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981.
982.
Tao Chen Lifei Gan Ran Wang Yuhua Deng Fangzhi Peng Mark Lautens Zhihui Shao 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(44):15966-15970
The strong binding ability of P‐ylides with transition metals limits the utilization of stabilized P‐ylide as nucleophiles in asymmetric organometallic catalysis. Herein we describe the first rhodium‐catalyzed asymmetric ring‐opening reaction of P‐ylides utilizing oxabicyclic alkenes as the electrophilic partner. Various P‐ylides including ester‐, ketone‐ and amide‐style P‐ylides are all applicable. This asymmetric reaction occurs through the cleavage of two bridgehead C?O bonds and the formation of two C?C bonds, and oxabenzonorbornadienes are used as 1,4‐biselectrophiles, thus providing access to benzonorcaradienes in good yields with high enantioselectivity and perfect diastereoselectivity. The present protocol also constitutes the first highly enantioselective direct catalytic asymmetric cyclopropanation of stabilized P‐ylide nucleophiles. 相似文献
983.
Alex J. Plajer Edmundo G. Percstegui Marco Santella Felix J. Rizzuto Quan Gan Bo W. Laursen Jonathan R. Nitschke 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(13):4244-4248
The design of aqueous probes and binders for complex, biologically relevant anions presents a key challenge in supramolecular chemistry. Herein, a tetrahedral assembly with cationic faces and corners is reported that is capable of discriminating between anionic and neutral guests in water. Electrostatic repulsion between subcomponents can be overcome by the addition of an anionic template, or generating a robust covalent framework by incorporating tris(2‐aminoethyl)amine (TREN). The resultant TREN‐capped, water‐soluble, fluorescent cage binds mono‐ and poly‐phosphoric esters, including nucleotides. Its covalent skeleton renders it stable at micromolar concentrations in water, enabling the fluorometric detection of biologically relevant guests in an aqueous environment. Selective supramolecular encapsulants, such as 1 , could enable new sensing applications, such as recognition of toxins and drugs, under biological conditions. 相似文献
984.
Lizhong He Zibao Gan Nan Xia Lingwen Liao Zhikun Wu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(29):10002-10006
An assembly strategy for metal nanoclusters using electrostatic interactions with weak interactions, such as C?H???π and π???π interactions in which cationic [Ag26Au(2‐EBT)18(PPh3)6]+ and anionic [Ag24Au(2‐EBT)18]? nanoclusters gather and assemble in an unusual alternating array stacking structure is presented. [Ag26Au(2‐EBT)18(PPh3)6]+ [Ag24Au(2‐EBT)18]? is a new compound type, a double nanocluster ion compound (DNIC). A single nanocluster ion compound (SNIC) [PPh4]+ [Ag24Au(2‐EBT)18]? was also synthesized, having a k‐vector‐differential crystallographic arrangement. [PPh4]+ [Ag24Au(2,4‐DMBT)18]? adopts a different assembly mode from both [Ag26Au(2‐EBT)18(PPh3)6]+ [Ag24Au(2‐EBT)18]? and [PPh4]+ [Ag24Au(2‐EBT)18]?. Thus, the striking packing differences of [Ag26Au(2‐EBT)18(PPh3)6]+ [Ag24Au(2‐EBT)18]?, [PPh4]+ [Ag24Au(2‐EBT)18]? and the existing [PPh4]+ [Ag24Au(2,4‐DMBT)18]? from each other indicate the notable influence of ligands and counterions on the self‐assembly of nanoclusters. 相似文献
985.
Wei Li Binbin Li Xinyi Cai Lin Gan Zhida Xu Wenqi Li Kunkun Liu Dongcheng Chen Shi‐Jian Su 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(33):11423-11427
Blue thermally activated delayed fluorescence (TADF) emitters that can simultaneously achieve high efficiency in doped and nondoped organic light‐emitting diodes (OLEDs) are rarely reported. Reported here is a strategy using a tri‐spiral donor for such versatile blue TADF emitters. Impressively, by simply extending the nonconjugated fragment and molecular length, aggregation‐caused emission quenching (ACQ) can be greatly alleviated to achieve as high as a 90 % horizontal orientation dipole ratio and external quantum efficiencies (EQEs) of up to 33.3 % in doped and 20.0 % in nondoped sky‐blue TADF‐OLEDs. More fascinatingly, a high‐efficiency purely organic white OLED with an outstanding EQE of up to 22.8 % was also achieved by employing TspiroS‐TRZ as a blue emitter and an assistant host. This compound is the first blue TADF emitter that can simultaneously achieve high electroluminescence (EL) efficiency in doped, nondoped sky‐blue, and white TADF‐OLEDs. 相似文献
986.
