CO与Pt原子簇的轨道相互作用和CO的活化问题

本文用EHMO方法对CO在Pt原子簇上的化学吸附进行了量子化学计算。从群轨道系数和能量相关关系,考察了轨道相互作用。由于考虑了对称性,参数选择、近似问题不会影响得到的主要结果。计算表明,CO在Pt原子簇上吸附时,主要与Pt的s及p电子键合,而CO的活化过程则通过金属中的d电子进行。Blyholder的关于CO金属键合的简单分子轨道描述似有进一步补充和刻画的必要。     

苯分子与Rh(111)面相互作用的分子轨道研究

用群分解EHMO法研究了苯在Rh(111)面上的化学吸附和成键性质。以Rh_7原子簇模型模拟Rh(111)表面,得到结合能为41kJ/mol,吸附高度2.60。被吸附的苯分子通过π键和金属原子的d轨道相互作用而受到活化,有利于在(111)表而上的化学反应。     

拓扑量子方法及其在含C＝O和N＝O化合物性能估算中的应用

综合量子化学与拓扑化学知识, 提出了构建Y＝O (Y表示C, N)键拓扑量子键邻接矩阵的方法. 利用该矩阵特征根和量子化学原理, 计算了表征分子轨道能量、原子电荷和键级等的拓扑量子参数. 将这些参数对含C＝O, N＝O基团的有机分子的紫外吸收能量、红外伸缩振动频率和醛酮C＝O上的亲核加成反应速率等性质进行定量结构-性质相关, 得到的模型均具有良好的估算能力.     

桥基原子对金属—金属作用的影响

本文借助EHMO法得到的Mulliken集居数和经验公式,讨论了过渡金属原子簇分子构型的稳定性和桥基与金属原子形成的平面距离D对其稳定性的影响。指出可用D值与实验上得到的距离d值的差别,判断过渡金属原子簇化合物金属—金属作用的强弱。     

一些金属原子簇羰基化合物的流变性及其电子结构的EHMO研究

近年来,关于过渡金属原子簇化合物的研究工作发展很快。这类化合物的通式是 M_pL_q,其中 M_p 是 p 个以 M—M 键相结合的金属原子所形成的原子簇,L 则是与原子簇 M_p 相结合的配位体,如羰基、卤素离子、CN~-、膦等。这类化合物有许多特点,金属原子簇具有介于单原子和金属微晶之间的一种过渡型结构。配位体和被金属表面吸附了的分子或离子相似。由     

Experimental Foundations of Structural Chemistry

本书较全面地汇集结构化学基本数据,应用于物质结构,化学键和结构．性能关联的实际研究,是一本具有手册性的专著。书中系统提供如下数据：原子,自由基,分子和原子簇电离势;元素与化合物的功函数和能带隙;包括范德华分子在内的键能;相变热和单质与化合物晶体的原子化能;各类化合物在不同物态下的键长以及金属,共价,离子和范德华半径的最新数据。还提供了在静态与动态压力下的相变,元素和化合物的状态方程与弹性模量,以及一些纳米晶体材料的特殊性能等丰富资料。     

Roussin红盐和Roussin黑盐的电子结构

Roussin黑盐簇阴离子及其"元件化合物"Roussin红盐簇阴离子,是固氮酶活性中心福州模型I(网兜状原子簇模型)的模型物.本文用闭壳层CNDO/2(S,D方案)法计算了它们的电子结构.根据计算所得的Mulliken重叠集居,电荷密度,分子轨道能量和轨道特征等数据,对成键性质进行了分析,得出如下主要结论:两种簇阴离子骨架电子的非定域性都比较强,桥硫原子Sb在由红盐形成黑盐的电子转移过程中起施主作用,两种簇阴离子中都存在M-M键,强度与M-Sb键相近,其主要贡献都来源于金属的s,pz,dz2轨道与硫原子的s,pz轨道之间的σ作用,金属d轨道的π作用对整个骨架的成键贡献很小.     

