溶剂化金属原子浸渍法制备高分散负载型催化剂——Ⅸ.K-Fe/硅沸石催化剂的XRD、TEM、XPS和磁测定表征

用溶剂化金属原子浸渍(SMAI)法和普通浸渍(CI)法两种不同的方法制备了组成相同的K-Fe/硅沸石催化剂。TEM,XRD,XPS和磁测定结果表明,SMAI K-Fe/硅沸有催化剂中铁的分散度和还原度都大于CI催化剂,SMAI催化剂中金属颗粒直径小于4nm,具有超顺磁性,而CI催化剂中金属颗粒较大,表现铁磁性。两种方法制备的催化剂反应前后金属的状态发生明显的改变,对CO+H_2反应的催化性质不同。     

CS2和O(3P)及N(4S)原子化学反应动力学

含硫化合物的氧化是大气化学中特别感兴趣的领域之一。研究较多的含硫化合物有SO_2、OCS和CS_2。其中O(~3P)+CS_2化学反应动力学研究在文献中已见过报导。通常认为O(~3P)和CS_2反应有三个反应通道:     

Preparation of Highly Dispersed Supported Metal Catalysts via Solvated Metal Atom Impregnation ( V) --The Effects of Hydroxyl Group on the Surface Concentrations of SiO2 on the Properties of Supported Fe Clusters

Two kinds of small iron clusters supported on SiO2-200 (dehydroxylated at 200℃ and SiO2-600 (de-hydroxylated at 600℃) were prepared by Solvated Metal Atom Impregnation (SMAI) techniques. The iron atom precursor complex, bis (toluene) iron(0) formed in the metal atom reactor, was impregnated into SiO2 having different concentrations of surface hydroxyl groups to study the effect of surface hydroxylation on the crucial stage of iron cluster formation. Catalysts prepared in this way were characterized by THM, Mosbauer and chemisorption measurements, and the resules show that higher concentration of surface hydroxyl groups of SiO2-200 favours the formation of more positively charged support iron cluster Fen/SiO2-200 and the lower concentration of surface hydroxyl groups of SiO2-600 favours the formation of basically neutral supported iron cluster Fe2/SiO2-600. The measured results also indicate that the higher concentration of surface hydroxyl groups causes the precursor complex,bis(toluene) fron(0), to d     

Skeletal Editing: Interconversion of Arenes and Heteroarenes

Skeletal editing involves making specific point-changes to the core of a molecule through the selective insertion, deletion or exchange of atoms. It thus represents a potentially powerful strategy for the step-economic modification of complex substrates and is a perfect complement to methods such as C−H functionalization that target the molecular periphery. Given their ubiquity in biologically active compounds, the ability to perform skeletal editing on – and therefore interconvert between – aromatic heterocycles is especially valuable. This review summarizes both recent and key historical examples of skeletal editing as applied to interconversion of aromatic rings; we anticipate that it will serve to highlight not only the innovative and enabling nature of current skeletal editing methods, but also the tremendous opportunities that still exist in the field.     

Atom transfer coupling reactions performed with benign reducing agents and radical traps

Monobrominated polystyrene (PSBr) was prepared by ATRP, and the resulting chain ends were activated in the presence of radical traps to induce chain end‐coupling. In atom transfer radical coupling (ATRC) with radical trap assistance, to achieve significant coupling requires excess metal catalyst, ligand, and a reducing agent that is often additional metal. In this work, activators generated by electron transfer (AGET) and radical trap assistance are used in the ATRC sequence to successfully lead to chain‐end coupling without the need for the oxidatively unstable copper (I) and with environmentally friendlier agents in place of copper metal. High extents of coupling (Xc) were achieved using ascorbic acid (AA) as the reducing agent and copper(II) bromide as the oxidized version of the catalyst, and when combined with AGET ATRP to prepare the PSBr precursor, only a fraction of the total metal was required compared to traditional atom transfer reactions, while still retaining similar Xc values. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 2113–2120     

包含平面五配位和平面四配位碳化合物的结构和稳定性

在B3LYP/6-311+G**水平上,研究了包含平面五配位碳(ppC)和平面四配位碳(ptC)的化合物CB5C2H2(C3B2)nC2H2CB5(n=1-5)的结构、能隙、IR光谱、电子光谱、Wiberg键指数以及芳香性.计算结果表明,这五种化合物的能量最低结构均位于势能面的极小值点,HOMO-LUMO能隙在0.5到1.2eV之间,第一电子的激发能在1780到2910nm之间,且与分子尺寸呈现非单调变化趋势.Wiberg键指数和键长表明这五种化合物的能量最低结构均包含平面五配位和平面四配位碳.C3B2单元和右侧CB5单元中三元环中心的核独立化学位移(NICS(0))值均为负值,而左侧CB5单元中的三元环中心的NICS(0)值中两个为正值,另两个为负值,NICS(1)值与NICS(0)值也一致,因此电子的局域离域对结构的稳定是很重要的.     

