Copper-catalyzed amidation of benzoic acids using tetraalkylthiuram disulfides as amine sources

A facile method for the copper-catalyzed synthesis of N-substituted benzamides was explored. In the presence of CuBr and di-tert-butyl peroxide, various N-substituted benzamides were prepared through amidation of benzoic acid by using commercially available and cheap tetraalkylthiuram disulfides as amine sources. With this protocol, a series of 14 N-substituted benzamides were furnished in good to excellent yields. The broad substrate scope and good to excellent yield show its practical synthetic value in organic synthesis.     

Syntheses,Structures, and Photophysical Properties of Two Coordination Polymers Based on 2,3‐Dioxo‐1,2,3,4‐tetrahydroquinoxaline‐6‐carboxylic Acid

Two complexes based on the ligand 1,4‐dihydro‐2,3‐quinoxalinedione, namely [Mn(H₂L)₂(H₂O)₂]_n ( 1 ) and {[Zn₂(H₂L)₂(tz)₂] · 5H₂O}_n ( 2 ) (H₃L = 2,3‐dioxo‐1,2,3,4‐tetrahydroquinoxaline‐6‐carboxylic acid, Htz = 1,2,4‐triazole) were hydrothermally synthesized and characterized by elemental analyses, IR spectroscopy, as well as single‐crystal and powder X‐ray diffraction. Complex 1 exhibited a 1D comb‐like chain formed by H₂L^– anions linking Mn^II ions, whereas complex 2 was a 2D layer‐like structure with square‐shaped windows and outstretched arms built by combination of H₂L^– and tz^– ligands with Zn^II ions. The adjacent chains or layers connected with each other by intermolecular hydrogen bonding and π–π stacking to further extend to a 3D supermolecular framework. In addition, the thermal stabilities, luminescence properties, and optical energy gap of 1 and 2 were investigated in detail.     

Synthesis,Structures, and Luminescent Properties of Lanthanide Complexes with Triphenylphospine Oxide

Seven lanthanide complexes [Ln(OPPh₃)₃(NO₃)₃] ( 1 – 3 ) (OPPh₃ = triphenylphosphine oxide, Ln = Nd, Sm, Gd), [Dy(OPPh₃)₄(NO₃)₂](NO₃) ( 4 ), [Ln(OPPh₃)₃(NO₃)₃]₂ ( 5 – 7 ) (Ln = Pr, Eu, Gd) were synthesized by the reactions of different lanthanide salts and OPPh₃ ligand in the air. These complexes were characterized by single‐crystal X‐ray diffraction analysis, elemental analysis, IR and fluorescence spectra. Structure analysis shows that complexes 1 – 4 are mononuclear complexes formed by OPPh₃ ligands and nitrates. The asymmetric units of complexes 5 – 7 consist of two crystallographic‐separate molecules. Complex 1 is self‐assembled to construct a 2D layer‐structure of (4,4) net topology by hydrogen bond interactions. The other complexes show a 1D chain‐like structure that was assembled by OPPh₃ ligands and nitrate ions through C–H ··· O interactions. Solid emission spectra of compounds 4 and 6 are assigned to the characteristic fluorescence of Tb³⁺ (λ_em = 480, 574 nm) and Eu³⁺ (λ_em = 552, 593, 619, 668 nm).     

Thickness difference induced pore structure variations in cellulosic separators for lithium-ion batteries

The pore structure of the separator is crucial to the performance of a lithium-battery as it affects the cell resistance. Herein, a straightforward approach to vary the pore structure of Cladophora cellulose (CC) separators is presented. It is demonstrated that the pore size and porosity of the CC separator can be increased merely by decreasing the thickness of the CC separator by using less CC in the manufacturing of the separator. As the pore size and porosity of the CC separator are increased, the mass transport through the separator is increased which decreases the electrolyte resistance in the pores of the separator. This enhances the battery performance, particularly at higher cycling rates, as is demonstrated for LiFePO₄/Li half-cells. A specific capacity of around 100 mAh g^?1 was hence obtained at a cycling rate of 2 C with a 10 µm thick CC separator while specific capacities of 40 and close to 0 mAh g^?1 were obtained for separators with thicknesses of 20 and 40 µm, respectively. As the results also showed that a higher ionic conductivity was obtained for the 10 µm thick CC separator than for the 20 and 40 µm thick CC separators, it is clear that the different pore structure of the separators was an important factor affecting the battery performance in addition to the separator thickness. The present straightforward, yet efficient, strategy for altering the pore structure hence holds significant promise for the manufacturing of separators with improved performance, as well as for fundamental studies of the influence of the properties of the separator on the performance of lithium-ion cells.     

非晶态Co-B的局域电子结构的X_α原子簇计算

金属玻璃TM-Met(TM为过渡金属原子,Met为类金属原子,如硼、磷等)由于其优异性能已成为非晶态研究的重要课题之一。实验研究表明,类金属原子与过渡金属原子构成非晶态合金(即金属玻璃)后,平均原子磁矩随Met的含量在一定范围内的变化呈线性下降关系.相当多的文献用“电荷转移刚性能带”模型来解释.认为金属玻璃的能带是     

非晶态Co-B的局域电子结构的Xα原子簇计算

In the research on metallic glass, there are arguments against the "rigid band charge transfer", model which assumes a charge transfer from metalloid atoms to transition metal atoms to explain the experimental evidence of linear reduction of average atomic magnetic moment with the increasing concentration of metalloid atoms, but they could not explain the experimental relation of the reduction. In the present work, spin-polarized SCC-DV-X_a calculation for atomic clusters for metallic glass Co-B has been empoloyed to investigate the local electronic structure and magnetic property of the metallic glass. As opposed to the "rigid band charge transfer" model, calculation in the present work indicates that charge transfers from Co4s to both B and Co3d. It is found that there is Co3d4s-B2p hybird bonding in Co-B, which leads to the linear reduction of average atomic magnetic moment. Thus the explanation removes the above controversy.     

基于函数系数自回归模型的风速时间序列预测

准确预测风电场风速是解决风能对电力系统所造成的安全、稳定运行和电能质量等问题的有效途径之一.风速的难以预测是由于它的高度随机和非线性.基于一种非参数的非线性自回归随机模型来预测风速,模型的自回归系数随模型依赖变量的变化而变化,因而它有灵活的非线性结构.数值实验和比较结果表明了这种函数系数自回归模型在风电场风速预测中的有效性.     

具有N-各向异性拉普拉斯算子的超线性问题的先验界

通过改进Brezis和Merle的方法,结合Moser-Trudinger不等式,移动平面方法及比较原理,得到了方程-Q_Nu=f(u),u∈W_0~(1,N)(Ω)的正解的先验界,其中Ω是R~N中的一个有界光滑区域,非线性项f至多具有指数型增长.