Langli Luo  Yao Nian  Shuangbao Wang  Zejian Dong  Yang He  You Han  Chongmin Wang 《Angewandte Chemie (International ed. in English)》2020,59(6):2505-2509

By using in situ aberration‐corrected environmental transmission electron microscopy, for the first time at atomic level, the dynamic evolution of the Cu surface is captured during CO oxidation. Under reaction conditions, the Cu surface is activated, typically involving 2–3 atomic layers with the formation of a reversible metastable phase that only exists during catalytic reactions. The distinctive role of CO and O₂ in the surface activation is revealed, which features CO exposure to lead to surface roughening and consequently formation of low‐coordinated Cu atoms, while O₂ exposure induces a quasi‐crystalline CuOx phase. Supported by DFT calculations, it is shown that crystalline CuOx reversibly transforms into the amorphous phase, acting as an active species to facilitate the interaction of gas reactants and catalyzing CO oxidation.  相似文献   

    

Yi Han  Zibo Xue  Guangwu Li  Yanwei Gu  Yong Ni  Shaoqiang Dong  Chunyan Chi 《Angewandte Chemie (International ed. in English)》2020,59(23):9026-9031

Incorporation of a non‐hexagonal ring into a nanographene framework can lead to new electronic properties. During the attempted synthesis of naphthalene‐bridged double [6]helicene and heptagon‐containing nanographene by the Scholl reaction, an unexpected azulene‐embedded nanographene and its triflyloxylated product were obtained, as confirmed by X‐ray crystallographic analysis and 2D NMR spectroscopy. A 5/7/7/5 ring‐fused substructure containing two formal azulene units is formed, but only one of them shows an azulene‐like electronic structure. The formation of this unique structure is explained by arenium ion mediated 1,2‐phenyl migration and a naphthalene to azulene rearrangement reaction according to an in‐silico study. This report represents the first experimental example of the thermodynamically unfavorable naphthalene to azulene rearrangement and may lead to new azulene‐based molecular materials.  相似文献   

    

Shufang Ji  Yang Qu  Tao Wang  Yuanjun Chen  Guofeng Wang  Xue Li  Juncai Dong  QiuYu Chen  Wanying Zhang  Zedong Zhang  Shiyou Liang  Rong Yu  Yu Wang  Dingsheng Wang  Yadong Li 《Angewandte Chemie (International ed. in English)》2020,59(26):10651-10657

The solar‐driven photocatalytic reduction of CO₂ (CO₂RR) into chemical fuels is a promising route to enrich energy supplies and mitigate CO₂ emissions. However, low catalytic efficiency and poor selectivity, especially in a pure‐water system, hinder the development of photocatalytic CO₂RR owing to the lack of effective catalysts. Herein, we report a novel atom‐confinement and coordination (ACC) strategy to achieve the synthesis of rare‐earth single erbium (Er) atoms supported on carbon nitride nanotubes (Er₁/CN‐NT) with a tunable dispersion density of single atoms. Er₁/CN‐NT is a highly efficient and robust photocatalyst that exhibits outstanding CO₂RR performance in a pure‐water system. Experimental results and density functional theory calculations reveal the crucial role of single Er atoms in promoting photocatalytic CO₂RR.  相似文献   

    

Dong‐Hao Li  Cynthia L. Schreiber  Bradley D. Smith 《Angewandte Chemie (International ed. in English)》2020,59(29):12154-12161

The near‐infrared window of fluorescent heptamethine cyanine dyes greatly facilitates biological imaging because there is deep penetration of the light and negligible background fluorescence. However, dye instability, aggregation, and poor pharmacokinetics are current drawbacks that limit performance and the scope of possible applications. All these limitations are simultaneously overcome with a new molecular design strategy that produces a charge balanced and sterically shielded fluorochrome. The key design feature is a meso‐aryl group that simultaneously projects two shielding arms directly over each face of a linear heptamethine polyene. Cell and mouse imaging experiments compared a shielded heptamethine cyanine dye (and several peptide and antibody bioconjugates) to benchmark heptamethine dyes and found that the shielded systems possess an unsurpassed combination of photophysical, physiochemical, and biodistribution properties that greatly enhance bioimaging performance.  相似文献   

