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```rss <![CDATA[ACS Catalysis]]> https://pubs.acs.org/toc/accacs/0/0 RSSHub i@diygod.me (DIYgod) zh-cn Sat, 30 Jul 2022 17:25:38 GMT 5 <![CDATA[Theoretical Insights into Nitrate Reduction to Ammonia over Pt/TiO2: Reaction Mechanism, Activity Regulation, and Catalyst Design]]>

Rational design of improved catalysts is one of the ultimate goals in catalytic research, the basis of which is clarifying the reaction mechanism and regulation trends. Here, we took nitrate reduction to ammonia as an example and revealed the complete reaction mechanism, rate-determining steps, and charge density regulation trends over Pt/TiO2. The dissociation of the three N–O bonds in NO3– favors the H*-assisted pathway via HONO2*, ONOH*, and HNOH* intermediates, producing the preliminary ammonia source in the form of NH*. Subsequent hydrogenation steps of NH* + H* → NH2* + * and NH2* + H* → NH3* + * show the two largest reaction barriers, being the rate-determining steps of the reaction. Further, by regulating the Pt charge density, we showed that all of the dissociation steps are slightly deactivated, whereas the hydrogenation steps, particularly those involving NH* and NH2*, are apparently promoted as positive charges accumulate on Pt particles. Accordingly, doping of Zn or Cu into TiO2 was proposed and furthermore verified as an effective strategy to improve the nitrate reduction activity. Such a promotional effect was attributed to the reduced H* adsorption energy on the metal surface as it became positively charged, manifesting itself as a general principle in boosting the hydrogenation activity.

]]> Sat, 30 Jul 2022 00:00:00 GMT 10.1021/acscatal.2c01694 https://pubs.acs.org/doi/10.1021/acscatal.2c01694 <![CDATA[Kinetic Solvent Isotope Effect in P450-Mediated Cyclization in Indolactams: Evidence for Branched Reactions and Guide for Their Modulation in Heterocy...]]>

Cytochrome P450s demonstrate potential as biocatalysts for selective C–H bond functionalization in heterocycle synthesis. P450 monooxygenase (HinD) can catalyze cyclization for the biosynthesis of indolactam-like natural products. Moreover, the modification of N13 in the substrates leads to the formation of 6/5/6 tricyclic products as the minor product, which demonstrates potential for cancer treatment. However, the biosynthesis of indole-fused 6/5/6 tricyclic products is challenging as relatively few studies focus on the modulation of the minor products from P450 reactions to become dominant products for their bioproduction. Here, the isotopically sensitive branching method was employed to identify the conversion to 6/5/6 tricyclic products as the minor branch in wild-type HinD catalysis, originating from a common intermediate, in addition to the formation of 9-membered indolactam. The observed large kinetic solvent isotope effect (∼5.6) revealed that catalytic flow between two branches is sensitive and that the original minor product can be inverted to the dominant product by directing catalytic flow from the original major branch to the minor branch. Finally, 6/5/6 tricyclic products can be modulated and chemoenzymatically prepared as the major product. Data offer an insight into the rational design for the chemo-enzymatic synthesis of heterocyclic compounds.

]]> Fri, 29 Jul 2022 00:00:00 GMT 10.1021/acscatal.2c02556 https://pubs.acs.org/doi/10.1021/acscatal.2c02556 <![CDATA[Stereoselective Access to Silicon-Stereogenic Silacycles via the Carbene-Catalyzed Desymmetric Benzoin Reaction of Siladials]]>

The catalytic asymmetric synthesis of silicon-stereogenic organosilicon compounds has been a long-standing challenging task and was recently accomplished through a handful of transition-metal-catalyzed approaches. Herein we report an organocatalytic desymmetrization strategy for constructing optically active silicon-stereogenic silacycles. In the presence of a chiral N-heterocyclic carbene (NHC) catalyst, two identical formyl groups on the tetrasubstituted silanes are successfully discriminated to undergo stereoselective intramolecular benzoin reactions, affording enantioenriched dibenzo[b,f]silepin-10-ones featuring carbon- and silicon-stereogenic centers at the 1,4-positions, respectively. This catalytic process can be readily expanded to the gram scale, and the products can be further converted to other valuable molecules. DFT calculations were also conducted to unveil the reaction mechanism and the origins of the stereoselectivities.

]]> Fri, 29 Jul 2022 00:00:00 GMT 10.1021/acscatal.2c02805 https://pubs.acs.org/doi/10.1021/acscatal.2c02805 <![CDATA[Boxlike Assemblages of Few-Layer MoS2 Nanosheets with Edge Blockage for High-Efficiency Hydrogenation of CO2 to Methanol]]>

Direct hydrogenation of CO2 into methanol is a promising strategy for reducing excessive dependence on fossil fuels and alleviating environmental concerns. Recently, in-plane sulfur vacancies in two-dimensional MoS2 nanosheets were unveiled as efficient catalytic active sites for methanol synthesis from CO2, whereas edge vacancies facilitated hydrogenation of CO2 to methane. Herein, we developed boxlike assemblages of quasi-single-layer MoS2 nanosheets, which were edge-blocked by ZnS crystallites (denoted as h-MoS2/ZnS) via a metal–organic framework (MOF)-engaged solvothermal route and subsequent heat treatments. The spatial confinement of the ZnS can restrain the growth and aggregation of MoS2 and ensure the stability of few-layer or even single-layer MoS2 in the assemblages. More importantly, the presence of ZnS can prevent reactants from approaching the edge sulfur vacancies of MoS2. With more exposed in-plane sulfur vacancies and less edge sulfur vacancies, the h-MoS2/ZnS exhibits 67.3% methanol selectively, 9.0% CO2 conversion, and a high methanol space-time yield of up to 0.93 gMeOH·gMoS2–1·h–1 at 260 °C, 5 MPa, and 15 000 mL·gcat.–1·h–1. The catalytic activity was stable for at least 120 h. By removing the ZnS phase from h-MoS2/ZnS and thus deliberately creating more edge sulfur vacancies, it was further confirmed that edge sulfur vacancies are active catalytic sites for excessive hydrogenation of CO2 to methane. Furthermore, the reaction mechanism of our catalyst was also investigated by a high-pressure in situ DRIFTS study. Thus, this MOF-templated strategy for assembling and confining quasi-single-layer MoS2 provides insights into the development of highly efficient transition-metal dichalcogenide catalysts for CO2 hydrogenation with excellent stability.

]]> Fri, 29 Jul 2022 00:00:00 GMT 10.1021/acscatal.2c02838 https://pubs.acs.org/doi/10.1021/acscatal.2c02838 <![CDATA[Biocatalytic C14-Hydroxylation on Androstenedione Enabled Modular Synthesis of Cardiotonic Steroids]]>

Cardiotonic steroids are a unique class of natural products, possessing a steroid framework with a characteristic hydroxyl group at C14 and a β-oriented five- or six-membered unsaturated lactone substituent at C17. Installation of a hydroxyl group at the C14 position by direct C–H hydroxylation is proved to be challenging through chemical transformation. Herein, we report the identification of two P450 enzymes, CYP11411 and CYP44476, each of which can convert androstenedione (AD) to 14α-OH-AD directly, from the plant Calotropis gigantea and the toad Bufo gargarizans, respectively. The obtained 14α-OH-AD can then be chemically converted to a key 14β-OH steroid intermediate, which serves as a basis for the total synthesis of cardiotonic steroids including bufotalin, bufogenin B, and digitoxigenin by the modular installation of a five- or six-membered lactone ring at the C17 position.

]]> Thu, 28 Jul 2022 00:00:00 GMT 10.1021/acscatal.2c02185 https://pubs.acs.org/doi/10.1021/acscatal.2c02185 <![CDATA[Elucidating Cooperative Interactions between Grafted Amines and Tin or Titanium Sites on Silica]]>

The efficient promotion of cooperative catalytic interactions on solid surfaces can be of great benefit for a range of important reactions. Herein, we demonstrate that the cooperative interactions of isolated tin (Sn) and titanium (Ti) sites on silica with grafted primary amines (NH2) can be tuned by changing the immediate chemical environment of the metal sites (M). We show that, by tethering various size organic ligands (RO) to the M sites, we can govern the interactions between the sites as measured by the presence of NH3+. We show that the concentration of NH3+ is directly correlated with the activity of the model Henry reaction. We further find that the selectivity to the olefinic product increased from 59% for the cooperative interactions of grafted NH2 and surface silanols to 84–92% for the cooperative interactions between grafted NH2 and the isolated Sn or Ti sites. An analysis by DFT shows that these cooperative interactions are enabled by the presence of a trace amount (two molecules per M site) of water near the metal sites and a resulting hydrolysis, which depends on the hydrophobicity of the RO group and the nature of the metal. Hence, the current work provides advanced molecular-level insights into the underlying principles of cooperative interactions on a solid surface and guidance for governing such interactions by tuning the chemical environment.

]]> Thu, 28 Jul 2022 00:00:00 GMT 10.1021/acscatal.2c02276 https://pubs.acs.org/doi/10.1021/acscatal.2c02276 <![CDATA[Toward Industrially Relevant Sn-BETA Zeolites: Synthesis, Activity, Stability, and Regeneration]]>

Lewis acidic Snβ zeolites have emerged as highly interesting catalysts for a variety of biomass-related reactions. During the last decades, a vast body of research has focused on unravelling the identity of the (most) active Sn sites. Recent research has shifted its focus from fine-tuning one single type of active Sn-site toward optimizing the overall catalytic activity and stability of the Snβ zeolite, which is more suitable from an industrial point of view. After delving into a discussion of the Sn active sites, this Perspective highlights the recent developments that are essential for industrial implementation of Snβ zeolites, with an emphasis on the most recent insights and findings for improving the catalyst’s productivity and stability.

]]> Thu, 28 Jul 2022 00:00:00 GMT 10.1021/acscatal.2c02527 https://pubs.acs.org/doi/10.1021/acscatal.2c02527 <![CDATA[Engineering Imine Reductase for Efficient Biosynthesis of 1-Aryl-Tetrahydro-β-Carbolines and Their N-Methylation Products]]>

Chiral 1-aryl-tetrahydro-β-carboline (THβC) is an important substructure in natural products and pharmaceuticals. The application of imine reductase (IRED) for their enantioselective synthesis is attractive yet has not been realized, owing to the bulkiness and rigidness of the framework. In this study, through in silico and mutational analysis of the steric hindrance-tolerant IRED IR45, we identified a critical binding mode for 1-phenyl dihydro-β-carbolines (DHβCs). Engineering the key residues at L228′, M250′, and E251′ in the subunit B significantly expanded the substrate tolerance of the enzyme, enabling efficient, stereoselective synthesis of a series of ortho-, meta-, para-, and multi-substituted (S)-1-phenyl-THβCs. By combining enzymatic imine reduction and whole-cell N-methylation in one pot, we further developed a cost-effective strategy to directly synthesize (S)-N-methyl 1-phenyl-THβCs from DHβC substrates. Our results not only provide an effective route to the biosynthesis of the important 1-aryl THβC frameworks but also significantly expand the substrate specificity of IRED, which will be useful for the broad application of IREDs in the synthesis of other sterically hindered amines.

