Substituted Biphenyls: A Stress Tensor And Vector-Based Perspective Within The Quantum Theory Of Atoms In Molecules(QTAIM) Framework

This dissertation is devoted to the analysis of the physical and chemical properties of biphenyl and substituted biphenyls using quantum theory of atoms in molecules(QTAIM) and the stress tensor topological. All calculations are performed with Gaussian 09 package and the topological analysis for total electronic charge density distribution p(r) of molecules carried out with AIMALL. The main contents contains six relatively independent chapters.This thesis begins with an introduction of the basic quantum theories and computational chemistry methods. We simply introduce the Hartree-Fock theory and other high level methods. Meanwhile we mainly introduce the ab initio method and DFT used in our works in this chapter.In chapter 2, we focus on the quantum theory of atoms in molecules (QTAIM), developed by Richard F.W. Bader and his coworkers. QTAIM has had many successes in prediction and correlation with experimental data. Therefore, the basic principles and quantities of QTAIM are presented in this chapter seeks to provide the readers with a general understanding of QTAIM.Starting from chapter 3, We used quantum theory of atoms in molecules (QTAIM) and the stress tensor topological explain the effects of the torsion cp of the C-C bond linking the two phenyl rings of the biphenyl molecule on a bond-by-bond basis using both a scalar and vector-based analysis.In chapter 4, we expand the research content to substituents of biphenyl. We consider the specific case of substituted biphenyl to quantify the effects of a torsion φ,0.0°≤φ≤180.0°, of the C-C bond linking the two phenyl ring for C12H9-x, where x= N(CH3)2, NH2, CH3, CHO, CN, NO2. The investigation shows that local properties can be related quantitatively to measures traditionally connected to experimental data, such as Hammett constants. Therefore we combine Hammett equation and QTAIM, and conclude a new method to gain Hammett constant.In chapter 5, we explain the H---H BCPs interactions in biphenyl and investigate the QTAIM and quantum topology properties of H---H BCPs.In the last chapter, provide a few outlook about our research work on the basic of this thesis.