    

Chao Wang  Jiafang Piao  Yujie Li  Xiancheng Tian  Yuanchen Dong  Dongsheng Liu 《Angewandte Chemie (International ed. in English)》2020,59(35):15176-15180

The shape of eukaryotic cells is determined by the cytoskeleton associated with membrane proteins; however, the detailed mechanism of how the integral morphologies with structural stability is generated and maintained is still not fully understood. Here, based on the Frame‐Guided Assembly (FGA) strategy, we successfully prepared hetero‐liposomes with structural composition similar to that of eukaryotic cells by screening a series of transmembrane peptides as the leading hydrophobic groups (LHGs). It was demonstrated that the conformation and transmembrane mode of the LHGs played dominant roles during the FGA process. The FGA liposomes were formed with excellent stability, which may further provide evidence for the cytoskeleton–membrane protein–lipid bilayer model. Taking advantage of the biocompatibility and stability, the FGA liposomes were also applied to prepare novel drug delivery vehicles, which is promising in diagnostic imaging and cancer therapy applications.  相似文献   

    

Kai Chen  Gang Huang  Jin‐Ling Ma  Jin Wang  Dong‐Yue Yang  Xiao‐Yang Yang  Yue Yu  Xin‐Bo Zhang 《Angewandte Chemie (International ed. in English)》2020,59(38):16661-16667

The lithium (Li)–air battery has an ultrahigh theoretical specific energy, however, even in pure oxygen (O₂), the vulnerability of conventional organic electrolytes and carbon cathodes towards reaction intermediates, especially O₂^?, and corrosive oxidation and crack/pulverization of Li metal anode lead to poor cycling stability of the Li‐air battery. Even worse, the water and/or CO₂ in air bring parasitic reactions and safety issues. Therefore, applying such systems in open‐air environment is challenging. Herein, contrary to previous assertions, we have found that CO₂ can improve the stability of both anode and electrolyte, and a high‐performance rechargeable Li–O₂/CO₂ battery is developed. The CO₂ not only facilitates the in situ formation of a passivated protective Li₂CO₃ film on the Li anode, but also restrains side reactions involving electrolyte and cathode by capturing O₂^?. Moreover, the Pd/CNT catalyst in the cathode can extend the battery lifespan by effectively tuning the product morphology and catalyzing the decomposition of Li₂CO₃. The Li–O₂/CO₂ battery achieves a full discharge capacity of 6628 mAh g^?1 and a long life of 715 cycles, which is even better than those of pure Li–O₂ batteries.  相似文献   

    

Hai‐Dong Xia  Zhong‐Liang Li  Qiang‐Shuai Gu  Xiao‐Yang Dong  Jia‐Heng Fang  Xuan‐Yi Du  Li‐Lei Wang  Xin‐Yuan Liu 《Angewandte Chemie (International ed. in English)》2020,59(39):16926-16932

We describe a photoinduced copper‐catalyzed asymmetric radical decarboxylative alkynylation of bench‐stable N‐hydroxyphthalimide(NHP)‐type esters of racemic alkyl carboxylic acids with terminal alkynes, which provides a flexible platform for the construction of chiral C(sp³)?C(sp) bonds. Critical to the success of this process are not only the use of the copper catalyst as a dual photo‐ and cross‐coupling catalyst but also tuning of the NHP‐type esters to inhibit the facile homodimerization of the alkyl radical and terminal alkyne, respectively. Owing to the use of stable and easily available NHP‐type esters, the reaction features a broader substrate scope compared with reactions using the alkyl halide counterparts, covering (hetero)benzyl‐, allyl‐, and aminocarbonyl‐substituted carboxylic acid derivatives, and (hetero)aryl and alkyl as well as silyl alkynes, thus providing a vital complementary approach to the previously reported method.  相似文献   

