Boosted hydrogen evolution kinetics of heteroatom-doped carbons with isolated Zn as an accelerant.

Carbon-based single-atom catalysts, a promising candidate in electrocatalysis, offer insights into electron-donating effects of metal center on adjacent atoms. Herein, we present a practical strategy to rationally design a model catalyst with a single zinc (Zn) atom coordinated with nitrogen and sulfur atoms in a multilevel carbon matrix. The Zn site exhibits an atomic interface configuration of ZnN4S1, where Zn's electron injection effect enables thermal-neutral hydrogen adsorption on neighboring atoms, pushing the activity boundaries of carbon electrocatalysts toward electrochemical hydrogen evolution to an unprecedented level. Experimental and theoretical analyses confirm the low-barrier Volmer-Tafel mechanism of proton reduction, while the multishell hollow structures facilitate the hydrogen evolution even at high current intensities. This work provides insights for understanding the actual active species during hydrogen evolution reaction and paves the way for designing high-performance electrocatalysts.

Modulating Decarboxylative Oxidation Photocatalysis by Ligand Engineering of Atomically Precise Copper Nanoclusters.

Copper nanoclusters (Cu NCs) characterized by their well-defined electronic and optical properties are an ideal platform for organic photocatalysis and exploring atomic-level behaviors. However, their potential as greener, efficient catalysts for challenging reactions like decarboxylative oxygenation under mild conditions remains unexplored. Herein, we present Cu13(Nap)3(PPh3)7H10 (hereafter Cu13Nap), protected by 1-naphthalene thiolate (Nap), which performs well in decarboxylative oxidation (90% yield) under photochemical conditions. In comparison, the isostructural Cu13(DCBT)3(PPh3)7H10 (hereafter Cu13DCBT), stabilized by 2,4-dichlorobenzenethiolate (DCBT), yields only 28%, and other previously reported Cu NCs (Cu28, Cu29, Cu45, Cu57, and Cu61) yield in the range of 6-18%. The introduction of naphthalene thiolate to the surface of Cu13 NCs influences their electronic structure and charge transfer in the ligand shell, enhancing visible light absorption and catalytic performance. Density functional theory (DFT) and experimental evidence suggest that the reaction proceeds primarily through an energy transfer mechanism. The energy transfer pathway is uncommon in the context of previous reports for decarboxylative oxidation reactions. Our findings suggest that strategically manipulating ligands holds significant potential for creating composite active sites on atomically precise copper NCs, resulting in enhanced catalytic efficacy and selectivity across various challenging reactions.

Planar Core and Macrocyclic Shell Stabilized Atomically Precise Copper Nanocluster Catalyst for Efficient Hydroboration of C-C Multiple Bond.

Atomically precise metal nanoclusters (NCs) have become an important class of catalysts due to their catalytic activity, high surface area, and tailored active sites. However, the design and development of bond-forming reaction catalysts based on copper NCs are still in their early stages. Herein, we report the synthesis of an atomically precise copper nanocluster with a planar core and unique shell, [Cu45(TBBT)29(TPP)4(C4H11N)2H14]2+ (Cu45) (TBBT: 4-tert-butylbenzenethiol; TPP: triphenylphosphine), in high yield via a one-pot reduction method. The resulting structurally well-defined Cu45 is a highly efficient catalyst for the hydroboration reaction of alkynes and alkenes. Mechanistic studies show that a single-electron oxidation of the in situ-formed ate complex enables the hydroboration via the formation of boryl-centered radicals under mild conditions. This work demonstrates the promise of tailored copper nanoclusters as catalysts for C-B heteroatom bond-forming reactions. The catalysts are compatible with a wide range of alkynes and alkenes and functional groups for producing hydroborated products.

Selective Mono-Defluorinative Cross-Coupling of Trifluoromethyl arenes via Multiphoton Photoredox Catalysis.