]]> Wed, 27 Jul 2022 00:00:00 GMT 10.1021/acscatal.1c06012 https://pubs.acs.org/doi/10.1021/acscatal.1c06012 <![CDATA[Crystal Structure of the Bifunctional Wax Synthase 1 from Acinetobacter baylyi Suggests a Conformational Change upon Substrate Binding and Formation o...]]>

Wax esters (WE) are neutral lipids that are formed by the transesterification of an activated fatty acyl moiety to a fatty alcohol. Due to their diverse physicochemical properties, WE are used as industrial lubricants, in cosmetics, or for coating. There is substantial interest in producing WE in bacteria and plants by genetic engineering to improve their sustainability and to reduce production costs. However, we lack a detailed understanding of the catalytic mechanism and structural determinants that influence substrate specificities of WE-synthesizing enzymes, which is essential for tailored WE production. One class of well-studied WE-producing enzymes are the bifunctional bacterial wax synthases/acyl-CoA:diacylglycerol O-acyltransferases (WSD). Here, we report the 1.95 Å crystal structure of Acinetobacter baylyi WSD1 (AbWSD1) with a fatty acid molecule bound in the active site. The location of a cocrystallized myristic acid confirms a previously proposed acyl-CoA binding site. A comparison of this AbWSD1 structure to a published Marinobacter aquaeolei WSD1 (MaWSD1) structure of the apoenzyme revealed a major structural difference in the C-terminal part of AbWSD1. This leads us to propose a conformational change in AbWSD1 induced by substrate binding. This conformational change forms then a potential coenzyme A (CoA) binding site. Furthermore, we have identified an additional cavity in AbWSD1 and could show through mutational studies that two amino acids lining the cavity are crucial for the acyl-CoA:diacylglycerol O-acyltransferase (DGAT) activity of the enzyme. Our findings provide a foundation for designing WSD variants that lack DGAT activity.

]]> Wed, 27 Jul 2022 00:00:00 GMT 10.1021/acscatal.2c01712 https://pubs.acs.org/doi/10.1021/acscatal.2c01712 <![CDATA[Selective Three-Component Reductive Alkylalkenylation of Unbiased Alkenes via Carbonyl-Directed Nickel Catalysis]]>

A Ni-catalyzed enantioselective reductive three-component alkylalkenylation of β,γ-alkenyl ketones with cis-alkenyl iodides and fluoroalkyl iodides in the presence of Mn is reported. By leveraging five-membered nickellacycles stabilized by pendant ketone group and chiral bis(oxazoline) (BiOx) ligand, this three-component protocol allows efficient access to enantioenriched β-alkenyl ketones from simple starting materials. Ni-catalyzed three-component alkylalkenylation of diverse electronically unbiased alkenes beyond β,γ-alkenyl ketones that enables regioselective construction of two C(sp3)–C(sp3) and C(sp3)–(sp2) bonds in one single operation is also demonstrated.

]]> Wed, 27 Jul 2022 00:00:00 GMT 10.1021/acscatal.2c02163 https://pubs.acs.org/doi/10.1021/acscatal.2c02163 <![CDATA[Inductive Heating for Research in Electrocatalysis: Theory, Practical Considerations, and Examples]]>

Inductive heating in neutral or slightly reducing gaseous atmosphere has become one of the most effective methods to thermally pretreat oxygen-sensitive monocrystalline electrodes for interfacial electrochemistry and electrocatalytic research. In this contribution, we discuss the principles and theory of inductive heating, and we explain how an alternating current passing through a coil induces a resistive current inside a conductive sample. The thermodynamics and heat transport phenomena of how the thermal energy propagates and heats the sample are then discussed. Practical considerations with examples are given about how to best utilize this technique and avoid sample damage by controlling the gaseous atmosphere surrounding the sample being treated. Finally, a Ni(111) electrode is used to demonstrate the applicability of the method to interfacial electrochemistry and electrocatalysis research. The post-thermal treatment demonstrates the effect of the presence of small amounts of oxygen in the gaseous atmosphere on cyclic voltammetry profiles acquired in aqueous alkaline media.

]]> Wed, 27 Jul 2022 00:00:00 GMT 10.1021/acscatal.2c02174 https://pubs.acs.org/doi/10.1021/acscatal.2c02174 <![CDATA[Activating MnO with Embedded Ru for Enhanced Selective Hydrogenolysis of C–O Bonds in Lignin-Derived Ethers over Ru–MnO/Al2O3]]>

While C–O bond cleavage is pivotal in the depolymerization/valorization of lignin, it is still challenging to control the reaction selectivity under high activity due to the higher dissociation energy of aromatic C–O bonds relative to other reactions such as direct ring hydrogenation. Herein, we report the activation of Al2O3-supported earth-abundant MnO with embedded Ru to enhance the selective hydrogenolysis of aromatic C–O bonds in both a model compound and real lignin. Complementary characterizations demonstrate that the embedment of Ru into the MnO phase generates vacancy-enriched MnO under a hydrogen atmosphere, and such abundant active sites enable about threefold enhancement of the specific reaction rate for C–O bond hydrogenolysis. Moreover, the defective MnO overlayer on Ru nanoparticles has a stronger interaction with the O in diphenyl ether with preferential vertical adsorption, which inhibits the activation and hydrogenation of the aromatic ring, leading to higher selectivity for direct C–O bond cleavage. In the depolymerization of real lignin, the bimetallic Ru–MnO shows significantly higher (fivefold) activity than monometallic Ru under the tested condition. This work provides a general framework for the rational design of highly efficient catalysts for selective C–O bond cleavage.

]]> Wed, 27 Jul 2022 00:00:00 GMT 10.1021/acscatal.2c02188 https://pubs.acs.org/doi/10.1021/acscatal.2c02188 <![CDATA[Multiple Substrate Binding Mode-Guided Engineering of a Thermophilic PET Hydrolase]]>

Thermophilic polyester hydrolases (PES-H) have recently enabled biocatalytic recycling of the mass-produced synthetic polyester polyethylene terephthalate (PET), which has found widespread use in the packaging and textile industries. The growing demand for efficient PET hydrolases prompted us to solve high-resolution crystal structures of two metagenome-derived enzymes (PES-H1 and PES-H2) and notably also in complex with various PET substrate analogues. Structural analyses and computational modeling using molecular dynamics simulations provided an understanding of how product inhibition and multiple substrate binding modes influence key mechanistic steps of enzymatic PET hydrolysis. Key residues involved in substrate-binding and those identified previously as mutational hotspots in homologous enzymes were subjected to mutagenesis. At 72 °C, the L92F/Q94Y variant of PES-H1 exhibited 2.3-fold and 3.4-fold improved hydrolytic activity against amorphous PET films and pretreated real-world PET waste, respectively. The R204C/S250C variant of PES-H1 had a 6.4 °C higher melting temperature than the wild-type enzyme but retained similar hydrolytic activity. Under optimal reaction conditions, the L92F/Q94Y variant of PES-H1 hydrolyzed low-crystallinity PET materials 2.2-fold more efficiently than LCC ICCG, which was previously the most active PET hydrolase reported in the literature. This property makes the L92F/Q94Y variant of PES-H1 a good candidate for future applications in industrial plastic recycling processes.

]]> Wed, 27 Jul 2022 00:00:00 GMT 10.1021/acscatal.2c02275 https://pubs.acs.org/doi/10.1021/acscatal.2c02275 <![CDATA[Radical Termination via β-Scission Enables Photoenzymatic Allylic Alkylation Using “Ene”-Reductases]]>

Allylations are practical transformations that forge C–C bonds while introducing an alkene for further chemical manipulations. Here, we report a photoenzymatic allylation of α-chloroamides with allyl silanes using flavin-dependent “ene”-reductases (EREDs). An engineered ERED can catalyze annulative allylic alkylation to prepare 5, 6, and 7-membered lactams with high levels of enantioselectivity. Ultrafast transient absorption spectroscopy indicates that radical termination occurs via β-scission of the silyl group to afford a silyl radical, a distinct mechanism by comparison to traditional radical allylations involving allyl silanes. Moreover, this represents an alternative strategy for radical termination using EREDs. This mechanism was applied to intermolecular couplings involving allyl sulfones and silyl enol ethers. Overall, this method highlights the opportunity for EREDs to catalyze radical termination strategies beyond hydrogen atom transfer.

]]> Wed, 27 Jul 2022 00:00:00 GMT 10.1021/acscatal.2c02294 https://pubs.acs.org/doi/10.1021/acscatal.2c02294 <![CDATA[Designing Cu-Based Tandem Catalysts for CO2 Electroreduction Based on Mass Transport of CO Intermediate]]>

Electrochemical reduction of CO2 to high-value hydrocarbons and oxygenates is an attractive technique to store intermittent renewable energy. Diverse catalysts are capable of catalyzing the CO2 to CO conversion, while further reduction of CO occurs almost exclusively on Cu. Monocomponent Cu catalysts suffer from the high overpotential and low Faradaic efficiency of hydrocarbons and oxygenates. Combining CO2 to CO conversion on Au, Ag, single-atom catalysts, etc., with CO reduction on Cu is a promising strategy to achieve high selectivity and a high formation rate of highly reduced products. Numerous tandem catalysts have been developed based on this idea, and the mass transport of a CO intermediate from a CO-formation catalyst to Cu is the key factor that needs to be considered in the design of tandem catalysts. Rational analysis of the different modes of CO mass transport in the reported designs is needed for further development of tandem catalysts for CO2 reduction. In this review, we elucidate how the spatial distribution of the CO-formation catalyst and Cu determines the mode of CO mass transport and consequently affects the utilization efficiency and reduction rate of the CO intermediate. We also discuss the challenges and perspectives in understanding the interaction between the CO-formation catalyst and Cu and improving their catalytic performance in the CO2 tandem reduction.

]]> Wed, 27 Jul 2022 00:00:00 GMT 10.1021/acscatal.2c02579 https://pubs.acs.org/doi/10.1021/acscatal.2c02579 <![CDATA[Synthesis of Sulfur-Stereogenic Sulfoximines via Co(III)/Chiral Carboxylic Acid-Catalyzed Enantioselective C–H Amidation]]>

Sulfoximines bearing stereogenic sulfur atoms are ubiquitous motifs in pharmaceuticals, agricultural chemicals, and bioactive compounds. Herein, we report the synthesis of sulfur-stereogenic sulfoximines via Co(III)/chiral carboxylic acid-catalyzed enantioselective C–H amidation. A broad range of cyclic and acyclic sulfur-stereogenic sulfoximines were isolated in good yields and enantioselectivities (up to an 86% yield and 1.5:98.5 er). The acyclic amidation products can be reduced to potential N,S-chiral sulfoxide ligands, which could be further transformed into recyclable chiral auxiliaries in the Pd-catalyzed diastereoselective C(sp3)–H activation of aliphatic carboxylic acids.

