氢化物发生-电感耦合等离子体原子发射光谱法测定环境样品中痕量硒

环境样品经硝酸-过氧化氢-氢氟酸体系微波消解,利用自制雾化器采用氢化物发生-电感耦合等离子体原子发射光谱法测定其中的痕量硒。选择硒的分析谱线为196.090nm。硒的质量浓度在32μg·L-1以内与其发射强度呈线性关系,方法的检出限(3S/N)为0.71μg·L-1。方法应用于国家标准物质中硒的的测定,测定值与认定相符,加标回收率在85.8%~102%之间,测定值的相对标准偏差(n=6)在0.38%~2.3%之间。     

Steric,Electronic and Conformational Synergistic Effects in the Gold(I)-catalyzed α-C−H Bond Functionalization of Tertiary Amines**

Direct C−H bond functionalization is a useful strategy for the straightforward formation of C−C and C−Heteroatom bonds. In the present work, a unique approach for the challenging electrophilic Au-catalyzed α-C−H bond functionalization of tertiary amines is presented. Electronic, steric and conformational synergistic effects exerted by the use of a malonate unit in the substrate were key to the success of this transformation. This new reactivity was applied to the synthesis of tetrahydro-γ-carboline products which, under oxidative conditions, could be converted into valuable structural motifs found in bioactive alkaloid natural products.     

Simultaneous co-Photocatalytic CO2 Reduction and Ethanol Oxidation towards Synergistic Acetaldehyde Synthesis

Photocatalytic conversion of CO₂ is of great interest but it often suffers sluggish oxidation half reaction and undesired by-products. Here, we report for the first the simultaneous co-photocatalytic CO₂ reduction and ethanol oxidation towards one identical value-added CH₃CHO product on a rubidium and potassium co-modified carbon nitride (CN-KRb). The CN-KRb offers a record photocatalytic activity of 1212.3 μmol h⁻¹g⁻¹ with a high selectivity of 93.3 % for CH₃CHO production, outperforming all the state-of-art CO₂ photocatalysts. It is disclosed that the introduced Rb boosts the *OHCCHO fromation and facilitates the CH₃CHO desorption, while K promotes ethanol adsorption and activation. Moreover, the H⁺ stemming from ethanol oxidation is confirmed to participate in the CO₂ reduction process, endowing near ideal overall atomic economy. This work provides a new strategy for effective use of the photoexcited electron and hole for high selective and sustainable conversion of CO₂ paired with oxidation reaction into identical product.     

A Tailored Versatile and Efficient NHC-Based NNC-Pincer Manganese Catalyst for Hydrogenation of Polar Unsaturated Compounds

The reactivity of metal-hydride complexes can be harnessed by the modification of ancillary ligands. With the aim of improving the hydride-donor ability of the key Mn−H intermediate and reducing steric hindrance, we herein report the rational design of a versatile and efficient NHC-based NNC-pincer Mn catalyst for hydrogenation reactions. This newly developed catalyst exhibited higher activity than the corresponding NNP-pincer Mn catalyst owing to its reduced steric hindrance and enhanced Mn−H σ-bonding orbital energy level through a π-antibonding interaction. Using this highly active NNC-pincer Mn catalyst, a rich array of polar unsaturated compounds (>80 examples) including esters, N-heteroarenes, amides, carbonates, and urea derivatives, were successfully hydrogenated under relatively mild conditions. This work represents a rare example of a general phosphine-free Mn-catalyzed hydrogenation system.     

Hybrid Double Perovskite Derived Halides Based on Bi and Alkali Metals (K,Rb): Diverse Structures,Tunable Optical Properties and Second Harmonic Generation Responses

Double perovskites (DP) have attracted extensive attention due to their rich structures and wide application prospects in the field of optoelectronics. Here, we report 15 new Bi-based double perovskite derived halides with the general formula of A₂BBiX₆ (A=organic cationic ligand, B=K or Rb, X=Br or I). These materials are synthesized using organic ligands to coordinate with metal ions with a sp³ oxygen, and diverse structure types have been obtained with distinct dimensionalities and connectivity modes. The optical band gaps of these phases can be tuned by changing the halide, the organic ligand and the alkali metal, varying from 2.0 to 2.9 eV. The bromide phases exhibit increasing photoluminescence (PL) intensity with decreasing temperature, while the PL intensity of iodide phases changes nonmonotonically with temperature. Because the majority of these phases are non-centrosymmetric, second harmonic generation (SHG) responses are also measured for selected non-centrosymmetric materials, showing different particle-size-dependent trends. Our findings give rise to a series of new structural types to the DP family, and provide a powerful synthetic handle for symmetry breaking.     

