Search

Over the last fifty years, the use of nickel catalysts for facilitating organic transformations has skyrocketed. Nickel(0) sources act as useful precatalysts because they can enter a catalytic cycle through ligand exchange, without needing to undergo additional elementary steps. However, most Ni(0) precatalysts are synthesized with stoichiometric aluminum–hydride reductants, pyrophoric reagents that are not atom‐economical and must be used at cryogenic temperatures. Here, we demonstrate that Ni(II) salts can be reduced on preparative scale using electrolysis to yield a variety of Ni(0) and Ni(II) complexes that are widely used as precatalysts in organic synthesis, including bis(1,5‐cyclooctadiene)nickel(0) [Ni(COD)2]. This method overcomes the reproducibility issues of previously reported methods by standardizing the procedure, such that it can be performed anywhere in a robust manner. It can be transitioned to large scale through an electrochemical recirculating flow process and extended to an in situ reduction protocol to generate catalytic amounts of Ni(0) for organic transformations. We anticipate that this work will accelerate adoption of preparative electrochemistry for the synthesis of low‐valent organometallic complexes in academia and industry. [ABSTRACT FROM AUTHOR]

Self‐assembly of proteinaceous biomolecules into functional materials with ordered structures that span length scales is common in nature yet remains a challenge with designer peptides under ambient conditions. This report demonstrates how charged side‐chain chemistry affects the hierarchical co‐assembly of a family of charge‐complementary β‐sheet‐forming peptide pairs known as CATCH(X+/Y−) at physiologic pH and ionic strength in water. In a concentration‐dependent manner, the CATCH(6K+) (Ac‐KQKFKFKFKQK‐Am) and CATCH(6D−) (Ac‐DQDFDFDFDQD‐Am) pair formed either β‐sheet‐rich microspheres or β‐sheet‐rich gels with a micron‐scale plate‐like morphology, which were not observed with other CATCH(X+/Y−) pairs. This hierarchical order was disrupted by replacing D with E, which increased fibril twisting. Replacing K with R, or mutating the N‐ and C‐terminal amino acids in CATCH(6K+) and CATCH(6D−) to Qs, increased observed co‐assembly kinetics, which also disrupted hierarchical order. Due to the ambient assembly conditions, active CATCH(6K+)‐green fluorescent protein fusions could be incorporated into the β‐sheet plates and microspheres formed by the CATCH(6K+/6D−) pair, demonstrating the potential to endow functionality. [ABSTRACT FROM AUTHOR]

Creation of intrapenetrated mesopores with open highway from external surface into the interior of zeolite crystals are highly desirable that can significantly improve the molecular transport and active sites accessibility of microporous zeolites to afford enhanced catalytic properties. Here, different from traditional zeolite‐seeded methods that generally produced isolated mesopores in zeolites, nanosized amorphous protozeolites with embryo structure of zeolites were used as seeds for the construction of single‐crystalline hierarchical ZSM‐5 zeolites with intrapenetrated mesopores (mesopore volume of 0.51 cm3 g−1) and highly complete framework. In this strategy, in contrast to the conventional synthesis, only a small amount of organic structure directing agents and a low crystallization temperature were adopted to promise the protozeolites as the dominant growth directing sites to induce crystallization. The protozeolite nanoseeds provided abundant nucleation sites for surrounding precursors to be crystallized, followed by oriented coalescence of crystallites resulting in the formation of intrapenetrated mesopores. The as‐prepared hierarchical ZSM‐5 zeolites exhibited ultra‐long lifetime of 443.9 hours and a high propylene selectivity of 47.92 % at a WHSV of 2 h−1 in the methanol‐to‐propylene reaction. This work provides a facile protozeolite‐seeded strategy for the synthesis of intrapenetrated hierarchical zeolites that are highly effective for catalytic applications. [ABSTRACT FROM AUTHOR]

The need of carbon sources for the chemical industry, alternative to fossil sources, has pointed to CO2 as a possible feedstock. While CO2 electroreduction (CO2R) allows production of interesting organic compounds, it suffers from large carbon losses, mainly due to carbonate formation. This is why, quite recently, tandem CO2R, a two‐step process, with first CO2R to CO using a solid oxide electrolysis cell followed by CO electroreduction (COR), has been considered, since no carbon is lost as carbonate in either step. Here we report a novel copper‐based catalyst, silver‐doped copper nitride, with record selectivity for formation of propanol (Faradaic efficiency: 45 %), an industrially relevant compound, from CO electroreduction in gas‐fed flow cells. Selective propanol formation occurs at metallic copper atoms derived from copper nitride and is promoted by silver doping as shown experimentally and computationally. In addition, the selectivity for C2+ liquid products (Faradaic efficiency: 80 %) is among the highest reported so far. These findings open new perspectives regarding the design of catalysts for production of C3 compounds from CO2. [ABSTRACT FROM AUTHOR]