]]> Wed, 27 Jul 2022 00:00:00 GMT 10.1021/acscatal.2c02691 https://pubs.acs.org/doi/10.1021/acscatal.2c02691 <![CDATA[Pathways for Reactions of Esters with H2 over Supported Pd Catalysts: Elementary Steps, Site Requirements, and Particle Size Effects]]>

The direct reduction of esters to ethers offers an efficient pathway to ethers from renewable intermediates. This chemistry previously required homogeneous catalysts and utilized costly and unstable hydride reagents. Here, we elucidate pathways for reactions of propyl acetate (C5H10O2) in the presence of hydrogen (H2) over Pd nanoparticles supported on high-surface-area Nb2O5. Over Pd-Nb2O5, C5H10O2 reacts by three competing primary pathways: hydrogenation to form ethyl propyl ether (C5H12O) by apparent C═O bond rupture, hydrogenolysis to form acetaldehyde and propanol (Cacyl–O bond rupture), and hydrolysis to form acetic acid and propanol. Secondary reactions yield other alcohols, esters, ethers, and hydrocarbons. Hydrogenation and hydrogenolysis rates do not change with the pressure of C5H10O2 and increase with a sublinear dependence on H2 pressure. Furthermore, these dependencies and apparent activation enthalpies remain similar for Pd nanoparticles with different mean diameters (4–22 nm), which shows that the extent of undercoordination of Pd does not significantly affect the mechanism or kinetics for C–O bond rupture steps. Ether formation rates remain constant when D2 replaces H2 as the reductant, which together with the rate dependence on H2 suggests that ethers form by kinetically relevant C–O bond cleavage in a partially hydrogenated intermediate (e.g., hemiacetal). Ex situ titration of Brønsted acid sites by exchange with K+ ions suppresses mass-averaged rates of C5H12O formation by sevenfold, and physical mixtures of Pd-SiO2 and Nb2O5 give rates more than 10 times lower than Pd-Nb2O5. These results demonstrate that C5H12O formation requires Brønsted acid sites that reside in close proximity to Pd nanoparticles. Collectively, these observations suggest a reaction mechanism for the reduction of esters that hydrogenates the carbonyl by stepwise addition of H* atoms to form a hemiacetal that dehydrates at proximal Brønsted acid sites or cleaves the Cacyl–O bond to form lower carbon number products. These findings reveal a pathway to convert renewable oxygenates, such as carboxylic acid derivatives, into value-added chemicals useful as surfactants and solvents.

]]> Tue, 26 Jul 2022 00:00:00 GMT 10.1021/acscatal.2c02129 https://pubs.acs.org/doi/10.1021/acscatal.2c02129 <![CDATA[Tuning Ionic Screening To Accelerate Electrochemical CO2 Reduction in Ionic Liquid Electrolytes]]>

Electric double layer formation often governs the rate and selectivity of CO2 electrochemical reduction. Ionic correlations critically define double layer properties that are essential to electrocatalytic performance, including capacitance and localization of potential gradients. However, the influence of ionic correlations on CO2 electroreduction remains unexplored. Here, we use electrochemical conversion of CO2 to CO in ionic liquid-based electrolytes to investigate how the emergence of ionic correlations with increasing ion concentration influences reaction rates and selectivity. Remarkably, we find substantial acceleration of potential-dependent CO2 reduction rates and enhancement of faradaic efficiency to CO at intermediate concentrations of 0.9 M ionic liquid in acetonitrile, a concentration regime that has not been studied previously. We find that onset potentials for CO2 reduction remain relatively unchanged at −2.01 V vs Ag/Ag+ from 0.025 M up to 1.1 M and increase to −2.04 V vs Ag/Ag+ in the limit of neat ionic liquids. Hence, the acceleration of CO2 reduction we observe originates from the amplification of potential-dependent driving forces, as opposed to changes in onset potential. Importantly, our findings are general across cocatalytic and noncatalytic ions. We propose that concentrations of maximum reactivity correspond to conditions where electric double layers exhibit the strongest screening, which would localize electric fields to stabilize polar intermediates. Our study demonstrates that tuning bulk electrostatic screening lengths via modulation of ionic clustering provides a general approach to accelerating both inner-sphere and outer-sphere electrochemical reactions.

]]> Tue, 26 Jul 2022 00:00:00 GMT 10.1021/acscatal.2c02154 https://pubs.acs.org/doi/10.1021/acscatal.2c02154 <![CDATA[Rh(III)-Catalyzed Intra- and Intermolecular 3,4-Difunctionalization of 1,3-Dienes via Rh(III)-π-Allyl Amidation with 1,4,2-Dioxazolones]]>

We herein report a modular strategy, which enables Rh(III)-catalyzed diastereoselective 3,4-amino oxygenation and diamination of 1,3-dienes using different O- and N-nucleophiles in combination with readily available 3-substituted 1,4,2-dioxazolones (78 examples, 37–91% yield). Previous attempts to functionalize the internal double bond rested on the use of plain alcoholic solvents as nucleophilic coupling partners thus dramatically limiting the scope of this transformation. We have now identified hexafluoroisopropanol as a non-nucleophilic solvent that allows the use of diverse nucleophiles and greatly expands the scope, including an unprecedented amino hydroxylation to selectively install valuable, unprotected β-amino alcohols across 1,3-dienes. Moreover, various elaborate alcohols prove to be compatible providing unique access to complex organic molecules. Finally, this method is employed in a series of intramolecular reactions to deliver valuable nitrogen heterocycles as well as γ- and δ-lactones.

]]> Tue, 26 Jul 2022 00:00:00 GMT 10.1021/acscatal.2c02537 https://pubs.acs.org/doi/10.1021/acscatal.2c02537 <![CDATA[Spatial Organization of Photocatalysts and Enzymes on Janus-Type DNA Nanosheets for Efficient CO2 Conversion]]>

Bioinspired photosynthetic systems composed of photocatalysts and enzymes are a notable framework for converting CO2 to high-value chemicals. However, catalyst/enzyme deactivation and poor electron transfer kinetics in multistep photochemical processes severely limit their catalytic efficiencies. In this study, Janus-type DNA nanosheets (NSs) presenting two different DNA sequences on each face were utilized as a support for the selective immobilization of a Rh complex and formate dehydrogenase (FDH) for concerted catalytic reactions for CO2 reduction. Based on the face selectivity, DNA-conjugated Rh complex and FDH were immobilized on NSs into four different configurations: Rh complex on NS (NS1), FDH on NS (NS2), Rh complex and FDH on opposite faces of NS (NS3), FDH and Rh complex on the same face of NS (NS4). The catalytic system exhibited CO2 conversion efficiencies highly dependent on the spatial organization of Rh complex and FDH, showing the reactivity for the formate production in the order of NS1 coupled with free FDH > NS3 > NS2 coupled with free Rh complex > NS4 > free Rh complex and FDH. The NS1 coupled with free FDH showed turnover number (TON) of 1360 for the formate production based on NAD+, which is the highest value reported thus far for Rh-based photocatalyst/enzyme coupled systems. The results demonstrate that the compartmentalization of photocatalysts and biological enzymes is a viable approach for improving the efficiency of CO2 conversion and provide important design rules for building efficient artificial photosynthetic systems.

]]> Tue, 26 Jul 2022 00:00:00 GMT 10.1021/acscatal.2c02911 https://pubs.acs.org/doi/10.1021/acscatal.2c02911 <![CDATA[Perfluoroarene Interaction-Controlled Chiral Phosphoric Acid-Catalyzed Enantioselective Michael Addition of Difluoroenoxysilanes to Azadienes: a Combi...]]>

A catalytic and highly enantioselective Mukaiyama–Michael addition of difluoroenoxysilanes to azadienes has been developed using perfluorinated aryl-incorporating chiral monophosphoric acid (PF-CPA) as an effective, multipoint-controlled chiral catalyst. The inherent perfluoroaryl substituent is finely beneficial not only for achieving high catalytic activity but also for creating a compact and confined chiral environment for highly enantioselective transformations. Theoretical studies showed that the π–π interaction and hydrogen bond between PF-CPA and substrates play a crucial role in determining the stereochemical outcomes in comparison with those of phenyl, binaphthyl, and partially fluorinated aryls.

]]> Mon, 25 Jul 2022 00:00:00 GMT 10.1021/acscatal.2c01671 https://pubs.acs.org/doi/10.1021/acscatal.2c01671 <![CDATA[Polymer-Supported Chiral Heterogeneous Copper Catalyst for Asymmetric Conjugate Addition of Ketones and Imines under Batch and Flow]]>

Enantioselective conjugate addition reactions are powerful methods in synthesizing optically active molecules. Procedures that employ chiral homogeneous catalysts have been developed extensively, but ones that use chiral heterogeneous catalysts are less explored and remain a challenge. Here we report a polymer-supported chiral heterogeneous copper catalyst that demonstrated high reactivity and enantioselectivity in asymmetric conjugate addition reactions of both ketones and imines. It was found that reduced steric hindrance inside the micro catalytic environment and a 1:1 ligand to metal ratio was crucial for the high efficiency and reusability of the chiral heterogeneous catalyst. Various α,β-unsaturated carbonyl substrates, including pharmaceutical intermediates and natural products, could be transformed in high yields with high enantioselectivities. Successful application of this methodology in a continuous flow fashion further broadened its usage in dealing with sensitive organozinc reagents. In addition, production was successfully scaled up under the flow condition.

]]> Mon, 25 Jul 2022 00:00:00 GMT 10.1021/acscatal.2c02056 https://pubs.acs.org/doi/10.1021/acscatal.2c02056 <![CDATA[A Career in Catalysis: Jens Kehlet Nørskov]]>

Jens Nørskov has led the development of theory and the application of computational methods to study catalysis for more than four decades; we honor his contributions to the field with this Account on the occasion of his 70th birthday. A hallmark of Nørskov’s approach to science is his ability to distill complex problems down to simple models and apply these models to yield intuitive and practical insights. At the same time, he recognizes the true complexity of catalytic systems, and constantly pushes to develop more accurate theoretical models of catalysis. Regardless of the complexity involved, Nørskov is always capable of communicating the results of his work with conciseness and clarity, ensuring that it is accessible to experimental and theoretical colleagues and trainees. His insightful approach and clear communication skills have led to numerous impactful developments in the field of catalysis, a few of which are reviewed in this work.

