Biomimetic Hydrogenation Catalyzed by a Manganese Model of [Fe]‐Hydrogenase

[Fe]‐hydrogenase is an efficient biological hydrogenation catalyst. Despite intense research, Fe complexes mimicking the active site of [Fe]‐hydrogenase have not achieved turnovers in hydrogenation reactions. Herein, we describe the design and development of a manganese(I) mimic of [Fe]‐hydrogenase. This complex exhibits the highest activity and broadest scope in catalytic hydrogenation among known mimics. Thanks to its biomimetic nature, the complex exhibits unique activity in the hydrogenation of compounds analogous to methenyl‐H₄MPT⁺, the natural substrate of [Fe]‐hydrogenase. This activity enables asymmetric relay hydrogenation of benzoxazinones and benzoxazines, involving the hydrogenation of a chiral hydride transfer agent using our catalyst coupled to Lewis acid‐catalyzed hydride transfer from this agent to the substrates.     

1,3‐Difunctionalizations of [1.1.1]Propellane via 1,2‐Metallate Rearrangements of Boronate Complexes

1,3‐Disubstituted bicyclo[1.1.1]pentanes (BCPs) are valuable bioisosteres of para‐substituted aromatic rings. The most direct route to these structures is via multicomponent ring‐opening reactions of [1.1.1]propellane. However, challenges associated with these transformations mean that difunctionalized BCPs are more commonly prepared by multistep reaction sequences with BCP‐halide intermediates. Herein, we report three‐ and four‐component 1,3‐difunctionalizations of [1.1.1]propellane with organometallic reagents, organoboronic esters, and a variety of electrophiles. This process is achieved by trapping intermediate BCP‐metal species with boronic esters to form boronate complexes, which are versatile intermediates whose electrophile‐induced 1,2‐metallate rearrangement chemistry enables a broad range of C?C bond‐forming reactions.     

Palladium‐Catalyzed Asymmetric [8+2] Dipolar Cycloadditions of Vinyl Carbamates and Photogenerated Ketenes

Higher‐order cycloadditions, particularly [8+2] cycloadditions, are a straightforward and efficient strategy for constructing significant medium‐sized architectures. Typically, configuration‐restrained conjugated systems are utilized as 8π‐components for higher‐order concerted cycloadditions. However, for this reason, 10‐membered monocyclic skeletons have never been constructed via catalytic asymmetric [8+2] cycloaddition with high peri‐ and stereoselectivity. Here, we accomplished an enantioselective [8+2] dipolar cycloaddition via the merger of visible‐light activation and asymmetric palladium catalysis. This protocol provides a new route to 10‐membered monocyclic architectures bearing chiral quaternary stereocenters with high chemo‐, peri‐, and enantioselectivity. The success of this strategy relied on the facile in situ generation of Pd‐containing 1,8‐dipoles and their enantioselective trapping by ketene dipolarophiles, which were formed in situ via a photo‐Wolff rearrangement.     

The Direct Partial Oxidation of Methane to Dimethyl Ether over Pt/Y2O3 Catalysts Using an NO/O2 Shuttle

Using a mixture of NO + O₂ as the oxidant enabled the direct selective oxidation of methane to dimethyl ether (DME) over Pt/Y₂O₃. The reaction was carried out in a fixed bed reactor at 0.1 MPa over a temperature range of 275–375 °C. During the activity tests, the only carbon‐containing products were DME and CO₂. The DME productivity (μmol g_cat^?1 h^?1) was comparable to oxygenate productivities reported in the literature for strong oxidants (N₂O, H₂O₂, O₃). The NO + O₂ mixture formed NO₂, which acted as the oxygen atom carrier for the ultimate oxidant O₂. During the methane partial oxidation reaction, NO and NO₂ were not reduced to N₂. In situ FTIR showed the formation of surface nitrate species, which are considered to be key intermediate species for the selective oxidation.     

A Photochemical/Thermal Switch Based on 4,4′-Bis(benzimidazolio)stilbene: Synthesis and Supramolecular Properties.

Stilbene derivatives are well-recognised substructures of molecular switches based on photochemically and/or thermally induced (E)/(Z) isomerisation. We combined a stilbene motif with two benzimidazolium arms to prepare new sorts of supramolecular building blocks and examined their binding properties towards cucurbit[n]urils (n=7, 8) and cyclodextrins (β-CD, γ-CD) in water. Based on the ¹H NMR data and molecular dynamics simulations, we found that two distinct complexes with different stoichiometry, i. e., guest@β-CD and guest@β-CD₂, coexist in equilibrium in a water solution of the (Z)-stilbene-based guests. We also demonstrated that the bis(benzimidazolio)stilbene guests can be transformed from the (E) into the (Z) form via UV irradiation and back via thermal treatment in DMSO.     