2,2''-双氨基苯氧基二硫化物及其聚合物的合成研究

在不同的锂或锂离子二次电池正极材料中 ,新型的聚有机二硫化物有可能成为最有应用前景的电池正极材料之一 [1] ,Visco等 [2 ]首次提出利用二硫化物中双硫键的断裂与再接 (即电聚合与电解聚 )化学性能应用于锂二次电池的充放电 .目前 ,对有代表性的有机二硫化物 2 ,5 -二巯基 -1 ,3 ,4-噻二唑(DMc T)进行了大量的研究[3～ 5] ,最近又提出通过合成新的聚有机二硫化物来提高其电化学性能[6 ,7] .为了得到一种新型高电化学活性和高导电性的锂或锂离子二次电池正极材料 ,本文通过化学方法合成2 ,2 -双氨基苯氧基二硫化物 (DAPD)单体 ,并通…     

对羟基二联苯诱导的表面金属-有机键断裂

金属-有机杂化结构是表面在位反应过程中常见的中间体. 金属-有机杂化结构中金属-有机键的断裂需要克服较高的活化能垒, 往往会引起一系列竞争副反应以及分子的脱附. 本文利用扫描隧道显微镜研究了 4,4′-二羟基联苯分子在金属表面与预先制备的金属-有机链的作用, 发现其氧端能有效地降低金属有机杂化体系断键的能垒, 使得金属-有机键的断键反应能在较低的温度下进行. 该结果提供了一种调控表面反应中间物的新手段.     

合成氨铁催化剂七铁原子簇对分子氮的活化件用

前文提出了合成氨铁催化剂活化分子氮的活性中心是由α-Fe(11)晶面的七铁原子簇所组成(图1)。本文简报采用推广的休克尔方法对该模型,以及缺少一至三个铁原子的结构对氮分子的活化作用进行计算,所得结果(见表)。计算时选用的参数见参考文献[2]。分子氮的化学吸附采取直插式。计算结果表明:N-Nσ键,在1Fe上氮分子端配位时稍有减弱,而在侧配位时则有所加强。从Fe_4N_2到Fe_7 N_2,σ键的变化不大,基本上同自由 N_2分子中的σ键。     

二苯二硫和二苄二硫润滑性能的量子化学研究

The molecular geometries optimization and electronic structures of diphenyl disulfide (DPDS) and dibenzyl disulfide (DBDS) compounds were investigated by density functional theory (DFT) and ab initio method at the 6-31G basis set level. The active atoms and bonds of reaction were provided by frontier molecular orbital theory. The molecular orbital parameters of DPDS and DBDS compounds and iron atom cluster were calculated by using density functional theory. The interaction pattern between the organic disulfide compounds and iron atom cluster was discussed based on the approximate rule of orbital energy. Some parameters characterizing the action strength between the organic disulfide compounds and iron atom cluster, including the bonding strength, reactive strength and static action strength, were analyzed by using frontier electron density, super de-localizability, net atomic charge and the interaction energy of chemical adsorption as criteria. The results indicate that S-S chemical bond and C-S chemical bond of the compounds are inclined to be broken when DPDS and DBDS interact with the metal. The anti wear ability order of DPDS and DBDS compounds is DPDS>DBDS, and the extreme pressure ability order of DPDS and DBDS compounds is DBDS>DPDS, and the prediction results based on quantum chemistry calculations are in good accordance with the friction and wear test results.     

First examples of oxidizing secondary alcohols to ketones in the presence of the disulfide functional group: synthesis of novel diketone disulfides

The disulfide functionality is present in a number of organic compounds of interest in the fields of both chemistry and biology. Because the disulfide group is known to be highly susceptible to further oxidation by a wide range of agents, performing a chemoselective oxidation without further oxidizing the disulfide moiety poses a synthetic challenge. Reported herein are the first examples of such a chemoselective oxidation in which a series of novel secondary alcohol disulfides 2a-f have been converted to the corresponding symmetrical diketones 3a-f utilizing a modified Swern oxidation.     

