Cyclization of propargylamines with CO2 to obtain 2‐oxazolidone heterocyclic compounds is an essential reaction in industry but it is usually catalyzed by noble‐metal catalysts with organic bases as ...co‐catalysts under harsh conditions. We have synthesized a unique CuI/CuII mixed valence copper‐based framework {(CuI6I5)Cu3IIL6(DMA)3(NO3)⋅9DMA}n (1) with good solvent and thermal stability, as well as a high density of uncoordinated amino groups evenly distributed in the large nanoscopic channels. Catalytic experiments show that 1 can effectively catalyze the reaction of propargylamines with CO2, and the yield can reach 99 %. The turnover frequency (TOF) reaches a record value of 230 h−1, which is much higher than that of reported noble‐metal catalysts. Importantly, this is the first report of heterogeneously catalyzed green conversion of propargylamines with CO2 without solvents and co‐catalysts under low temperature and atmospheric pressure. A mechanistic study reveals that a triply synergistic catalytic effect between CuI/CuII and uncoordinated amino groups promotes highly efficient and green conversion of CO2. Furthermore, 1 directly catalyzes this reaction with high efficiency when using simulated flue gas as a CO2 source.
A mixed valence copper‐based cationic framework {(CuI6I5)Cu3IIL6(DMA)3(NO3)⋅9DMA}n was synthesized. The material realized the efficient and green conversion of propargylamine with CO2 in flue gas under solvent‐free and co‐catalyst free conditions.
Abstract
Catalytic reductive coupling of two electrophiles and one unsaturated bond represents an economic and efficient way to construct complex skeletons, which is dominated by transition-metal ...catalysis via two electron transfer. Herein, we report a strategy of visible-light photoredox-catalyzed successive single electron transfer, realizing dearomative arylcarboxylation of indoles with CO
2
. This strategy avoids common side reactions in transition-metal catalysis, including ipso-carboxylation of aryl halides and β-hydride elimination. This visible-light photoredox catalysis shows high chemoselectivity, low loading of photocatalyst, mild reaction conditions (room temperature, 1 atm) and good functional group tolerance, providing great potential for the synthesis of valuable but difficultly accessible indoline-3-carboxylic acids. Mechanistic studies indicate that the benzylic radicals and anions might be generated as the key intermediates, thus providing a direction for reductive couplings with other electrophiles, including D
2
O and aldehyde.
Over the past decades, organometallic complexes with precious elements, such as ruthenium and iridium, are widely used as visible‐light photoredox catalysts. Recently, more and more complexes based ...on earth‐abundant and inexpensive elements have been used as sensitizers in photochemistry. Although the photoexcited state lifetimes of iron complexes are typically shorter than those of traditional photosensitizers, the utilization of iron catalysts in photochemistry has sprung up owing to their abundance, low price, nontoxicity, and novel properties, including exhibiting ligand to metal charge transfer states. This concept focuses on recent advances in light‐driven iron catalysis in organic transformations, including iron/photoredox dual catalysis, light‐induced iron photoredox catalysis and light‐induced generation of active iron catalysts. The prospect for the future of this field is also discussed.
Light runs across iron catalysts: This Concept summarizes the recent advances in iron/photoredox dual catalysis, photoactive iron catalysts in photochemistry, as well as light‐induced generation of active iron catalysts in organic transformations. Prospects for the future of the field are also discussed.
The existing susceptance-based methods adopt the constant susceptance matrix as the voltage sensitivities and have been widely applied in voltage security enhancement of power systems. However, the ...existing methods may be inefficient under the heavy loading condition in which the fundamental of decoupled power flow fails to hold. In this case, the inaccurate voltage sensitivities in the existing method lead to the inefficient voltage security enhancement with more required iterations of the numerical convergence. In order to improve such deficiency, the distributed voltage security enhancement method using the measurement-based voltage sensitivities is proposed in this paper. By using real-time measurements of phasor measurement units (PMUs), the multi-port equivalent models of the power grid are built and used to derive the measurement-based voltage sensitivities and the system transmission capability sensitivities. By using the measurement-based sensitivities, the proposed method can be formulated as the measurement-based optimization problem and further implemented in the distributed framework through using alternating direction method of multipliers (ADMM). Simulations on IEEE 118-bus and IEEE 300-bus test systems are presented to validate the effectiveness of the proposed method.
