materials, primarily composed of polymers and polymer composites with both high electrical performance and skinl...
373 citations
TL;DR: This Account highlights the recent efforts on the fabrication of ligand-stabilized coinage nanocluster with atomic precision from the viewpoint of surface coordination chemistry in particular and provides a perspective on the principles of surface coordination chemistry of metal nanoclusters and their potential applications with regards to catalysis of protected metal clusters.
Abstract: ConspectusA comprehensive understanding of chemical bonding and reactions at the surface of nanomaterials is of great importance in the rational design of their functional properties and applicatio...
TL;DR: Advances in total synthesis chemistry of metal NCs could not only serve as guidelines for future synthetic practice of NCs, but also provide molecular-level clues for many pending fundamental puzzles in nanochemistry, including nucleation growth, alloying chemistry, surface engineering and evolution of metamaterials.
Abstract: ConspectusTotal synthesis, where desired organic- and/or biomolecules could be produced from simple precursors at atomic precision and with known step-by-step reactions, has prompted centuries-lasting bloom of organic chemistry since its conceptualization in 1828 (Wohler synthesis of urea). Such expressive science is also highly desirable in nanoscience, since it represents a decisive step toward atom-by-atom customization of nanomaterials for basic and applied research. Although total synthesis chemistry is less established in nanoscience, recent years have witnessed seminal advances and increasing research efforts devoted into this field. In this Account, we discuss recent progress on introducing and developing total synthesis routes and mechanisms for atomically precise metal nanoclusters (NCs). Due to their molecular-like formula and properties (e.g., HOMO–LUMO transition, strong luminescence and stereochemical activity), atomically precise metal NCs could be regarded as “molecular metals”, holding po...
TL;DR: An enantioselective cyanations and arylations of benzylic radicals have been demonstrated in the presence of chiral Box/Cu(I) catalysts, and a series of asymmetric difunctionalizations of styrenes have been successfully achieved.
Abstract: ConspectusThe direct transformation of C–H bonds into diverse functional groups represents one of the most atom- and step-economical strategies for organic synthesis and has received substantial attention over the last few decades. Despite recent advances, asymmetric C–H bond functionalizations are less developed, especially asymmetric oxidations of sp3 C–H bonds. Inspired by enzyme (e.g., P450) catalysis, chemists have made great efforts to develop non-enzymatic systems for enantioselective oxidations of sp3 C–H bonds. However, the involvement of highly reactive radical intermediates makes enantioselective transformations extremely challenging.In this Account, we present our recent studies on the enantioselective induction of prochiral benzylic radicals using a chiral bisoxazoline (Box)/Cu catalytic system. This reaction system was developed on the basis of our extensive studies of copper-catalyzed intermolecular alkene difunctionalizations, such as azidotrifluoromethylations, trifluoromethylcyanations, ...
TL;DR: The nanoarray-based surface engineering technology can achieve the superwetting properties, in which high roughness of the nanoarray architecture is discovered to be a critical factor for constructing superaerophobic and superaerophilic surfaces.
Abstract: ConspectusGas-involving electrochemical reactions, including gas evolution reactions and gas consumption reactions, are essential components of the energy conversion processes and gathering elevating attention from researchers. Besides the development of highly active catalysts, gas management during gas-involving electrochemical reactions is equally critical for industrial applications to achieve high reaction rates (hundreds of milliamperes per square centimeter) under practical operation voltages. Biomimetic surfaces, which generally show regular micro/nanostructures, offer new insights to address this issue because of their special wetting capabilities. Although a series of nanoarray-based structured electrodes have been constructed and demonstrated with excellent performances for gas-involving electrochemical reactions, understanding of bubble wetting behavior remains elusive. In this Account, our recent works including understanding the way to achieve the superwetting properties of solid electrode s...
TL;DR: It is demonstrated that SPNs serve as a multimodal biophotonic nanoplatform to provide unprecedented opportunities for molecular imaging, noninvasive bioactivation, and advanced therapy.
