Electrochemical Knocking-Down of Zn Metal Clusters into Single Atoms.

Single Atoms Catalysts (SACs) have emerged as a class of highly promising heterogeneous catalysts, where the traditional bottom-up synthesis approaches often encounter considerable challenges in relation to aggregation issues and poor stability. Consequently, achieving densely dispersed atomic species in a reliable and efficient manner remains a key focus in the field. Herein, we report a new facile electrochemical knock-down strategy for the formation of SACs, whereby the metal Zn clusters are transformed into single atoms. While a defect-rich substrate plays a pivotal role in capturing and stabilizing isolated Zn atoms, the feasibility of this novel strategy is demonstrated through a comprehensive investigation, combining experimental and theoretical studies. Furthermore, when studied in exploring for potential applications, the material prepared shows a remarkable improvement of 58.21% for the Li+ storage and delivers a capacity over 300 Wh kg-1 after 500 cycles upon the transformation of Zn clusters into single atoms.

"Hard" Emulsion-Induced Interface Super-Assembly: A General Strategy for Two-Dimensional Hierarchically Porous Metal-Organic Framework Nanoarchitectures.

Two-dimensional (2D) hierarchically porous metal-organic framework (MOF) nanoarchitectures with tailorable meso-/macropores hold great promise for enhancing mass transfer kinetics, augmenting accessible active sites, and thereby boosting performance in heterogeneous catalysis. However, achieving the general synthesis of 2D free-standing MOF nanosheets with controllable hierarchical porosity and thickness remains a challenging task. Herein, we present an ingenious "hard" emulsion-induced interface super-assembly strategy for preparing 2D hierarchically porous UiO-66-NH2 nanosheets with highly accessible pore channels, tunable meso-/macropore sizes, and adjustable thicknesses. The methodology relies on transforming the geometric shape of oil droplet templates within appropriate oil-in-water emulsions from conventional zero-dimensional (0D) "soft" liquid spheres to 2D "hard" solid sheets below the oil's melting/freezing point. Subsequent surfactant exchange on the surface of 2D "hard" emulsions facilitates the heterogeneous nucleation and interfacial super-assembly of in situ formed mesostructured MOF nanocomposites, serving as structural units, in a loosely packed manner to produce 2D MOF nanosheets with multimodal micro/meso-/macroporous systems. Importantly, this strategy can be extended to prepare other 2D hierarchically porous MOF nanosheets by altering metal-oxo clusters and organic ligands. Benefiting from fast mass transfer and highly accessible Lewis acidic sites, the resultant 2D hierarchically porous UiO-66-NH2 nanosheets deliver a fabulous catalytic yield of approximately 96% on the CO2 cycloaddition of glycidyl-2-methylphenyl ether, far exceeding the yield of approximately 29% achieved using conventional UiO-66-NH2 microporous crystals. This "hard" emulsion-induced interface super-assembly strategy paves a new path toward the rational construction of elaborate 2D nanoarchitecture of hierarchical MOFs with tailored physicochemical properties for diverse potential applications.

Copper/O2-Mediated Oxidative C-C Activation of Nitriles for Selective Acylation-Bromination of Anilines.

This study reports selective dual amino acylation and C-H bromination of aniline compounds enabled by Cu/O2 catalyst systems. This method involves crucial oxidation-induced C-CN bond cleavage of α-methylene nitriles to generate an acylcyanide intermediate that is facilely intercepted by anilines. After amino acylation, the Cu(II) precatalyst in combination with NBS generates Cu(III)-Br in situ that engages in selective electrophilic para- or ortho-C-H bromination. The substrate scope, mechanistic aspects, and late-stage functionalization of biologically active anilines are studied. This study shows the synthetic potential of oxidative C-CN bond activation of nitriles for the development of valuable reactions.

Dual Oxidation of Epoxides with a High-Valent Cu(III)-CF3 Compound and DMSO to Access 1,2-Diketones.