Ternary Pd‐In2O3/ZrO2 catalysts exhibit technological potential for CO2‐based methanol synthesis, but developing scalable systems and comprehending complex dynamic behaviors of the active phase, promoter, and carrier are key for achieving high productivity. Here, we show that the structure of Pd‐In2O3/ZrO2 systems prepared by wet impregnation evolves under CO2 hydrogenation conditions into a selective and stable architecture, independent of the order of addition of Pd and In phases on the zirconia carrier. Detailed operando characterization and simulations reveal a rapid restructuring driven by the metal‐metal oxide interaction energetics. The proximity of InPdx alloy particles decorated by InOx layers in the resulting architecture prevents performance losses associated with Pd sintering. The findings highlight the crucial role of reaction‐induced restructuring in complex CO2 hydrogenation catalysts and offer insights into the optimal integration of acid‐base and redox functions for practical implementation. [ABSTRACT FROM AUTHOR]

Photo‐assisted reverse water gas shift (RWGS) reaction is regarded green and promising in controlling the reaction gas ratio in Fischer Tropsch synthesis. But it is inclined to produce more byproducts in high H2 concentration condition. Herein, LaInO3 loaded with Ni‐nanoparticles (Ni NPs) was designed to obtain an efficient photothermal RWGS reaction rate, where LaInO3 was enriched with oxygen vacancies to roundly adsorbing CO2 and the strong interaction with Ni NPs endowed the catalysts with powerful H2 activity. The optimized catalyst performed a large CO yield rate (1314 mmol gNi−1 h−1) and ≈100 % selectivity. In situ characterizations demonstrated a COOH* pathway of the reaction and photoinduced charge transfer process for reducing the RWGS reaction active energy. Our work provides valuable insights on the construction of catalysts concerning products selectivity and photoelectronic activating mechanism on CO2 hydrogenation. [ABSTRACT FROM AUTHOR]

Chiral inorganic superstructures have received considerable interest due to the chiral communication between inorganic compounds and chiral organic additives. However, the demanding fabrication and complex multilevel structure seriously hinder the understanding of chiral transfer and self‐assembly mechanisms. Herein, we use chiral CuO superstructures as a model system to study the formation process of hierarchical chiral structures. Based on a simple and mild synthesis route, the time‐resolved morphology and the in situ chirality evolution could be easily followed. The morphology evolution of the chiral superstructure involves hierarchical assembly, including primary nanoparticles, intermediate bundles, and superstructure at different growth stages. Successive redshifts and enhancements of the CD signal support chiral transfer from the surface penicillamine to the inorganic superstructure. Full‐field electro‐dynamical simulations reproduced the structural chirality and allowed us to predict its modulation. This work opens the door to a large family of chiral inorganic materials where chiral molecule‐guided self‐assembly can be specifically designed to follow a bottom‐up chiral transfer pathway. [ABSTRACT FROM AUTHOR]

Bicyclo[1.1.1]pentane (BCP) motifs are of growing importance to the pharmaceutical industry as sp3‐rich bioisosteres of benzene rings and as molecular building blocks in materials science. Herein we explore the behavior of 1,3‐disubstituted BCP moieties on metal surfaces by combining low‐temperature scanning tunneling microscopy / non‐contact atomic force microscopy studies with density functional theory modeling. We examine the configuration of individual BCP‐containing precursors on Au(111), their supramolecular assembly and thermally activated dehalogenative coupling reactions, affording polymeric chains with incorporated electronically isolating units. Our studies not only provide the first sub‐molecular insights of the BCP scaffold behavior on surfaces, but also extend the potential application of BCP derivatives towards integration in custom‐designed surface architectures. [ABSTRACT FROM AUTHOR]

In the last decade, major advances have been made in homogeneous gold catalysis. However, AuI/AuIII catalytic cycle remains much less explored due to the reluctance of AuI to undergo oxidative addition and the stability of the AuIII intermediate. Herein, we report activation of aryl halides at gold(I) enabled by NHC (NHC=N‐heterocyclic carbene) ligands through the development of a new class of L‐shaped heterobidentate ImPy (ImPy=imidazo[1,5‐a]pyridin‐3‐ylidene) N,C ligands that feature hemilabile character of the amino group in combination with strong σ‐donation of the carbene center in a rigid conformation, imposed by the ligand architecture. Detailed characterization and control studies reveal key ligand features for AuI/AuIII redox cycle, wherein the hemilabile nitrogen is placed at the coordinating position of a rigid framework. Given the tremendous significance of homogeneous gold catalysis, we anticipate that this ligand platform will find widespread application. [ABSTRACT FROM AUTHOR]

We report here computational evidence for a metalla‐Claisen rearrangement (MCR) in the case of gold‐catalyzed [4+2] cycloaddition reaction of yne‐dienes. The [4+2] reaction starts from exo cyclopropanation, followed by MCR and reductive elimination. The cyclopropane moiety formed in the first step is crucial for a low barrier of the MCR step. In addition, the importance of an appropriate combination of the tether group and the terminal substituent on alkyne in the yne‐diene substrates was studied. The mechanism of rhodium‐catalyzed [4+2] reaction of yne‐dienes was also investigated to see whether an MCR mechanism is involved or not. The findings and new understanding hereby reported represent an important advance in the catalysis field. [ABSTRACT FROM AUTHOR]