]]> Mon, 25 Jul 2022 00:00:00 GMT 10.1021/acscatal.2c02217 https://pubs.acs.org/doi/10.1021/acscatal.2c02217 <![CDATA[C–Doping Induced Oxygen-Vacancy in WO3 Nanosheets for CO2 Activation and Photoreduction]]>

Sluggish charge kinetics and low CO2 affinity seriously limit the photocatalytic CO2 reduction reaction. Herein, the simultaneous promotion of charge transfer and CO2 activation over two-dimensional (2D) WO3 nanosheets is achieved by coupling surface C-doping and oxygen vacancy. The surface-doped C atoms reconstruct the atomic surface of WO3 by extracting oxygen lattice to generate the intimate oxygen vacancy (C–OV coordination) as the active center, which facilitates the CO2 adsorption/activation, thus inducing the formation *CO2 species. As a charge delivery channel, an exclusive W–O–C covalent bond formed by C–OV coordination could enhance the electron transfer. As a result, the as-designed catalyst exhibits 85.8% selectivity for CO2 photoreduction to CO under the gas–solid phase reaction, with a yield rate of 23.2 μmol g–1 h–1 and a stable long-term reactivity over 24 h. Moreover, the in situ DRIFTS and DFT results reveal that this specific C–OV coordination enables the spontaneous CO2 activation and proton-coupled electron transfer to guarantee the sustained formation of *COOH and, thus, smooth the photocatalytic CO2 reduction reaction. This work develops a feasible strategy for electronic structure modification of photocatalysts with doping-induced oxygen vacancy to boost CO2 activation and photoreduction.

]]> Mon, 25 Jul 2022 00:00:00 GMT 10.1021/acscatal.2c02390 https://pubs.acs.org/doi/10.1021/acscatal.2c02390 <![CDATA[Promoted Type I and II ROS Generation by a Covalent Organic Framework through Sonosensitization and PMS Activation]]>

Reactive oxygen species (ROS) are one of the most useful chemicals in photo-therapeutic and catalytic applications. In order to effectively generate ROS, the role of light-absorbing photosensitizers or activators for pre-ROS sources like peroxymonosulfate (PMS) is significantly essential. Although metal-based ROS-generating materials have been widely utilized due to the affordable heavy atom effect or viable catalytic sites, the potential toxicity of leached metal ions can be sometimes an undesirable hazard to humans and ecosystems. Herein, we prepare a covalent organic framework (COF) that generates both type I and II ROS upon ultrasound irradiation. In addition, the COF effectively generated ROS through PMS activation even without light sources or catalytic metal sites. We also observed synergistic ROS generation by sonosensitization and PMS activation by the COF. This work is a demonstration of the COF material functioning as both a sonosensitizer and a PMS activator.

]]> Mon, 25 Jul 2022 00:00:00 GMT 10.1021/acscatal.2c02414 https://pubs.acs.org/doi/10.1021/acscatal.2c02414 <![CDATA[Tuning the Oxidative Mono- or Double-Carbonylation of Alkanes with CO by Choosing a Co or Cu Catalyst]]>

The control of reaction selectivity is a core of organic synthesis, which requires the rational design of the catalytic system. Carbonylation reactions involving CO, such as monocarbonylation and double-carbonylation, are some of the most powerful tools for constructing carbonyl compounds. However, tunable mono- and double-carbonylation still remain a great challenge, especially for C–H bonds. In this work, we introduced metal-controlled mono- and double-carbonylation reactions of alkanes with amines to prepare alkyl amides and alkyl α-ketoamides, respectively (58 examples, yields up to 99%). The Co catalysis system afforded solely monocarbonylation products, and the Cu catalysis system afforded highly selective double-carbonylation products (more than 20:1). Only the choice of the Co or Cu catalyst precursor was the key to producing a dramatic switch in the reaction selectivity.

]]> Mon, 25 Jul 2022 00:00:00 GMT 10.1021/acscatal.2c02569 https://pubs.acs.org/doi/10.1021/acscatal.2c02569 <![CDATA[Influence of Silica-Supported Alkylaluminum on Heterogeneous Zwitterionic Anilinonaphthoquinone Nickel and Palladium-Catalyzed Ethylene Polymerization...]]>

The development of the heterogeneous late transition metal-catalyzed olefin (co)polymerization is a challenge in current research. Here, we report the preparation of heterogeneous anilinonaphthoquinone nickel and palladium catalysts by the binding of SiO2-supported alkylaluminums to a quinone oxygen of the ligand (Mt-AlR3/SiO2). The heterogeneous nickel catalyst exhibited a very high activity (up to 10.4 × 106 g mol–1 h–1) for ethylene polymerizations to produce semicrystalline high-molecular-weight (Mn up to 54.3 × 104 g mol–1) polyethylenes with a low degree of branching (<11.1/1000 C), high Tm values (121–131 °C), and well-regulated particle morphologies. The polymerization behavior depended on the electron density of the metal center modulated by the Lewis acidity of the remotely bound alkylaluminum as can be analyzed and verified through model optimizations and density functional theory (DFT) calculations. Most importantly, these nickel catalysts were able to produce semicrystalline ethylene/5-hexene-1-yl copolymers with a high activity and high molecular weight. The heterogeneous palladium catalyst can promote the copolymerization of ethylene with commercial methyl acrylate or polar norbornene derivatives with a moderate activity, affording a polar functionalized polyethylene and a cyclic olefin copolymer.

]]> Mon, 25 Jul 2022 00:00:00 GMT 10.1021/acscatal.2c02705 https://pubs.acs.org/doi/10.1021/acscatal.2c02705 <![CDATA[Access to Enantioenriched 1,n-Diamines via Ni-Catalyzed Hydroamination of Unactivated Alkenes with Weakly Coordinating Groups]]>

Enantioenriched 1,2- and 1,3-diamines with chiral α-branched aliphatic amine motifs are important substructures in bioactive compounds and related molecules and serve as privileged chiral ligands in both organo- and transition-metal-catalysis. However, direct access to such structural motifs remains a formidable challenge. Herein, a straightforward method to access 1,n-diamines (n = 2, 3, 4) containing a chiral α-branched aliphatic amine is achieved by Ni-catalyzed asymmetric hydroamination of unactivated aliphatic alkenes. Facilitated by a remote weakly coordinating group, the reaction is applicable to both terminal and internal unactivated alkenes, delivering enantioenriched 1,2-, 1,3-, and 1,4-diamine precursors in good yields and excellent enantioselectivities with diverse substitution patterns. Unactivated aliphatic alkenes serve as secondary alkyl nucleophile surrogates in the presence of Ni–H, forging the C–N bond enantioselectively with aminating reagents. In addition, the reaction proceeds at room temperature with excellent functional group tolerance.

]]> Mon, 25 Jul 2022 00:00:00 GMT 10.1021/acscatal.2c02892 https://pubs.acs.org/doi/10.1021/acscatal.2c02892 <![CDATA[Copper-Catalyzed Asymmetric Conjugate Addition of Alkene-Derived Nucleophiles to Alkenyl-Substituted Heteroarenes]]>

We herein report the copper-catalyzed asymmetric conjugate addition of β-substituted alkenyl heteroarenes, the one of most challenging Michael acceptors, with alkenes as the latent nucleophiles. Diverse chiral heteroarenes bearing two vicinal stereocenters were obtained in good to excellent yields, generally excellent enantioselectivity, and a good level of diastereoselectivity. The products of the Michael addition can be readily transformed into other valuable acyclic enantioenriched structures bearing three contiguous stereocenters via chiral amine catalysis. Mechanistic studies, including an isotope labeling experiment, a nonlinear effect study, kinetic isotope effect experiments, and initial-rate kinetics studies, were implemented, and the experimental results indicated that the hydrocupration step might be the turnover-limiting step. Moreover, the origin of preferential alkene hydrocupration in the presence of β-substituted alkenyl heteroarenes and the Ph-BPE-ligated CuH catalyst was also elucidated via some control experiments.

]]> Fri, 22 Jul 2022 00:00:00 GMT 10.1021/acscatal.2c01629 https://pubs.acs.org/doi/10.1021/acscatal.2c01629 <![CDATA[Cooperativity in Diiron(III)porphyrin Dication Diradical-Catalyzed Oxa-Diels–Alder Reactions: Spectroscopic and Mechanistic Insights]]>

Here, we delineate a maiden example of a diiron(III) dication diradical porphyrin dimer as a competent catalyst for the oxa-Diels–Alder type reaction of aldehydes with 1,3-dienes, which is a cardinal reaction in the syntheses of natural products. This catalyzed process does not demand the use of electron-deficient aldehydes such as glyoxylic acid derivatives or activated electron-rich 1,3-dienes such as Danishefsky’s, Brassard’s, or Rawal’s diene. The robust catalyst exhibited high functional group tolerance. The computational studies corroborated the detailed spectroscopic investigation, which focused on the pivotal roles played by the metal ion as the Lewis acidic center in combination with counteranions and also enabled us to delve deeper into the reaction mechanism. Previously developed methodologies invariably require dissociation of the iron-axial bond of the catalyst; on the contrary, the axial ligand of the catalyst remains intact during the catalysis reported here. The use of a dication diradical iron(III)porphyrin as the Lewis acid catalyst facilitates activation of the aldehyde via coordination whose formation has also been confirmed experimentally. Moreover, the counteranion has a considerable effect on the reaction pathway; its coordination to the metal inhibits the coordination of the substrate to form the product. The efficacy of employing such a diheme catalyst over a monoheme analogue is manifested in the cooperative effect, which resulted in a lower catalyst loading with excellent yields.

]]> Fri, 22 Jul 2022 00:00:00 GMT 10.1021/acscatal.2c02479 https://pubs.acs.org/doi/10.1021/acscatal.2c02479 <![CDATA[Fully Exposed Platinum Clusters on a Nanodiamond/Graphene Hybrid for Efficient Low-Temperature CO Oxidation]]>

A fundamental understanding of the active sites in heterogeneous catalysts is extremely important in the development of effective catalysts. In general, it is difficult to identify the catalytically active sites due to their structural complexity, including the size and specific atomic configurations. In this paper, we prepare different Pt species (single atoms, fully exposed clusters, and nanoparticles) on a nanodiamond/graphene (ND@G) hybrid support to understand their evolution in structure for low-temperature CO oxidation. Remarkably, the atomically dispersed and fully exposed Pt clusters with an ensemble of a few Pt atoms showed the maximum atom utilization of low-coordinated metal sites. As determined by a catalytic performance evaluation, detailed characterizations, and theoretical calculations, the 0.5 wt % Ptn/ND@G catalyst showed a catalytic performance for CO oxidation at low temperature superior to those of single-atom and nanoparticle catalysts, which was attributed to the weakened CO adsorption and facilitated O2 dissociative adsorption on these atomically dispersed and fully exposed Pt cluster catalysts.