This study reports sequential dehydrogenation and transfer oxygenation of 1,2-diarylepoxides by high-valent phenCu(III)(CF3)3 and DMSO to produce 1,2-diketones. The Cu(III)-CF3 compound serves as a CF3 radical source to abstract the hydrogen atom of the epoxide ring. The resulting ether α-carbon radical undergoes ring-opening rearrangement to give a ketone α-carbon radical intermediate, which is oxygenated by DMSO with the release of Me2S. The combination of a Cu(III)-CF3 compound and DMSO may be exploited to develop other novel oxidation reactions.

Direct formylation of phenols using difluorocarbene as a safe CO surrogate.

A convenient method to prepare aryl formates is reported herein that exploits difluorocarbene to serve as a CO surrogate. This reaction is proposed to occur through a sequential O-difluoromethylation of phenol, followed by α-C-F bond functionalization of the resulting aryl difluoromethyl ether intermediate by phenol or moisture through fluorosemiacetal or orthoformate intermediates. Late-stage modification of biologically and materially active compounds is demonstrated.

High-valent Cu(III)-CF3 compound-mediated esterification reaction.

Cu(III)-CF3 compounds are reported herein as novel coupling reagents to mediate ester synthesis from carboxyl acids and alcohols/phenols. Carboxylic acids are transformed to trifluoromethyl ester and acyl fluoride activated species that interact with each other. The broad substrate scope and late-stage application of this method are demonstrated. This study opens up new opportunities to develop interesting reactions using Cu(III)-CF3 compounds without transferring a CF3 group to the products.

Three-Component Coupling of Anilines, Amines, and Difluorocarbene to Access Formamidines.

A one-pot three-component reaction of two anilines (or one aniline and one alkylamine) and in situ-generated difluorocarbene is developed herein to enable efficient construction of formamidines. Crucial formimidoyl fluoride intermediate RN═CHF is proposed from the reaction of a primary aniline and difluorocarbene. Ensuing nucleophilic iminyl substitution of this intermediate with a second amine allows cross-condensation of the two amines to produce formamidines. When only one type of primary aniline is used as the substrate, the difluoromethylated homo-condensation products can also be produced under a 1:1 molar ratio of aniline/difluorocarbene. Intramolecular variant of this method allows concise synthesis of benzimidazoquinazolines and nitrogen-fused/spirocyclic compounds, showing the potential of this method in organic synthesis. More interesting reactions are anticipated by exploiting the reactivity of difluorocarbene and primary amines to isocyanides or the formimidoyl fluoride intermediates.

Direct Arene Trifluoromethylation Enabled by a High-Valent CuIII -CF3 Compound.

Direct C-H trifluoromethylation of arenes and heteroarenes poses an important synthetic challenge that is highly desirable. High-valent CuIII -CF3 compounds have often been invoked in copper-mediated trifluoromethylation reactions, but the fundamental reactivity toward arenes is elusive. Herein, direct C-H trifluoromethylation of arenes/heteroarenes by a high-valent CuIII -CF3 compound is disclosed for the first time. The CuIII -CF3 compound serves CF3 radical and a CuII oxidant by homolytic cleavage of a CuIII -CF3 bond, which engage synergistically in a SE Ar type reaction with arenes. The presence of K2 S2 O8 co-oxidant can significantly improve the reaction yields. This reaction shows good efficiency, broad functional group tolerance, and the potential in late-stage functionalization. The reactivity of high-valent CuIII -CF3 compounds disclosed in this study represents an important progress in organofluorine and CuIII chemistry.

Engineering Platinum-Cobalt Nano-alloys in Porous Nitrogen-Doped Carbon Nanotubes for Highly Efficient Electrocatalytic Hydrogen Evolution.