A new cross-coupling of trifluoromethyl arenes has been realized via multiphoton photoredox catalysis. Trifluoromethyl arenes were demonstrated to undergo selective mono-defluorinative alkylation under mild reaction conditions providing access to a series of valuable α,α-difluorobenzylic compounds. The reaction shows broad substrate scope and general functional group tolerance. In addition to the electron-deficient trifluoromethyl arenes that are easily reduced to the corresponding radical anion, more challenging electron-rich substrates were also successfully applied. Steady-State Stern-Volmer quenching studies indicated that the trifluoromethyl arenes were reduced by the multiphoton excited Ir-based photocatalyst.

s-Block Metal Catalysts for the Hydroboration of Unsaturated Bonds.

The addition of a B-H bond to an unsaturated bond (polarized or unpolarized) is a powerful and atom-economic tool for the synthesis of organoboranes. In recent years, s-block organometallics have appeared as alternative catalysts to transition-metal complexes, which traditionally catalyze the hydroboration of unsaturated bonds. Because of the recent and rapid development in the field of hydroboration of unsaturated bonds catalyzed by alkali (Li, Na, K) and alkaline earth (Mg, Ca, Sr, Ba) metals, we provide a detailed and updated comprehensive review that covers the synthesis, reactivity, and application of s-block metal catalysts in the hydroboration of polarized as well as unsaturated carbon-carbon bonds. Moreover, we describe the main reaction mechanisms, providing valuable insight into the reactivity of the s-block metal catalysts. Finally, we compare these s-block metal complexes with other redox-neutral catalytic systems based on p-block metals including aluminum complexes and f-block metal complexes of lanthanides and early actinides. In this review, we aim to provide a comprehensive, authoritative, and critical assessment of the state of the art within this highly interesting research area.

Metallaphotoredox catalysis for sp3 C-H functionalizations through hydrogen atom transfer (HAT).

In recent years, the integration of photocatalytic hydrogen atom transfer (HAT) with transition metal catalysis has emerged as a formidable strategy for the construction of C(sp3)-carbon and C(sp3)-hetero bonds. The fusion of these two methodologies has been utilized widely in organic synthesis, leading to new transformations in chemical synthesis. In this review, we aim to summarize the recent advances made in sp3 C-H functionalizations through photocatalytic HAT followed by transition metal catalysis. Our focus will be on the diverse strategies and their synthetic applications, in addition to detailed mechanisms involved in these reactions. An in-depth understanding of these mechanisms is crucial for the rational design of new catalysts and reaction conditions to further enhance the efficiency of these transformations. We hope that this review will serve as a valuable resource for researchers in the area of metallaphotoredox catalysis, and will inspire the further development of this application in green chemistry, drug synthesis, material science, and other related fields.

Photoexcitation of Distinct Divalent Palladium Complexes in Cross-Coupling Amination Under Air.

The development of metal complexes that function as both photocatalyst and cross-coupling catalyst remains a challenging research topic. So far, progress has been shown in palladium(0) excited-state transition metal catalysis for the construction of carbon-carbon bonds where the oxidative addition of alkyl/aryl halides to zero-valent palladium (Pd0 ) is achievable at room temperature. In contrast, the analogous process with divalent palladium (PdII ) is uphill and endothermic. For the first time, we report that divalent palladium can act as a light-absorbing species that undergoes double excitation to realize carbon-nitrogen (C-N) cross-couplings under air. Differently substituted aryl halides can be applied in the mild, and selective cross-coupling amination using palladium acetate as both photocatalyst and cross-coupling catalyst at room temperature. Density functional theory studies supported by mechanistic investigations provide insight into the reaction mechanism.

Halogen Bonding Initiated Difunctionalization of [1.1.1]Propellane via Photoinduced Polarity Match Additions.

Bicyclo[1.1.1]pentane (BCP), recognized as a bioisostere for para-disubstituted benzene, has gained widespread interest in drug development due to its ability to enhance the physicochemical properties of pharmaceuticals. In this work, we introduce a photoinduced, halogen bonding-initiated, metal-free strategy for synthesizing various BCP derivatives. This method involves the generation of nucleophilic α-aminoalkyl radicals via halogen-bonding adducts. These undergo selective radical addition to [1.1.1]propellane, yielding electrophilic BCP radicals that subsequently participate in polarity-matched additions, culminating in the difunctionalization of bicyclopentane. The versatility and practicality of this metal-free approach are underscored by its broad substrate scope, which includes late-stage functionalization and a series of valuable transformations, all conducted under mild reaction conditions.