Two-dimensional confined hydrogen: An entropy and complexity approach

The position and momentum spreading of the electron distribution of the two-dimensional confined hydrogenic atom, which is a basic prototype of the general multidimensional confined quantum systems, is numerically studied in terms of the confinement radius for the 1s, 2s, 2p, and 3d quantum states by means of the main entropy and complexity information-theoretical measures. First, the Shannon entropy and the Fisher information, as well as the associated uncertainty relations, are computed and discussed. Then, the Fisher-Shannon, lopezruiz-mancini-alvet, and LMC-Rényi complexity measures are examined and mutually compared. We have found that these entropy and complexity quantities reflect the rich properties of the electron confinement extent in the two conjugated spaces.     

高里德堡态氢原子与氦原子散射的高分辨研究

A high resolution study of the high-n Rydberg H atom scattering with helium was carried out using the H atom Rydberg tagging time-of-flight technique. Differential cross sections were measured for scattering process of H(n)+He→H(n′)+He at the collision energy of 0.526 eV. Experimental result indicates that the scattered H(n′) product is mainly forward distributed, with signals observed in the wide range of angles at the sideway and forward scattering directions. At the sideway and forward directions, a lot of oscillatory structures in the angular distributions are present. Detailed analysis also shows that the principle quantum number, n, is not changed much for the Rydberg H atom at the forward scattering direction. This work provides a good test ground to investigate theoretically the exact collision dynamics between the high-n Rydberg H atom and the helium atom.     

表面温敏聚合物刷的原子力显微镜和石英晶体微天平研究

通过表面引发的原子转移自由基聚合在硅片表面制备了聚（N-异丙基丙烯酰胺）（PNIPAAm）聚合物刷。用原子力显微镜（AFM）分别研究了PNIPAAm的接枝动力学、温度和溶剂性质对厚度的影响以及PNIPAAm链与原子力针尖间的粘附力。结果表明,PNIPAAm链在硅片表面的生长具有很好的可控性。常温下厚度为33nm的PNIPAAm膜在水溶液中的增加到82.4nm;而在甲醇/水（v/v,1:1）溶液中,PNIPAAm分子链处于坍塌收缩状态,厚度降低为45nm;在55℃下干燥所得厚度则仅为22nm。力-距离测量结果表明,在溶液中,PNIPAAm链与原子力针尖之间的粘附力远小于在干态下的粘附力。用石英晶体微天平（QCM-D）对PNIPAAm的可逆相转变进行了研究,结果表明PNIPAAm分子链随温度变化的构象转变是发生在30-34℃之间的连续过程。     

Asymmetric nitrogen. 76. Quantum chemical study of geometry and configurational stability of ketenimines

MNDO calculations were carried out of the ground and transitional states of the planar inversion of the N atom for ketenimines containing (Me, NH₂, OH, OMe, and F) and (CH = O) acceptor N substituents as well as for C-amino- and C-formylketenimines. Configurationally stable N-amino-, N-alkoxy-, and N-fluoroketenimines (inversion barriers 27–45 kcal/mole) are of interest for further experimental stereochemical studies. The geometry of the ketenimine fragment is determined in general byn _N-_CC* conjugation. Other orbital and Coulombic interactions affect C- and N-substituent orientation relative to this fragment.For previous communication, see [1].N. N. Semenov Institute of Chemical Physics, Russian Academy of Sciences, 117977 Moscow. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 11, pp. 2572–2578, November, 1992.     

