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161.
过渡金属催化有机腈和叠氮酸钠反应机理的研究一直是一个具有挑战性的课题.本工作组合理论和实验方法,对其反应机理作了深入的探讨.基于对两种类型中间体(H2O)3M…N3–和(H2O)3M…NCCH3稳定性的理论分析和中间体Cd2(μ3-N3)(μ3-OH)(μ5-CHDA)(1)和Cd(μ2-N3)(μ3-IBA)(2)(H2CHDA为1,3-环己二酸, HIBA为4’-(咪唑-1-基)苯甲酸)的成功捕获,首次从实验和理论上揭示了过渡金属离子在反应中起活化叠氮酸根的作用.此外,基于中间体(H2O)3M…N3-和乙腈分子的静电势盆分析的结果,揭示了叠氮酸根未配位的端基N原子可以进攻... 相似文献
162.
Synthesis,Structures, and Photocatalytic Properties of Zinc(II) and Cobalt(II) Supramolecular Complexes Constructed with Flexible Bis(thiabendazole) and Dicarboxylate Linkers 下载免费PDF全文
Three coordination complexes, namely, [Zn(btbp)(3‐npa)]n ( 1 ), [Co(btbh)(3‐npa)]n ( 2 ), and {[Co(btbb)(5‐nipa)(H2O)] · H2O}n ( 3 ) (btbp = 1,3‐bis(thiabendazole)propane, btbh = 1,6‐bis(thiabendazole)hexane, btbb = 1,4‐bis(thiabendazole)butane, 3‐H2npa = 3‐nitrophthalic acid and 5‐H2nipa = 5‐nitroisophthalic acid) were synthesized under hydrothermal conditions and characterized by physicochemical and spectroscopic methods as well as by single‐crystal X‐ray diffraction. Complex 1 features a fascinating meso‐helical chain, which is further extended into a 2D supramolecular framework involving π ··· π stacking interactions. Complexes 2 and 3 show dinuclear structures. Complex 2 is further connected through C–H ··· O hydrogen bonding interactions to afford a 2D supramolecular layer, whereas complex 3 is further extended to a rare 2‐nodal (3,4)‐connected supramolecular sheet with a point symbol of {3.42.5.6.7}2{3.82} by O–H ··· O hydrogen bonding interactions. The electrochemical behaviors of the two cobalt complexes 2 and 3 were reported. Moreover, the luminescent properties for 1 and the photocatalytic properties for the complexes were investigated. 相似文献
163.
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165.
在(298.15 ±0.01) K下用转动弹热量计测定了离子液体硫酸乙酯-1-甲基-3-乙基咪唑(EMIES)及合成它的原料1-甲基咪唑的恒容燃烧热,通过计算得到它们的标准燃烧焓 分别为(-2671±2) 和(-286.3±0.5) kJ·mol-1;标准生成焓 分别为(-3060±3) kJ·mol-1和(-2145±4) kJ·mol-1.结合文献上硫酸二乙酯的标准生成焓数据,得到了合成离子液体EMIES的反应热(-102.3±1.0) kJ·mol-1,与合成实验中观察到的强烈放热现象是一致的.根据离子液体EMIES的热容数据,计算了不同温度下EMIES的标准生成焓. 相似文献
166.
采用等温溶解平衡法研究了四元体系Na+,K+//Br-,SO42--H2O在323 K的相平衡关系,测定了该体系323 K的溶解度及平衡液相的密度,绘制了该体系的相图。研究发现:平衡体系存在复盐钾芒硝Na2SO4·3K2SO4的结晶区。其相图由3个共饱和点,7条单变量曲线和5个结晶区组成。相区分别对应NaBr·2H2O、Na2SO4、K2SO4、KBr和Na2SO4·3K2SO4结晶区。其中复盐钾芒硝Na2SO4·3K2SO4,Na2SO4和K2SO4有较大结晶区,而NaBr·2H2O和KBr有较小结晶区。对比了等温条件下四元体系Na+,K+//Cl-,SO42--H2O相平衡结果。实验结果表明溴化物对硫酸盐有较强盐析作用。 相似文献
167.