Abstract: ConspectusBiophotonics as an interdisciplinary frontier plays an increasingly important role in modern biomedical science. Optical agents are generally involved in biophotonics to interpret biomolecular events into readable optical signals for imaging and diagnosis or to convert photons into other forms of energy (such as heat, mechanical force, or chemical radicals) for therapeutic intervention and biological stimulation. Development of new optical agents including metallic nanoparticles, quantum dots, up-conversion nanoparticles, carbon dots, and silica nanoparticles has contributed to the advancement of this field. However, most of these agents have their own merits and demerits, making them less effective as multimodal biophotonic platforms.In this Account, we summarize our recent work on the development of near-infrared (NIR) semiconducting polymer nanoparticles (SPNs) as multimodal light converters for advanced biophotonics. SPNs are composed of π-electron delocalized semiconducting polymers (SPs) a...
TL;DR: Major efforts are summarized on copper-, palladium-, and nickel-catalyzed difluoroalkylations of aromatics with low-cost and widely available difLUroalkyl halides as fluoroALKyl sources for transition-metal-catalystzed d ifluoroalksylation reactions via cross-coupling.
Abstract: ConspectusDifluoroalkylated compounds play a remarkably important role in life and materials sciences because of the unique characteristics of the difluoromethylene (CF2) group. In particular, precise introduction of a CF2 group at the benzylic position can dramatically improve the biological properties of the corresponding molecules. As a consequence, difluoroalkylation of aromatic compounds has become a powerful strategy in modulating the bioactivities of organic molecules. However, efficient strategies to selectively synthesize difluoroalkylated arenes had been very limited before 2012. Traditional synthetic methods in this regard suffer from either harsh reaction conditions or narrow substrate scope, significantly restricting their widespread applications, particularly for late-stage difluoroalkylation of bioactive molecules. To overcome these limitations, a straightforward route to access these valuable difluoroalkylated skeletons is the direct introduction of the difluoroalkylated group (CF2R) onto ...
TL;DR: A comprehensive description, at the molecular level, of the fundamental photophysical processes behind TADF emitters is laid out, such as the need to balance the efficiency of thermal activation of triplet excitons into the singlet manifold with theefficiency of radiative transition to the ground state.
Abstract: Since the seminal work of Tang and Vanslyke in 1987 on small-molecule emitters and that of Friend and co-workers in 1990 on conjugated-polymer emitters, organic light-emitting diodes (OLEDs) have attracted much attention from academia as well as industry, as the OLED market is estimated to reach the $30 billion mark by the end of 2018. In these first-generation organic emitters, on the basis of simple spin statistics, electrical excitation resulted in the formation of ∼25% singlet excitons and ∼75% triplet excitons. Radiative decay of the singlet excitons to the singlet ground state leads to a prompt fluorescence emission, while the triplet excitons only lead to weak phosphorescence due to the very small spin-orbit couplings present in purely organic molecules. The consequence is a ca. 75% energy loss, which triggered wide-ranging efforts to try and harvest as many of the triplet excitons as possible. In 1998, Thompson, Forrest, and their co-workers reported second-generation OLED emitters based on coordination complexes with heavy transition metals (e.g., iridium or platinum). Here, the triplet excitons stimulate efficient and fast phosphorescence due to the strong spin-orbit couplings enabled by the heavy-metal atoms. Internal quantum efficiencies (IQE) up to 100% have been reported, which means that for every electron injected into the device, a photon is emitted. While these second-generation emitters are those mainly exploited in current OLED applications, there is strong impetus from both cost and environmental standpoints to find new ways of exploiting purely organic emitters, which in addition can offer greater flexibility to fine-tune the electronic and optical properties by exploiting the synthetic organic chemistry toolbox. In 2012, Adachi and co-workers introduced a promising strategy, based on thermally activated delayed fluorescence (TADF), to harvest the triplet excitons in purely organic molecular materials. These materials now represent the third generation of OLED emitters. Impressive photophysical properties and device performances have been reported, with internal quantum efficiencies also reaching nearly 100%. Our objectives in this Account are threefold: (i) to lay out a comprehensive description, at the molecular level, of the fundamental photophysical processes behind TADF emitters; (ii) to discuss some of the challenges facing the design of TADF emitters, such as the need to balance the efficiency of thermal activation of triplet excitons into the singlet manifold with the efficiency of radiative transition to the ground state; and (iii) to highlight briefly some of the recent molecular-design strategies that pave the way to new classes of TADF materials.
TL;DR: How fundamental investigations into the host-guest chemistry of capsules prepared through subcomponent self-assembly have led to the design of useful functions and new applications is highlighted.
