分子反应活性位点以及分子结构性质的研究

发布时间：2018-06-01 23:45

本文选题：活性位点 + 分子结构　；参考：《北京科技大学》2017年博士论文

【摘要】：通过量子化学计算方法可以方便且容易地得到分子各种参数,利用理论分析方法能够描述、解释、预测或确定分子的物理、化学性质。近年来,反应活性位点的预测以及分子结构等影响因素已成为研究的热点。在分子反应活性位点的研究中,目前已有许多方法被提出,但它们的可靠性都缺乏系统的检验和对比,关于理论方法的预测值与化学反应速率的相关性方面也缺乏系统的研究。在分子结构性质的研究中,传统分子结构理论模型往往基于参与成键原子的电负性差异,没有考虑不同化学体系以及不同电子态所形成的化学环境差异,不具有普适性。因此,分子反应活性位点和分子结构性质的理论研究仍需要不断的完善和发展。本文主要研究内容如下：首先,本文将碳基化合物、芳香族化合物、吡啶及其衍生物和杂环化合物共4类分子作为测试体系,对14种预测反应活性位点方法的可靠性进行了详细的比较分析。我们发现,体现局部电子软度的方法可以很好地预测反应活性位点,例如简缩双描述符方法,但是表现静电效应的预测方法整体表现很差,例如静电势分析方法。对于本文中所用的测试体系来说,其分子反应活性位点预测最准确的方法是简缩双描述符和Hirshfeld电荷分析方法。其次,在前面工作的基础上,选择7种能够准确预测亲核和亲电反应活性位点方法来分析实验反应速率和理论预测结果之间的相关性。结果表明,对于芳香族化合物而言,不论是亲电反应,还是亲核反应,体系局部电子硬度的方法,例如分子范德华表面1.6A处的静电势以及Hirshfeld电荷方法,’其预测结果能较好地反应实验反应速率的相对大小,但体现局部电子软度的方法,例如简缩福井函数和简缩双描述符,其预测结果和实验反应速率的相关性较小。再次,研究了基态极性分子的键角和键偶极矩之间的关系。我们采用ADCH电荷来计算分子的键偶极矩,电子局域函数和键临界点处的局域函数值来分析键的电子结构,通过对IVA族(IVA=C, Si, Ge), VA族(VA=N, P, As), VIA族(VIA=O, S, Se)和ⅦA族(VIIA=F, Cl, Br)元素形成的系列共价型基态分子,以及环状基态分子的键角和键偶极矩数据进行分析,发现在键的电子结构类似的情况下,由于键偶极矩的排斥作用,这些分子的键角随键偶极矩的增加而增大。这一发现有助于加深我们对分子几何结构的认识。最后,提出了一种新的能量外推方法。完全活性空间组态相互作用计算与完全活性空间中的活性电子数和活性轨道数有关,但完全活性空间组态相互作用的能量不是活性电子数和活性轨道数的单调递减函数,因此活性轨道数和活性电子数不能用来外推完全活性空间组态相互作用的能量。为此,我们定义了一个新的变量：活性空间中的最大未占满轨道数。我们对一系列单重态、双重态和三重态分子进行了完全活性空间组态相互作用的计算,并利用活性空间中的活性电子数和最大未占满轨道数这两个变量,对这些基态能量进行了拟合和外推,拟合的均方根误差都在10-6数量级。外推能量的精度优于MP4,对小分子体系,其精度高于CCSD。外推的FCI能量值和实际计算的FCI值也很接近。另外,我们还利用外推能量来优化双原子分子的平衡键长,并计算谐振平率,其精度优于CASSCF。
[Abstract]:The molecular parameters can be easily and easily obtained by quantum chemical calculation. The physical and chemical properties of the molecules can be described, explained, predicted or determined by theoretical analysis. In recent years, the prediction of the reactive sites and the molecular structure have become a hot spot in the study. At present, many methods have been proposed, but their reliability is lack of systematic examination and comparison. There is no systematic study on the correlation between the predictive value of theoretical methods and the rate of chemical reactions. In the study of the molecular structure, the traditional molecular structure theory model is often based on the electronegativity difference involved in the bond forming atoms. It does not consider the chemical environment differences between different chemical systems and different electronic states, and it is not universally suitable. Therefore, the theoretical study of the molecular reaction active sites and molecular structure properties needs to be perfected and developed. The main contents of this paper are as follows: first, the carbon based compounds, aromatic compounds, pyridine and their properties are studied. A total of 4 groups of derivatives and heterocyclic compounds are used as test systems, and the reliability of the 14 methods for predicting reactive sites is compared in detail. We find that the method of local electronic softness can predict the reactive sites, such as the simplified double descriptor method, but the prediction method of the electrostatic effect is complete. The body performance is very poor, such as the method of electrostatic potential analysis. For the test system used in this paper, the most accurate method for the prediction of the molecular reactive sites is the simplified double descriptor and the Hirshfeld charge analysis method. Secondly, on the basis of the previous work, 7 methods can be used to accurately predict the active sites of nucleophilic and electrophilic reactions. The correlation between the experimental reaction rate and the theoretical prediction results is analyzed. The results show that, for aromatic compounds, whether it is an electrophilic reaction or a nucleophilic reaction, a method of local electron hardness, such as the electrostatic potential at the 1.6A surface at the molecular Fan Dehua surface and the Hirshfeld charge method, 'is a good reaction to the experimental reaction. The relative size of the rate, but the method of reflecting the local electronic softness, such as the contraction Fukui function and the contraction double descriptor, has a little correlation with the experimental reaction rate. Again, the relationship between the bond angle and the dipole moment of the ground state polarity molecule is studied. We use the ADCH charge to calculate the molecular bond dipole moment, the electronic Bureau. The domain function and the local function value at the critical point of the key are used to analyze the electronic structure of the key. By analyzing the IVA group (IVA=C, Si, Ge), the VA group (VA=N, P, As), the VIA group (VIA=O, S, Se) and VII, the bond angle and the bond dipole moment data of the ring ground state are analyzed, and the key is found in the key. In the case of similar substructure, the bond angles of these molecules increase with the increase of bond dipole moments due to the repulsion of the bond dipole moments. This discovery helps to deepen our understanding of the molecular geometry. Finally, a new energy extrapolation method is proposed. The calculation of fully active space group state interaction and the full active space. The number of active electrons is related to the number of active orbits, but the energy of the fully active space configuration interaction is not a monotone decreasing function of the number of active electrons and the number of active orbits. Therefore, the number of active orbits and the number of active electrons can not be used to extrapolate the energy of the interaction of the fully active space configuration. The maximum unoccupied orbit in a sexual space. We calculate the interaction of a series of singlet, double and three states, and use the two variables of the active electrons in the active space and the maximum number of unoccupied orbit, to fit and extrapolate the energy of these basic states, and to fit the root mean square. The error is in the order of 10-6. The precision of extrapolation energy is better than MP4. For small molecular system, its precision is higher than that of CCSD. extrapolated FCI energy and the FCI value of actual calculation. In addition, we also use extrapolation energy to optimize the equilibrium bond length of diatomic molecules and calculate the Xie Zhenping rate, which is better than CASSCF..
【学位授予单位】：北京科技大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O641

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