A theoretical study on the cyclopropane adsorption onto the copper surfaces by density functional theory and quantum chemical molecular dynamics methods

We report a theoretical study on the cyclopropane adsorption onto Cu(1 1 1) surfaces by density functional theory (DFT) and quantum chemical molecular dynamics methods. The equilibrium geometry of the physisorbed species was obtained using both periodic and cluster models by DFT methods that employ Cambridge serial total energy package (CASTEP), DMol ab initio quantum chemistry software of Accelrys’ materials studio (DMol), and Amsterdam density functional (ADF) program. It was found that the adsorbate molecule was tilted towards the metal surface with one C---C bond (upwards) parallel to the surface and that the physisorption occurred via a third carbon atom pointing (downwards) towards the surface. The electronic distribution and geometrical structure of physisorbed cyclopropane were slightly deviated from its gas phase molecule. The calculated vibrational frequencies and adsorption energies are close to experimental data, confirming the reliability of our DFT results. The adsorption process was simulated using our novel tight-binding quantum chemical molecular dynamics program, ‘Colors’. The calculation results indicated that both the adsorption and desorption processes of cyclopropane took place molecularly. The electron transfer and structural properties of equilibrium position obtained by ‘Colors’ are consistent with those by the first principles DFT methods.     

过渡金属异核原子簇化学键研究 1: Ⅷ-Ⅷ, ⅥB-Ⅷ族双金属原子簇电子结构研究

本文对18个Ⅷ族双金属四面体簇和16个ⅥB-Ⅷ异金属四核簇进行了量子化学研究, 用DV-Xα方法讨论了它们的化学键、电荷转移、能级态密度。计算结果表明: Ⅷ族四面体簇需36个金属电子, 其中12个形成6个金属簇骼轨道, 24个与配体成键; ⅥB-Ⅷ异金属簇核中, 因两金属能带、电负性差异, ⅥB原子易向Ⅷ原子转移电荷, 环戊二烯基配体促进这一过程; 异金属簇能级总价带比单金属簇收缩, 而d能带比单金属簇展宽。     

Site-specific protein modification by genetic encoded disulfide compatible thiols

Cysteine chemistry provides a low cost and convenient way for site-specific protein modification.However,recombinant expression of disulfide bonding containing protein with unpaired cysteine is technically challenging and the resulting protein often suffers from significantly reduced yield and activity.Here we used genetic code expansion technique to introduce a surface exposed self-paired dithiol functional group into proteins,which can be selectively reduced to afford active thiols.Two compounds containing self-paired disulfides were synthesized,and their genetic incorporations were validated using green fluorescent proteins(GFP).The compatibility of these self-paired di-thiols with natural disulfide bond was demonstrated using antibody fragment to afford site-specifically labeled antibody.This work provides another valuable building block into the chemical tool-box for site-specific labeling of proteins containing internal disulfides.     

Action mechanism of antioxidation and anticorrosion and molecular design for perfluoropolyether fluid additives (I) --Action mechanism of additive and property of donating-accepting electron

The combination energy and chemical adsorption energy of N-substituted perfluoropoly- alkyletherphenylamide (PFPEA) additive to perfluoropolyalkylether oxygen radical (RfO.) and to Fe atom have been calculated by quantum chemical methods. Structural characteristics, action mechanism, property of donating-accepting electron and substituent effect for antioxidant and anticorrosive additive are investigated. It is found that HOMO of the additives is a p-molecular orbital with lone pair electron of heteroatom. The HOMO of PFPEA additive reacts with LUMO of Fe atom to result in chemical adsorption. The LUMO of additive can interact with the SOMO of RfO. and accept electron of RfO. to form stable addition product. The additives have the property of donating-accepting electron. The electron-releasing group, particularly, the phenyl group, introduced to N atom of phenylamide can increase the combination energy and chemical adsorption energy, and enhance the antioxidant and anticorrosive efficiency. The research achievements can provide useful information for the designing of new antioxidant and anticorrosive additive. Based on the calculated results, antioxidant and anticorrosive efficiency can be predicted roughly as the following order: compounds III＞II＞I＞IV＞V.     