The cathode materials work as the host framework for both Li+ diffusion and electron transport in Li‐ion batteries. The Li+ diffusion property is always the research focus, while the electron transport property is less studied. Herein, we propose a unique strategy to elevate the rate performance through promoting the surface electric conductivity. Specifically, a disordered rock‐salt phase was coherently constructed at the surface of LiCoO2, promoting the surface electric conductivity by over one magnitude. It increased the effective voltage (Veff) imposed in the bulk, thus driving more Li+ extraction/insertion and making LiCoO2 exhibit superior rate capability (154 mAh g−1 at 10 C), and excellent cycling performance (93 % after 1000 cycles at 10 C). The universality of this strategy was confirmed by another surface design and a simulation. Our findings provide a new angle for developing high‐rate cathode materials by tuning the surface electron transport property. [ABSTRACT FROM AUTHOR]

Protein and peptide drugs are predominantly administered by injection to achieve high bioavailability, but this greatly compromises patient compliance. Oral and transdermal drug delivery with minimal invasiveness and high adherence represent attractive alternatives to injection administration. However, oral and transdermal administration of bioactive proteins must overcome biological barriers, namely the gastrointestinal and skin barriers, respectively. The rapid development of new materials and technologies promises to address these physiological obstacles. This review provides an overview of the latest advances in oral and transdermal protein delivery, including chemical strategies, synthetic nanoparticles, medical microdevices, and biomimetic systems for oral administration, as well as chemical enhancers, physical approaches, and microneedles in transdermal delivery. We also discuss challenges and future perspectives of the field with a focus on innovation and translation. [ABSTRACT FROM AUTHOR]

We have employed in situ electrochemical shell‐isolated nanoparticle‐enhanced Raman spectroscopy (SHINERS) and density functional theory (DFT) calculations to study the CO reduction reaction (CORR) on Cu single‐crystal surfaces under various conditions. Coadsorbed and structure‐/potential‐dependent surface species, including *CO, Cu−Oad, and Cu−OHad, were identified using electrochemical spectroscopy and isotope labeling. The relative abundance of *OH follows a "volcano" trend with applied potentials in aqueous solutions, which is yet absent in absolute alcoholic solutions. Combined with DFT calculations, we propose that the surface H2O can serve as a strong proton donor for the first protonation step in both the C1 and C2 pathways of CORR at various applied potentials in alkaline electrolytes, leaving adsorbed *OH on the surface. This work provides fresh insights into the initial protonation steps and identity of key interfacial intermediates formed during CORR on Cu surfaces. [ABSTRACT FROM AUTHOR]

Laboratory‐based X‐ray absorption spectroscopy (XAS) and especially X‐ray absorption near‐edge structure (XANES) offers new opportunities in catalyst characterization and presents not only an alternative, but also a complementary approach to precious beamtime at synchrotron facilities. We successfully designed a laboratory‐based setup for performing operando, quasi‐simultaneous XANES analysis at multiple K‐edges, more specifically, operando XANES of mono‐, bi‐, and trimetallic CO2 hydrogenation catalysts containing Ni, Fe, and Cu. Detailed operando XANES studies of the multielement solid catalysts revealed metal‐dependent differences in the reducibility and re‐oxidation behavior and their influence on the catalytic performance in CO2 hydrogenation. The applicability of operando laboratory‐based XANES at multiple K‐edges paves the way for advanced multielement catalyst characterization complementing detailed studies at synchrotron facilities. [ABSTRACT FROM AUTHOR]

An efficient catalytic asymmetric [2+2] cycloaddition of allenyl imide and mono‐ or disubstituted alkenes is disclosed. The key feature of this method is the use of bidentate allenyl imide and weakly activated and less steric hindered alkene pair by utilizing chiral magnesium(II) complex of N,N′‐dioxide, which could provide through‐space dispersion interactions to orientate the arrangement of the alkene. This protocol allows the generation of a series of axially chiral cyclobutenes and four‐membered ring‐containing spirocycles (80 examples) in high yield (up to 99 %) with excellent enantioselectivity (up to >99 % ee), and the late‐stage modification of biologically active molecules as well. Experimental studies and DFT calculations revealed that this [2+2] cycloaddition proceeded via a stepwise mechanism involving a short‐lived zwitterionic intermediate. The π‐π interaction between the alkenes and the amide moiety in the ligand was crucial for the enantiocontrol. [ABSTRACT FROM AUTHOR]

