Latest ArticlesBased on three rationally designed pyrrole-appended o-carborane derivatives, we present that fluorescence properties of crystalline materials are highly dependent on intermolecular interaction and steric hinderance. Though the three molecules are similar in structure, single crystals of the three compounds showed obvious difference in molecular stacking and fluorescence behavior. Systematic studies indicate that fluorescence quantum yields, thermo-response as well as mechano-response are highly dependent on intermolecular interaction and steric hindrance. In the three crystalline materials, the CB-NMe crystals with weaker intermolecular interaction and looser molecular packing showed superior fluorescence quantum yield and temperature sensitivity. Accordingly, surface temperature detection strip with favorable reversibility is prepared by doping CB-NMe into the polymer. In addition, the CB-NMe aggregates can be used for monitoring bovine serum albumin (BSA) denaturation, as temperature response of the aggregates can be reversed when co-assembled with BSA.
Although fluorobis(phenylsulfonyl)methane (FBSM) and its cyclic analog 2-fluoro-1, 3-benzodithiole-1, 1, 3, 3-tetraoxide (FBDT) possess similar physicochemical properties, Shibata et al. found that FBSM failed to undergo nucleophilic monofluoromethylation of aldehydes regardless of the reaction conditions attempted (using various organic and inorganic bases). However, it was later discovered by Hu et al. that the nucleophilic monofluoromethylation could be accomplished by employing lithium hexamethyldisilazide (LiHMDS) as a base. Herein, we present an in-depth computational investigation into the intriguing effects of reagent structure and bases on the nucleophilic monofluoromethylation of aldehydes. The computations reveal the 1, 4-diazabicyclo[2.2.2]octane (DABCO) catalyzed nucleophilic monofluoromethylation of benzaldehyde with acyclic FBSM is a thermodynamically unfavorable process mainly due to the destabilizing O···O lone pair repulsions in FBSM product, whereas such repulsion could be largely avoided in FBDT product because of its constrained five-membered ring structure. Employing LiHMDS as a base can not only facilitate the nucleophilic monofluoromethylation via Li–O interactions but also render the monofluoromethylation of benzaldehyde with FBSM thermodynamically favored.
Though Olefin-linked covalent organic frameworks (oCOFs) possess excellent π-electron delocalization, the barely reversible olefin linkage brings challenges for oCOFs' synthesis and functionalization. Here, we synthesize new oCOFs with tertiary amine knots which have twisted configuration and electron-donating nature. Investigation into the structural variation and photoelectric performance shows that the twisted configuration of oCOF-TFPA could favor to the intramolecular charge transfer process and reduce the possibility of aggregation-caused quenching. Photoelectrical measurements and electric band structure calculation both verify the superiority of this oCOFs' structure in photoelectric sensing.
DNA methylation represents a major type of DNA modifications that play key roles in diverse biological processes. With the recent development of highly selective and sensitive bioanalytical techniques, N6-methyladenine (6mA) has been characterized as an important internal DNA modification dynamically occurring in multiple eukaryotes including humans. Increasing evidence has indicated that 6mA may act as a novel epigenetic modification involved in regulation of development, stress response and diseases such as cancer and neurodegenerative disorders. We review herein the recent advances in the detection and functional studies of 6mA modification, with special emphasis on its biological consequences and human health relevance as well as its dynamic regulation by various types of methyltransferases, demethylases and 6mA-binding proteins. It can be envisaged that further chemical and biological studies of 6mA modification will lead to a better understanding about its potentially important roles in normal and pathological biological processes.
Cationic polymers, also known as polycations, are considered to be the most potential non-viral gene carriers due to their unique advantages such as the ability to bind the negative charge of nucleic acid molecules. Multicomponent polymerization (MCP) is a one-step, tandem strategy to construct complex structures based on multicomponent reactions. Herein, we developed a metal-free MCP method based on three monomers of p-dinitrovinylbenzene (p-DNVB), 1, 1-dimethylethyl N, N-dibromocarbamate (BocNBr2), and bis-secondary-amines with a ratio of 1:2:1, to access a library of Boc-substituted polyamidines with well-defined structures and suitable molecular weights (Mw ranging from 4400 Da to 11, 000 Da) in high yields (up to 85%) under mild conditions. Upon the removal of Boc groups, a series of water-soluble polymers with cationic property were prepared and their gene binding capability was further evaluated.
