【作者】 李佳；

【导师】 王曙光；

【作者基本信息】 上海交通大学 ， 应用化学， 2009， 博士

【摘要】 团簇因尺寸介于原子和宏观体系之间,本身性质具有多样性和奇异性,因此成为实验和理论研究的重要对象。其中Au团簇,由于近年来实验发现的大量特殊性质,更是受到广泛的关注。另外对于配体保护的Au团簇化合物,由于合成上的尺寸可控性以及配体选择的多样性,加上高度稳定性,从而展现出很多独特的物理化学性质。而随着计算方法和计算机技术的飞速发展,使得对Au团簇以及Au团簇化合物的几何、电子结构以及许多其它信息,都可进行第一性原理计算。其中密度泛函理论方法由于计算量适中、计算精度较高,已成为量子化学领域中最为重要的理论方法之一。本文利用密度泛函理论研究配体保护的Au团簇化合物的各种性质,重点在于其中配体与Au团簇之间相互作用。在第一章中,首先简要介绍了团簇的基本性质,以及目前实验和理论方面的主要研究手段。然后详细地阐述了Au团簇及其化合物研究的重要性和挑战性,并系统地介绍了目前实验研究现状和已有的一些理论研究工作。最后,概况了本文在Au团簇及其化合物研究中所做的工作和意义。在第二章中,首先对量子化学的发展进行了简单回顾。在介绍密度泛函理论的发展过程中,本文重点介绍了Kohn-Sham方程,以及各种常用的交换相关泛函,同时简要介绍了含时密度泛函理论。另外对于Au团簇研究中重要的相对论效应以及文中常用的自然键轨道理论（NBO）也做了简单地介绍。最后,通过不同方法计算的金系列小分子结果与实验值对比,得出适于Au团簇体系计算的泛函方法。在第三章中,本文对Au团簇的稳定性做了详细的研究,系统地提出了影响Au团簇稳定性的各方面因素。并通过对Au₁₃⁵⁺团簇的研究对以上各个因素逐一说明。最后对实验和理论上表征团簇稳定与否的一些方法进行了阐述。在第四章中,本文详细研究了配体与Au团簇之间相互作用机理。首先确定了不同配体在Au团簇上具体吸附方式,通过对几何结构、前线轨道、NBO电荷以及结合能分解分析,得出配体与Au团簇相互作用机理。接着选择了系列膦配体与不同的Au团簇吸附,研究了之间相互作用的变化规律。得出对于σ给予能力较强的配体,更容易与带高正电荷,即电子接受能力强的Au团簇相结合的规律。最后还研究了Au–P键长变化如何影响配体与Au团簇间的相互作用。在第五章中,本文详细研究了[Au₁₃（PMe₂Ph）₁₀Cl₂]³⁺和[Au₂₅（SR）₁₈]^–金团簇化合物。两者均为Au₁₃⁵⁺团簇核与外围配体组成,前者配体为PMe₂Ph和Cl^–,后者则为[Au₂（SR）₃]^–。文中首先通过几何结构、轨道作用及结合能分解分析的研究,得出不同类型配体与Au团簇之间相互作用,及对团簇的稳定机制。其中,卤素配体主要抵消Au团簇过多的正电荷,减小库仑膨胀效应;膦配体和硫配体则分别以σ给体形式作用于Au团簇,并使团簇外围Au原子间距缩短而稳定团簇。另外对于Au团簇化合物的实验合成,应选择给予能力较强的配体。最后采用含时密度泛函理论（TDDFT）研究两者电子光谱,前者主要为团簇→配体跃迁,后者则主要是配体→团簇跃迁。在第六章中,对Au₂₀（PH₃）₄团簇化合物进行了详细地研究分析。首先研究了Au₂₀团簇的几何结构及稳定性。接着对配体于Au₂₀团簇上不同的吸附方式进行研究,通过几何结构、轨道作用及结合能分解分析得出团簇于顶端吸附方式更为稳定,并且解释了两种吸附方式的差异原因。最后研究该体系的电子光谱,其电子跃迁主要为团簇→配体跃迁。在第七章中,详细研究了[Au₅₅（PPh₃）₁₂Cl₆]^–金团簇化合物。首先计算比较了Au55与Au₅₅⁵⁺团簇的几种几何构型。在团簇化合物稳定性研究中,将Au₅₅⁵⁺团簇作为Au₁₃⁵⁺团簇嵌于笼状Au₃₂团簇中,并将两者结合能作为Au₅₅⁵⁺团簇稳定性指标。接着研究了该体系几何结构、轨道作用及结合能,得出配体使Au₅₅⁵⁺团簇明显收缩而稳定。最后研究了该体系的电子光谱,其中电子跃迁主要为团簇内核跃迁。更多还原