Rather than just focusing on the catalyst itself in the electrocatalytic CO2 reduction reaction (eCO2RR), as previously reviewed elsewhere, we herein extend the discussion to the special topic of the microenvironment around the electrocatalytic center and present a comprehensive overview of recent research progress. We categorize the microenvironment based on the components relevant to electrocatalytic active sites, i.e. the catalyst surface, substrate, co‐reactants, electrolyte, membrane, and reactor. Supported by most of the reported articles, the relevant factors affecting the catalytic performance of eCO2RR are then discussed in detail, and existing challenges and potential solutions are mentioned. Perspectives for the future research on eCO2RR, including the integration of different microenvironment factors, the extension to industrial application by coupling with carbon capture and conversion, and separation of products, are also discussed. [ABSTRACT FROM AUTHOR]

Strained rings are increasingly important for the design of pharmaceutical candidates, but cross‐coupling of strained rings remains challenging. An attractive, but underdeveloped, approach to diverse functionalized carbocyclic and heterocyclic frameworks containing all‐carbon quaternary centers is the coupling of abundant strained‐ring carboxylic acids with abundant aryl halides. Herein we disclose the development of a nickel‐catalyzed cross‐electrophile approach that couples a variety of strained ring N‐hydroxyphthalimide (NHP) esters, derived from the carboxylic acid in one step, with various aryl and heteroaryl halides under reductive conditions. The chemistry is enabled by the discovery of methods to control NHP ester reactivity, by tuning the solvent or using modified NHP esters, and the discovery that t‐BuBpyCamCN, an L2X ligand, avoids problematic side reactions. This method can be run in flow and in 96‐well plates. [ABSTRACT FROM AUTHOR]

We present an experimental and computational study on the conformers of N,N′‐diphenylthiourea substituted with different dispersion energy donor (DED) groups. While the unfolded anti–anti conformer is the most relevant for thiourea catalysis, intramolecular noncovalent interactions counterintuitively favor the folded syn–syn conformer, as evident from a combination of low‐temperature nuclear magnetic resonance measurements and computations. In order to quantify the noncovalent interactions, we utilized local energy decomposition analysis and symmetry‐adapted perturbation theory at the DLPNO‐CCSD(T)/def2‐TZVPP and sSAPT0/6‐311G(d,p) levels of theory. Additionally, we applied a double‐mutant cycle to experimentally study the effects of bulky substituents on the equilibria. We determined London dispersion as the key interaction that shifts the equilibria towards the syn–syn conformers. This preference is likely a factor why such thiourea derivatives can be poor catalysts. [ABSTRACT FROM AUTHOR]

Understanding the bonding of gold(I) species has been central to the development of gold(I) catalysis. Herein, we present the synthesis and characterization of the first gold(I)‐cyclobutadiene complex, accompanied with bonding analysis by state‐of‐the‐art energy decomposition analysis methods. Analysis of possible coordination modes for the new species not only confirms established characteristics of gold(I) bonding, but also suggests that Pauli repulsion is a key yet hitherto overlooked element. Additionally, we obtain a new perspective on gold(I)‐bonding by comparison of the gold(I)‐cyclobutadiene to congeners stabilized by p‐, d‐, and f‐block metals. Consequently, we refine the gold(I) bonding model, with a delicate interplay of Pauli repulsion and charge transfer as the key driving force for various coordination motifs. Pauli repulsion is similarly determined as a significant interaction in AuI‐alkyne species, corroborating this revised understanding of AuI bonding. [ABSTRACT FROM AUTHOR]

The impermeable barriers of solid tumors restrict the co‐delivery of protein‐based drugs and chemotherapeutics for cancer treatment. Therefore, we developed a ZIF‐DOX/RA@DG nanosystem that encapsulates ribonuclease A (RA) and doxorubicin (DOX) in a zeolitic imidazolate framework (ZIF‐8) core, with a dextran‐based coating (DG). The nanosystem exhibits dual‐responsiveness due to γ‐glutamyl transpeptidase‐activatable cationization and acidic microenvironment‐triggered degradation. The DG‐coating process was achieved using a microfluidic approach, which stabilized the polymer responsiveness, ZIF‐8‐based structure, and bioactivity of the encapsulated therapeutics. In vivo results confirmed that the nanosystem could co‐deliver RA and DOX to deep impermeable lesions with a synergistic anticancer therapeutic effects. Such a multi‐drug delivery system based on an intelligent‐responsive design and a microfluidics‐assisted synthesis strategy shows great clinical prospects. [ABSTRACT FROM AUTHOR]

We demonstrate catalytic organic synthesis by Resonant Acoustic Mixing (RAM): a mechanochemical methodology that does not require bulk solvent or milling media. Using as model reactions ruthenium‐catalyzed ring‐closing metathesis and copper‐catalyzed sulfonamide‐isocyanate coupling, RAM mechanosynthesis is shown to be faster, operationally simpler than conventional ball‐milling, while also providing the first example of a mechanochemical strategy for ruthenium‐catalyzed ene‐yne metathesis. Reactions by RAM are readily and directly scaled‐up without any significant changes in reaction conditions, as shown by the straightforward 200‐fold scaling‐up of the synthesis of the antidiabetic drug Tolbutamide, from hundreds of milligrams directly to 30 grams. [ABSTRACT FROM AUTHOR]