Unveiling the Activity Origin of Electrochemical Oxygen Evolution on Heteroatom-Decorated Carbon Matrix.

Chemical modification via functional dopants in carbon materials holds great promise for elevating catalytic activity and stability. To gain comprehensive insights into the pivotal mechanisms and establish structure-performance relationships, especially concerning the roles of dopants, remains a pressing need. Herein, we employ computational simulations to unravel the catalytic function of heteroatoms in the acidic oxygen evolution reaction (OER), focusing on a physical model of high-electronegative F and N co-doped carbon matrix. Theoretical and experimental findings elucidate that the enhanced activity originates from the F and pyridinic-N (Py-N) species that achieve carbon activation. This activated carbon significantly lowers the conversion energy barrier from O* to OOH*, shifts the potential-limiting step from OOH* formation to O* generation, and ultimately optimizes the energy barrier of the potential-limiting step. This wok elucidates that the critical role of heteroatoms in catalyzing the reaction and unlocks the potential of carbon materials for acidic OER.

Highly Dispersed Pd@ZIF-8 for Photo-Assisted Cross-Couplings and CO2 to Methanol: Activity and Selectivity Insights.

Our study unveils a pioneering methodology that effectively distributes Pd species within a zeolitic imidazolate framework-8 (ZIF-8). We demonstrate that Pd can be encapsulated within ZIF-8 as atomically dispersed Pd species that function as an excited-state transition metal catalyst for promoting carbon-carbon (C-C) cross-couplings at room temperature using visible light as the driving force. Furthermore, the same material can be reduced at 250 °C, forming Pd metal nanoparticles encapsulated in ZIF-8. This catalyst shows high rates and selectivity for carbon dioxide hydrogenation to methanol under industrially relevant conditions (250 °C, 50 bar): 7.46 molmethanol molmetal -1 h-1 and >99 %. Our results demonstrate the correlations of the catalyst structure with the performances at experimental and theoretical levels.

A review of recent advances in electrochemical and photoelectrochemical late-stage functionalization classified by anodic oxidation, cathodic reduction, and paired electrolysis.

With the resurgence of electrosynthesis in organic chemistry, there is a significant increase in the number of routes available for late-stage functionalization (LSF) of drugs. Electrosynthetic methods, which obviate the need for hazardous chemical oxidants or reductants, offer unprecedented control of reactions through the continuous variation of the applied potential and the possibility of combination with photochemical processes. This capability is a substantial advantage for performing electrochemical or photoelectrochemical LSF. Ultimately, these protocols are poised to become a vital component of the medicinal chemist's toolkit. In this review, we discuss electrochemical protocols that have been demonstrated to be applicable for the LSF of pharmaceutical drugs, their derivatives, and natural substrates. We present and analyze representative examples to illustrate the potential of electrochemistry or photoelectrochemistry for the LSF of valuable molecular scaffolds.

Bioengineering of air-filled protein nanoparticles by genetic and chemical functionalization.

BACKGROUND: Various bacteria and archaea, including halophilic archaeon Halobacterium sp. NRC-1 produce gas vesicle nanoparticles (GVNPs), a unique class of stable, air-filled intracellular proteinaceous nanostructures. GVNPs are an attractive tool for biotechnological applications due to their readily production, purification, and unique physical properties. GVNPs are spindle- or cylinder-shaped, typically with a length of 100 nm to 1.5 µm and a width of 30-250 nm. Multiple monomeric subunits of GvpA and GvpC proteins form the GVNP shell, and several additional proteins are required as minor structural or assembly proteins. The haloarchaeal genetic system has been successfully used to produce and bioengineer GVNPs by fusing several foreign proteins with GvpC and has shown various applications, such as biocatalysis, diagnostics, bioimaging, drug delivery, and vaccine development. RESULTS: We demonstrated that native GvpC can be removed in a low salt buffer during the GVNP purification, leaving the GvpA-based GVNP's shell intact and stable under physiological conditions. Here, we report a genetic engineering and chemical modification approach for functionalizing the major GVNP protein, GvpA. This novel approach is based on combinatorial cysteine mutagenesis within GvpA and genetic expansion of the N-terminal and C-terminal regions. Consequently, we generated GvpA single, double, and triple cysteine variant libraries and investigated the impact of mutations on the structure and physical shape of the GVNPs formed. We used a thiol-maleimide chemistry strategy to introduce the biotechnological relevant activity by maleimide-activated streptavidin-biotin and maleimide-activated SpyTag003-SpyCatcher003 mediated functionalization of GVNPs. CONCLUSION: The merger of these genetic and chemical functionalization approaches significantly extends these novel protein nanomaterials' bioengineering and functionalization potential to assemble catalytically active proteins, biomaterials, and vaccines onto one nanoparticle in a modular fashion.

