Latest ArticlesNegative thermal expansion (NTE) behavior has roused wide interest for the control of thermomechanical properties of functional materials. Although NTE behaviors have been found in kinds of compounds, it remains challenging for polymers to achieve intrinsic NTE property. In this work, we systematically studied the conformational change of dibenzocyclooctadiene (DBCOD) derivatives between chair (C) and twist-boat (TB) forms based on density-functional theory (DFT) calculations, and found clear evidence of the relationship between the structure of DBCOD units and the thermal contraction behavior of the related polymers. In order to obtain the polymer with NTE property, two conditions should be met for the thermal contracting DBCOD related units as follows: (i) the TB conformation can turn into C conformation as the temperature increases, and (ii) the volume of C conformation is smaller than that of TB conformation. This rule should offer a guidance to exploration of the new intrinsic NTE polymers in the future.
Dinuclear ytterbium and erbium based bifunction complexes Ln2L2(depma2)Cl2 (1-Ln, Ln=Yb and Er, H2L=N1, N3-bis(salicylideneimino)diethylenetriamine, depma2 = dimerized 9-diethyl-phosphonomethylanthracene) are reported. They undergo thermo-induced consecutive phase transitions, first the dissociation of depma2 ligand forming LnL(depma)Cl (2-Ln) and then the release of chloroethane forming LnL(epma) (3-Ln, epma=9-ethylphosphonomethylanthrancene). The structural transformations are accompanied with synergetic switch of the luminescence in visible and NIR regions and also magnetic dynamics.
We report a 2-iodoxybenzoic acid (IBX)-mediated intarmolecular oxidative spiro-fused tandem cyclization reaction of tryptophan analogs bearing an N-arylamides side-chain to rapidly afford polycyclic spiroindolines featuring multiple stereocenters including a quaternary stereocenters under mild reaction conditions. Among them, a novelty azaphosphol idine-containing spiroindoline compound is synthesized for the first time. It may open the door to azaphos pholidine-containing spiroindoline compound of potential interest in synthetic and medicinal chemistry. A plausible mechanism is proposed.
Disclosed herein is an efficient Ag-catalyzed [4+1] heteroannulation reaction of enamides with α-carbonyl sulfoxonium ylides. The diastereoselective transformation provides a practical access to a diverse range of multi-functionalized oxazoline derivatives. The synthetic utility of the resultant tetra-substituted oxazolines is further demonstrated by a series of useful manipulations into valuable building blocks of pharmaceutical relevance.
Diseases caused by microbial bacteria such as Haemophilus influenzae type b (Hib), Streptococcus pneumoniae and Neisseria meningitidis are still very serious disease, which has brought a lot of burden to many countries. Development of vaccine has brought hope for the prevention of such diseases. Polysaccharide conjugate vaccines have been shown to have very good effects in preventing such diseases. The polysaccharide conjugate vaccine adds the positive characteristics of protein antigens to the polysaccharide antigen, thereby improving the immunogenicity of the polysaccharide antigen, solving the problem that the polysaccharide vaccine cannot be effectively applicated in toddler or children, which greatly promoting the development of this vaccine. This review introduces the progress of polysaccharide conjugate vaccines. We introduce the typical polysaccharide conjugate vaccines currently on the market firstly, and then elucidate the protein carriers, the coupling chemistry methods and quality control that required in the preparation of polysaccharide conjugate vaccines. We can see that polysaccharide conjugate vaccine is a kind of vaccine with great development potential, which can be a sharp edge for us to prevent diseases.
Further enhancement in the energy density of rechargeable lithium batteries calls for high-voltage cathode materials and stable anodes, as well as matched high-voltage electrolytes without compromising the overall property of batteries. Sulfone-based electrolytes have aroused great interest in recent years owing to their wide electrochemical window and high safety. However, significant challenges such as the complexity of synthesis, high melting point (typically above room temperature), high viscosity, and their poor compatibility with graphite-based anodes have drastically impeded their practical applications. In this review, recent progress of sulfone solvents in high energy density rechargeable lithium batteries is summarized theoretically and experimentally. More importantly, general improvement methods of sulfone-based electrolytes, such as adding additives and cosolvents, structural modifications of sulfone, superconcentrated salt strategy are briefly discussed. We expect that this review provides inspiration for the future developments of sulfone-based high-voltage electrolytes (SHVEs) and their widespread applications in high specific energy lithium batteries.