]]> Fri, 22 Jul 2022 00:00:00 GMT 10.1021/acscatal.2c02769 https://pubs.acs.org/doi/10.1021/acscatal.2c02769 <![CDATA[Graphene-Derived Carbon Support Boosts Proton Exchange Membrane Fuel Cell Catalyst Stability]]>

The lack of efficient and durable proton exchange membrane fuel cell electrocatalysts for the oxygen reduction reaction is still restraining the present hydrogen technology. Graphene-based carbon materials have emerged as a potential solution to replace the existing carbon black (CB) supports; however, their potential was never fully exploited as a commercial solution because of their more demanding properties. Here, a unique and industrially scalable synthesis of platinum-based electrocatalysts on graphene derivative (GD) supports is presented. With an innovative approach, highly homogeneous as well as high metal loaded platinum-alloy (up to 60 wt %) intermetallic catalysts on GDs are achieved. Accelerated degradation tests show enhanced durability when compared to the CB-supported analogues including the commercial benchmark. Additionally, in combination with X-ray photoelectron spectroscopy Auger characterization and Raman spectroscopy, a clear connection between the sp2 content and structural defects in carbon materials with the catalyst durability is observed. Advanced gas diffusion electrode results show that the GD-supported catalysts exhibit excellent mass activities and posse ```

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```rss <![CDATA[Journal of the American Chemical Society]]> https://pubs.acs.org/toc/jacsat/0/0 RSSHub i@diygod.me (DIYgod) zh-cn Sat, 30 Jul 2022 17:25:41 GMT 5 <![CDATA[Mechanistic Insights into OC–COH Coupling in CO2 Electroreduction on Fragmented Copper]]>

The carbon–carbon (C–C) bond formation is essential for the electroconversion of CO2 into high-energy-density C2+ products, and the precise coupling pathways remain controversial. Although recent computational investigations have proposed that the OC–COH coupling pathway is more favorable in specific reaction conditions than the well-known CO dimerization pathway, the experimental evidence is still lacking, partly due to the separated catalyst design and mechanistic/spectroscopic exploration. Here, we employ density functional theory calculations to show that on low-coordinated copper sites, the *CO bindings are strengthened, and the adsorbed *CO coupling with their hydrogenation species, *COH, receives precedence over CO dimerization. Experimentally, we construct a fragmented Cu catalyst with abundant low-coordinated sites, exhibiting a 77.8% Faradaic efficiency for C2+ products at 300 mA cm–2. With a suite of in situ spectroscopic studies, we capture an *OCCOH intermediate on the fragmented Cu surfaces, providing direct evidence to support the OC–COH coupling pathway. The mechanistic insights of this research elucidate how to design materials in favor of OC–COH coupling toward efficient C2+ production from CO2 reduction.

]]> Fri, 29 Jul 2022 00:00:00 GMT 10.1021/jacs.2c01044 https://pubs.acs.org/doi/10.1021/jacs.2c01044 <![CDATA[Chemical Conformation of the Essential Glutamate Site of the c-Ring within Thermophilic Bacillus FoF1-ATP Synthase Determined by Solid-State NMR Based...]]>

Proton translocation through the membrane-embedded Fo component of F-type ATP synthase (FoF1) is facilitated by the rotation of the Fo c-subunit ring (c-ring), carrying protons at essential acidic amino acid residues. Cryo-electron microscopy (Cryo-EM) structures of FoF1 suggest a unique proton translocation mechanism. To elucidate it based on the chemical conformation of the essential acidic residues of the c-ring in FoF1, we determined the structure of the isolated thermophilic Bacillus Fo (tFo) c-ring, consisting of 10 subunits, in membranes by solid-state NMR. This structure contains a distinct proton-locking conformation, wherein Asn23 (cN23) CγO and Glu56 (cE56) CδOH form a hydrogen bond in a closed form. We introduced stereo-array-isotope-labeled (SAIL) Glu and Asn into the tFoc-ring to clarify the chemical conformation of these residues in tFoF1-ATP synthase (tFoF1). Two well-separated 13C signals could be detected for cN23 and cE56 in a 505 kDa membrane protein complex, respectively, thereby suggesting the presence of two distinct chemical conformations. Based on the signal intensity and structure of the tFoc-ring and tFoF1, six pairs of cN23 and cE56 surrounded by membrane lipids take the closed form, whereas the other four in the a–c interface employ the deprotonated open form at a proportion of 87%. This indicates that the a–c interface is highly hydrophilic. The pKa values of the four cE56 residues in the a–c interface were estimated from the cN23 signal intensity in the open and closed forms and distribution of polar residues around each cE56. The results favor a rotation of the c-ring for ATP synthesis.

]]> Fri, 29 Jul 2022 00:00:00 GMT 10.1021/jacs.2c03580 https://pubs.acs.org/doi/10.1021/jacs.2c03580 <![CDATA[Peptide-RNA Coacervates as a Cradle for the Evolution of Folded Domains]]>

Peptide-RNA coacervates can result in the concentration and compartmentalization of simple biopolymers. Given their primordial relevance, peptide-RNA coacervates may have also been a key site of early protein evolution. However, the extent to which such coacervates might promote or suppress the exploration of novel peptide conformations is fundamentally unknown. To this end, we used electron paramagnetic resonance spectroscopy (EPR) to characterize the structure and dynamics of an ancient and ubiquitous nucleic acid binding element, the helix-hairpin-helix (HhH) motif, alone and in the presence of RNA, with which it forms coacervates. Double electron–electron resonance (DEER) spectroscopy applied to singly labeled peptides containing one HhH motif revealed the presence of dimers, even in the absence of RNA. Moreover, dimer formation is promoted upon RNA binding and was detectable within peptide-RNA coacervates. DEER measurements of spin-diluted, doubly labeled peptides in solution indicated transient α-helical character. The distance distributions between spin labels in the dimer and the signatures of α-helical folding are consistent with the symmetric (HhH)2-Fold, which is generated upon duplication and fusion of a single HhH motif and traditionally associated with dsDNA binding. These results support the hypothesis that coacervates are a unique testing ground for peptide oligomerization and that phase-separating peptides could have been a resource for the construction of complex protein structures via common evolutionary processes, such as duplication and fusion.

]]> Fri, 29 Jul 2022 00:00:00 GMT 10.1021/jacs.2c03819 https://pubs.acs.org/doi/10.1021/jacs.2c03819 <![CDATA[Molecular Carbon Imides]]>

The creation and development of new forms of nanocarbons have fundamentally transformed the scientific landscape in the past three decades. As new members of the nanocarbon family with accurate size, shape, and edge structure, molecular carbon imides (MCIs) have shown unexpected and unique properties. Particularly, the imide functionalization strategy has endowed these rylene-based molecular carbons with fascinating characteristics involving flexible syntheses, tailor-made structures, diverse properties, excellent processability, and good stability. This Perspective elaborates molecular design evolution to functional landscapes, and illustrative examples are given, including a promising library of multi-size and multi-dimensional MCIs with rigidly conjugated π-architectures, ranging from 1D nanoribbon imides and 2D nanographene imides to cross-dimensional MCIs. Although researchers have achieved substantial progress in using MCIs as functional components for exploration of charge transport, photoelectric conversion, and chiral luminescence performances, they are far from unleashing their full potential. Developing highly efficient and regioselective coupling/ring-closure reactions involving the formation of multiple C–C bonds and the annulation of electron-deficient aromatic units is crucial. Prediction by theory with the help of machine learning and artificial intelligence research along with reliable nanotechnology characterization will give an impetus to the blossom of related fields. Future investigations will also have to advance toward─or even focus on─the emerging potential functions, especially in the fields of chiral electronics and spin electronics, which are expected to open new avenues.

]]> Fri, 29 Jul 2022 00:00:00 GMT 10.1021/jacs.2c04642 https://pubs.acs.org/doi/10.1021/jacs.2c04642 <![CDATA[Polymerase η Recruits DHX9 Helicase to Promote Replication across Guanine Quadruplex Structures]]>

DNA polymerase η (Pol η) catalyzes accurate bypass of ultraviolet light-induced cyclobutane pyrimidine dimers, and it also functions in several other related processes, including bypassing DNA with unusual structures. Here, we performed unbiased proteome-wide profiling of Pol η-interacting proteins by using two independent approaches, i.e., proximity labeling and affinity pull-down followed by LC-MS/MS analysis. We identified several helicases, including DHX9, as novel Pol η-interacting proteins. Additionally, ChIP-Seq analysis showed that Pol η is enriched at guanine quadruplex (G4) structure sites in chromatin. Moreover, Pol η promotes the recruitment of DHX9 to G4 structure loci in chromatin and facilitates DHX9-mediated unwinding of G4 structures. Deficiency in Pol η or DHX9 leads to attenuated replication across G4 regions in genomic DNA. Together, we unveiled the interaction between Pol η and DHX9 and demonstrated that the interaction promotes the replicative bypass of G4 structures in chromatin.

]]> Fri, 29 Jul 2022 00:00:00 GMT 10.1021/jacs.2c05312 https://pubs.acs.org/doi/10.1021/jacs.2c05312 <![CDATA[Sub-Nanometer Mapping of the Interfacial Electric Field Profile Using a Vibrational Stark Shift Ruler]]>

The characterization of electrical double layers is important since the interfacial electric field and electrolyte environment directly affect the reaction mechanisms and catalytic rates of electrochemical processes. In this work, we introduce a spectroscopic method based on a Stark shift ruler that enables mapping the electric field strength across the electric double layer of electrode/electrolyte interfaces. We use the tungsten-pentacarbonyl(1,4-phenelenediisocyanide) complex attached to the gold surface as a molecular ruler. The carbonyl (CO) and isocyanide (NC) groups of the self-assembled monolayer (SAM) provide multiple vibrational reporters situated at different distances from the electrode. Measurements of Stark shifts under operando electrochemical conditions and direct comparisons to density functional theory (DFT) simulations reveal distance-dependent electric field strength from the electrode surface. This electric field profile can be described by the Gouy–Chapman–Stern model with Stern layer thickness of ∼4.5 Å, indicating substantial solvent and electrolyte penetration within the SAM. Significant electro-induction effect is observed on the W center that is ∼1.2 nm away from the surface despite rapid decay of the electric field (∼90%) within 1 nm. The applied methodology and reported findings should be particularly valuable for the characterization of a wide range of microenvironments surrounding molecular electrocatalysts at electrode interfaces and the positioning of electrocatalysts at specific distances from the electrode surface for optimal functionality.

]]> Fri, 29 Jul 2022 00:00:00 GMT 10.1021/jacs.2c05563 https://pubs.acs.org/doi/10.1021/jacs.2c05563 <![CDATA[Electrochemical Upgrading of Formic Acid to Formamide via Coupling Nitrite Co-Reduction]]>

Formic acid (HCOOH) can be exclusively prepared through CO2 electroreduction at an industrial current density (0.5 A cm–2). However, the global annual demand for formic acid is only ∼1 million tons, far less than the current CO2 emission scale. The exploration of an economical and green approach to upgrading CO2-derived formic acid is significant. Here, we report an electrochemical process to convert formic acid and nitrite into high-valued formamide over a copper catalyst under ambient conditions, which offers the selectivity from formic acid to formamide up to 90.0%. Isotope-labeled in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy and quasi in situ electron paramagnetic resonance results reveal the key C–N bond formation through coupling *CHO and *NH2 intermediates. This work offers an electrochemical strategy to upgrade CO2-derived formic acid into high-value formamide.