Group†14 Elements Hetero-Difunctionalizations via Nickel-Catalyzed Electroreductive Cross-Coupling.

The difunctionalization of unsaturated bonds plays a vital role in the enrichment of molecular complexity. While various catalytic methods for alkene and alkyne difunctionalization have been developed in recent years, hetero-functionalization the introduction of two different atoms has been less explored. This is mainly due to the challenges associated with achieving high chemo-, regio-, and stereoselectivity, especially when adding two similar atoms from the same group across unsaturated bonds. In this study, we describe a nickel-catalyzed, three-component reductive protocol for group 14 element hetero-difunctionalization of 1,3-enynes using electrochemistry. This new method is mild, selective, and general, allowing for the silyl-, germanyl-, and stannyl-alkylation of enynes. Various chlorosilanes as well as chlorogermans, and chlorostannanes can be successfully used in combination with aryl/alkyl-substituted 1,3-enynes and primary, secondary, and tertiary alkyl bromides in the electroreductive coupling.

Organoboron Reagent-Controlled Selective (Deutero)Hydrodefluorination.

(Deuterium-labeled) CF2 H- and CFH2 -moieties are of high interest in drug discovery. The high demand for the incorporation of these fluoroalkyl moieties into molecular structures has witnessed significant synthetic progress, particularly in the (deutero)hydrodefluorination of CF3 -containing compounds. However, the controllable replacement of fluorine atoms while maintaining high chemoselectivity remains challenging. Herein, we describe the development of a selective (deutero)hydrodefluorination reaction via electrolysis. The reaction exhibits a remarkable chemoselectivity control, which is enabled by the addition of different organoboron sources. The procedure is operationally simple and scalable, and provides access in one step to high-value building blocks for application in medicinal chemistry. Furthermore, density functional theory (DFT) calculations have been carried out to investigate the reaction mechanism and to rationalize the chemoselectivity observed.

Isolated Electron Trap-Induced Charge Accumulation for Efficient Photocatalytic Hydrogen Production.

The solar-driven evolution of hydrogen from water using particulate photocatalysts is considered one of the most economical and promising protocols for achieving a stable supply of renewable energy. However, the efficiency of photocatalytic water splitting is far from satisfactory due to the sluggish electron-hole pair separation kinetics. Herein, isolated Mo atoms in a high oxidation state have been incorporated into the lattice of Cd0.5 Zn0.5 S (CZS@Mo) nanorods, which exhibit photocatalytic hydrogen evolution rate of 11.32 mmol g-1 h-1 (226.4 µmol h-1 ; catalyst dosage 20 mg). Experimental and theoretical simulation results imply that the highly oxidized Mo species lead to mobile-charge imbalances in CZS and induce the directional photogenerated electrons transfer, resulting in effectively inhibited electron-hole recombination and greatly enhanced photocatalytic efficiency.

Isostructural Nanocluster Manipulation Reveals Pivotal Role of One Surface Atom in Click Chemistry.

