Study On Generalized Hydrogen Bond And Molecular Acidity And Basicity By Density Functional Theory And Information-theoretic Approach

Density Functional Theory(DFT)is developed by solving Schr(?)dinger's equation.From the DFT equation,many chemistry-related concepts are defined.It can be said that density functional theory is an indispensable tool in the hands of modernists.It greatly satisfies calculation requirements for chemical accuracy.In the past thirty years,density functional theory has been widely used and is considered to be a general method of describing chemical reactivity,providing a powerful theoretical framework for the study of reactivity and selectivity.What we currently use is based on the electron density to describe the nature of molecular reactions,that is,Density Functional Reactivity Theory(DFRT).In addition,combined with the Information Theory Approach(ITA),the formal feature of the probability distribution function is usually used.The electron density in DFT can be regarded as such a continuous probability distribution function.Some variables related to electron density(such as Shannon entropy,GBP entropy,etc.)are used as indicators to quantify the amount of chemical correlation,that is,ITA.The purpose of this paper is to use DFT and ITA to accurately describe molecular acid-base and molecular hydrogen bonds using appropriate molecular models.Therefore,the research content of this article is mainly divided into three parts:(1)In order to expand the scope of application of DFRT,explore the nature of molecular acidity and alkalinity from the perspective of electron density.This thesis selects the amine molecular system as the research object,and uses the combination of conceptual density functional theory and information theory to describe the basicity of amine molecules.The results show that there is a strong correlation between the p K_a value and the amount of MEP,NAO,and ITA.Combining the CDFT descriptor and ITA can generate a more accurate and robust model to predict molecular acidity and alkalinity.(2)DFRT and ITA can be successfully applied to explain molecular acidity and alkalinity.In order to expand and perfect the application of DFRT in acid-base molecular systems,this chapter takes superacid molecules as the research object.Similarly,the results prove that the combination of ITA and MEP and NAO can be predict the acidity of superacid molecules well.(3)Considering the intermolecular and intramolecular hydrogen bonds respectively,using DFT energy decomposition method,Liu's new energy decomposition method,SAPT energy decomposition research and study combined with ITA to describe hydrogen bonds.The results show that although different energy decomposition methods are slightly different,the three energy relations all show that the energy component of the hydrogen bond is determined by multiple energies,and the electrostatic term has an important contribution.From the perspective of information theory,Shannon entropy,Fisher information,GBP entropy and hydrogen bonding energy are strongly correlated,and these three quantities are good indicators for quantifying hydrogen bonding.Through the calculation and analysis of amine molecules,superacid molecules and hydrogen-bonded molecules.In this chapter,it is clear that the information theory method in density functional theory is a good quantitative indicator for studying the acid-base and hydrogen-bonding of molecules.The work of these three systems has greatly enriched the development content of density functional theory in chemical reaction activity theory,and deepened and expanded the application range of information theory methods to describe different physical and chemical properties.