The Investigation Of The Structures And Properties Of Halogen Bond Complexes Based On The Ab Initio Method And Molecular Face Theory

A halogen bond is a non-covalent interaction of a neutral or negatively charged Lewis base with a halogen atom in a Lewis acid.With the wide application of halogen bonds in drug design and biological sciences,the structures and properties of halogen bond complexes have become the focus of many researchers.In this thesis,we use the ab initio calculation and molecular face theory to investigate the structures and properties of the halogen bond complexes from the perspective of the binding energy of the dimer molecule,the single electron potential barrier D_pb,the surface area,the volume,the characteristic contour value and the charge transfer quantity.The detailed contents are as follows:(1)We have calculated the binding energies of 18 dimer molecules at the MP2/aug-cc-p VDZ level of theory.The polarity and electronegativity of dihalogenated diatomic molecules have an effect on the binding energy of the complex.At the same time,the order of their binding energies is:FCl…B>Cl Br…B>Br₂…B>Cl₂…B>F₂…B.(2)We have obtained the distance between the Lewis base and the dihalogenated diatomic molecule between the above two dimer molecules at the theoretical level of MP2/aug-cc-p VDZ,the distance from the central nucleus of the central atom of B to the PAEM bond Dis(B-nbc),the ratio of the distance between the PAEM bond center to the central atom of B and the distance to the X atom,and the single electron potential barrier D_pb.The linear correlation coefficients of Dis(B-nbc)and n BL,Dis(B-nbc)and Ra,n BL and Ra are 0.9800,0.9347,and 0.8456,They can be used to characterize the strength of the halogen bond.(3)We have calculated the surface area and volume of the above 18 dimer molecules at MP2/aug-cc-p VDZ level of theory,and obtained the values of their characteristic contour,the molecular face of the six halogen bond dimers and monomers is drawn.There is no correlation of the strength of the halogen bond with the surface area and volume of the molecule.The feature contour value predicts the direction in which the halogen bond is formed between the monomers.On the molecular face,the halogen bond B…XY bond angle was observed to be about 180°,and the"?-hole"of the monomer was also observed.(4)We have altered the substituent groups on the Lewis base of 15 dimer molecules,calculated the physical quantity which can characterize the strength of the halogen bond at the theoretical level of MP2/aug-cc-p VDZ.The weaker the electron-withdrawing ability of the substituent on the Lewis base,the stronger the halogen bond formed,the more stable its complex.(5)We have obtained charge transfer quantities of 15 dimer molecules at the theoretical level of MP2/6-311++G(d,p)by using of 6 methods.The charge transfer between dimer molecules has a positive correlation ratio with the binding energy.The amount of charge transfer between molecules can be used as one of the physical quantity for characterizing the strength of a halogen bond.In this thesis,the ab initio calculation method and molecular face theory are used to study the influence of substituent changes or dihalogenated diatomic molecular changes on the strength of halogen bonds in dimers,and the correlation between the physical quantities of halogen bonds is studied.It provides a theoretical reference for further exploration of the structure and properties of halogen bond complexes.