A formal CH2−CH2 homologation conducted with C1 carbenoids on a carbon electrophile for the obtainment of a four‐membered cycle is reported. The logic proposes the consecutive delivery of two single nucleophilic CH2 units to an isothiocyanate—as competent electrophilic partner—resulting in the assembling of a rare imino‐thietane cluster. The single synthetic operation procedure documents genuine chemocontrol, as indicated by the tolerance to various reactive elements decorating the starting materials. Significantly, the double homologation protocol is accomplished directly on a carbon electrophile, thus not requiring the installation of heteroatom‐centered manifolds (e.g. boron). [ABSTRACT FROM AUTHOR]

Reducing CO2 to long‐chain carbon products is attractive considering such products are typically more valuable than shorter ones. However, the best electrocatalyst for making such products from CO2, copper, lacks selectivity. By studying alternate C2+ producing catalysts we can increase our mechanistic understanding, which is beneficial for improving catalyst performance. Therefore, we investigate CO reduction on silver, as density functional theory (DFT) results predict it to be good at forming ethanol. To address the current disagreement between DFT and experimental results (ethanol vs. no ethanol), we investigated CO reduction at higher surface coverage (by increasing pressure) to ascertain if desorption effects can explain the discrepancy. In terms of product trends, our results agree with the DFT‐proposed acetaldehyde‐like intermediate, yielding ethanol and propanol as C2+ products—making the CO2 electrochemistry of silver very similar to that of copper at sufficiently high coverage. [ABSTRACT FROM AUTHOR]

We report herein a new family of carbene ligands based on an indolizine‐ylidene (Indolizy) moiety. The corresponding gold(I) complexes are easily obtained from the gold(I)‐promoted cyclization of allenylpyridine precursors. Evaluation of the electronic properties by experimental methods and also by DFT calculations confirms strong σ‐donating and π‐accepting properties of these ligands. Cationization of the gold(I) complexes generates catalytic species that trigger diverse reactions of (poly)unsaturated precursors. When armed with a methylene phosphine oxide moiety on the stereogenic center adjacent to the nitrogen atom, the corresponding bifunctional carbene ligands give rise to highly enantioselective heterocyclizations. DFT calculations brought some rationalization and highlighted the critical roles played by the phosphine oxide group and the tosylate anion in the asymmetric cyclization of γ‐allenols. [ABSTRACT FROM AUTHOR]

Single‐atom metal‐insulator‐semiconductor (SMIS) heterojunctions based on Sn‐doped Fe2O3 nanorods (SF NRs) were designed by combining atomic deposition of an Al2O3 overlayer with chemical grafting of a RuOx hole‐collector for efficient CO2‐to‐syngas conversion. The RuOx‐Al2O3‐SF photoanode with a 3.0 nm thick Al2O3 overlayer gave a >5‐fold‐enhanced IPCE value of 52.0 % under 370 nm light irradiation at 1.2 V vs. Ag/AgCl, compared to the bare SF NRs. The dielectric field mediated the charge dynamics at the Al2O3/SF NRs interface. Accumulation of long‐lived holes on the surface of the SF NRs photoabsorber aids fast tunneling transfer of hot holes to single‐atom RuOx species, accelerating the O2‐evolving reaction kinetics. The maximal CO‐evolution rate of 265.3 mmol g−1 h−1 was achieved by integration of double SIMS‐3 photoanodes with a single‐atom Ni‐doped graphene CO2‐reduction‐catalyst cathode; an overall quantum efficiency of 5.7 % was recorded under 450 nm light irradiation. [ABSTRACT FROM AUTHOR]

Ni‐promoted electrocatalytic biomass reforming has shown promising prospect in enabling high value‐added product synthesis. Here, we developed a novel hybrid catalyst with Ni nanosheet forests anchored on carbon paper. The hybrid catalyst exhibits high efficiency in electrooxidation of HMF to FDCA coupling with H2 production in high purity. The Ni nanosheets have small crystal grain sizes with abundant edges, which is able to deliver an efficient HMF oxidation to FDCA (selectivity >99 %) at low potential of 1.36 VRHE with high stability. The post‐reaction structure analysis reveals the Ni nanosheets would transfer electrons to carbon and readily turn into NiOx and Ni(OH)x during the reaction. DFT results suggest high valence Ni species would facilitate the chemical adsorption (activation) of HMF revealing the reaction pathway. This work emphasizes the importance of the precise control of Ni activity via atomic structure engineering. [ABSTRACT FROM AUTHOR]