    

Xing‐Cai Huang  Jia‐Xin Li  Yong‐Zhi Chen  Wen‐Yan Wang  Rui Xu  Jin‐Xia Tao  Dong Shao  Yi‐Quan Zhang 《化学:亚洲杂志》2020,15(9):1469-1477

Tuning the magnetic anisotropy of metal ions remains highly interesting in the design of improved single‐molecule magnets (SMMs). We herein report synthetic, structural, magnetic, and computational studies of four mononuclear Co^II complexes, namely [Co(hfac)₂(MeCN)₂] ( 1 ), [Co(hfac)₂(Spy)₂] ( 2 ), [Co(hfac)₂(MBIm)₂] ( 3 ), and [Co(hfac)₂(DMF)₂] ( 4 ) (MeCN=acetonitrile, hfac=hexafluoroacetylacetone, Spy=4‐styrylpyridine, MbIm=5,6‐dimethylbenzimidazole, DMF=N,N‐dimethylformamide), with distorted octahedral geometry constructed from hexafluoroacetylacetone (hfac) and various axial ligands. By a building block approach, complexes 2 – 4 were synthesized by recrystallization of the starting material of 1 from various ligands containing solution. Magnetic and theoretical studies reveal that 1 – 4 possess large positive D values and relative small E parameters, indicating easy‐plane magnetic anisotropy with significant rhombic anisotropy in 1 – 4 . Dynamic alternative current (ac) magnetic susceptibility measurements indicate that these complexes exhibit slow magnetic relaxation under external fields, suggesting field‐induced single‐ion magnets (SIMs) of 1 – 4 . These results provide a promising platform to achieve fine tuning of magnetic anisotropy through varying the axial ligands based on Co(II) bis(hexafluoroacetylacetonate) complexes.  相似文献   

    

Lingmei Liu  Ning Wang  Chongzhi Zhu  Xiaona Liu  Yihan Zhu  Peng Guo  Lujain Alfilfil  Xinglong Dong  Daliang Zhang  Yu Han 《Angewandte Chemie (International ed. in English)》2020,59(2):819-825

Integrated differential phase‐contrast scanning transmission electron microscopy (iDPC‐STEM) is capable of directly probing guest molecules in zeolites, owing to its sufficient and interpretable image contrast for both heavy and light elements under low‐dose conditions. This unique ability is demonstrated by imaging volatile organic compounds adsorbed in zeolite Silicalite‐1; iDPC‐STEM was then used to investigate molybdenum supported on various zeolites including Silicalite‐1, ZSM‐5, and mordenite. Isolated single‐Mo clusters were observed in the micropores of ZSM‐5, demonstrating the crucial role of framework Al in driving Mo atomically dispersed into the micropores. Importantly, the specific one‐to‐one Mo‐Al interaction makes it possible to locate Al atoms, that is, catalytic active sites, in the ZSM‐5 framework from the images, according to the positions of Mo atoms in the micropores.  相似文献   

    

Yunyu Sun  Mingcheng Yang  Yutong Guo  Mengjiao Cheng  Bin Dong  Feng Shi 《Angewandte Chemie (International ed. in English)》2020,59(3):1098-1102

Light‐driven micropumps, which are based on electro‐osmosis with the electric field generated by photocatalytic reactions, are among most attractive research topics in chemical micromotors. Until now, research in this field has mainly been focused on the directional motion or collective behavior of microparticles, which lack practical applications. In this study, we have developed a photowelding strategy for repeated photoinduced conductivity recovery of cracked flexible circuits. We immersed the circuit in a suspension of conductive healing particles and applied photoillumination to the crack; photocatalysis of a predeposited pentacene (PEN) layer triggered electro‐osmotic effects to gather conductive particles at the crack, thus leading to conductivity recovery of the circuit. This photowelding strategy is a novel application of light‐driven micropumps and photocatalysis for conductivity restoration.  相似文献