Highly efficient electrocatalysts are essential for the production of green hydrogen from water electrolysis. Herein, a metal-organic framework-assisted pyrolysis-replacement-reorganization approach is developed to obtain ultrafine Pt-Co alloy nanoparticles (sub-10 nm) attached on the inner and outer shells of porous nitrogen-doped carbon nanotubes (NCNT) with closed ends. During the thermal reorganization, the migration of Pt-Co nano-alloys to both surfaces ensures the maximized exposure of active sites while maintaining the robust attachment to the porous carbon matrix. Density functional theory calculations suggest a nearly thermodynamically-neutral free energy of adsorption for hydrogen intermediates and diversified active sites induced by alloying, thus resulting in a great promotion in intrinsic activity towards the hydrogen evolution reaction (HER). Benefiting from the delicate structural design and compositional modulation, the optimized Pt3 Co@NCNT electrocatalyst manifests outstanding HER activity and superior stability in both acidic and alkaline media.

Phosphorized CoNi2 S4 Yolk-Shell Spheres for Highly Efficient Hydrogen Production via Water and Urea Electrolysis.

Exploring earth-abundant electrocatalysts with excellent activity, robust stability, and multiple functions is crucial for electrolytic hydrogen generation. Porous phosphorized CoNi2 S4 yolk-shell spheres (P-CoNi2 S4 YSSs) were rationally designed and synthesized by a combined hydrothermal sulfidation and gas-phase phosphorization strategy. Benefiting from the strengthened Ni3+ /Ni2+ couple, enhanced electronic conductivity, and hollow structure, the P-CoNi2 S4 YSSs exhibit excellent activity and durability towards hydrogen/oxygen evolution and urea oxidation reactions in alkaline solution, affording low potentials of -0.135 V, 1.512 V, and 1.306 V (versus reversible hydrogen electrode) at 10 mA cm-2 , respectively. Remarkably, when used as the anode and cathode simultaneously, the P-CoNi2 S4 catalyst merely requires a cell voltage of 1.544 V in water splitting and 1.402 V in urea electrolysis to attain 10 mA cm-2 with excellent durability for 100 h, outperforming most of the reported nickel-based sulfides and even noble-metal-based electrocatalysts. This work promotes the application of sulfides in electrochemical hydrogen production and provides a feasible approach for urea-rich wastewater treatment.

Construction of Co-Mn Prussian Blue Analog Hollow Spheres for Efficient Aqueous Zn-ion Batteries.

Prussian blue analogs (PBAs) are considered as reliable and promising cathode materials for aqueous Zn-ion batteries (AZIBs), but they suffer from low capacity and poor cycling stability due to insufficient active sites and structural damage caused by the ion insertion/extraction processes. Herein, a template-engaged ion exchange approach has been developed for the synthesis of Co-substituted Mn-rich PBA hollow spheres (CoMn-PBA HSs) as cathode materials for AZIBs. Benefiting from the multiple advantageous features including hollow structure, abundant active sites, fast Zn2+ ion diffusion, and partial Co substitution, the CoMn-PBA HSs electrode shows efficient zinc ion storage properties in terms of high capacity, decent rate capability and prolonged cycle life.

Trimetallic Spinel NiCo2-x Fex O4 Nanoboxes for Highly Efficient Electrocatalytic Oxygen Evolution.

The development of efficient and low-cost electrocatalysts toward the oxygen evolution reaction (OER) is critical for improving the efficiency of several electrochemical energy conversion and storage devices. Here, we report an elaborate design and synthesis of porous Co-based trimetallic spinel oxide nanoboxes (NiCo2-x Fex O4 NBs) by a novel metal-organic framework engaged strategy, which involves chemical etching, cation exchange, and subsequent thermal oxidation processes. Owing to the structural and compositional advantages, the optimized trimetallic NiCo2-x Fex O4 NBs (x is about 0.117) deliver superior electrocatalytic performance for OER with an overpotential of 274 mV at 10 mA cm-2 , a small Tafel slope of 42 mV dec-1 , and good stability in alkaline electrolyte, which is much better than that of Co-based bi/monometallic spinel oxides and even commercial RuO2 .