]]> Fri, 29 Jul 2022 00:00:00 GMT 10.1021/jacs.2c05660 https://pubs.acs.org/doi/10.1021/jacs.2c05660 <![CDATA[Stable, Bright, and Long-Fluorescence-Lifetime Dyes for Deep-Near-Infrared Bioimaging]]>

Near-infrared (NIR) fluorophores absorbing maximally in the region beyond 800 nm, i.e., deep-NIR spectral region, are actively sought for biomedical applications. Ideal dyes are bright, nontoxic, photostable, biocompatible, and easily derivatized to introduce functionalities (e.g., for bioconjugation or aqueous solubility). The rational design of such fluorophores remains a major challenge. Silicon-substituted rhodamines have been successful for bioimaging applications in the red spectral region. The longer-wavelength silicon-substituted congeners for the deep-NIR spectral region are unknown to date. We successfully prepared four silicon-substituted bis-benzannulated rhodamine dyes (ESi5a–ESi5d), with an efficient five-step cascade on a gram-scale. Because of the extensive overlapping of their HOMO–LUMO orbitals, ESi5a–ESi5d are highly absorbing (λabs ≈ 865 nm and ε > 105 cm–1 M–1). By restraining both the rotational freedom via annulation and the vibrational freedom via silicon-imparted strain, the fluorochromic scaffold of ESi5 is highly rigid, resulting in an unusually long fluorescence lifetime (τ > 700 ps in CH2Cl2) and a high fluorescence quantum yield (ϕ = 0.14 in CH2Cl2). Their half-lives toward photobleaching are 2 orders of magnitude longer than the current standard (ICG in serum). They are stable in the presence of biorelevant concentration of nucleophiles or reactive oxygen species. They are minimally toxic and readily metabolized. Upon tail vein injection of ESi5a (as an example), the vasculature of a nude mouse was imaged with a high signal-to-background ratio. ESi5 dyes have broad potentials for bioimaging in the deep-NIR spectral region.

]]> Fri, 29 Jul 2022 00:00:00 GMT 10.1021/jacs.2c05826 https://pubs.acs.org/doi/10.1021/jacs.2c05826 <![CDATA[Engineered Cytochrome P450-Catalyzed Oxidative Biaryl Coupling Reaction Provides a Scalable Entry into Arylomycin Antibiotics]]>

We report herein the first example of a cytochrome P450-catalyzed oxidative carbon–carbon coupling process for a scalable entry into arylomycin antibiotic cores. Starting from wild-type hydroxylating cytochrome P450 enzymes and engineered Escherichia coli, a combination of enzyme engineering, random mutagenesis, and optimization of reaction conditions generated a P450 variant that affords the desired arylomycin core 2d in 84% assay yield. Furthermore, this process was demonstrated as a viable route for the production of the arylomycin antibiotic core on the gram scale. Finally, this new entry affords a viable, scalable, and practical route for the synthesis of novel Gram-negative antibiotics.

]]> Fri, 29 Jul 2022 00:00:00 GMT 10.1021/jacs.2c06019 https://pubs.acs.org/doi/10.1021/jacs.2c06019 <![CDATA[The Energy Gap Law at Work: Emission Yield and Rate Fluctuations of Single NIR Emitters]]>

Internal conversion (IC) often is the dominating relaxation pathway in NIR emitters, lowering their fluorescence quantum yield. Here, we investigate dibenzoterrylene (DBT) by bulk and single molecule spectroscopy. With increasing solvent polarity, the S1–S0 energy gap decreases leading to a decrease of the fluorescence quantum yield and an increase of the IC rate in full accordance with the energy gap law. Making use of the unexpectedly strong fluorescence solvatochromism of this aromatic hydrocarbon, the validity of the energy gap law could also be demonstrated at the single molecule level. The S1–S0 energy gap not only controls the fluorescence lifetime and quantum yield of single molecules but also dictates how these quantities develop during spectral fluctuations. Our results open new avenues into unexplored single molecule photophysics and appear as a promising tool for nanoscale probing of dynamic heterogeneities.

]]> Fri, 29 Jul 2022 00:00:00 GMT 10.1021/jacs.2c07188 https://pubs.acs.org/doi/10.1021/jacs.2c07188 <![CDATA[“Flash & Click”: Multifunctionalized Lipid Derivatives as Tools To Study Viral Infections]]>

In this perspective article, we describe the current status of lipid tools for studying host lipid–virus interactions at the cellular level. We discuss the potential lipidomic changes that viral infections impose on host cells and then outline the tools available and the resulting options to investigate the host cell lipid interactome. The future outcome will reveal new targets for treating virus infections.

]]> Thu, 28 Jul 2022 00:00:00 GMT 10.1021/jacs.2c02705 https://pubs.acs.org/doi/10.1021/jacs.2c02705 <![CDATA[Intracellular Communication between Synthetic Macromolecules]]>

Non-viral delivery is an important strategy for selective and efficient gene therapy, immunization, and RNA interference, which overcomes problems of genotoxicity and inherent immunogenicity associated with viral vectors. Liposomes and polymers are compelling candidates as carriers for intracellular, non-viral delivery, but maximal efficiencies of around 1% have been reported for the most advanced non-viral carriers. Here, we develop a library of dendronized bottlebrush polymers with controlled defects, displaying a level of precision surpassed only by biological molecules like DNA, RNA, and proteins. We test concurrent and competitive delivery of DNA and show for the first time that, while intracellular communication is thought to be an exclusively biomolecular phenomenon, such communication between synthetic macromolecular complexes can also take place. Our findings challenge the assumption that delivery agents behave as bystanders that enable transfection by passive intracellular release of genetic cargo and improve upon coarse strategies in intracellular carrier design lacking control over polymer sequence, architecture, and composition, leading to a hit-or-miss outcome. Understanding the communication that takes place between macromolecules will help improve the design of non-viral delivery agents and facilitate translation of genome engineering, vaccines, and nucleic acid-based therapies.

]]> Thu, 28 Jul 2022 00:00:00 GMT 10.1021/jacs.2c02793 https://pubs.acs.org/doi/10.1021/jacs.2c02793 <![CDATA[Engineering Electro- and Photocatalytic Carbon Materials for CO2 Reduction by Formate Dehydrogenase]]>

Semiartificial approaches to renewable fuel synthesis exploit the integration of enzymes with synthetic materials for kinetically efficient fuel production. Here, a CO2 reductase, formate dehydrogenase (FDH) from Desulfovibrio vulgaris Hildenborough, is interfaced with carbon nanotubes (CNTs) and amorphous carbon dots (a-CDs). Each carbon substrate, tailored for electro- and photocatalysis, is functionalized with positive (−NHMe2+) and negative (−COO–) chemical surface groups to understand and optimize the electrostatic effect of protein association and orientation on CO2 reduction. Immobilization of FDH on positively charged CNT electrodes results in efficient and reversible electrochemical CO2 reduction via direct electron transfer with >90% Faradaic efficiency and −250 μA cm–2 at −0.6 V vs SHE (pH 6.7 and 25 °C) for formate production. In contrast, negatively charged CNTs only result in marginal currents with immobilized FDH. Quartz crystal microbalance analysis and attenuated total reflection infrared spectroscopy confirm the high binding affinity of active FDH to CNTs. FDH has subsequently been coupled to a-CDs, where the benefits of the positive charge (−NHMe2+-terminated a-CDs) were translated to a functional CD-FDH hybrid photocatalyst. High rates of photocatalytic CO2 reduction (turnover frequency: 3.5 × 103 h–1; AM 1.5G) with dl-dithiothreitol as the sacrificial electron donor were obtained after 6 h, providing benchmark rates for homogeneous photocatalytic CO2 reduction with metal-free light absorbers. This work provides a rational basis to understand interfacial surface/enzyme interactions at electrodes and photosensitizers to guide improvements with catalytic biohybrid materials.

]]> Thu, 28 Jul 2022 00:00:00 GMT 10.1021/jacs.2c04529 https://pubs.acs.org/doi/10.1021/jacs.2c04529 <![CDATA[Photooxidation of the Phenolate Anion is Accelerated at the Water/Air Interface]]>

Molecular photodynamics can be dramatically affected at the water/air interface. Probing such dynamics is challenging, with product formation often probed indirectly through its interaction with interfacial water molecules using time-resolved and phase-sensitive vibrational sum-frequency generation (SFG). Here, the photoproduct formation of the phenolate anion at the water/air interface is probed directly using time-resolved electronic SFG and compared to transient absorption spectra in bulk water. The mechanisms are broadly similar, but 2 to 4 times faster at the surface. An additional decay is observed at the surface which can be assigned to either diffusion of hydrated electrons from the surface into the bulk or due to increased geminate recombination at the surface. These overall results are in stark contrast to phenol, where dynamics were observed to be 104 times faster and for which the hydrated electron was also a photoproduct. Our attempt to probe phenol showed no electron signal at the interface.

]]> Thu, 28 Jul 2022 00:00:00 GMT 10.1021/jacs.2c04935 https://pubs.acs.org/doi/10.1021/jacs.2c04935 <![CDATA[105 K Wide Room Temperature Spin Transition Memory Due to a Supramolecular Latch Mechanism]]>

Little is known about the mechanisms behind the bistability (memory) of molecular spin transition compounds over broad temperature ranges (>100 K). To address this point, we report on a new discrete FeII neutral complex [FeIIL2]0 (1) based on a novel asymmetric tridentate ligand 2-(5-(3-methoxy-4H-1,2,4-triazol-3-yl)-6-(1H-pyrazol-1-yl))pyridine (L). Due to the asymmetric cone-shaped form, in the lattice, the formed complex molecules stack into a one-dimensional (1D) supramolecular chain. In the case of the rectangular supramolecular arrangement of chains in methanolates 1-A and 1-B (both orthorhombic, Pbcn) differing, respectively, by bent and extended spatial conformations of the 3-methoxy groups (3MeO), a moderate cooperativity is observed. In contrast, the hexagonal-like arrangement of supramolecular chains in polymorph 1-C (monoclinic, P21/c) results in steric coupling of the transforming complex species with the peripheral flipping 3MeO group. The group acts as a supramolecular latch, locking the huge geometric distortion of complex 1 and in turn the trigonal distortion of the central FeII ion in the high-spin state, thereby keeping it from the transition to the low-spin state over a large thermal range. Analysis of the crystal packing of 1-C reveals significantly changing patterns of close intermolecular interactions on going between the phases substantiated by the energy framework analysis. The detected supramolecular mechanism leads to a record-setting robust 105 K wide hysteresis spanning the room temperature region and an atypically large TLIESST relaxation value of 104 K of the photoexcited high-spin state. This work highlights a viable pathway toward a new generation of cleverly designed molecular memory materials.

