噻吩基卟啉衍生物的单光子和双光子吸收性质的理论研究

本文理论上研究了两个系列的噻吩基卟啉衍生物,这种衍生物在可见光区具有大的双光子吸收截面。用密度泛函理论和ZINDO-SOS方法,计算了分子的几何构型、电子结构,单光子和双光子吸收性质。结果显示噻吩单元的数目影响分子的单光子和双光子吸收性质。具有两个或三个噻吩基团的噻吩基卟啉衍生物在较大范围内具有可用于实际应用中的双光子吸收响应,这一性质有利于这类分子在光限幅中的应用。插入乙炔基有利于扩大共轭范围,增加分子的双光子吸收截面。同时,乙炔基团的加入导致了单光子和双光子波长的红移。从高透明性和相对大的非线性光学响应考虑,噻吩基卟啉衍生物是一类有应用前景的双光子吸收材料。     

Study on mechanism of hydrogen adsorption on WO3, W20O58, and W18O49

The density functional theory (DFT) calculation of hydrogen adsorption on tungsten oxides and calculation of the crystal structure of WO₃, W₂₀O₅₈, and W₁₈O₄₉ were performed_. These calculations suggest that the length of W-O bonds in WO₃ are 1.913 Å, the length of 66% W-O bonds in W₂₀O₅₈ is 1.8 to 1.9 Å, and the length of 43.48% W-O bonds in W₁₈O₄₉ is longer than 2.0 Å. The hydrate (WO₂[OH]₂), as an autocatalyst in the hydrogen reduction process, was found in the particular adsorption configuration of W₁₈O₄₉. The WO₃ and W₂₀O₅₈ were completely reduced within 40 to 60 minutes at a temperature of 1000°C and at a hydrogen flow rate of 200 mL/min, while W₁₈O₄₉ was completely reduced within 20 to 40 minutes. The phase composition and micromorphology of raw material and production were studied by both X-ray diffraction analysis (XRD) and FE-SEM technology. The differences of the mechanism of hydrogen adsorption on WO₃, W₂₀O₅₈, and W₁₈O₄₉ were explored based on the density functional theory calculation and the hydrogen reduction experiments.     

A Nano-shield Design for Separators to Resist Dendrite Formation in Lithium-Metal Batteries

Lithium dendrite growth during repeated charge and discharge cycles of lithium-metal anodes often leads to short-circuiting by puncturing the porous separator. Here, a morphological design, the nano-shield, for separators to resist dendrites is presented. Through both mechanical analysis and experiment, it is revealed that the separator protected by the nano-shield can effectively inhibit the penetration of lithium dendrites owing to the reduced stress intensity generated and therefore mitigate the short circuit of Li metal batteries. More than 110 h of lithium plating life is achieved in cell tests, which is among the longest cycle life of lithium metal anode and five times longer than that of blank separators. This new aspect of morphological and mechanical design not only provides an alternative pathway for extending lifetime of lithium metal anodes, but also sheds light on the role of separator engineering for various electrochemical energy storage devices.     

A Nano‐shield Design for Separators to Resist Dendrite Formation in Lithium‐Metal Batteries

Lithium dendrite growth during repeated charge and discharge cycles of lithium‐metal anodes often leads to short‐circuiting by puncturing the porous separator. Here, a morphological design, the nano‐shield, for separators to resist dendrites is presented. Through both mechanical analysis and experiment, it is revealed that the separator protected by the nano‐shield can effectively inhibit the penetration of lithium dendrites owing to the reduced stress intensity generated and therefore mitigate the short circuit of Li metal batteries. More than 110 h of lithium plating life is achieved in cell tests, which is among the longest cycle life of lithium metal anode and five times longer than that of blank separators. This new aspect of morphological and mechanical design not only provides an alternative pathway for extending lifetime of lithium metal anodes, but also sheds light on the role of separator engineering for various electrochemical energy storage devices.     

A Remarkable cis‐ and trans‐Spanning Dibenzylidene Acetone Diphosphine Chelating Ligand (dbaphos)

A multidentate and flexible diolefin–diphosphine ligand, based on the dibenzylidene acetone core, namely dbaphos ( 1 ), is reported herein. The ligand adopts an array of different geometries at Pt, Pd and Rh. At Pt^II the dbaphos ligand forms cis‐ and trans‐diphosphine complexes and can be defined as a wide‐angle spanning ligand. ¹H NMR spectroscopic analysis shows that the β‐hydrogen of one olefin moiety interacts with the Pt^II centre (an anagostic interaction), which is supported by DFT calculations. At Pd⁰ and Rh^I, the dbaphos ligand exhibits both olefin and phosphine interactions with the metal centres. The Pd⁰ complex of dbaphos is dinuclear, with bridging diphosphines. The complex exhibits the coordination of one olefin moiety, which is in dynamic exchange (intramolecular) with the other “free” olefin. The Pd⁰ complex of dbaphos reacts with iodobenzene to afford trans‐[Pd^II(dbaphos)I(Ph)]. In the case of Rh^I, dbaphos coordinates to form a structure in which the phosphine and olefin moieties occupy both axial and equatorial sites, which stands in contrast to a related bidentate olefin, phosphine ligand (“Lei” ligand), in which the olefins occupy the equatorial sites and phosphines the axial sites, exclusively.