An aerobic and green C-H cyanation of terminal alkynes.

This study describes a benign C-H cyanation of terminal alkynes with α-cyanoesters serving as a nontoxic cyanide source. In situ generation of the key copper cyanide intermediate is proposed by a sequence of α-C-H oxidation and copper-mediated ß-carbon elimination of α-cyanoesters, releasing the α-ketoester byproduct observed experimentally. The ensuing reaction of copper cyanide with terminal alkynes delivers preferentially cyanoalkynes and surpasses the possible Glaser type dimerization of terminal alkynes or the undesired accumulation of HCN under protic conditions. The presence of the co-oxidant K2S2O8 is crucial to this selectivity, probably by promoting oxidative transmetalation and the resulting formation of the Cu(iii)(acetylide)(CN) intermediate. All the reagents and salts used are commercially available, cheap and nontoxic, avoiding the use of highly toxic cyanide salts typically required in cyanation studies. The scope of this reaction is demonstrated with a set of alkynes and α-cyanoesters. The application of this method to late-stage functionalization of the terminal alkyne group in an estrone derivative is also feasible, showing its practical value for drug design.

The effects of exogenous organic acids on the growth, photosynthesis and cellular ultrastructure of Salix variegata Franch. Under Cd stress.

We studied the effects of three organic acids (citric acid, tartaric acid and malic acid) on the biomass, photosynthetic pigment content and photosynthetic parameters of Salix variegata under Cd stress and observed the ultrastructure of mesophyll cells in each treatment. Cd stress significantly reduced photosynthesis by reducing the content of pigments and disrupting chloroplast structure, which consequently decreased the biomass. However, respective addition of three organic acids greatly increased the biomass of S. variegata under Cd stress. Among them, the effect of malic acid or tartaric acid on shoot and total biomass accumulation was greater than that of citric acid. The alleviation of biomass probably related with the photosynthetic process. Results revealed that treatment with each organic acid enhanced the net photosynthesis rate under Cd stress. Malic acid promoted plant growth and biomass by increasing the chlorophyll content and mitigating damage to the photosynthetic apparatus resulting from Cd stress. Tartaric acid had little impact on the photosynthetic pigment content, but it was important in mitigating the ultrastructural damage of plants caused by Cd. Addition of citric acid significantly increased the carotenoid as well as the number and volume of chloroplasts in mesophyll cells, while the mitigation of structural damage in the photosynthetic apparatus was weaker than that in tartaric acid or malic acid treatment. It is concluded that application of tartaric acid or malic acid is effective in increasing the growth potential of S. variegata under Cd stress and thus can be a promising approach for the phytoremediation of Cd-contaminated soil.

Formation of Hierarchical FeCoS2 -CoS2 Double-Shelled Nanotubes with Enhanced Performance for Photocatalytic Reduction of CO2.

Hierarchical FeCoS2 -CoS2 double-shelled nanotubes have been rationally designed and constructed for efficient photocatalytic CO2 reduction under visible light. The synthetic strategy, engaging the two-step cation-exchange reactions, precisely integrates two metal sulfides into a double-shelled tubular heterostructure with both of the shells assembled from ultrathin two-dimensional (2D) nanosheets. Benefiting from the distinctive structure and composition, the FeCoS2 -CoS2 hybrid can reduce bulk-to-surface diffusion length of photoexcited charge carriers to facilitate their separation. Furthermore, this hybrid structure can expose abundant active sites for enhancing CO2 adsorption and surface-dependent redox reactions, and harvest incident solar irradiation more efficiently by light scattering in the complex interior. As a result, these hierarchical FeCoS2 -CoS2 double-shelled nanotubes exhibit superior activity and high stability for photosensitized deoxygenative CO2 reduction, affording a high CO-generating rate of 28.1 µmol h-1 (per 0.5 mg of catalyst).