Abstract: ConspectusCoordination-driven self-assembly can produce large, symmetrical, hollow cages that are synthetically easy to access The functions provided by these aesthetically attractive structures provide a driving force for their development, enabling practical applications For instance, cages have provided new methods of molecular recognition, chirality sensing, separations, stabilization of reactive species, and catalysisWe have fruitfully employed subcomponent self-assembly to prepare metal–organic capsules from simple building blocks via the simultaneous formation of dynamic coordinative (N→metal) and covalent (N═C) bonds Design strategies employ multidentate pyridyl–imine ligands to define either the edges or the faces of polyhedral structures Octahedral metal ions, such as FeII, CoII, NiII, ZnII, and CdII, constitute the vertices The generality of this technique has enabled the preparation of capsules with diverse three-dimensional structures This Account highlights how fundamental investigati
TL;DR: A photoswitchable "Band-Aid"-like hydrogel doped with artificial enzymes was developed for efficiently killing bacteria without compromising mammal cell proliferation, which was promising for accelerating wound healing and is expected to boost the development of artificial enzymes with different formulations as novel antibacterial agents for clinical and industrial applications.
Abstract: ConspectusBacterial infection continues to be a growing global health problem with the most widely accepted treatment paradigms restricted to antibiotics. However, antibiotics overuse and misuse have triggered increased multidrug resistance, frustrating the therapeutic outcomes and leading to higher mortalities. Even worse, the tendency of bacteria to form biofilms on living and nonliving surfaces further increases the difficulty in confronting bacteria because the extracellular matrix can act as a robust barrier to prevent the penetration of antibiotics and resist environmental stress. As a result, the inability to completely eliminate bacteria and biofilms often leads to persistent infection, implant failure, and device damage. Therefore, it is of paramount importance to develop alternative antimicrobial agents while avoiding the generation of bacterial resistance. Taking lessons from natural enzymes for destroying cellular structural integrity or interfering with metabolisms such as proliferation, quor...
TL;DR: Main factors that need to be considered for the design of a conjugated polymer for applications in bioelectronics are highlighted, although there can be various figures of merit given the broad range of applications, as emphasized in this Account.
Abstract: ConspectusThe emerging field of organic bioelectronics bridges the electronic world of organic-semiconductor-based devices with the soft, predominantly ionic world of biology. This crosstalk can occur in both directions. For example, a biochemical reaction may change the doping state of an organic material, generating an electronic readout. Conversely, an electronic signal from a device may stimulate a biological event. Cutting-edge research in this field results in the development of a broad variety of meaningful applications, from biosensors and drug delivery systems to health monitoring devices and brain–machine interfaces. Conjugated polymers share similarities in chemical “nature” with biological molecules and can be engineered on various forms, including hydrogels that have Young’s moduli similar to those of soft tissues and are ionically conducting. The structure of organic materials can be tuned through synthetic chemistry, and their biological properties can be controlled using a variety of funct...
TL;DR: This Account describes the development of coinage metal nanoclusters protected with alkynyl ligands, and presents the direct reduction method for the synthesis of the following four categories ofnanoclusters: gold nanocluster with mixed-ligand shells, all alkyny-protected gold nanocusters, (c) heterobimetallic gold Nanoclusters, and (d) silver nanocl clusters.
Abstract: ConspectusThe past decades have witnessed great advances in the synthesis, structure determination, and properties investigation of coinage metal nanoclusters. These monodisperse clusters have well...
TL;DR: This Account describes efforts at focusing down into mechanical properties of organic molecular crystals from the viewpoint of crystal engineering, which is the synthesis and design of functional molecular solids and presents examples where complex properties may be deliberately turned on or off in organic crystals.
Abstract: ConspectusMechanical properties of organic molecular crystals have been noted and studied over the years but the complexity of the subject and its relationship with diverse fields such as mechanochemistry, phase transformations, polymorphism, and chemical, mechanical, and materials engineering have slowed understanding. Any such understanding also needs conceptual advances—sophisticated instrumentation, computational modeling, and chemical insight—lack of such synergy has surely hindered progress in this important field. This Account describes our efforts at focusing down into this interesting subject from the viewpoint of crystal engineering, which is the synthesis and design of functional molecular solids. Mechanical properties of soft molecular crystals imply molecular movement within the solid; the type of property depends on the likelihood of such movement in relation to the applied stress, including the ability of molecules to restore themselves to their original positions when the stress is removed...