Elucidating single-atom effects on the fundamental properties of nanoparticles is challenging because single-atom modifications are typically accompanied by appreciable changes to the overall particle's structure. Herein, we report the synthesis of a [Cu58 H20 PET36 (PPh3 )4 ]2+ (Cu58 ; PET: phenylethanethiolate; PPh3 : triphenylphosphine) nanocluster-an atomically precise nanoparticle-that can be transformed into the surface-defective analog [Cu57 H20 PET36 (PPh3 )4 ]+ (Cu57 ). Both nanoclusters are virtually identical, with five concentric metal shells, save for one missing surface copper atom in Cu57 . Remarkably, the loss of this single surface atom drastically alters the reactivity of the nanocluster. In contrast to Cu58 , Cu57 shows promising activity for click chemistry, particularly photoinduced [3+2] azide-alkyne cycloaddition (AAC), which is attributed to the active catalytic site in Cu57 after the removal of one surface copper atom. Our study not only presents a unique system for uncovering the effect of a single-surface atom modification on nanoparticle properties but also showcases single-atom surface modification as a powerful means for designing nanoparticle catalysts.

Atomically Precise Defective Copper Nanocluster Catalysts for Highly Selective C-C Cross-Coupling Reactions.

Point defects in nanoparticles have long been hypothesized to play an important role in governing the particle's electronic structure and physicochemical properties. However, single point defects in material systems usually exist with other heterogeneities, obscuring the chemical role of the effects. Herein, we report the synthesis of novel atomically precise, copper hydride nanoclusters (NCs), [Cu28 H10 (C7 H7 S)18 (TPP)3 ] (Cu28 ; TPP: triphenylphosphine; C7 H7 S: o-thiocresol) with a defined defect in the gram scale via a one-pot reduction method. The Cu28 acts as a highly selective catalyst for C-C cross-couplings. The work highlights the potential of defective NCs as model systems for investigating individual defects, correlating defects with physiochemical properties, and rationally designing new nanoparticle catalysts.

Visible-Light Copper Nanocluster Catalysis for the C-N Coupling of Aryl Chlorides at Room Temperature.

Activation of aryl chlorides in cross-coupling reactions is a long-standing challenge in organic synthesis that is of great interest to industry. Ultrasmall (<3 nm), atomically precise nanoclusters (NCs) are considered one of the most promising catalysts due to their high surface area and unsaturated active sites. Herein, we introduce a copper nanocluster-based catalyst, [Cu61(StBu)26S6Cl6H14] (Cu61NC) that enables C-N bond-forming reactions of aryl chlorides under visible-light irradiation at room temperature. A range of N-heterocyclic nucleophiles and electronically and sterically diverse aryl/hetero chlorides react in this new Cu61NC-catalyzed process to afford the C-N coupling products in good yields. Mechanistic studies indicate that a single-electron-transfer (SET) process between the photoexcited Cu61NC complex and aryl halide enables the C-N-arylation reaction.

Aza-Ortho-Quinone Methides as Reactive Intermediates: Generation and Utility in Contemporary Asymmetric Synthesis.

The aza-ortho-quinone methide (aza-o-QM) chemistry has overwhelmingly progressed in the past few decades. This review aims to integrate various transition metal-catalyzed and organocatalytic strategies in taming aza-o-QM intermediates, including the aza-ortho-vinylidene quinone methide (aza-o-VQM), aza-ortho-alkynyl quinone methide (aza-o-AQM), aza-para-quinone methide (aza-p-QM), and indole-based aza-o-QM analog. These transient species are often utilized for the direct and enantioselective synthesis of complex (hetero)polycyclic or fused-ring molecular scaffolds such as tetrahydroquinoline and indoline, among others, which are abundant in many natural products, bioactive compounds, and pharmaceuticals.

Reactivity in Nickel-Catalyzed Multi-component Sequential Reductive Cross-Coupling Reactions.

The nickel-catalyzed three-component reductive carbonylation of alkyl halides, aryl halides, and ethyl chloroformate is described. Ethyl chloroformate is utilized as a safe and readily available source of CO in this multi-component protocol, providing an efficient and practical alternative for the synthesis of aryl-alkyl ketones. The reaction exhibits a wide substrate scope and good functional group compatibility. Experimental and DFT mechanistic studies highlight the complexity of the cross-electrophile coupling and provide insight into the sequence of the three consecutive oxidative additions of aryl halide, chloroformate, and alkyl halide.