Si(111) Electrode/Electrolyte Interracial Studied by in-situ Second Harmonic Generation

Si(111) electrode has been widely used in electrochemical and photoelectrochemical studies. The potential dependent measurements of the second harmonic generation (SHG) were performed to study Si(111) electrode interface. At different azimuthal angles of the Si(111) and under different polarization combinations, the curve of the intensity of SHG with extern potential has a different form of line or parabola. Quantitative analysis showed that these differences in the potential-dependence can be explained by the isotropic and anisotropic contribution of the Si(111) electrode. The change in the isotropic and anisotropic contribution of the Si(111) electrode may be attributed to the increase in the doping concentration of Si(111) electrodes.     

A Simple and Strong Electron‐Deficient 5,6‐Dicyano[2,1,3]benzothiadiazole‐Cored Donor‐Acceptor‐Donor Compound for Efficient Near Infrared Thermally Activated Delayed Fluorescence

Despite the success of thermally activated delayed fluorescent (TADF) materials in steering the next generation of organic light‐emitting diodes (OLEDs), effective near infrared (NIR) TADF emitters are still very rare. Here, we present a simple and extremely high electron‐deficient compound, 5,6‐dicyano[2,1,3]benzothiadiazole (CNBz), as a strong electron‐accepting unit to develop a sufficiently strong donor‐acceptor (D?A) interaction for NIR emission. End‐capping with the electron‐donating triphenylamine (TPA) unit created an effective D?A?D type system, giving rise to an efficient NIR TADF emissive molecule (λ_em=750 nm) with a very small ΔE_ST of 0.06 eV. The electroluminescent device using this NIR TADF emitter exhibited an excellent performance with a high maximum radiance of 10020 mW Sr^?1 m^?2, a maximum EQE of 6.57% and a peak wavelength of 712 nm.     

[100]LiF单晶在60 GPa以内冲击加载下的高压屈服强度特性

获取光学窗口自身的高压强度特性是开展材料高压高应变率冲击响应行为精密测量和数据反演的重要基础。利用平板撞击和双屈服面法,通过冲击-卸载、冲击-再加载原位粒子速度剖面精细测量和数据反演,获得了约60 GPa范围内[100]LiF屈服强度特性随冲击压力的变化规律。结果表明:在实验压力范围内,[100]LiF的屈服强度随加载压力的提高而显著提高,压力硬化效应显著;同时,LiF在冲击加载下的屈服强度高于磁驱准等熵加载结果,应变率硬化效应强于热软化效应。采用Huang-Asay模型确定了可描述冲击加载[100]LiF强度特性的本构模型参数,为LiF在强度、相变、层断裂等加窗测量实验中的深入应用和数据准确解读提供了重要支撑。     

甲醇在Au(111)表面吸附的密度泛函研究

 采用基于第一性原理的密度泛函理论和周期平板模型相结合的方法,对CH3OH分子在Au(111)表面top, fcc, hcp和bridge位的吸附模型进行了构型优化、能量计算以及Mulliken布居分析,结果表明top位是较有利的吸附位. 吸附的CH3OH解离产生甲氧基CH3O和H, 对它们在Au(111)面的吸附进行的计算表明, bridge和fcc位分别是二者的最佳吸附位. 对过渡态的计算给出了CH3OH在Au表面解离吸附的可能机理: 首先发生 O-H 键的断裂,继而生成甲氧基中间体.     

Synthesis of 1-O-R-5-deoxy-β-D-ribofuranosides with (CH3)2As and (CH3)2AsO as substituents at the 5-position and a methyl or 2′,3′-dihydroxypropyl group as the aglycone in the 1-position

Six arsenic-containing β-D -ribofuranosides, including the naturally occurring (2′R)-dimethyl[1-O-(2′,3′-dihydroxypropyl)-5-deoxy-β-D -ribofuranos-5-yl]arsine oxide, were prepared in multi-step reactions from D -ribose and tetramethyldiarsine. The synthetic procedure uses the early substitution of the hydroxy group with bromine at C5, subsequent attachment of a chiral three-carbon aglycone at C1, and final delivery of arsenic at C5. The synthesis provides a viable route for the preparation of multigram quantities of the natural product.