TL;DR: A novel class of solid materials for adsorption and separation, nonporous adaptive crystals (NACs), which function at the supramolecular level are described, which will not only exert a significant influence on scientific research but also show practical applications in chemical industry.
Abstract: ConspectusPorous materials with high surface areas have drawn more and more attention in recent years because of their wide applications in physical adsorption and energy-efficient adsorptive separation processes. Most of the reported porous materials are macromolecular porous materials, such as zeolites, metal–organic frameworks (MOFs), or porous coordination polymers (PCPs), and porous organic polymers (POPs) or covalent organic frameworks (COFs), in which the building blocks are linked together by covalent or coordinative bonds. These materials are barely soluble and thus are not solution-processable. Furthermore, the relatively low chemical, moisture, and thermal stability of most MOFs and COFs cannot be neglected. On the other hand, molecular porous materials such as porous organic cages (POCs), which have been developed very recently, also show promising applications in adsorption and separation processes. They can be soluble in organic solvents, making them solution-processable materials. However, ...
TL;DR: The chemistry described here provides a practical approach to functionalize common amide and ester functional groups in organic synthesis and establishes straightforward access to acyl-metal intermediates that enable nonconventional cross-coupling strategies.
Abstract: ConspectusTransition-metal-catalyzed cross-coupling reactions represent a most powerful tool for the rapid construction of C–C and C–X bonds available to synthetic chemists. Recently, tremendous progress has been made in the burgeoning area of cross-coupling reactions of amides and esters enabled by regio- and chemoselective acyl C–X (X = N, O) cleavage using well-defined Pd(II)–NHC complexes. The use of N-heterocyclic carbenes as ligands in palladium-catalyzed cross-couplings permits reactions of amides and esters that were previously impossible using palladium or could be achieved only under harsh conditions. These reactions provide an attractive method to synthetic chemists to manipulate the traditionally inert amide and ester bonds with the broad cross-coupling generality inherent to palladium catalysis. Research in the area of cross-coupling of stable acyl electrophiles can be broadly categorized by the type of electrophile undergoing the cross-coupling. Recent studies have shown that cross-coupling ...
TL;DR: The phosphoramide-based bifunctional catalysts achieved better enantiofacial control than the analogous H-bond-donor-derived catalysts in these reactions, suggesting the potential of the former in new chiral catalyst development.
Abstract: Conspectus3,3-Disubstituted oxindoles are widely distributed in natural products, drugs, and pharmaceutically active compounds. The absolute configuration and the substituents on the fully substituted C3 stereocenter of the oxindole often significantly influence the biological activity. Therefore, tremendous efforts have made to develop catalytic enantioselective syntheses of this prominent structural motif. Research in this area is further fueled by the ever-increasing demand for modern probe- and drug-discovery programs for synthetic libraries of chiral compounds that are derived from privileged scaffolds with high structural diversity. Notably, the efficient construction of fully substituted C3 stereocenters of oxindole, tetrasubstituted or all-carbon quaternary, spirocyclic or not, also becomes a test ground for new synthetic methodologies.We have been engaged in developing efficient methods for diversity-oriented synthesis of chiral 3,3-disubstituted oxindoles from readily available starting material...
TL;DR: This Account will focus on the recent advance on construction of stimuli-responsive functional materials through HSA involving coordination interactions, which suggests that combining coordination and other NCIs in a well-defined and precise manner is a highly efficient strategy to achieve the complex architectures and functional materials.
Abstract: ConspectusSupramolecular self-assembly, which creates the ordered structures as a result of spontaneous organization of building blocks driven by noncovalent interactions (NCIs), is ubiquitous in nature. Recently, it has become increasingly clear that nature often builds up complex structures by employing a hierarchical self-assembly (HSA) strategy, in which the components are brought together in a stepwise process via multiple NCIs. Inspired by the dedicated biological structures in nature, HSA has been widely explored to construct well-defined assemblies with increasing complexity.The employment of direct metal–ligand bonds to drive the formation of discrete metallosupramolecular architectures has proven to be a highly efficient strategy to prepare structurally diverse architectures like two-dimensional (2-D) polygons and three-dimensional (3-D) polyhedra with well-defined shapes, sizes, and geometries. Such well-defined organometallic assemblies provide an ideal platform for designing novel artificial ...
