Carbon nitride with encapsulated nickel for semi-hydrogenation of acetylene: pyridinic nitrogen is responsible for hydrogen dissociative adsorption

A new mechanism of catalyst has been demonstrated in this article. With the interaction between carbon nitride (CN) and encapsulated nickel, the CN in the catalyst has been endowed with new active sites for the adsorption and activation of hydrogen while nickel itself is physically isolated from the contact with reactive molecules. For the selective hydrogenation of acetylene in large amount of ethylene, the catalyst shows excellent ethylene selectivity than the nickel catalyst itself, which is almost totally unselective. Meanwhile, the CN itself is inactive for the reaction. The results of characterization demonstrate that pyridinic nitrogen doped in the carbon matrix should be the active sites for hydrogen dissociative adsorption. The theoretical calculations further confirm the results and provide with the detail in the electron transfer between nickel and CN in the catalyst. The current results supply a new concept for design of high performance catalyst.     

Effect of metal cations [Li+, Na+, K+, Be2+, Mg2+, and Ca2+] on the structure of 2‐(3′‐hydroxy‐2′‐pyridyl)benzoxazole: A theoretical investigation

Density functional theory calculations were performed at the B3LYP/6‐311++G(d,p) level to systematically explore the geometrical multiplicity and binding strength for the complexes formed by alkaline and alkaline earth metal cations, viz. Li⁺, Na⁺, K⁺, Be²⁺, Mg²⁺, and Ca²⁺ (Mⁿ⁺, hereinafter), with 2‐(3′‐hydroxy‐2′‐pyridyl)benzoxazole. A total of 60 initial structures were designed and optimized, of which 51 optimized structures were found, which could be divided into two different types: monodentate complexes and bidentate complexes. In the cation‐heteroatom complex, bidentate binding is generally stronger than monodentate binding, and of which the bidentate binding with five‐membered ring structure has the strongest interaction. Energy decomposition revealed that the total binding energies mainly come from electrostatic interaction for alkaline metal ion complexes and orbital interaction energy for alkaline earth metal ion complex. In addition, the electron localization function analysis show that only the Be? O and Be? N bond are covalent character, and others are ionic character. © 2012 Wiley Periodicals, Inc.     

Halogen bonds and metal bonds involving superalkalies M2OCN/M2NCO (M = Li,Na) complexes

Structural Chemistry - A new type of halogen bond formed by supermetals or superalkalies with dihalogen molecules was analyzed by means of ab initio at the MP2/aug-cc-pVTZ level. The results reveal...     

Positively Charged Nanoaggregates Based on Zwitterionic Pillar[5]arene that Combat Planktonic Bacteria and Disrupt Biofilms

Bacterial biofilms are difficult to eradicate because they are less susceptible to antibiotics and more easily develop resistance. Therefore, there is an urgent need for new materials that can combat planktonic bacteria and disrupt established biofilms. To tackle this challenge, we design a multifunctional zwitterionic pillar[5]arene, which can self‐assemble into weakly positively charged nanoaggregates that exhibit antibacterial activity against Gram‐negative Escherichia coli (DH5α) and Gram‐positive Staphylococcus aureus (SH1000) bacterial strains in solution. In addition, the zwitterionic pillar[5]arene can efficiently disrupt pre‐existing Escherichia coli (DH5α) biofilms and kill the biofilm‐enclosed bacteria without rapid generation of resistance.     

Pd/ZnO催化甲醇水蒸气重整理论研究

随着化石能源的日渐枯竭和人们对环境保护的日益重视,发展清洁高效的新能源成为世界各国高度关注的战略课题。甲醇水蒸气重整是生产氢能的有效方法之一,Pd/ZnO催化剂热稳定性好、选择性高,是可能替代Cu/ZnO的催化剂。本文综述了近十年来采用理论方法对Pd/ZnO催化甲醇水蒸气重整制氢机理的研究工作。文章首先论述了催化剂的研究进展,然后对水在单体和聚集状态下在单层及多层平整的和阶梯状的合金表面的吸附和解离进行了总结;接着对甲醇、甲氧基和甲醛在合金表面的吸附和化学反应的热力学和动力学作了介绍;随后基于计算结果,对甲醇反应机理给予了详细的描述。最后对全文进行了总结并对未来的研究作了展望。     

Study on the nature of interaction of BrCl with HF,H2O,and NH3

By counterpoise‐corrected optimization method, the interactions of BrCl with the first‐row hydrides (HF, H₂O, NH₃) have been investigated at the MP2/6–311++G(3d,3p) level. To understand that the X? Br‐type (X = F, O, N) structure is more stable than the corresponding hydrogen‐bonded structure in these complexes, the electronic properties were also investigated. Symmetry‐adapted perturbation theory (SAPT) analysis has been carried out to understand the nature of the weak hydrogen bond and X? Br‐type interactions. On the other hand, for the weak hydrogen‐bonded complexes and the X? Br‐type complexes charges transfer is well correlated with the total induction energies. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

四唑及其衍生物的理论研究（6）

对7个肼基四唑衍生物进行了HF／6－31G水平的几何构型全优化及MP2／6－31G／／HF／6－31G水平的总能量计算．结果表明，四唑环基本上取平面构型，肼基不与环共面．键长与重叠布居之间不存在平行关系．环上N1和N4原子荷负电多、利于质子化．1H．肼基四唑的HOMO－LUMO能级差（△E）较2H式的大，中性分子的△E教相应的负离子的大．还计算研究了7个标题物的红外光谱并由此求得了它们的热力学性质．     

Investigation on the mechanism and applications of the reaction Cl2+2HBr=2HCl+Br2

The mechanism of reaction Cl₂+2HBr=2HCl+Br₂ has been carefully investigated with density functional theory (DFT) at B3LYP/6-311G^** level. A series of three-centred and four-centred transition states have been obtained. The activation energy (138.96 and 147.24 kJ/mol, respectively) of two bimolecular elementary reactions Cl₂+HBr→HCl+BrCl and BrCl+HBr→HCl+Br₂ is smaller than the dissociation energy of Cl₂, HBr and BrCl, indicating that it is favorable for the title reaction occurring in the bimolecular form. The reaction has been applied to the chemical engineering process of recycling Br₂ from HBr. Gaseous Cl₂ directly reacts with HBr gas, which produces gaseous mixtures containing Br₂, and liquid Br₂ and HCl are obtained by cooling the mixtures and further separated by absorption with CCl₄. The recovery percentage of Br₂ is more than 96%, and the Cl₂ remaining in liquid Br₂ is less than 3.0%. The paper provides a good example of solving the difficult problem in chemical engineering with basic theory.     

四唑及其衍生物的理论研究Ⅷ: 硝氨四唑衍生物的从头算

运用从头计算法,在HF/6-31G^*水平下,全优化计算了7种硝氨四唑衍生物的分子几何和电子结构。结果表明,标题物的四唑环近似为平面构型;2H式中性分子的芳香性大于相应的1H式异构体。5-硝氨-1H四唑分子内氢键使硝氨基与环共面;其余标题物中硝氨基与环垂直。不同水平下的总能量计算表明,标题物中电子相关效应显著;1H式中性分子较2H式的能量高,5-硝氨四唑负离子在三个负离子中最稳定。根据电荷分布阐明了四唑环质子化位置和标题物与金属的配位方式。此外还计算了各标题物的红外光谱及热力学性质。