Latest ArticlesHerein, the origin of the diastereoselectivity of N-heterocyclic carbene (NHC)-catalyzed cross-benzoin reactions between an α-amino aldehyde and furfural was studied by density functional theory. The computational results showed that the reaction proceeded through four steps:nucleophilic addition of NHC onto furfural, formation of a Breslow intermediate, cross-coupling reaction between Breslow intermediate and α-amino aldehyde, and dissociation of the catalyst. The cross-coupling was identified as the diastereoselectivity-determining step, with the R-configured product generated preferentially. Noncovalent interaction (NCI) analysis showed that the C-H ··· O and C-H ··· F interactions were responsible for determining the diastereoselectivity.
A versatile and efficient telescoped reaction sequence for the synthesis of tetrahydroisoquinolines (THIQs) is reported that uses TiCl4 to promote cyclization of a benzylaminoacetal derivative and Et3SiH for reduction of the intermediate 4-hydroxy-THIQ. This method is complimentary to the classical Pomeranz-Fritsch and related reactions since it tolerates electron-withdrawing substituents and allows access to 8-substituted THIQs.
High-performance anodes of sodium ion batteries (SIBs) largely depends on rational architecture design and binder-free smart hybridization. Herein, we report TiC/C core/shell nanowires arrays prepared by a one-step chemical vapor deposition (CVD) method and apply it as the anode of SIBs for the first time. The conductive TiC core is intimately decorated with carbon shell. The as-obtained TiC/C nanowires are homogeneously grown on the substrate and show core/shell heterostructure and porous architecture with high electronic conductivity and reinforced stability. Owing to these merits, the TiC/C electrode displays good rate performance and outstanding cycling performance with a capacity of 135.3 mAh/g at 0.1 A/g and superior capacity retention of 90.14% after 1000 cycles at 2 A/g. The reported strategy would provide a promising way to construct binder-free arrays electrodes for sodium ion storage.
Considering the importance and complexity of benzene oxidation on mineral oxide aerosol surfaces in the atmosphere, gas-phase 3d-transition metal oxide cations were used as models of active sites on mineral oxide aerosols to mimic the corresponding reactions. The various cations have been prepared by laser ablation and reacted with benzene in a linear ion trap reactor. Of the 103 systematically investigated cations, 39 clusters can oxidize benzene at room temperature. In addition to the adsorption channel, other five types of reaction channels were observed, including dehydrogenation of C6H6, charge exchange, hydrogen atom transfer, oxygen atom transfer, and the formation of C6H5O·radical, among which the first two pathways are prevalent and the formation of C6H6O+ cations has not been reported in literature. The insight into the benzene oxidation reactions derived from the gas-phase model systems is helpful to build a detailed picture of oxidative mechanisms of C6H6 and its derivatives over corresponding mineral oxide aerosols.
A nonanuclear Cu4ⅡTi5Ⅳ heterometallic cluster, [Ti5Cu4O6(ba)16] (1, Hba=benzoic acid) was synthesized in one-pot reaction under the solvothermal condition. The metallic skeleton 1 contains a Ti5 core constructed from two vertex-shared Ti3 triangles and four separated Cu atoms outside which are connected together by μ3-O2- ions. Total 16 ba- ligands adopt μ2-η1:η1 coordination mode to protect the overall heterometallic core. Due to the unique d-d transitions of CuⅡ ion, the reflectance spectrum of 1 displays broad and strong absorption towards visible light extending to the near-infrared region. Moreover, 1 shows almost purely paramagnetic behavior with the presence of weak antiferromagnetic interactions at low temperatures.
Recent development of self-healing material has attracted tremendous attention, owing to its biomimetic ability to restore structure and functionality when encountering damages. Here, we develop a threedimensional (3D) printable self-healing composite conductive polymer by mixing hydrogen-bond-based supramolecular polymer with low-cost carbon black. It has a room-temperature self-healing capability in both conductivity and mechanical property, while its shear-thinning behavior enables fabrication of a self-healable circuit by 3D printing technology. As an application, the circuit shows an excellent temperature-dependent behavior of the resistance, indicating its great potential for practical application in the artificial intelligence field.
Developing enzyme-free sensors with high sensitivity and selectivity for H2O2 and glucose is highly desirable for biological science. Especially, it is attractive to exploit noble-metal-free nanomaterials with large surface area and good conductivity as highly active and selective catalysts for molecular detection in enzyme-free sensors. Herein, we successfully fabricate hollow frameworks of Co3O4/N-doped carbon nanotubes (Co3O4/NCNTs) hybrids by the pyrolysis of metal-organic frameworks followed by calcination in the air. The as-prepared novel hollow Co3O4/NCNTs hybrids exhibit excellent electrochemical performance for H2O2 reduction in neutral solutions and glucose oxidation in alkaline solutions. As sensor electrode, the Co3O4/NCNTs show excellent non-enzymatic sensing ability towards H2O2 response with a sensitivity of 87.40 μA (mmol/L)-1 cm-2, a linear range of 5.00 μmol/L-11.00 mmol/L, and a detection limitation of 1 μmol/L in H2O2 detection, and a good glucose detection performance with 5 μmol/L. These excellent electrochemical performances endow the hollow Co3O4/NCNTs as promising alternative to enzymes in the biological applications.
Polymer electrolytes are essential for next-generation lithium batteries because of their excellent safety record. However, low ionic conductivity is the main obstacle restricting their commercial application. Composites with nanoparticles are a promising route to overcome this obstacle. In this work, lithium polystyrene sulfonate brushes (LiPSS) is anchored to silicon dioxide nanoparticles with chemical bonding using atom transfer radial polymerization (SI-ATRP). The composite polymer electrolytes are made by mixing vinylene carbonate and nanoparticles via a facile in situ polymerization process. The ionic conductivity of composite polymer electrolytes is improved to 7.2 ×10-4 S/cm at room temperature, which is attributed to the low degree of crystallinity of polymer electrolyte and the fast ion transport on the surfaces of polymer brush layers that act as a conductive network. The composite polymer electrolytes show a wide electrochemical window of approximately 4.5 V vs. Li+/Li and excellent cycling performance retention of approximately 95% after 100 cycles at ambient temperature. The results also prove that surface groups of ceramic nanoparticles are an important way to increase the electrochemical properties of composite polymer electrolytes.
Botrytis cinerea is a necrotrophic fungus that affects various plant species. Chemical control is a necessity and as much as possible, eco-friendly conditions and bioresources to obtain these chemicals should be used. In this context, a series of products was obtained from salicylaldehyde using zinc as a powerful reagent and tested for antifungal activity against Botrytis cinerea.
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