]]> Thu, 28 Jul 2022 00:00:00 GMT 10.1021/jacs.2c05417 https://pubs.acs.org/doi/10.1021/jacs.2c05417 <![CDATA[Constitutionally Selective Dynamic Covalent Nanoparticle Assembly]]>

The future of materials chemistry will be defined by our ability to precisely arrange components that have considerably larger dimensions and more complex compositions than conventional molecular or macromolecular building blocks. However, exerting structural and constitutional control in the assembly of nanoscale entities presents a considerable challenge. Dynamic covalent nanoparticles are emerging as an attractive category of reaction-enabled solution-processable nanosized building block through which the rational principles of molecular synthetic chemistry can be extended into the nanoscale. From a mixture of two hydrazone-based dynamic covalent nanoparticles with complementary reactivity, specific molecular instructions trigger selective assembly of intimately mixed heteromaterial (Au–Pd) aggregates or materials highly enriched in either one of the two core materials. In much the same way as complementary reactivity is exploited in synthetic molecular chemistry, chemospecific nanoparticle-bound reactions dictate building block connectivity; meanwhile, kinetic regioselectivity on the nanoscale regulates the detailed composition of the materials produced. Selectivity, and hence aggregate composition, is sensitive to several system parameters. By characterizing the nanoparticle-bound reactions in isolation, kinetic models of the multiscale assembly network can be constructed. Despite ignoring heterogeneous physical processes such as aggregation and precipitation, these simple kinetic models successfully link the underlying molecular events with the nanoscale assembly outcome, guiding rational optimization to maximize selectivity for each of the three assembly pathways. With such predictive construction strategies, we can anticipate that reaction-enabled nanoparticles can become fully incorporated in the lexicon of synthetic chemistry, ultimately establishing a synthetic science that manipulates molecular and nanoscale components with equal proficiency.

]]> Thu, 28 Jul 2022 00:00:00 GMT 10.1021/jacs.2c05446 https://pubs.acs.org/doi/10.1021/jacs.2c05446 <![CDATA[Hidden Local Symmetry Breaking in a Kagome-Lattice Magnetic Weyl Semimetal]]>

Exploring the relationship between intriguing physical properties and structural complexity is a central topic in studying modern functional materials. Co3Sn2S2, a newly discovered kagome-lattice magnetic Weyl semimetal, has triggered intense interest owing to the intimate coupling between topological semimetallic states and peculiar magnetic properties. However, the origins of the magnetic phase separation and spin glass state below TC in this ordered compound are two unresolved yet important puzzles in understanding its magnetism. Here, we report the discovery of local symmetry breaking surprisingly co-emerges with the onset of ferromagnetic order in Co3Sn2S2, by a combined use of neutron total scattering and half-polarized neutron diffraction. An anisotropic distortion of the cobalt kagome lattice at the atomic/nano level is also found, with distinct distortion directions among the two Co1 and four Co2 atoms. The mismatch of local and average symmetries occurs below TC, indicating that Co3Sn2S2 evolves to an intrinsically lattice disordered system when the ferromagnetic order is established. The local symmetry breaking with intrinsic lattice disorder provides new understanding of the puzzling magnetic properties. Our density functional theory (DFT) calculation indicates that the local symmetry breaking is expected to reorient local ferromagnetic moments, unveiling the existence of the ferromagnetic instability associated with the lattice instability. Furthermore, DFT calculation unveils that the local symmetry breaking could affect the Weyl property by breaking the mirror plane. Our findings highlight the fundamentally important role that the local symmetry breaking plays in advancing our understanding on the magnetic and topological properties in Co3Sn2S2, which may draw attention to explore the overlooked local symmetry breaking in Co3Sn2S2, its derivatives and more broadly in other topological Dirac/Weyl semimetals and kagome-lattice magnets.

]]> Thu, 28 Jul 2022 00:00:00 GMT 10.1021/jacs.2c05665 https://pubs.acs.org/doi/10.1021/jacs.2c05665 <![CDATA[Total Synthesis of Darobactin A]]>

The collaborative total synthesis of darobactin A, a recently isolated antibiotic that selectively targets Gram-negative bacteria, has been accomplished in a convergent fashion with a longest linear sequence of 16 steps from d-Garner’s aldehyde and l-serine. Scalable routes toward three non-canonical amino acids were developed to enable the synthesis. The closure of the bismacrocycle was realized through sequential, halogen-selective Larock indole syntheses, where the proper order of cyclizations proved crucial for the formation of the desired atropisomer of the natural product.

]]> Thu, 28 Jul 2022 00:00:00 GMT 10.1021/jacs.2c05891 https://pubs.acs.org/doi/10.1021/jacs.2c05891 <![CDATA[Ru-Catalyzed Hydroboration of Ynones Leads to a Nontraditional Mode of Reactivity]]>

Although hydroboration of simple ketones and alkynes have been well-established, little is known about the unique hydroboration reactivity for ynones, a family of important building blocks. Herein we report a new reaction mode of ynones leading to structurally novel and synthetically useful but previously inaccessible products, vinyl α-hydroxylboronates, under mild ruthenium-catalyzed hydroboration conditions. This reaction features high efficiency, a broad scope, and complete chemo-, regio-, and stereoselectivity, in spite of many possible competitive pathways. Both control experiments and detailed DFT studies suggested a two-step mechanism, involving initial rate-determining conjugate addition of hydroborane to form the key boryl allenolate intermediate followed by a fast second hydroboration of the enolate motif of the allenolate. Notably, direct 1,4-addition of hydroborane to carbonyl-conjugated alkynes also represents a new mode of reactivity. Despite the overwhelming complexity of this process, which involves selectivity control in almost every step, a thorough and detailed computation on a large set of possible transition states explained the unusual reactivity and intrinsic origin of selectivity.

]]> Thu, 28 Jul 2022 00:00:00 GMT 10.1021/jacs.2c06024 https://pubs.acs.org/doi/10.1021/jacs.2c06024 <![CDATA[Nanolab in a Cell: Crystallization-Induced In Situ Self-Assembly for Cancer Theranostic Amplification]]>

Conducting crystallization-assisted self-assembly in living biosystems to obtain large-size nanoparticles and achieve a specific physiological purpose remains an appealing yet significantly challenging task. In this study, we designed Au(I)–disulfide nanosheets containing an aggregation-induced emission photosensitizer, namely, NSs@TTVP, which exhibited pH-responsive crystallization-driven self-assembly capability in lysosomes of cancer cells and tumor tissues of mice. The crystallization process endowed NSs@TTVP with a microscale morphology, stronger fluorescence output, and highly enhanced reactive oxygen species production efficiency. The in vivo results demonstrated that NSs@TTVP shows both long-term retention in tumors and extensive destruction to cancer cells, making it supremely powerful for fluorescence imaging-guided tumor tracking and inhibition.

]]> Thu, 28 Jul 2022 00:00:00 GMT 10.1021/jacs.2c06111 https://pubs.acs.org/doi/10.1021/jacs.2c06111 <![CDATA[A Concise Synthesis of Pleurotin Enabled by a Nontraditional C–H Epimerization]]>

An 8-step synthesis of a known pentacyclic intermediate toward the natural product pleurotin (1) is described. Pleurotin and related benzoquinone natural products are of great interest for their powerful anticancer and antibiotic activities. The route features a regio- and diastereoselective intermolecular photoenolization/Diels–Alder cycloaddition and an alkoxy-radical-induced hydrogen atom transfer-mediated C–H epimerization to construct pleurotin’s carbon framework with appropriate relative stereochemical relationships. The synthesis concludes with a ring-forming benzylic C–H oxidation to deliver oxepane 19.

]]> Thu, 28 Jul 2022 00:00:00 GMT 10.1021/jacs.2c06504 https://pubs.acs.org/doi/10.1021/jacs.2c06504 <![CDATA[Structure and Function of a Dehydrating Condensation Domain in Nonribosomal Peptide Biosynthesis]]>

Dehydroamino acids are important structural motifs and biosynthetic intermediates for natural products. Many bioactive natural products of nonribosomal origin contain dehydroamino acids; however, the biosynthesis of dehydroamino acids in most nonribosomal peptides is not well understood. Here, we provide biochemical and bioinformatic evidence in support of the role of a unique class of condensation domains in dehydration (CmodAA). We also obtain the crystal structure of a CmodAA domain, which is part of the nonribosomal peptide synthetase AmbE in the biosynthesis of the antibiotic methoxyvinylglycine. Biochemical analysis reveals that AmbE-CmodAA modifies a peptide substrate that is attached to the donor carrier protein. Mutational studies of AmbE-CmodAA identify several key residues for activity, including four residues that are mostly conserved in the CmodAA subfamily. Alanine mutation of these conserved residues either significantly increases or decreases AmbE activity. AmbE exhibits a dimeric conformation, which is uncommon and could enable transfer of an intermediate between different protomers. Our discovery highlights a central dehydrating function for CmodAA domains that unifies dehydroamino acid biosynthesis in diverse nonribosomal peptide pathways. Our work also begins to shed light on the mechanism of CmodAA domains. Understanding CmodAA domain function may facilitate identification of new natural products that contain dehydroamino acids and enable engineering of dehydroamino acids into nonribosomal peptides.

]]> Wed, 27 Jul 2022 00:00:00 GMT 10.1021/jacs.1c13404 https://pubs.acs.org/doi/10.1021/jacs.1c13404 <![CDATA[Optically Induced Long-Lived Chirality Memory in the Color-Tunable Chiral Lead-Free Semiconductor (R)/(S)-CHEA4Bi2BrxI10–x (x = 0–10)]]>

Hybrid organic–inorganic networks that incorporate chiral molecules have attracted great attention due to their potential in semiconductor lighting applications and optical communication. Here, we introduce a chiral organic molecule (R)/(S)-1-cyclohexylethylamine (CHEA) into bismuth-based lead-free structures with an edge-sharing octahedral motif, to synthesize chiral lead-free (R)/(S)-CHEA4Bi2BrxI10–x crystals and thin films. Using single-crystal X-ray diffraction measurements and density functional theory calculations, we identify crystal and electronic band structures. We investigate the materials’ optical properties and find circular dichroism, which we tune by the bromide–iodide ratio over a wide wavelength range, from 300 to 500 nm. We further employ transient absorption spectroscopy and time-correlated single photon counting to investigate charge carrier dynamics, which show long-lived excitations with optically induced chirality memory up to tens of nanosecond timescales. Our demonstration of chirality memory in a color-tunable chiral lead-free semiconductor opens a new avenue for the discovery of high-performance, lead-free spintronic materials with chiroptical functionalities.