The field of anion supramolecular chemistry has received more and more attention in recent years. Anions with diverse types and geometries have been widely used for the synthesis of ionic spin ...crossover (SCO) complexes. This review is devoted to anion effects on the molecular, supramolecular structures and magnetic properties of discrete SCO compounds. Firstly, typical anions used in the synthesis of these compounds are briefly summarized according to their various geometries. This is followed by a collection of representative examples of anion‐based SCO compounds, whose SCO properties are analyzed in terms of supramolecular interactions, geometry and charge of anions. In the third part, anion effects on SCO complexes of different kinds of metal centers and ligands are outlined and finally remarks on the synthesis new type of ionic SCO complexes in the future are described.
Anions with diverse types and geometries have been widely used for the synthesis of ionic spin crossover (SCO) complexes. Anions can be classified into different configurations, and the various configurations and types of anions can significantly influence the supramolecular interactions and stacking modes between anions and cations in compounds, ultimately leading to changes in the SCO properties.
In this letter, the expectation-maximization-based secondary voltage control scheme is proposed to achieve the robust secondary voltage control (SVC) in the presence of stochastic measurement error ...under wide-area measurement system (WAMS). The proposed control scheme is implemented iteratively in the two steps, expectation and maximization steps. Since stochastic measurement error, following arbitrary parametric or nonparametric probability distribution, can be considered in the proposed control scheme, the proposed work can provide a robust and generalized solution for SVC in the presence of stochastic measurement error. Case studies on IEEE 300-bus test system are presented to verify the accuracy of the proposed control scheme.
•Co-HTC of PVC and bamboo was employed to prepare high-efficiency adsorbent.•The contents of hydroxyl and carboxyl groups of hydrochar increased during Co-HTC.•Adsorption capacity of MB on hydrochar ...produced by addition of PVC increased significantly.•Electrostatic and hydrogen-bonding interactions are the main mechanisms.
Polyvinyl chloride (PVC) was blended into bamboo powder during co-hydrothermal carbonization (Co-HTC) to understand the effects on the physicochemical properties and adsorbing ability of hydrochar. The properties of hydrochar were characterized by Zeta potential, elemental analyses, BET, FTIR, XPS, Boehm titration and SEM. The addition of PVC into bamboo in Co-HTC decreased the BET area, and pore volume and radius of hydrochar, but increased the contents of surface hydroxyl and carboxyl groups. The adsorption ability of hydrochar produced by addition of PVC at 473 K over methylene blue (MB) increased significantly. The main adsorption mechanism was electrostatic attraction by –N(CH3)2+ of MB and carboxylate of hydrochar, and hydrogen-bonding interaction through N atom of phenothiazine in MB and C–OH of hydrochar. Thus, Co-HTC offers a facile, green and economical alternative for conversion of waste into high-value adsorbents.
The interplay of host‐guest interactions and controlled modulation of spin‐crossover (SCO) behavior is one of the most exploited topics regarding data storage, molecular sensing, and optical ...technologies. This study examines the effect of solvents on the spin‐crossover (SCO) behavior of manganese(III) complexes Mn(sal‐N‐1,5,8,12)I•S (S=CH3OH, C2H5OH, CH3CN) (1) and Mn(sal‐N‐1,5,8,12)I3 (2), where (sal‐N‐1,5,8,12)2− is 2,2′‐((1E,13E)‐2,6,9,13‐tetraazatetradeca‐1,13‐diene‐1,14‐diyl)diphenol synthesized by salicylaldehyde and 1,2‐bis(3‐aminopropylamino)ethane. The complexes, crystallizing in orthorhombic or monoclinic systems, exhibit similar supramolecular arrangements with one‐dimensional cationic chains at low temperatures. Magnetic studies reveal that solvent inclusion sharpens the SCO transition and lowers the transition temperature. Specifically, 1⋅CH3OH shows a 13 K thermal hysteresis due to methanol‘s mobility through the channels in the cationic framework. Although the solvent‐free compound was not obtained, compound 2 with a linear I3− anion was synthesized, displaying extensive cation‐anion contacts and a distinct 13 K thermal hysteresis upon heating due to altered intermolecular cooperativity. This emphasizes the significant role of solvent introduction and variation in crystal packing and their impact on the SCO properties.
