Atomically precise enantiomeric metal clusters are scarce, and copper(I) alkynyl clusters with intense circularly polarized luminescence (CPL) responses have not been reported. A pair of chiral ...alkynyl ligands, (R/S)‐2‐diphenyl‐2‐hydroxylmethylpyrrolidine‐1‐propyne (abbreviated as R/S‐DPM) we successfully prepared and single crystals were characterized of optically pure enantiomeric pair of atomically‐precise copper(I) clusters, Cu14(R/S‐DPM)8(PF6)6 (denoted as R/S‐Cu14), which feature bright red luminescence and CPL with a high luminescence anisotropy factor (glum). A dilute solution containing R/S‐Cu14 was nonluminescent and CPL inactive at room temperature. Crystallization‐ and aggregation‐induced emission (CIE and AIE, respectively) contribute to the triggering of the CPL of R/S‐Cu14 in the crystalline and aggregated states. Their AIE behavior and good biocompatibility indicated applications of these copper(I) clusters in cell imaging in HeLa and NG108‐15 cells.
Atomically precise chiral CuI alkynyl nanoclusters R/S‐Cu14 with inherent chirality were synthesized for the first time. Crystallization‐ and aggregation‐induced emission (CIE and AIE, respectively) trigger circularly polarized luminescence (CPL) with an unprecedented luminescence anisotropy factor (glum).
The mechanism of copper-mediated coupling reactions has aroused widespread interest, and it has been found to not be as simple as initially thought. In this article, we give an overview of the recent ...advances in this field. Notably, we focus on whether the presence of Cu
III
is adopted in the catalytic cycle. Attention is paid to the key Cu
II
species, which can be generated by radical-type or single electron transfer (SET) oxidation of Cu
I
. The Cu
II
species can be oxidized to Cu
III
by SET or using a nucleophilic radical for further reductive elimination. Alternatively, radical-type substitution or bimetallic reductive elimination can avoid formation of Cu
III
, and coupling reactions can also be achieved.
The different pathways have been summarized to disclose the key intermediate in copper-mediated coupling reactions.
Divergent synthesis for precise constructions of cyclic unsymmetrical diaryl disulfides or diselenides and polythiophenes from CF3‐containing 1,3‐enynes and S8 was developed when the ortho group is ...F, Cl, Br, and NO2 on aromatic rings. Meanwhile, disulfides (diselenides) were also quickly constructed when the ortho group is H. These transformations undergo cascade thiophene construction/selective C3‐position thiolation process, featuring simple operations, divergent synthesis, broad substrate scope, readily available starting materials, and valuable products. A novel plausible radical annulation process was proposed and validated by DFT calculations for the first time. A series of derivatizations about the thiophene (TBT) and disulfides were also well‐represented.
A divergent synthesis for construction of cyclic unsymmetrical diaryl disulfides, diselenides, and polythiophenes from CF3‐containing 1,3‐enynes (ortho=F, Cl, Br, NO2, S8) was developed. Disulfides (diselenides) were constructed under mild conditions for ortho=H. These transformations undergo a cascade thiophene construction/selective C3‐position thiolation process, with mild conditions, broad substrate scope, and good functional‐group tolerance.
Considering the ubiquitous nature and ready synthesis of amides, and the great significance of organofluorine‐containing species, the cross‐coupling of amides and polyfluoroarenes, leading to new ...carbon–carbon bond‐forming methodologies, would find useful applications in synthesis, late‐stage functionalization, and rapid generation of molecular diversity. Herein, we present a novel synthesis of α‐polyfluoroaryl amines via Sm/SmI2‐mediated deoxygenative cross‐coupling of aromatic amides with polyfluoroarenes through direct C−H functionalization. The structural and functional diversity of these readily available precursors provides a versatile and flexible strategy for the streamlined synthesis of α‐polyfluoroaryl amines. Combining experimental and theoretical studies, a novel plausible mechanism of the α‐aminocarbene‐mediated C−H insertion has been revealed, which may stimulate future work for the development of novel methods in amine synthesis.
An attractive deoxygenative cross‐coupling of amides with polyfluoroarenes was successfully achieved. Aromatic amides act as readily available carbene precursors through a Sm/SmI2‐mediated deoxygenation process, and the insertion of the carbene into the C−H bond of polyfluoroarene affords architecturally complex and functionally diverse α‐polyfluoroaryl amines in a single step.
Carbon coating layers have been found to improve the catalytic performance of transition metals, which is usually explained as an outcome of electronic synergistic effect. Herein we reveal that the ...defective graphitic carbon, with a unique interlayer gap of 0.342 nm, can be a highly selective natural molecular sieve. It allows efficient diffusion of hydrogen molecules or radicals both along the in‐plane and out‐of‐plane direction, but sterically hinders the diffusion of molecules with larger kinetic diameter (e.g., CO and O2) along the in‐plane direction. As a result, poisonous species lager than 0.342 nm are sieved out, even when their adsorption on the metal is thermodynamically strong; at the same time, the interaction between H2 and the metal is not affected. This natural molecular sieve provides a very chance for constructing robust metal catalysts for hydrogen‐relevant processes, which are more tolerant to chemical or electrochemical oxidation or CO‐relevant poisoning.
