Theoretical Studies On Noncovalent Interactions In Some Supramolecular Systems

Supramolecular chemistry is a research hotspot of chemical theory,and supramolecular system has great application prospect in material science,environmental science and life science.The non-covalent interaction is the key to the chemical research of supramolecular system.The non-covalent interaction in supramolecular system mainly includes hydrogen bond,?-?interaction and van der Waals force.The following non-covalent interactions in supramolecular systems are studied theoretically:(1)Intramolecular hydrogen bonding,?-?stacking interactions,and substituent effects of8-hydroxyquinoline derivative supramolecular structures:a theoretical study8-hydroxyquinoline(8-HQ)is a better metal ion chelating agent,and in the structure containing 8-hydroxyquinoline,due to the 8-HQ of antibacterial,anti-hiv-1 and other aspects of a wide range of biological activities,it is widely used in traditional medicine.The main purpose of this work is to predict the effects of intramolecular hydrogen bonding,?-?stacking and substituent effects on the supramolecular structure of 8-hydroxyquinoline derivatives(substituent X=OH,CH₃,H,F,Cl,CF₃,CN,NO₂)by means of quantum chemistry.We calculated the Basis Set Superposition Error(BSSE)corrected binding energy,hydrogen bond,bond length,the distance between the molecules and the corresponding Hammett electronic parameters to predict the supramolecular structure.At the same time,we used the molecular atom theory(AIM)and electrostatic potential(ESP)obtain the?-?stacking 8-HQ derivatives of supramolecular system structure and the properties of weak interaction.(2)Hydrogen bonding in supramolecular systems of arsine and H-X molecules:A theoretical studyArsenic gas plays an important role in industrial toxicology.The purpose of this work is to identify and characterize the hydrogen bonding in the supramolecular systems formed by arsine and H-X(X=F,Cl,Br,HO,NC,CN,CH₃,C₂H)molecules.These analyses and calculations are helpful to understand the nature of the chemical bonding in the supramolecular systems formed by arsine and other molecules.In this paper,various methods including electrostatic potential(ESP),natural bond orbital(NBO),molecular atom theory(AIM),electron density difference plots(EDD)are used to characterize the interaction of these supramolecular systems.(3)The weak interaction between 5-chlorouracil and water molecules:a theoretical study5-chlorouracil(5ClU)has good anti-inflammatory and anti-tumor activity,the purpose of this work was to study the weak interactions between 5-chlorouracil and water molecules,we used the quantum chemistry calculation to study the geometric structure of 13 kinds of5-chlorouracil isomers in the gas phase and water phase,and by means of the thermal energy,enthalpy and gibbs free energy to predict the stability of the 5-chlorouracil structures.In addition,we studied the formation of transition state structure in the interaction between 5-chlorouracil and H₂O molecules,and the goal is to explain the 5-chlorouracil and H₂O molecules to form the supramolecular structure and the characteristics of weak interactions.