Efficient conversion of straw cellulose to chemicals or fuels is an attracting topic today for the utilization of biomass to substitute for fossil resources. The development of catalysts is of vital importance. In this work, a composite catalyst metal-organic frameworks (MOFs) immobilized on three-dimensional reduced graphene oxide (3D-rGO) were synthesized by in situ growth of the MIL-101(Cr) within the 3D-rGO matrix. The supporting of 3D-rGO guaranteed the dispersion and acid site density of MIL-101(Cr). The MIL-101(Cr)@3D-rGO nanocomposite possesses excellent catalytic activity, stability, recyclability and is an idea catalyst for the efficient degradation of straw cellulose into formic acid (FA), acetic acid (AA) and oxalic acid (OA). A maximum FA conversion rates of 95.36% was obtained by using MIL-101(Cr)@3D-rGO(1:1) as catalyst and hydrothermal reaction at mild conditions of 200 ℃ for 1h in alkaline aqueous medium. The MIL-101(Cr)@3D-rGO nanocomposite can be reused with high catalytic activity without any collapse of structure or leaching of chromium.
Molybdenum trioxide (MoO3) can be employed as an excellent host for intercalation due to its 2D layered structure that connected by van der Waals interactions. Herein, a series of polyoxometalate-based MoO3 composites (Al13@MoO3) were successfully prepared by interpolating the Keggin-type polycationic AlO4Al12(OH)24(H2O)127+ (Al13) into MoO3 gallery. These composites can be applied to rapidly adsorb the anionic dye methyl orange (MO) through strong electrostatic interactions lead to compact and stable gathering in the surrounding of the numerous charged Al13. Adsorption behaviors of composites with the different amount of Al13 were determined, these results revealed that Al13-3.34%@MoO3 exhibited the most remarkable adsorption capacity. More importantly, the composite maintains superior adsorption capacity for five consecutive adsorption/desorption cycles, suggesting that Al13@MoO3 can be an efficient and durable adsorbent.
Electrochemical carbon dioxide reduction (CO2RR) plays an important role in solving the problem of high concentration of CO2 in the atmosphere and realizing carbon cycle. Core-shell structure has many unique features including tandem catalysis, lattice strain effect, defect engineering, which exhibit great potential in electrocatalysis. In this review, we focus on the advanced core-shell metal-based catalysts (CMCs) for electrochemical CO2RR. The recent progress of CMCs in electrocatalytic CO2RR is described as the following aspects: (1) The mechanism of electrochemical CO2RR and evaluation parameters of electrocatalyst performance, (2) preparation methods of core-shell metal catalysts and core-shell structural advantages and (3) advanced CMCs towards electrochemical CO2RR. Finally, we make a brief conclusion and propose the opportunities and challenges in the field of electrochemical CO2RR.
The first intermolecular electrophilic dearomatization of halonaphthols with benzyl/allyl bromides is described. Halonaphthols are used as carbon-nucleophiles in dearomatization to form three-dimensional cyclic enones with excellent chemoselectivity, in which etherification of phenolic hydroxyl group could be restrained well by using cesium carbonate as the base. A wide range of cyclic enones is directly prepared from various substituted benzyl/allyl bromides and halonaphthols. Mechanistic investigations suggest a direct SN2 reaction pathway.
A new relay C–H functionalization of di([1, 1′-biphenyl]-2-yl)phosphine oxide to obtain esterified and hydroxylated products with different hypervalent iodines as oxidants under palladium catalysis is disclosed. This reaction provides a more effective and concise strategy for the synthesis of novel structural hybrid-arylcyclophosphorus ligand precursors with a wide range of substrates and good functional group tolerance.
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