]]> Wed, 27 Jul 2022 00:00:00 GMT 10.1021/jacs.2c01994 https://pubs.acs.org/doi/10.1021/jacs.2c01994 <![CDATA[Unconventional Charge Transport in MgCr2O4 and Implications for Battery Intercalation Hosts]]>

Ion transport in solid-state cathode materials prescribes a fundamental limit to the rates batteries can operate; therefore, an accurate understanding of ion transport is a critical missing piece to enable new battery technologies, such as magnesium batteries. Based on our conventional understanding of lithium-ion materials, MgCr2O4 is a promising magnesium-ion cathode material given its high capacity, high voltage against an Mg anode, and acceptable computed diffusion barriers. Electrochemical examinations of MgCr2O4, however, reveal significant energetic limitations. Motivated by these disparate observations; herein, we examine long-range ion transport by electrically polarizing dense pellets of MgCr2O4. Our conventional understanding of ion transport in battery cathode materials, e.g., Nernst–Einstein conduction, cannot explain the measured response since it neglects frictional interactions between mobile species and their nonideal free energies. We propose an extended theory that incorporates these interactions and reduces to the Nernst–Einstein conduction under dilute conditions. This theory describes the measured response, and we report the first study of long-range ion transport behavior in MgCr2O4. We conclusively show that the Mg chemical diffusivity is comparable to lithium-ion electrode materials, whereas the total conductivity is rate-limiting. Given these differences, energy storage in MgCr2O4 is limited by particle-scale voltage drops, unlike lithium-ion particles that are limited by concentration gradients. Future materials design efforts should consider the interspecies interactions described in this extended theory, particularly with respect to multivalent-ion systems and their resultant effects on continuum transport properties.

]]> Wed, 27 Jul 2022 00:00:00 GMT 10.1021/jacs.2c03491 https://pubs.acs.org/doi/10.1021/jacs.2c03491 <![CDATA[Structure, Organization, and Heterogeneity of Water-Containing Deep Eutectic Solvents]]>

The spectroscopy and structural dynamics of a deep eutectic mixture (KSCN/acetamide) with varying water content is investigated from 2D IR (with the C–N stretch vibration of the SCN– anions as the reporter) and THz spectroscopy. Molecular dynamics simulations correctly describe the nontrivial dependence of both spectroscopic signatures depending on water content. For the 2D IR spectra, the MD simulations relate the steep increase in the cross-relaxation rate at high water content to the parallel alignment of packed SCN– anions. Conversely, the nonlinear increase of the THz absorption with increasing water content is mainly attributed to the formation of larger water clusters. The results demonstrate that a combination of structure-sensitive spectroscopies and molecular dynamics simulations provides molecular-level insights into the emergence of heterogeneity of such mixtures by modulating their composition.

]]> Wed, 27 Jul 2022 00:00:00 GMT 10.1021/jacs.2c04169 https://pubs.acs.org/doi/10.1021/jacs.2c04169 <![CDATA[Portable Models for Entropy Effects on Kinetic Selectivity]]>

Differences in entropies of competing transition states can direct kinetic selectivity. Understanding and modeling such entropy differences at the molecular level is complicated by the fact that entropy is statistical in nature; i.e., it depends on multiple vibrational states of transition structures, the existence of multiple dynamically accessible pathways past these transition structures, and contributions from multiple transition structures differing in conformation/configuration. The difficulties associated with modeling each of these contributors are discussed here, along with possible solutions, all with an eye toward the development of portable qualitative models of use to experimentalists aiming to design reactions that make use of entropy to control kinetic selectivity.

]]> Wed, 27 Jul 2022 00:00:00 GMT 10.1021/jacs.2c04683 https://pubs.acs.org/doi/10.1021/jacs.2c04683 <![CDATA[Photoinduced Charge Transfer from Quantum Dots Measured by Cyclic Voltammetry]]>

Measuring and modulating charge-transfer processes at quantum dot interfaces are crucial steps in developing quantum dots as photocatalysts. In this work, cyclic voltammetry under illumination is demonstrated to measure the rate of photoinduced charge transfer from CdS quantum dots by directly probing the changing oxidation states of a library of molecular charge acceptors, including both hole and electron acceptors. The voltammetry data demonstrate the presence of long-lived charge donor states generated by native photodoping of the quantum dots as well as a positive correlation between driving force and rate of charge transfer. Changes to the voltammograms under illumination follow mechanistic predictions from the ErCi′ zone diagram, and electrochemical modeling allows for measurement of the rate of productive electron transfer. Observed rates for photoinduced charge transfer are on the order of 0.1 s–1, which are distinct from the picosecond dynamics measured by conventional transient optical spectroscopy methods and are more closely connected to the quantum yield of light-mediated chemical transformations.

]]> Wed, 27 Jul 2022 00:00:00 GMT 10.1021/jacs.2c04991 https://pubs.acs.org/doi/10.1021/jacs.2c04991 <![CDATA[Supramolecular Complex of Photochromic Diarylethene and Cucurbit[7]uril: Fluorescent Photoswitching System for Biolabeling and Imaging]]>

Photoswitchable fluorophores─proteins and synthetic dyes─whose emission is reversibly switched on and off upon illumination, are powerful probes for bioimaging, protein tracking, and super-resolution microscopy. Compared to proteins, synthetic dyes are smaller and brighter, but their photostability and the number of achievable switching cycles in aqueous solutions are lower. Inspired by the robust photoswitching system of natural proteins, we designed a supramolecular system based on a fluorescent diarylethene (DAE) and cucurbit[7]uril (CB7) (denoted as DAE@CB7). In this assembly, the photoswitchable DAE molecule is encapsulated by CB7 according to the host–guest principle, so that DAE is protected from the environment and its fluorescence brightness and fatigue resistance in pure water improved. The fluorescence quantum yield (Φfl) increased from 0.40 to 0.63 upon CB7 complexation. The photoswitching of the DAE@CB7 complex, upon alternating UV and visible light irradiations, can be repeated 2560 times in aqueous solution before half-bleaching occurs (comparable to fatigue resistance of the reversibly photoswitchable proteins), while free DAE can be switched on and off only 80 times. By incorporation of reactive groups [maleimide and N-hydroxysuccinimidyl (NHS) ester], we prepared bioconjugates of DAE@CB7 with antibodies and demonstrated both specific labeling of intracellular proteins in cells and the reversible on/off switching of the probes in cellular environments under irradiations with 355 nm/485 nm light. The bright emission and robust photoswitching of DAE-Male3@CB7 and DAE-NHS@CB7 complexes (without exclusion of air oxygen and addition of any stabilizing/antifading reagents) enabled confocal and super-resolution RESOLFT (reversible saturable optical fluorescence transitions) imaging with apparent 70–90 nm optical resolution.

]]> Wed, 27 Jul 2022 00:00:00 GMT 10.1021/jacs.2c05036 https://pubs.acs.org/doi/10.1021/jacs.2c05036 <![CDATA[Difluoromethylation of Unactivated Alkenes Using Freon-22 through Tertiary Amine-Borane-Triggered Halogen Atom Transfer]]>

The application of abundant and inexpensive fluorine feedstock sources to synthesize fluorinated compounds is an appealing yet underexplored strategy. Here, we report a photocatalytic radical hydrodifluoromethylation of unactivated alkenes with an inexpensive industrial chemical, chlorodifluoromethane (ClCF2H, Freon-22). This protocol is realized by merging tertiary amine-ligated boryl radical-induced halogen atom transfer (XAT) with organophotoredox catalysis under blue light irradiation. A broad scope of readily accessible alkenes featuring a variety of functional groups and drug and natural product moieties could be selectively difluoromethylated with good efficiency in a metal-free manner. Combined experimental and computational studies suggest that the key XAT process of ClCF2H is both thermodynamically and kinetically favored over the hydrogen atom transfer pathway owing to the formation of a strong boron–chlorine (B–Cl) bond and the low-lying antibonding orbital of the carbon–chlorine (C–Cl) bond.

]]> Wed, 27 Jul 2022 00:00:00 GMT 10.1021/jacs.2c05356 https://pubs.acs.org/doi/10.1021/jacs.2c05356 <![CDATA[Boryl-Dictated Site-Selective Intermolecular Allylic and Propargylic C–H Amination]]>

For internal alkenes possessing two or more sets of electronically and sterically similar allylic protons, the site-selectivity for allylic C–H functionalization is fundamentally challenging. Previously, the negative inductive effect from an electronegative atom has been demonstrated to be effective for several inspiring regioselective C–H functionalization reactions. Yet, the use of an electropositive atom for a similar purpose remains to be developed. α-Aminoboronic acids and their derivatives have found widespread applications. Their current syntheses rely heavily on functional group manipulations. Herein we report a boryl-directed intermolecular C–H amination of allyl N-methyliminodiacetyl boronates (B(MIDA)s) and propargylic B(MIDA)s to give α-amino boronates with an exceptionally high level of site-selectivities (up to 300:1). A wide variety of highly functionalized secondary and tertiary α-amino boronates are formed in generally good to excellent yields, thanks to the mildness of the reaction conditions. The unsaturated double and triple bonds within the product leave room for further decorations. Mechanistic studies reveal that the key stabilization effect of the B(MIDA) moiety on its adjacent developing positive charge is responsible for the high site-selectivity and that a closed transition state might be involved, as the reaction is fully stereoretentive. An activation effect of B(MIDA) is also found.

]]> Wed, 27 Jul 2022 00:00:00 GMT 10.1021/jacs.2c06117 https://pubs.acs.org/doi/10.1021/jacs.2c06117 <![CDATA[Asymmetric Total Synthesis of (+)-Alstonlarsine A]]>

The first asymmetric total synthesis of (+)-alstonlarsine A has been realized. The prominent features of the current synthesis include the following: (i) a Pd/self-adaptable ligand complex-catalyzed asymmetric allylic alkylation of 2-methyl-2-cyclopentenyl carbonate with 2-indolylsubstituted dimethyl malonate to establish the key stereocenter of C15, (ii) an intramolecular nitrile oxide-alkene [3 + 2] cycloaddition (INOC [3 + 2]) to construct the cyclohepta[b]indole backbone with the installment of the requisite stereochemistry of the all-carbon quaternary center of C20, and (iii) a late-stage interrupted Pictet–Spengler reaction (IPSR) to rapidly assemble the core structure of (+)-alstonlarsine A.

]]> Wed, 27 Jul 2022 00:00:00 GMT 10.1021/jacs.2c06518 https://pubs.acs.org/doi/10.1021/jacs.2c06518 <![CDATA[(n-Bu)4NBr-Promoted N2 Splitting to Molybdenum Nitride]]>

Splitting of N2 via six-electron reduction and further functionalization to value-added products is one of the most important and challenging chemical transformations in N2 fixation. However, most N2 splitting approaches rely on strong chemical or electrochemical reduction to generate highly reactive metal species to bind and activate N2, ```

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