With interlayer gap of 0.342 nm, graphite armor serves as a natural molecule sieve screening out bulky adversative molecules like O2 or CO but allowing H2 to diffuse along both the out‐of‐plane and in‐plane direction. This creates perfect chance for fabricating robust HOR electrocatalysts.
C‐Acyl glycosides are versatile intermediates to natural products and medicinally relevant entities. Conventional cross‐coupling strategies to secure these molecules often relied on two‐component ...manifolds in which a glycosyl precursor is coupled with an acyl donor (pre‐synthesized or generated in situ) under transition metal or dual catalysis to forge a C−C bond. Here, we disclose a three‐component Ni‐catalyzed reductive regime that facilitates the chemoselective union of glycosyl halides, organoiodides and commercially available isobutyl chloroformate as a CO surrogate. The method tolerates multiple functionalities and the resulting products are obtained in high diastereoselectivities. Theoretical calculations provide a mechanistic rationale for the unexpectedly high chemoselectivity of sequential cross‐electrophile couplings. This approach enables the expeditious assembly of difficult‐to‐synthesize C‐acyl glycosides, as well as late‐stage keto‐glycosylation of oligopeptides.
Reductive nickel catalysis was leveraged to orchestrate the multicomponent union of glycosyl halides, organoiodides and isobutyl chloroformate to assemble C‐acyl glycosides in high anomeric selectivities. Computational studies provided insights that rationalize the origin of the high chemoselectivity. The method is applicable to the synthesis of complex C‐linked disaccharides and late‐stage keto‐glycosylation of peptides.
Abstract
The determination of the absolute and relative position of a spacecraft is critical for its operation, observations, data analysis, scientific studies, as well as deep-space exploration in ...general. A spacecraft that can determine its own absolute position autonomously may perform better than those that must rely on transmission solutions. In this work, we report an absolute navigation accuracy of ∼20 km using 16 day Crab pulsar data observed with Fermi’s Gamma-ray Burst Monitor (GBM). In addition, we propose a new method with the inverse process of the triangulation for joint navigation using repeated bursts like those from the magnetar SGR J1935+2154 observed by the Gravitational-wave High-energy Electromagnetic Counterpart All-sky Monitor and GBM.
Abstract
Nationwide prospective surveillance of all-age patients with acute respiratory infections was conducted in China between 2009‒2019. Here we report the etiological and epidemiological ...features of the 231,107 eligible patients enrolled in this analysis. Children <5 years old and school-age children have the highest viral positivity rate (46.9%) and bacterial positivity rate (30.9%). Influenza virus, respiratory syncytial virus and human rhinovirus are the three leading viral pathogens with proportions of 28.5%, 16.8% and 16.7%, and
Streptococcus pneumoniae
,
Mycoplasma pneumoniae
and
Klebsiella pneumoniae
are the three leading bacterial pathogens (29.9%, 18.6% and 15.8%). Negative interactions between viruses and positive interactions between viral and bacterial pathogens are common. A Join-Point analysis reveals the age-specific positivity rate and how this varied for individual pathogens. These data indicate that differential priorities for diagnosis, prevention and control should be highlighted in terms of acute respiratory tract infection patients’ demography, geographic locations and season of illness in China.
Developing high‐performance electromagnetic interference (EMI) shielding materials has become increasingly important along with the upcoming 5G communication era and the boom of wearable devices. ...However, the large thickness and poor mechanical properties of most of EMI shielding materials cannot satisfy the above critical requirements. Here, flexible and ultrathin poly(vinylidene fluoride) (PVDF)/MXene/Ni chain composite films are fabricated. Interestingly, by combining quasi‐1D Ni chains and 2D MXenes, the average EMI shielding effectiveness of the PVDF/MXene/Ni chain composite films can reach 19.3 dB with only 0.10 mm thickness, and increases to 34.4 dB with 0.36 mm thickness. Besides, the tensile strength, Young's modulus, and toughness of the PVDF/MXene/Ni chain composite films are 41.9 ± 1.6 MPa, 1.18 ± 0.007 GPa, and 2.9 ± 0.08 MJ m−3, respectively. All of which are better than when using MXenes or Ni chains alone at the same loading. It is attributed to synergistic effects induced by unique 3D network constituted by MXenes and Ni chains. Moreover, the possible synergistic mechanisms for enhanced EMI shielding and mechanical properties are discussed. This work offers a promising solution for EMI shielding challenges in modern smaller and smaller wearable devices.
A flexible and ultrathin poly(vinylidene fluoride)/MXene/Ni chain composite film is fabricated. The prepared Mxenes and Ni chains are characterized. The electrical conductivity, electromagnetic interference shielding, and mechanical properties of composite films are investigated. The synergistic mechanisms between MXenes and Ni chains for enhanced electromagnetic interference shielding and mechanical properties are clarified.
A Mn(III)‐mediated radical cyclization reaction of o‐vinylaryl isocyanides and arylboronic acids or diphenylphosphine oxides to access various 2‐functionalized quinolines under mild conditions was ...developed. With the introduction of radical stabilizing substituents (e. g. aryl and methyl group) on vinyl group, this reaction provides a regiospecific 6‐endo‐trig radical cyclization of o‐vinylaryl isocyanides, giving a number of structurally unique and biologically potential 2‐functionalized quinoline derivatives.
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