Three new solvent adducts Mn(sal‐N‐1,5,8,12)I⋅CH3OH, Mn(sal‐N‐1,5,8,12)I⋅C2H5OH and Mn(sal‐N‐1,5,8,12)I⋅CH3CN, as well as a rare compound, Mn(sal‐N‐1,5,8,12)I3 are synthesized. Surprisingly, the solvent in compound Mn(sal‐N‐1,5,8,12)I⋅CH3OH easily escapes, and with a slight increase in temperature, the crystal collapses, eventually turning into a powdered state. The magnetic properties undergo significant changes accompanying the loss of the solvent.
Optical grating devices based on micro/nanostructured functional surfaces are widely employed to precisely manipulate light propagation, which is significant for information technologies, optical ...data storage, and light sensors. However, the parameters of rigid periodic structures are difficult to tune after manufacturing, which seriously limits their capacity for in situ light manipulation. Here, a novel anti-eavesdropping, anti-damage, and anti-tamper dynamic optical encryption strategy are reported via tunable mechanical composite wrinkle micrograting encryption systems (MCWGES). By mechanically composing multiple in-situ tunable ordered wrinkle gratings, the dynamic keys with large space capacity are generated to obtain encrypted diffraction patterns, which can provide a higher level of security for the encrypted systems. Furthermore, a multiple grating cone diffraction model is proposed to reveal the dynamic optical encryption principle of MCWGES. Optical encryption communication using dynamic keys has the effect of preventing eavesdropping, damage, and tampering. This dynamic encryption method based on optical manipulation of wrinkle grating demonstrates the potential applications of micro/nanostructured functional surfaces in the field of information security.
This study aims to investigate the role of circular antisense non-coding RNA at the INK4 locus (cANRIL) in the inflammatory response of vascular endothelial cells (ECs) in a rat model of coronary ...atherosclerosis (AS). A rat model of AS was established with rats that were injected with a large dose of vitamin D3 and fed a high-fat diet.
Sixty Wistar rats were randomly assigned into control, model, empty vector, over-expressed cANRIL and low-expressed cANRIL groups (12 rats in each group). Sixteen weeks later, the ultrastructure of their coronary arteries was observed via transmission electron microscopy. Rat serum lipid levels were analyzed using an automatic biochemical analyzer, and their atherogenic index (AI) values were calculated. Hematoxylin and eosin staining was used to observe the endothelial morphology of rats. Additionally, rat EC apoptosis was tested via a TUNEL assay. Enzyme-linked immunosorbent assays (ELISAs) were applied to measure serum levels of interleukin-1 (IL-1), IL-6, matrix metalloproteinase-9 (MMP-9) and C-reactive protein (CRP). The cANRIL, Bax, bcl-2 and caspase-3 mRNA expression levels were measured with a quantitative real-time polymerase chain reaction (qRT-PCR). The protein expression levels of Bax, bcl-2 and caspase-3 were detected using immunohistochemistry.
In the control group, ECs were closely arranged with normal structures, and there was no proliferation. In the model, empty vector and over-expressed cANRIL groups, some cells were not present, and atherosclerotic plaques and thrombi appeared. However, in the under-expressed cANRIL group, the cells had a normal structure. Compared with the model and empty vector groups, the levels of total cholesterol (CHOL), triglycerides (TGs), low density lipoprotein (LDL), IL-1, IL-6, MMP-9, CRP, cANRIL, Bax, and caspase-3, AI values, and rates of EC apoptosis decreased in the low-expressed cANRIL group, while HDL (high density lipoprotein) levels and mRNA and protein expression levels of bcl-2 were increased. The changes in expression levels in the over-expressed cANRIL group were the opposite of those in the low-expressed cANRIL group.
Our study provides evidence that reduced cANRIL expression could prevent coronary AS by reducing vascular EC apoptosis and inflammatory factor expression.
PDF