Chemistry at surfaces: from ab initio structures to quantum dynamics

Recent years have witnessed an ever growing interest in theoretically studying chemical processes at surfaces. Apart from the interest in catalysis, electrochemistry, hydrogen economy, green chemistry, atmospheric and interstellar chemistry, theoretical understanding of the molecule–surface chemical bonding and of the microscopic dynamics of adsorption and reaction of adsorbates are of fundamental importance for modeling known processes, understanding new experimental data, predicting new phenomena, controlling reaction pathways. In this work, we review the efforts we have made in the last few years in this exciting field. We first consider the energetics and the structural properties of some adsorbates on metal surfaces, as deduced by converged, first-principles, plane-wave calculations within the slab-supercell approach. These studies comprise water adsorption on Ru(0001), a subject of very intense debate in the past few years, and oxygen adsorption on aluminum, the prototypical example of metal passivation. Next, we address dynamical processes at surfaces with classical and quantum methods. Here the main interest is in hydrogen dynamics on metallic and semi-metallic surfaces, because of its importance for hydrogen storage and interstellar chemistry. Hydrogen sticking is studied with classical and quasi-classical means, with particular emphasis on the relaxation of hot–atoms following dissociative chemisorption. Hot atoms dynamics on metal surfaces is investigated in the reverse, hydrogen recombination process and compared to Eley–Rideal dynamics. Finally, Eley–Rideal, collision-induced desorption, and adsorbate-induced trapping are studied quantum mechanically on a graphite surface, and unexpected quantum effects are observed.     

Symbasis Between Formation Entalpies,Activation Energies of the Electrical Conductivity in Wüstite and in the Clusters of Its Crystal Lattice

It is shown that formation enthalpy and activation energy of the electrical conductivity in stoichiometric wüstite can be estimated with the methods of quantum chemistry using the properties of its clusters. The clusters are represented by crystal lattice fragments with fixed or optimized geometric parameters. The formation enthalpy is determined by extrapolating the energy of clusters according to the formulas of simple theories of clusters. The activation energy of electrical conductivity is calculated from relative total energies of formula units for various spin states of wüstite clusters. Calculations were performed with efficient quantum chemical methods PM7 and PBE/sbk which were chosen according to test calculations of bonding and ionization energies for the ground states of the iron atom, its ions, and some of its compounds. The results are in satisfactory agreement with experimental literature data.     

Surface modification of iron particles with bis(3-oxa-2-chloroperfluorobutyl)disulfide

Gas-liquid chromatography has been employed to study bis(3-oxa-2-chloroperfluorobutyl)disulfide (S60Cl) adsorption from solutions in perfluoromethylcyclohexane, perfluorodimethylcyclohexane, perfluorodecalin, anisole, toluene, and butyl acetate on the surfaces of two iron particle samples, namely, carbonyl iron and iron produced by electric-arc recondensation. It has been shown that the pattern of adsorption isotherms is characteristic of monolayer adsorption. Parameters of S60Cl adsorption have been calculated using the linear form of the Langmuir equation. The structure of adsorption layers that provide iron particles with aggregation stability and corrosion resistance in various dispersion media has been discussed.     

A Quantum Chemistry Study of Inhibition Properties of Imidazole and Its Derivatives on Iron Surface Corrosion

The geometries of imidazole and its derivatives were respectively optimized by using ab initio method, and the molecular orbital energy levels and the charge densities were obtained for their optimum geometries. The frontier orbital energy levels, and the net charges of N (1) atom and the imidazole ring of those molecules were obtained with ab initio and SCC-DV-Xα methods. It was found that the inhibition properties of those compounds change with the highest occupied molecular orbital energy levels, and the net charges of N (1) atom. We took four iron atoms on the crystal plane (100) of α-iron as the surface which was used to study the adsorption towards the inhibitors. The adsorption models of the inhibitor to be adsorbed on the Fe-cluster surface were optimized with SCC-DV-Xα method. It turns out that the most favorable model is that the inhibitor molecule is adsorbed on the Fe-cluster surface in an inclined state. The calculation shows that the stabilization energies of the systems are well correlated with the inhibition efficiencies.