Electrochemical carbon dioxide (CO2) reduction reaction (CO2RR) is an attractive approach to deal with the emission of CO2 and to produce valuable fuels and chemicals in a carbon‐neutral way. Many efforts have been devoted to boost the activity and selectivity of high‐value multicarbon products (C2+) on Cu‐based electrocatalysts. However, Cu‐based CO2RR electrocatalysts suffer from poor catalytic stability mainly due to the structural degradation and loss of active species under CO2RR condition. To date, most reported Cu‐based electrocatalysts present stabilities over dozens of hours, which limits the advance of Cu‐based electrocatalysts for CO2RR. Herein, a porous chlorine‐doped Cu electrocatalyst exhibits high C2+ Faradaic efficiency (FE) of 53.8 % at −1.00 V versus reversible hydrogen electrode (VRHE). Importantly, the catalyst exhibited an outstanding catalytic stability in long‐term electrocatalysis over 240 h. Experimental results show that the chlorine‐induced stable cationic Cu0/Cu+ species and the well‐preserved structure with abundant active sites are critical to the high FE of C2+ in the long‐term run of electrochemical CO2 reduction. [ABSTRACT FROM AUTHOR]

High roughness has been proved to be an effective design strategy for electrocatalyst in many systems. Especially, high selectivity of carbon monoxide reduction (CORR) in competition with the hydrogen evolution reaction has been observed on high roughness electrocatalysts. However, the two well‐known mechanisms, i.e., decreasing the energy barrier of CORR and increasing local pH, failed to understand the roughness‐enhanced selectivity in a recent experiment. Herein we unravel the hidden mechanism by establishing a comprehensive kinetic model for CORR on catalysts with different roughness factors. We conclude that the roughness‐enhanced CORR selectivity is actually kinetic controlled by local‐electric‐field‐directed mass transfer of adsorbed species on the electrode surface. Several ways to optimize CORR selectivity are predicted. Our work highlights the kinetics in electrocatalysis on nanocatalysts, and provides a conceptually new principle for future catalyst design. [ABSTRACT FROM AUTHOR]

The design and synthesis of a novel rotaxane/foldaxane hybrid architecture is reported. The winding of an aromatic oligoamide helix host around a dumbbell‐shaped thread‐like guest, or axle, already surrounded by a macrocycle was evidenced by NMR spectroscopy and X‐ray crystallography. The process proved to depend on the position of the macrocycle along the axle and the associated steric hindrance. The macrocycle thus behaves as a switchable shield that modulates the affinity of the helix for the axle. Reciprocally, the foldamer helix acts as a supramolecular auxiliary that compartmentalizes the axle. In some cases, the macrocycle is forced to move along the axle to allow the foldamer to reach its best recognition site. [ABSTRACT FROM AUTHOR]

The direct dehydrogenation of alkanes is among the most efficient ways to access valuable alkene products. Although several catalysts have been designed to promote this transformation, they have unfortunately found limited applications in fine chemical synthesis. Here, we report a conceptually novel strategy for the catalytic, intermolecular dehydrogenation of alkanes using a ruthenium catalyst. The combination of a redox‐active ligand and a sterically hindered aryl radical intermediate has unleashed this novel strategy. Importantly, mechanistic investigations have been performed to provide a conceptual framework for the further development of this new catalytic dehydrogenation system. [ABSTRACT FROM AUTHOR]

The formal (4+3) cycloaddition of 1,3‐dienes with Rh(II) and Au(I) non‐acceptor vinyl carbenes, generated from vinylcycloheptatrienes or alkoxyenynes, respectively, leads to 1,4‐cycloheptadienes featuring complex and diverse substitution patterns, including natural dyctiopterene C′ and a hydroxylated derivative of carota‐1,4‐diene. A complete mechanistic picture is presented, in which Au(I) and Rh(II) non‐acceptor vinyl carbenes were shown to undergo a vinylcyclopropanation/Cope rearrangement or a direct (4+3) cycloaddition that takes place in a non‐concerted manner. [ABSTRACT FROM AUTHOR]

Photochemistry is a fascinating branch of chemistry that is concerned with molecules and light. However, the importance of simulating light‐induced processes is reflected also in fields as diverse as biology, material science, and medicine. This Minireview highlights recent progress achieved in theoretical chemistry to calculate electronically excited states of molecules and simulate their photoinduced dynamics, with the aim of reaching experimental accuracy. We focus on emergent methods and give selected examples that illustrate the progress in recent years towards predicting complex electronic structures with strong correlation, calculations on large molecules, describing multichromophoric systems, and simulating non‐adiabatic molecular dynamics over long time scales, for molecules in the gas phase or in complex biological environments. [ABSTRACT FROM AUTHOR]

There are a large number of zeolites, such as ITH, that cannot be prepared in the aluminosilicate form. Now, the successful synthesis of aluminosilicate ITH zeolite using a simple cationic oligomer as an organic template is presented. Key to the success is that the cationic oligomer has a strong complexation ability with aluminum species combined with a structural directing ability for the ITH structure similar to that of the conventional organic template. The aluminosilicate ITH zeolite has very high crystallinity, nanosheet‐like crystal morphology, large surface area, fully four‐coordinated Al species, and abundant acidic sites. Methanol‐to‐propylene (MTP) tests reveal that the Al‐ITH zeolite shows much higher selectivity for propylene and longer lifetime than commercial ZSM‐5. FCC tests show that Al‐ITH zeolite is a good candidate as a shape‐selective FCC additive for enhancing propylene and butylene selectivity. [ABSTRACT FROM AUTHOR]