【Abstract】 Clusters have the sizes between those of atoms and macroscopical systems, and have many unique properties. So many experimental and theoretical researches have been done on them. Even more focuses have been put on gold clusters, which have many unique properties. Ligand-stabilized gold clusters have the extraordinary stability and many unique physicochemical properties, which can be“tuned”through chemical modification and choice of the passivating ligands. Along with the rapid development of computational methods and computer technology, now computational chemistry is possible to study geometry, electronic structures and many other properties of clusters from first-principles calculations. And due to its moderate computational consume and high precision, density functional theory （DFT） has become one of the most important methods in quantum chemistry. This dissertation is to study the properties of ligand-stabilized gold clusters from DFT method and focus on the interaction between ligands and clusters.In Chapter 1, we give a brief introduction to clusters firstly. Then, some common methods in experimental and theoretical studies on clusters are discussed. Then, we expatiate the significance and the challenge in the research of ligand-stabilized gold clusters and introduce the main works of gold clusters in experimental and theoretical studies in detail. At last, we simply describe the purpose of our work on gold clusters.In Chapter 2, we introduce the progress of quantum chemistry. In the fundament of DFT, Kohn-Sham equation is introduced in detail. In addition, we introduce several functionals, TDDFT, the relativistic effect, and the natural bond orbital （NBO）, which are often considered and used in this thesis. As last, we carry out test calculations on well-defined small molecule to determine the optimum method in the study of gold clusters. In Chapter 3, we investigate the stability of gold cluster in detail and suggest the factors impacting the stability of gold clusters. In addition, we have studied the Au₁₃⁵⁺ to testify the factors. At last, we introduce some methods to denote the stability of gold clusters in experimental and theoretical studies.In Chapter 4, we investigate the mechanism of interaction between ligand and gold cluster in detail. Firstly, we confirm the type of ligand adsorption on gold cluster. Then, we investigate the geometric structure, the frontier orbital, NBO analysis and energy decomposition analysis （EDA） of the complex WAu₁₂PH₃, and gain the mechanism of interaction. In addition, we investigate the geometries and Au–P bonding of [MAu₁₂]qPR₃, which is changed in different ligands and clusters. The ligand with strong ability ofσdonor is prone to interact with the gold cluster with high positive charges. At last, we investigate the correlation between the interaction and the distance of Au–P bond.In Chapter 5, we investigate the complexes [Au₁₃（PMe₂Ph）₁₀Cl₂]³⁺ and [Au₂₅（SR）₁₈]^–, which have the same core Au₁₃⁵⁺ and different ligands. Firstly, we have studied the geometric structures, the frontier orbitals, and energy decomposition analysis （EDA） of the complexes to gain the mechanism of interaction between ligand and gold clusters. In the complexes, Cl^– ligand withdraws charges from the gold core. And phosphines and thiol ligands attach on the gold core asσdonor, which coordinate to the gold core surface by dative bonds. The ligand with strong ability of electron donor should be chosen to stabilize the clusters. At last, we investigate the electronic spectrum of the two complexes, which are composed of the transition between the gold core and the ligands.In Chapter 6, we investigate the complexes Au₂₀（PR₃）₄ in detail. Firstly, we have studied the geometric structure and stability of Au20 cluster. Then, the different adsorption types in the complex are investigated. And we investigate the geometric structure, the frontier orbital and the EDA to explain the difference in two types. At last, we investigate the electronic spectra of the complex, which is composed of the transition from the gold core to the ligand. In Chapter 7, we investigate the complexes [Au₅₅（PPh₃）₁₂Cl₆]^– in detail. The Au₅₅⁵⁺ core in different geometric structures is investigated. We investigate the Au₅₅⁵⁺ core as a Au₁₃⁵⁺ embedding a Au32 cluster and take the bond energy between Au₁₃⁵⁺ and Au32 to denote the stability of Au₅₅⁵⁺. Then, we have studied the geometric structure, electronic configuration and EDA of the complex. At last, we investigate the electronic spectra of the complex, which is composed of transition in the gold core.更多还原