一些含锗有机酸的快原子轰击质谱

本文报道了一系列含锗有机酸在甘油中的快原子轰击质谱（ＦＡＢＭＳ）及共在间硝基苄醇（ＮＢＡ）中的正、负离子ＦＡＢＭＳ。这些含锗有机酸在不同的底物中的ＦＡＢＭＳ显示了不同的特征。负离子谱提供了分子量信息，正、负离子谱可为这类化合物的结构鉴定提供互相补充的信息。讨论了底物和取代基对ＦＡＢＭＳ的影响，正、负离子的产生机制及离子的亚稳分解途径。     

Photocatalytic C−H Functionalization of Nitrogen Heterocycles Mediated by a Redox Active Protecting Group

Herein, we report a photocatalytic strategy for the C−H functionalization of saturated azaheterocycles under mild conditions with only one equivalent of starting material. Our strategy is based on a redox active benzamide protecting group that is activated via a halogen-atom transfer (XAT) process to trigger the formation of an α-amino radical. This nucleophilic radical intermediate was then engaged in Giese additions and radical cross couplings to afford C−H alkylated and arylated products.     

Hierarchical atom type definitions and extensible all‐atom force fields

The extensibility of force field is a key to solve the missing parameter problem commonly found in force field applications. The extensibility of conventional force fields is traditionally managed in the parameterization procedure, which becomes impractical as the coverage of the force field increases above a threshold. A hierarchical atom‐type definition (HAD) scheme is proposed to make extensible atom type definitions, which ensures that the force field developed based on the definitions are extensible. To demonstrate how HAD works and to prepare a foundation for future developments, two general force fields based on AMBER and DFF functional forms are parameterized for common organic molecules. The force field parameters are derived from the same set of quantum mechanical data and experimental liquid data using an automated parameterization tool, and validated by calculating molecular and liquid properties. The hydration free energies are calculated successfully by introducing a polarization scaling factor to the dispersion term between the solvent and solute molecules. © 2015 Wiley Periodicals, Inc.     

Mo(CO)5L的氧原子转移反应动力学和机理研究

近期我们报道了M(CO)_2(M=Cr,Mo,W)与Me_2NO反应的动力学研究结果。 本文报道在CH_2Cl_2,-CH_2CN(体积比1:1)混合溶剂中,三甲胺氧化物存在下的二取代反应: Mo(CO)_5L Me_3NO L→顺-Mo(CO)_4L_2 Me_3N CO_3 (1)式中L=P(c-hx)_3,P(n-Bu)_3,NMe_3Pyr,PPh_3,AsPh_3,P(OEt)和P(OMe)_3,在金属原子不变的情况下对配体的电子效应(以Mo(CO)_5L的羰基伸缩振动频率表现出来)和立体效应做探讨。     

从核磁共振氢谱推导的重质油氢碳原子摩尔比计算式

通过对炼油厂的催化油浆、重催油浆和催化重焦蜡油核磁共振氢谱中质子归属和重质油结构的假设，推导出计算这3种重质油的氢碳原子摩尔比计算式；结果表明，氢碳原子摩尔比的计算值与实测值非常接近，平均误差仅为3．1％。     

A new approach to counterpoise correction to BSSE

In the present work the intermolecular BSSE, associated to the A-B interaction, is obtained by subtracting the intramolecular BSSE of the fragments from the intramolecular BSSE of the supermolecule, and considering every atom as a fragment in the calculation of each intramolecular BSSE. This atom by atom scheme (CP(aa)) is based on the consideration that the proximity of the fragments may affect the intramolecular BSSE of every involved species, and artificially influences the value of the BSSE associated to the supermolecule formation. It drastically decreases the reported counterpoise overcorrection of the A-B interaction, even though it does not deal with all the overcorrection because it includes all the orbitals, and not only the unoccupied ones. This new approach has been tested on the water dimer, some hydrogen fluoride weakly bonded complexes, the conformational analysis of 1,2-dichloroethane, and the reaction profile of formaldehyde + OH reaction.     

Understanding topological symmetry: a heuristic approach to its determination

An algorithm based on heuristic rules for topological symmetry perception of organic structures having heteroatoms, multiple bonds, and any kind of cycle, and configuration, is presented. This algorithm identifies topological symmetry planes and sets of equivalent atoms in the structure, named symmetry atom groups (SAGs). This approach avoids both the need to explore the entire graph automorphism groups, and to encompass cycle determination, resulting in a very effective computer processing. Applications to several structures, some of them highly symmetrical such as dendrimers, are presented.     

Iron‐catalyzed carbon–sulfur bond formation: Atom‐economic construction of thioethers with diaryliodonium salts

Diaryliodonium salts are characterized by poor atom economy with the formation of one equivalent of an iodoarene as waste. We have developed an atom‐economic iron‐catalyzed protocol for the synthesis of a variety of thioethers with diaryliodonium salts. Not only cyclic diaryliodonium salts but also linear diaryliodonium salts were found to perform well in the reactions.