A series of Pd and Pd‐Ga bimetallic catalysts were prepared by a co‐impregnation method for 2‐ethylanthraquinone (EAQ) hydrogenation to produce hydrogen peroxide. Compared with 0.6Pd catalyst, the hydrogenation efficiency of 0.6Pd1.2Ga catalyst (11.9 g L?1) increases by 32.2%, and the stability of 0.6Pd1.2Ga catalyst is also higher than that of 0.6Pd catalyst. The structures of the samples were determined by N2 adsorption–desorption, ICP, XRD, CO chemisorption, TEM, H2‐TPR, in situ CO‐DRIFTS and XPS. The results suggest that incorporation of Ga species improves Pd dispersion and generates a strong interaction between Ga2O3 and Pd interface or between Pd and support. DFT calculation results indicate that the strong adsorption of carbonyl group on Ga2O3/Pd interface facilitates the activation of EAQ and promotes the hydrogenation efficiency. 相似文献
987.
Wei Li Xinyi Cai Binbin Li Lin Gan Yanmei He Kunkun Liu Dongcheng Chen Yuan‐Chun Wu Shi‐Jian Su 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(2):592-596
To date, blue dual fluorescence emission (DFE) has not been realized because of the limited choice of chemical moieties and severe geometric deformation of the DFE emitters leading to strong intramolecular charge transfer (ICT) with a large Stokes shift in excited states. Herein, an emitter (1′r,5′R,7′S)‐10‐(4‐(4,6‐diphenyl‐1,3,5‐triazin‐2‐yl)phenyl)‐10H‐spiro [acridine‐9,2′‐adamantane] (a‐DMAc‐TRZ) containing a novel adamantane‐substituted acridine donor is reported, which exhibits unusual blue DFE. The introduction of the rigid and bulky adamantane moiety not only suppressed the geometry relaxation in excited state, but also induced the formation of quasi‐axial conformer (QAC) and quasi‐equatorial conformer (QEC) geometries, leading to deep‐blue conventional fluorescence and sky‐blue thermally activated delayed fluorescence (TADF). The resulting organic light‐emitting diodes (OLEDs) achieved a maximum external quantum efficiency (EQE) of about 29 %, which is the highest reported for OLEDs based on dual‐conformation emitters. 相似文献
988.
Chao Zhan Gan Wang Xia‐Guang Zhang Zhi‐Hao Li Jun‐Ying Wei Yu Si Yang Yang Wenjing Hong Zhong‐Qun Tian 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(41):14676-14680
Adsorption plays a critical role in surface and interface processes. Fractional surface coverage and adsorption free energy are two essential parameters of molecular adsorption. However, although adsorption at the solid–gas interface has been well‐studied, and some adsorption models were proposed more than a century ago, challenges remain for the experimental investigation of molecular adsorption at the solid–liquid interface. Herein, we report the statistical and quantitative single‐molecule measurement of adsorption at the solid–liquid interface by using the single‐molecule break junction technique. The fractional surface coverage was extracted from the analysis of junction formation probability so that the adsorption free energy could be calculated by referring to the Langmuir isotherm. In the case of three prototypical molecules with terminal methylthio, pyridyl, and amino groups, the adsorption free energies were found to be 32.5, 33.9, and 28.3 kJ mol?1, respectively, which are consistent with DFT calculations. 相似文献
989.
Xia Yang Li Jiaojiao Wang Hongjie Ye Zhangjun Zhou Xiaozheng Huang Hui Gan Yongping Liang Chu Zhang Jun Zhang Wenkui 《Journal of Solid State Electrochemistry》2019,23(2):519-527
Journal of Solid State Electrochemistry - In this work, a series of rationally designed hybrid membranes composed of poly(vinylidene fluoride) (PVDF) as polymer matrix and silica nanoparticles... 相似文献
990.
Poly(2,3‐dimethylaniline)/nano‐Al2O3 composite (PAC) was synthesized by emulsion polymerization using dodecyl benzene sulfonic acid as emulsifier and dopant. The structure of PAC was characterized by Fourier fransformation infrared spectroscopy, UV–visible adsorption spectroscopy, and field emission scanning electron microscopy. The thermal stability was studied by thermogravimetric analysis, and the electrochemical performances were studied by cyclic voltammetry measurements. Epoxy coatings containing PAC and poly(2,3‐dimethylaniline) (P(2,3‐DMA)), respectively, were painted on steel, and accelerated immersion tests were performed to evaluate the anticorrosion property of the coatings in 3.5% NaCl solution. The results showed that the addition of PAC and P(2,3‐DMA) could improve the anticorrosion performance of epoxy coating significantly and the PAC coating had higher corrosion resistance than that of P(2,3‐DMA). Copyright © 2013 John Wiley & Sons, Ltd. 相似文献