【作者】 赵海涛；

【导师】 张文勤；

【作者基本信息】 天津大学 ， 化学工艺， 2004， 博士

【摘要】 本论文分为两部分,第一部分是钌原子簇的理论研究,第二部分是部分有机化学反应的量子化学研究。第一部分采用DFT的方法和平面波的基组对钌原子簇进行了系统的研究,研究结果表明在小的钌原子簇中,简单立方体结构的原子簇具有最稳定的结构。结果分析认为这种稳定结构可以保持到约40个原子,原子簇尺寸在40-147之间,二十面体结构的原子簇最为稳定,在超过147个原子直到堆积结构,立方-八面体的结构原子簇变得最为稳定。在线性原子簇钌有生成三聚体的倾向。所有本文研究的原子簇都具有很小的HOMO-LUMO带宽,说明它们是良好的导体,同时又是具有较大磁矩的铁磁性物质。本文还对钌原子簇的能量,电子性质和磁性随原子的体积和结构变化进行了定量相关性分析。分析计算的束缚能显示具有相似成键环境的原子具有相似的束缚能。同时,我们采用公式对平面和简单立方结构的钌原子簇的束缚能进行了估算,估算的结果和DFT的计算结果非常接近。第二部分的研究分为三部分。第一部分使用密度泛函和从头计算的方法研究了分子间的1,3-偶极环加成反应合成含有一个噁唑啉环的螺环化合物的反应机理和反应的区域选择性。本文通过自然键轨道分析、结构参数分析、能量分析和前线轨道分析的方法分析了合成5-螺环噁唑啉（路线1）和4-螺环噁唑啉（路线2）的两条路线。能量分析显示路线2的反应活化能和反应能都高于路线1。前线轨道分析认为LUMO_1,3-dipole-HOMO_{dipolarophile}交互作用控制了反应的区域选择性,在偶极子LUMO中有较大轨道因子的是O,而亲偶极子中较大轨道因子的是位于环上的C,所以轨道的重要重叠作用将发生在这两个原子上面。理论研究结果与实验结果一致。结构分析和NBO的分析认为这个反应是一个协同反应。第二部分研究了甲氧基自由基和羟甲基自由基的结构和分子内、分子间的异构化反应的过渡态的结构和能垒。研究发现分子内异构化反应的能垒较大,而分子间异构化反应的能垒小了很多,可以在室温下进行。在本研究中发现了一个文献未见报道的环状过渡态。第三部分研究2-硝基-3-苯甲氧基吡啶空间结构和振动频率。通过对硝基转动能垒的研究解释了硝基与吡啶非共平面的原因,还采用振动频率分析的方法对2-硝基-3-苯甲氧基吡啶的红外谱图进行了研究。同时本文还建立了部分模型考察硝基与吡啶基团之间的共轭作用,空间位阻作用和硝基与邻近基团的氢键作用,考察从头计算和密度泛函方法的不同计算结果。更多还原

【Abstract】 This dissertation contains two projects. The first project is a theoretical study of ruthenium clusters and the second project is a theoretical study of some organic reactions. A systematic investigation of ruthenium clusters was carried out using density functional theory with a plane wave basis set in the first project. The results have shown that the simple cubic structure is the most stable structure in the small ruthenium clusters. Analysis suggests that the simple cubic structure could be the most stable structure for clusters of up to 40 atoms, the icosahedron is the most stable structure for clusters of 40-147 atoms, and finally the cubo-octahedron, that is, the bulk structure, becomes the most stable structure for clusters of more than 147 atoms. A strong trend of trimer formation was found in linear ruthenium clusters. All the clusters investigated here have small HOMO-LUMO band gaps, which indicates that they are good electrical conductors. They are also ferromagnetic with large magnetic moments. A quantitative correlation was provided between the energetic, electronic, and magnetic properties of ruthenium clusters and the cluster structure and size. Analysis of the calculated binding energies indicates that the atoms in similar bonding environments have similar binding energies. On the basis of this analysis, estimations were made on the binding energies of planar and simple cubic ruthenium clusters. The estimated binding energies agree well with the density functional theory results. The second project is divided into three parts. In the first part the reaction mechanism and regioselectivity of spiro-isoxazoline derivatives synthesized by an intermolecular 1,3-dipolar cycloaddition reaction between 2,6-dichlorobenzonitrile oxide and 3-(4-chlorobenzylidene)-dihydrofuran-2-one were studied using density functional theory and ab initio theory. Two possible reaction channels, which are related to the formation of isoxazoline-5-spiro-cyclic (Channel 1) and isoxazoline-4-spiro-cyclic (Channel 2) are investigated using natural bond orbital analysis, geometrical parameters analysis, energy analysis and frontier molecular orbital analysis. The energy analysis shows that both the activation energy and reaction energy for Channel 2 are higher than those for Channel 1. The larger activation energy prevents the formation of isoxazoline-4-spiro-cyclic. Therefore, isoxazoline-5-spiro-cyclic is formed as the energetically favored product. The FMO analysis shows that the regioselectivity of this reaction is controlled by the LUMOdipole–HOMOdipolarophile interaction, and the reaction proceeds via Channel 1 which agrees with the experimental results. The natural bond order analysis shows the reaction follows a concerted mechanism with two bonds formed at about the same time. The second part investigated the structure of CH3O and CH2OH radical and their intramolecular and intermolecular isomerization reaction. The study found that reaction barrier of intramolecular isomerization is higher than that of intermolecular isomerization and intermolecular isomerization can produce in room temperature. A cyclical transition state was found which was not reported in literature.The third part investigated the structure and vibration frequencies 3-benzyloxy-2-nitro-pyridine. The NO2 group rotate out of the pyridine plane was explained by calculated the rotating barrier. The IR spectrum of 3-benzyloxy-2-nitro-pyridine was studied by vibration frequencies calculation. Some other substituted 2-nitro-pyridine were investigated and the conjugation effects, steric hindrance and hydrogen bond are explained.更多还原