Zwitterionic polymers as crucial antifouling materials exhibit excellent antifouling performance due to their strong hydration ability. The structure–property relationship at the molecular level still remains to be elucidated. In this work, the surface hydration ability of three antifouling polymer membranes grafting on polysiloxane membranes Poly(sulfobetaine methacrylate) (T4-SB), poly(3-(methacryloyloxy)propane-1-sulfonate) (T4-SP), and poly(2-(dimethylamino)ethyl methacrylate) (T4-DM) was investigated. An orderly packed, and tightly bound surface hydration layer above T4-SP and T4-SB antifouling membranes was found by means of analyzing the dipole orientation distribution, diffusion coefficient, and average residence time. To further understand the surface hydration ability of three antifouling membranes, the surface structure, density profile, roughness, and area percentage of hydrophilic surface combining electrostatic potential, RDFs, SDFs, and noncovalent interactions of three polymers’ monomers were studied. It was concluded that the broadest distribution of electrostatic potential on the surface and the nature of anionic SO3- groups led to the following antifouling order of T4-SB > T4-SP > T4-DM. We hope that this work will gain some insight for the rational design and optimization of ecofriendly antifouling materials. 相似文献
168.
Heng Liu Luozhen Jiang Javid Khan Xinxin Wang Jiamin Xiao Handong Zhang Haijiao Xie Prof. Lina Li Prof. Shuangyin Wang Prof. Lei Han 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2023,135(3):e202214988
The regulation of electron distribution of single-atomic metal sites by atomic clusters is an effective strategy to boost their intrinsic activity of oxygen reduction reaction (ORR). Herein we report the construction of single-atomic Mn sites decorated with atomic clusters by an innovative combination of post-adsorption and secondary pyrolysis. The X-ray absorption spectroscopy confirms the formation of Mn sites via Mn-N4 coordination bonding to FeMn atomic clusters (FeMnac/Mn-N4C), which has been demonstrated theoretically to be conducive to the adsorption of molecular O2 and the break of O−O bond during the ORR process. Benefiting from the structural features above, the FeMnac/Mn-N4C catalyst exhibits excellent ORR activity with half-wave potential of 0.79 V in 0.5 M H2SO4 and 0.90 V in 0.1 M KOH as well as preeminent Zn-air battery performance. Such synthetic strategy may open up a route to construct highly active catalysts with tunable atomic structures for diverse applications. 相似文献
169.
Numerical discretization-based kernel type estimation methods for ordinary differential equation models 下载免费PDF全文
We consider the problem of parameter estimation in both linear and nonlinear ordinary differential equation(ODE) models. Nonlinear ODE models are widely used in applications. But their analytic solutions are usually not available. Thus regular methods usually depend on repetitive use of numerical solutions which bring huge computational cost. We proposed a new two-stage approach which includes a smoothing method(kernel smoothing or local polynomial fitting) in the first stage, and a numerical discretization method(Eulers discretization method, the trapezoidal discretization method,or the Runge–Kutta discretization method) in the second stage. Through numerical simulations, we find the proposed method gains a proper balance between estimation accuracy and computational cost.Asymptotic properties are also presented, which show the consistency and asymptotic normality of estimators under some mild conditions. The proposed method is compared to existing methods in term of accuracy and computational cost. The simulation results show that the estimators with local linear smoothing in the first stage and trapezoidal discretization in the second stage have the lowest average relative errors. We apply the proposed method to HIV dynamics data to illustrate the practicability of the estimator. 相似文献
170.
Qiang Ma Heng Zhang Chongwang Zhou Liping Zheng Pengfei Cheng Prof. Jin Nie Prof. Wenfang Feng Prof. Yong‐Sheng Hu Prof. Hong Li Prof. Xuejie Huang Prof. Liquan Chen Prof. Michel Armand Prof. Zhibin Zhou 《Angewandte Chemie (International ed. in English)》2016,55(7):2521-2525
A novel single lithium‐ion (Li‐ion) conducting polymer electrolyte is presented that is composed of the lithium salt of a polyanion, poly[(4‐styrenesulfonyl)(trifluoromethyl(S‐trifluoromethylsulfonylimino)sulfonyl)imide] (PSsTFSI?), and high‐molecular‐weight poly(ethylene oxide) (PEO). The neat LiPSsTFSI ionomer displays a low glass‐transition temperature (44.3 °C; that is, strongly plasticizing effect). The complex of LiPSsTFSI/PEO exhibits a high Li‐ion transference number (tLi+=0.91) and is thermally stable up to 300 °C. Meanwhile, it exhibits a Li‐ion conductivity as high as 1.35×10?4 S cm?1 at 90 °C, which is comparable to that for the classic ambipolar LiTFSI/PEO SPEs at the same temperature. These outstanding properties of the LiPSsTFSI/PEO blended polymer electrolyte would make it promising as solid polymer electrolytes for Li batteries. 相似文献