Co-Fe Alloy/N-Doped Carbon Hollow Spheres Derived from Dual Metal-Organic Frameworks for Enhanced Electrocatalytic Oxygen Reduction.

Metal-organic framework (MOF) composites have recently been considered as promising precursors to derive advanced metal/carbon-based materials for various energy-related applications. Here, a dual-MOF-assisted pyrolysis approach is developed to synthesize Co-Fe alloy@N-doped carbon hollow spheres. Novel core-shell architectures consisting of polystyrene cores and Co-based MOF composite shells encapsulated with discrete Fe-based MOF nanocrystallites are first synthesized, followed by a thermal treatment to prepare hollow composite materials composed of Co-Fe alloy nanoparticles homogeneously distributed in porous N-doped carbon nanoshells. Benefitting from the unique structure and composition, the as-derived Co-Fe alloy@N-doped carbon hollow spheres exhibit enhanced electrocatalytic performance for oxygen reduction reaction. The present approach expands the toolbox for design and preparation of advanced MOF-derived functional materials for diverse applications.

Mechanism and chemoselectivity origins of bioconjugation of cysteine with Au(iii)-aryl reagents.

Organometallic reagents, in particular Pd(ii)- and Au(iii)-aryl reagents, have recently emerged as an efficient tool for bioconjugation. However, the detailed mechanism and origins of chemoselectivity are not well established, but are highly desirable from both synthetic and theoretical viewpoints. In this paper, we report that a computational study dealing with the reaction mechanism of Au(iii)-aryl reagents enabled selective cysteine S-arylation of peptides and proteins developed by Maynard and Spokoyny et al. (J. Am. Chem. Soc., 2018, 140, 7065). Our calculation results suggest that the reaction proceeds by a cationic Au(iii)/Au(i) pathway involving elementary steps of (a) binding of the SH residue to the Au(iii) center, (b) deprotonation of the SH residue, and (c) reductive elimination from a key four-coordinate square planar (L)Au(iii)(thiolate)(Ar) (L is a P,N-bidentate ligand) intermediate. Furthermore, the chemoselectivity of S-arylation against arylation of other nucleophilic residues can be rationalized in terms of energy demand of the three elementary steps. For instance, amine N-arylation is more difficult than S-arylation due majorly to the much higher energy required for deprotonation of much more basic N-H bonds than for deprotonation of weakly acidic S-H bonds. Carboxylate O-arylation is challenging due to the high activation energy of reductive elimination from LAu(iii)(carboxylate)(aryl), because carboxylate is much less nucleophilic than thiolate. These results thus identify acidity and nucleophilicity of the residue as two inherent factors for bioconjugation. This study provides a useful and convenient approach for predicting and rationalizing the feasibility and chemoselectivity of related bioconjugation reactions.

Intrahepatic Cholangiocarcinoma Associated Paradoxical Peripheral Embolism and a Submassive Pulmonary Embolism.

Paradoxical peripheral embolism and submassive pulmonary embolism (PE), secondary to cancer-associated thrombosis, are yet to be reported in the literature. Here we describe a case presenting with an acute peripheral arterial embolism. Subsequent testing revealed a PE and an intrahepatic cholangiocarcinoma as the likely risk factors for thrombus, with arterial spread likely achieved through a patent foramen ovale. The patient's symptoms almost relieved upon catheter-directed thrombus fragmentation and aspiration, catheter-directed thrombolysis, and combined anticoagulation. Embolism and major bleeding did not occur during 6 months of follow-up under systemic anticoagulation with rivaroxaban. This case documents that catheter-directed thrombolysis and anticoagulation could be likely effective and safe in the treatment and prevention of recurrence of paradoxical embolism and PE secondary to cancer-associated thrombosis.

[Effect of microRNA-133b on Myocardial Fibrosis].