TL;DR: Current knowledge of the fundamental electrochemical properties of MXenes is described and attempts to clarify where intercalation capacitance ends and intercalated pseudocapacitance begins.
Abstract: ConspectusThe development of efficient electrochemical energy storage (EES) devices is an important sustainability issue to realize green electrical grids. Charge storage mechanisms in present EES devices, such as ion (de)intercalation in lithium-ion batteries and electric double layer formation in capacitors, provide insufficient efficiency and performance for grid use. Intercalation pseudocapacitance (or redox capacitance) has emerged as an alternative chemistry for advanced EES devices. Intercalation pseudocapacitance occurs through bulk redox reactions with ultrafast ion diffusion. In particular, the metal carbide/nitride nanosheets termed MXene discovered in 2011 are a promising class of intercalation pseudocapacitor electrode materials because of their compositional versatility for materials exploration (e.g., Ti2CTx, Ti3C2Tx, V2CTx, and Nb2CTx, where T is a surface termination group such as F, Cl, O, or OH), high electrical conductivity for high current charge, and a layered structure of stacked na...
TL;DR: The significant progress made in the field of nanoporous metal designed through electrochemical deposition approaches using hard templates and soft templates is described, pointing out how it accounts for precise control over the crystal growth and describe the unique physical and chemical properties emerging from these novel materials.
Abstract: ConspectusWell-constructed porous materials take an essential role in a wide range of applications, including energy conversion and storage systems, electrocatalysis, photocatalysis, and sensing. Although the tailored design of various nanoarchitectures has made substantial progress, simpler preparation methods are compelled to meet large-scale production requirements. Recently, advanced electrochemical deposition techniques have had a significant impact in terms of precise control upon the nanoporous architecture (i.e., pore size, surface area, pore structure, etc.), enabling access to a wide range of compositions. In this Account, we showcase the uniqueness of electrochemical deposition techniques, detail their implementation toward the synthesis of novel nanoporous metals, and finally outline the future research directions.Nanoporous metallic structures are attractive in that they can provide high surface area and large pore volume, easing mass transport of reactants and providing high accessibility to...
TL;DR: Efforts to probe and developCopolymerizations of polar vinyl monomers with ethylene using more functional group-tolerant late metal catalysts potentially offer an attractive alternative for generating value-added copolymers since ligand variations may provide more control of polymer microstructures and milder reaction conditions would apply.
Abstract: ConspectusThe most ubiquitous polymer, polyethylene (PE), is produced either through a radical-initiated process or, more commonly, through a coordination/insertion process employing early transition metal catalysts, particularly titanium- and chromium-based systems. These oxophilic early metal catalysts are not functional-group-tolerant and thus cannot be used to synthesize copolymers of ethylene and polar vinyl monomers such as alkyl acrylates and vinyl acetate. Such PE copolymers have enhanced properties relative to PE and are made through radical polymerization processes, requiring exceptionally high pressures and temperatures. Copolymerizations of polar vinyl monomers with ethylene using more functional group-tolerant late metal catalysts potentially offer an attractive alternative for generating such value-added copolymers since ligand variations may provide more control of polymer microstructures and milder reaction conditions would apply. This Account describes our efforts, particularly through de...
TL;DR: This Account discusses how the incorporation of various metal atoms into existing protected nanoclusters tunes their structure and properties and presents an overview of atomic-level doping in metal clusters and its importance for enriching the chemistry and photophysics of clusters and extending their applications.
Abstract: ConspectusAtomically precise noble metal (mainly silver and gold) nanoclusters are an emerging category of promising functional materials for future applications in energy, sensing, catalysis, and nanoelectronics. These nanoclusters are protected by ligands such as thiols, phosphines, and hydride and have sizes between those of atoms and plasmonic nanoparticles. In metallurgy, the properties of a pure metal are modified by the addition of other metals, which often offers augmented characteristics, making them more utilizable for real-life applications. In this Account, we discuss how the incorporation of various metal atoms into existing protected nanoclusters tunes their structure and properties.The process of incorporating metals into an existing cluster is known as doping; the product is known as a doped cluster, and the incorporated metal atom is called a dopant/foreign atom. We first present a brief historical overview of protected clusters and the need for doping and explain (with examples) the diff...