Resilient and compressible three‐dimensional nanomaterials comprising polymers, carbon, and metals have been prepared in diverse forms. However, the creation of thermostable elastic ceramic aerogels remains an enormous challenge. We demonstrate an in situ synthesis strategy to develop biomimetic silica nanofibrous (SNF) aerogels with superelasticity by integrating flexible electrospun silica nanofibers and rubber‐like Si−O−Si bonding networks. The stable bonding structure among nanofibers is in situ constructed along with a fibrous freeze‐shaping process. The resultant SNF aerogels exhibit integrated properties of ultralow density (>0.25 mg cm−3), temperature‐invariant superelasticity up to 1100 °C, and robust fatigue resistance over one million compressions. The ceramic nature also endows the aerogels with fire resistance and ultralow thermal conductivity. The successful synthesis of the SNF aerogels opens new pathways for the design of superelastic ceramic aerogels in a structurally adaptive and scalable form. [ABSTRACT FROM AUTHOR]

A family of cationic boron complexes was synthesized, using a dianilidopyridine pincer ligand, which imposes in‐plane distortion of the geometry at boron towards T‐shaped. Reactivity of these cations toward hydride and base was investigated, and the utility of these cations as precursors to a variety of π‐conjugated BN heterocycles was demonstrated. 300 nm irradiation of a deprotonated pincer boron complex triggered a C−N cleavage/C−C formation yielding a dearomatized boryl imine, which has a structure akin to the long‐proposed intermediate in the photochemical Hofmann–Martius rearrangement. The photo‐rearrangement triggers relief of the distortion imposed by the pincer ligand. [ABSTRACT FROM AUTHOR]

The gold(I)‐catalyzed reaction of acetylene gas with alkenes leads to (Z,Z)‐1,4‐disubstituted 1,3‐butadienes and biscyclopropanes depending on the donor ligand on gold(I). Acetylene was generated in situ from calcium carbide and water in a user‐friendly procedure. Reaction of acetylene with 1,5‐dienes gives rise stereoselectively to tricyclo[5.1.0.02,4]octanes. This novel double cyclopropanation has been applied to the one step total synthesis of the natural product waitziacuminone from acetylene and geranyl acetone. [ABSTRACT FROM AUTHOR]

Tropylium bromide undergoes noncatalyzed, regioselective additions to a large variety of Michael acceptors. In this way, acrylic esters are converted into β‐bromo‐α‐cycloheptatrienylpropionic esters. The reactions are interpreted as nucleophilic attack of bromide ions at the electron‐deficient olefins and the approach of the tropylium ion to the incipient carbanion. Quantum chemical calculations were performed to elucidate the analogy to the amine‐ or phosphine‐catalyzed Rauhut–Currier reactions. Subsequent synthetic transformations of the bromo‐cycloheptatrienylated adducts are reported. [ABSTRACT FROM AUTHOR]

A novel nickel pincer cofactor was recently discovered in lactate racemase. Reported here are three synthetic nickel pincer complexes that are both structural and functional models of the pincer cofactor in lactate racemase. DFT computations suggest the ipso‐carbon atom of the pyridinium pincer ligands act as a hydride acceptor for lactate isomerization, whereas an organometallic pathway involving nickel‐mediated β‐hydride elimination is less favored. [ABSTRACT FROM AUTHOR]

Production of multicarbon products (C2+) from CO2 electroreduction reaction (CO2RR) is highly desirable for storing renewable energy and reducing carbon emission. The electrochemical synthesis of CO2RR catalysts that are highly selective for C2+ products via electrolyte‐driven nanostructuring is presented. Nanostructured Cu catalysts synthesized in the presence of specific anions selectively convert CO2 into ethylene and multicarbon alcohols in aqueous 0.1 m KHCO3 solution, with the iodine‐modified catalyst displaying the highest Faradaic efficiency of 80 % and a partial geometric current density of ca. 31.2 mA cm−2 for C2+ products at −0.9 V vs. RHE. Operando X‐ray absorption spectroscopy and quasi in situ X‐ray photoelectron spectroscopy measurements revealed that the high C2+ selectivity of these nanostructured Cu catalysts can be attributed to the highly roughened surface morphology induced by the synthesis, presence of subsurface oxygen and Cu+ species, and the adsorbed halides. [ABSTRACT FROM AUTHOR]