Objective To investigate the effect of microRNA-133b(miR-133b)on cardiac fibrosis and its mechanism.Methods Human cardiac fibroblasts(CFs)were harvested.The proliferation of CFs was detected by CCK8 during the overexpression and knock-down of miR-133b.The expressions of connective tissue growth factor(CTGF),α-smooth muscle actin(α-SMA),collagen Ⅰ,and collagen Ⅲ were detected with qRT-PCR and Western blot analysis after miR-133b overexpression or downexpression.Target genes of miR-133b were predicted by bioinformatics software.Dual-luciferase activity assay were used to verify a target gene of miR-133b.Results qRT-PCR showed that the expression level of miR-133b in the miR-133b mimic group was significantly higher than that in the negative control group(t=26.219,P=0.000).The expression level of miR-133b in the miR-133b inhibitor group was significantly lower than that in the negative control group(t=6.738,P=0.003).After 21,45,69,93,and 117 hours of transfection,the proliferation ability of CFs significantly decreased in the miR-133b mimic group but significantly increased in the miR-133b group(all P<0.05,compared with the negative control group).After overexpression of miR-133b,the mRNA and protein levels of CTGF(t=9.213,P=0.001;t=8.195,P=0.001),α-SMA(t=6.511,P =0.003;t=4.434,P=0.011),collagenⅠ(t=3.172,P=0.034;t=4.053,P=0.015)and collagen Ⅲ(t=6.404,P=0.003;t=5.319,P=0.006)were significantly down-regulated.After the expression of miR-133b was knocked down,the mRNA and protein levels of CTGF(t=9.439,P=0.001;t=14.100,P=0.000),α-SMA(t=4.519,P=0.011;t=4.377,P=0.012),collagen Ⅰ(t=5.966,P=0.004;t=5.514,P=0.005)and collagen Ⅲ(t=4.622,P=0.010;t=4.996,P=0.008)were significantly increased.The relative luciferase activity of the cells co-transfected with miR-133b mimic and WT 3'UTR expression vector was significantly lower than that of the cells co-transfected with mimic control and WT 3'UTR expression vectors(t=5.654,P=0.005);however,there was no significant difference in relative luciferase activity between cells co-transfected with miR-133b mimic and MUT 3'UTR expression vectors and cells co-transfected with mimic control and MUT 3'UTR expression vectors(t=0.380,P=0.724).Conclusion miR-133b may affect the activation and proliferation of CFs by targeting CTGF and thus improve cardiac fibrosis.

[Study on dynamic changes of chemical constituents during different drying processes of Salvia miltiorrhiza].

There is no consensus on the drying methods of Salvia miltiorrhiza in ancient and modern times,especially on the content of phenolic acid in fresh S. miltiorrhiza. In order to further explore the content of main components in fresh S. miltiorrhiza and study the dynamic changes during the drying process,the content of main components was used as the index in this study to evaluate the processing method,drying method,correlation between dehydration rate and component content for fresh S. miltiorrhiza. In addition,the sealed and unsealed parallel control groups were set to carry out verification test during the drying process. UPLC method was used for determination of seven main components including rosmarinic acid,lithosperic acid,salvianolic acid B,cryptotanshinone,tanshinoneⅠ,methylene salianolate and tanshinone ⅡAin S. miltiorrhiza. The results showed that the fresh S. miltiorrhiza contained low levels of phenolic acid,and the content of phenolic acid increased significantly with the increase of dehydration rate during drying process,while the change of tanshinone was not obvious. In the comparison of three drying methods,we found that drying at 50 ℃ was better than drying in the sun,and drying in the sun was superior to drying in the shade. So,drying at 50 ℃ was the best drying method. The correlation between dehydration and phenolic acid content of S. miltiorrhiza was analyzed by verification test and SPSS software,which further proved that the dehydration rate was significantly positively correlated with the content of phenolic acid components. This study provides reference for the production processing and drying methods of S. miltiorrhiza medicinal materials,which is of great significance for improving the quality of S. miltiorrhiza.