Superatom-in-Superatom Nanoclusters: Synthesis,Structure, and Photoluminescence

We report a new strategy in which a thiolate-protected Ag₂₅ nanocluster can be doped with open d-shell group 8 (Ru, Os) and 9 (Ir) metals by forming metal hydride (RuH₂, OsH₂, IrH) superatoms with a closed d-shell. Structural analyses using various experimental and theoretical methods revealed that the Ag₂₅ nanoclusters were co-doped with the open d-shell metal and hydride species to produce superatom-in-superatom nanoclusters, establishing a novel superatom doping phenomenon for open d-shell metals. The synthesized superatom-in-superatom nanoclusters exhibited dopant-dependent photoluminescence (PL) properties. Comparative PL lifetime studies of the Ag₂₅ nanoclusters doped with 8–10 group metals revealed that both radiative and nonradiative processes were significantly dependent on the dopant. The former is strongly correlated with the electron affinity of the metal dopant, whereas the latter is governed predominantly by the kernel structure changed upon the doping of the metal hydride(s).     

Boosting Charge Transport in a 2D/3D Perovskite Heterostructure by Selecting an Ordered 2D Perovskite as the Passivator

We demonstrate that an ordered 2D perovskite can significantly boost the photoelectric performance of 2D/3D perovskite heterostructures. Using selective fluorination of phenyl-ethyl ammonium (PEA) lead iodide to passivate 3D FA_0.8Cs_0.2PbI₃, we find that the 2D/3D perovskite heterostructures passivated by a higher ordered 2D perovskite have lower Urbach energy, yielding a remarkable increase in photoluminescence (PL) intensity, PL lifetime, charge-carrier mobilities (ϕμ), and carrier diffusion length (L_D) for a certain 2D perovskite content. High performance with an ultralong PL lifetime of ≈1.3 μs, high ϕμ of ≈18.56 cm² V⁻¹ s⁻¹, and long L_D of ≈7.85 μm is achieved in the 2D/3D films when passivated by 16.67 % para-fluoro-PEA₂PbI₄. This carrier diffusion length is comparable to that of some perovskite single crystals (>5 μm). These findings provide key missing information on how the organic cations of 2D perovskites influence the performance of 2D/3D perovskite heterostructures.     

C−F Transformations of Benzotrifluorides by the Activation of Ortho-Hydrosilyl Group

Single C−F transformations of aromatic trifluoromethyl compounds are challenging issues due to the strong C−F bond. We have recently developed selective methods for single C−F transformations such as allylation of o-hydrosilyl-substituted benzotrifluorides through the hydride abstraction with trityl cations. Single C−F thiolation and azidation of o-(hydrosilyl)benzotrifluorides were achieved using trityl sulfides and trityl azide catalyzed by Yb(OTf)₃. Treatment of o-(hydrosilyl)benzotrifluorides with trityl chloride resulted in single C−F chlorination. The resulting fluorosilyl group served in further transformations including protonation, halogenation, and Hiyama cross-coupling with C−Si cleavage. We also synthesized benzyl fluorides by LiAlH₄-reduction of the resulting fluorosilanes and further C−F transformations. These methods enabled us to prepare a broad range of organofluorines from simple benzotrifluorides through C−F and C−Si transformations.     

Perfectly Encoding π-Conjugated Anions in the RE5(C3N3O3)(OH)12 (RE=Y,Yb, Lu) Family with Strong Second Harmonic Generation Response and Balanced Birefringence

Nonlinear optical (NLO) crystal, which simultaneously exhibits strong second-harmonic-generation (SHG) response and desired optical anisotropy, is a core optical material accessible to the modern optoelectronics. Accompanied by strong SHG effect in a NLO crystal, a contradictory problem of overlarge birefringence is ignored, leading to low frequency doubling efficiency and poor beam quality. Herein, a series of rare earth cyanurates RE₅(C₃N₃O₃)(OH)₁₂ (RE=Y, Yb, Lu) were successfully characterized by 3D electron diffraction technique. Based on a “three birds with one stone” strategy, they enable the simultaneous fulfillment of strong SHG responses (2.5–4.2× KH₂PO₄), short UV cutoff (ca. 220 nm) and applicable birefringence (ca. 0.15 at 800 nm) by the introduction of rare earth coordination control of π-conjugated (C₃N₃O₃)³⁻ anions. These findings provide high-performance short-wavelength NLO materials and highlight the exploration of cyanurates as a new research area.     

Striking Differences in Properties of Geometric Isomers of [Ir(tpy)(ppy)H]+: Experimental and Computational Studies of their Hydricities,Interaction with CO2, and Photochemistry

We prepared two geometric isomers of [Ir(tpy)(ppy)H]⁺, previously proposed as a key intermediate in the photochemical reduction of CO₂ to CO, and characterized their notably different ground‐ and excited‐state interactions with CO₂ and their hydricities using experimental and computational methods. Only one isomer, C‐trans‐[Ir(tpy)(ppy)H]⁺, reacts with CO₂ to generate the formato complex in the ground state, consistent with its calculated hydricity. Under photocatalytic conditions in CH₃CN/TEOA, a common reactive C‐trans‐[Ir(tpy)(ppy)]⁰ species, irrespective of the starting isomer or monodentate ligand (such as hydride or Cl), reacts with CO₂ and produces CO with the same catalytic efficiency.