Fluorescent sensing for specific detection of berberine is an important issue in view of its potential jeopardization to food safety and human health, but remains less investigated. To the best of our knowledge, there is no fluorescence turn-on and ratiometric sensors available for specific detection of berberine. In this study, calix[4]carbazole (3) has been synthesized and its property of recognizing berberine has been evaluated by UV–vis, fluorescence, NMR, DLS and TEM techniques. The results show that 3 selectively recognizes berberine among the tested drugs and detects it with turn-on and ratiometric fluorescence due to their co-assembly nature. Moreover, 3 is not only low toxic and can reduce toxicity of berberine to human normal liver L02 cell, but also can release berberine to tumor HepG2 cells at acid micro-environment. It therefore holds a great potential for further exploration
With excellent color purity (full-width half maximum (FWHM) < 40 nm) and high quantum yield, multi-resonance (MR) molecules can harvest both singlet and triplet excitons for highly efficient narrowband organic light-emitting diodes (OLEDs) owing to their thermally activated delayed fluorescence (TADF) nature. However, the highly rigid molecular skeleton with the oppositely positioned boron and nitrogen in generating MR effects results in the intrinsic difficulties in the solution-processing of MR-OLEDs. Here, we demonstrate a facile strategy to increase the solubility, enhance the efficiencies and modulate emission color of MR-TADF molecules by extending aromatic rings and introducing tert-butyls into the MR backbone. Two MR-TADF emitters with smaller singlet-triplet splitting energies (ΔEST) and larger oscillator strengths were prepared conveniently, and the solution-processed MR-OLEDs were fabricated for the first time, exhibiting efficient bluish-green electroluminescence with narrow FWHM of 32 nm and external quantum efficiency of 16.3%, which are even comparable to the state-of-the-art performances of the vacuum-evaporated devices. These results prove the feasibility of designing efficient solution-processible MR molecules, offering important clues in developing high-performance solution-processed MR-OLEDs with high efficiency and color purity.
Direct alcohol fuel cells (DAFCs) have received wide attention as a new type of clean energy device because of their high energy conversion efficiency, portability, non-toxicity and pollution-free. Anode catalysts are the key factors affecting the performance of DAFCs. Recently studies show that using the optical activity of semiconductor materials as the carriers of traditional precious metal electrocatalysts, under the illumination of light sources, can greatly improve the electrocatalytic activity and stability of electrodes. In this review, the research progress of photo-responsive metal/semiconductor hybrids as the electrocatalysts for DAFCs in recent years is summarized, including: (1) Mechanism and advantages of photo-assistant electrochemical alcohol oxidation reaction, (2) metal/semiconductor electrocatalyst for the different type of fuel cell reactions, (3) different kind of metals in photo-responsive metal/semiconductor hybrid nanostructure, (4) the personal prospects of the photo-responsive metal/semiconductor electrode for future application in DAFCs.
Benzo-21-crown-7 (B21C7) is one of the most important crown ethers, which not only shows excellent physicochemical properties but also exhibits promising binding capability with dialkylammonium salts. In this paper, we designed and synthesized a fixed-tetraphenylethylene (FTPE) motif bridged ditopic benzo-21-crown-7 molecule (H). The fixed tetraphenylethylene motif endows H with aggregation induced emission (AIE) property. In the presence of a ditopic dialkylammonium salt guest molecule (G), a fluorescent supramolecular polymer with golden luminescent property could be fabricated. This B21C7-based host-guest supramolecular polymer with golden fluorescence may have potential application in dynamic luminescent materials.
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