Given their great potential as new industrial catalysts and adsorbents, the search for new zeolite structures is of major importance in nanoporous materials chemistry. However, although innumerable theoretical frameworks have been proposed, none of them have been synthesized by a priori design yet. We generated a library of diazolium‐based cations inspired from the organic structure‐directing agents (OSDAs) recently reported to give two structurally related zeolites (PST‐21 and PST‐22) under highly concentrated, excess‐fluoride conditions and compared the stabilization energies of each OSDA cation in ten pre‐established hypothetical structures. A combination of the ability of the OSDA selected in this way with the excess‐fluoride approach has allowed us to crystallize PST‐30, the targeted aluminosilicate zeolite structure. We anticipate that our approach, which aims to rationally couple computational predictions of OSDAs with an experimental setup, will advance further development in the synthesis of zeolites with desired properties. [ABSTRACT FROM AUTHOR]

The polymorphic nature of G‐quadruplex (G4) DNA structures points to a range of potential applications in nanodevices and an opportunity to control G4 in biological settings. Light is an attractive means for the regulation of oligonucleotide structure as it can be delivered with high spatiotemporal precision. However, surprisingly little attention has been devoted towards the development of ligands for G4 that allow photoregulation of G4 folding. We report a novel G4‐binding chemotype derived from stiff‐stilbene. Surprisingly however, whilst the ligand induces high stabilization in the potassium form of human telomeric DNA, it causes the unfolding of the same G4 sequence in sodium buffer. This effect can be reversed on demand by irradiation with 400 nm light through deactivation of the ligand by photo‐oxidation. By fuelling the system with the photolabile ligand, the conformation of G4 DNA was switched five times. To fold or not to fold: A G‐quadruplex‐selective ligand derived from stiff‐stilbene strongly stabilises the potassium form of telomeric DNA, whilst causing the unfolding of the same sequence in sodium buffer. This effect can be reversed on demand by photoirradiation. [ABSTRACT FROM AUTHOR]

Rhodium carbenes are key intermediates in a range of cycloadditions and insertion reactions. Herein, we report the first generation of donor RhII carbenes by decarbenation of 7‐substituted 1,3,5‐cycloheptatrienes. This discovery unlocks an improved retro‐Buchner‐cyclopropanation sequence, a Si−H insertion reaction for a broad‐scope synthesis of allylsilanes, and a new method for the vinylogation of aldehydes. The last strategy led to the development of an iterative synthesis of E‐polyenes, and to the total synthesis of navenones B and C. Successful iteration: Donor rhodium(II) carbenes are generated by retro‐Buchner reaction (decarbenation) of 7‐substituted 1,3,5‐cycloheptatrienes, leading to broad‐scope synthesis of allylsilanes by Si−H insertion and a new method for the iterative vinylogation of aldehydes. [ABSTRACT FROM AUTHOR]

Abstract: A state‐of‐the‐art operando spectroscopic technique is applied to Co/TiO2 catalysts, which account for nearly half of the world's transportation fuels produced by Fischer–Tropsch catalysis. This allows determination of, at a spatial resolution of approximately 50 nm, the interdependence of formed hydrocarbon species in the inorganic catalyst. Observed trends show intra‐ and interparticular heterogeneities previously believed not to occur in particles under 200 μm. These heterogeneities are strongly dependent on changes in H2/CO ratio, but also on changes thereby induced on the Co and Ti valence states. We have captured the genesis of an active FTS particle over its propagation to steady‐state operation, in which microgradients lead to the gradual saturation of the Co/TiO2 catalyst surface with long chain hydrocarbons (i.e., organic film formation). [ABSTRACT FROM AUTHOR]

Abstract: A multiresponsive enamine‐based molecular switch is presented, in which forward/backward configurational rotation around the C=C bond could be precisely controlled by the addition of an acid/base or metal ions. Fluorescence turn‐on/off effects and large Stokes shifts were observed while regulating the switching process with CuII. The enamine functionality furthermore enabled double dynamic regimes, in which configurational switching could operate in conjunction with constitutional enamine exchange of the rotor part. This behavior was used to construct a prototypical dynamic covalent switch system through enamine exchange with primary amines. The dynamic exchange process could be readily turned on/off by regulating the switch status with pH. [ABSTRACT FROM AUTHOR]

Abstract: Transmissible spongiform encephalopathy is associated with misfolding of prion protein (PrP) into an amyloid β‐rich aggregate. Previous studies have indicated that PrP interacts with Alzheimer′s disease amyloid‐β peptide (Aβ), but it remains elusive how this interaction impacts on the misfolding of PrP. This study presents the first in vitro evidence that Aβ induces PrP‐amyloid formation at submicromolar concentrations. Interestingly, systematic mutagenesis of PrP revealed that Aβ requires no specific amino acid sequences in PrP, and induces the misfolding of other unrelated proteins (insulin and lysozyme) into amyloid fibrils in a manner analogous to PrP. This unanticipated nonspecific amyloidogenic effect of Aβ indicates that this peptide might be involved in widespread protein aggregation, regardless of the amino acid sequences of target proteins, and exacerbate the pathology of many neurodegenerative diseases. [ABSTRACT FROM AUTHOR]