Theoretical Study On Tetrel-bonded Complexes Of Two Oxygen-containing Molecules

Tetrel bond,a novel intermolecular interaction,plays an important role in constructing crystal materials,regulating chemical reactions and molecular recognition.In this dissertation,the formation,properties and laws of tetrel bond have been studied using theoretical calculations.The main contents are as follows:Dimethyl sulfoxide（DMSO）and TF₃X（T = C,Si;X= halogen atom）can form not only a tetrel bond but a halogen bond as well.With an exception of DMSO ··· CF₄ complex,DMSO is favourable to form a halogen bond with CF₃X,whereas DMSO is inclined to form a tetrel bond with SiF₃X.The influence of the halogen atom on the tetrel bond in the DMSO···CF₃X complex is small,while the tetrel bond in the DMSO···SiF₃X complex is greatly affected by the halogen atom.The tetrel bond in the DMSO···SiF₃X complex has a partially covalent interaction in nature and it is stronger than the tetrel bond formed by the anion.The substituent effect on the tetrel bond in the complex between DMSO and phenyl trifluorosilane has been studied.If the substituents are electron-donating groups of NH₃,OCH₃,CH₃ and OH,the tetrel bond is weakened.If the substituents are electron-donating groups of F,CHO,CN,NO₂ and SO₃ H,the tetrel bond is greatly enhanced.In the p-HO₃S-Ph SiF₃···DMSO complex,the tetrel bond is strongest with the interaction energy of-122 k J/mol.The tetrel bond is dominated by electrostatic interaction,but the charge transfer from the lone-pair orbital on the oxygen atom into the empty p orbital of Si is also important.When the substituents are NH₂ and OH,it is easier to form a hydrogen bond;when the substituents are CHO and NO₂,the tetrel bond is stronger than the π-hole interaction.In the complexes of PhTH₃···H₃ZO and Ph SiF₃···H₃ZO（T = Si,Ge,and Sn;Z = N,P,and As）,there are other weak interactions besides the main T···O tetrel bond.Binding energies of these complexes vary from 11 to 220 k J/mol,and T···O separations from 1.89 to 3.09 ?.For a given PhTH₃/PhSiF₃,the stability of the complex increases in the orderof Z = P < As < N;for a given H₃ ZO,the binding energy is also related to PhTH₃/Ph SiF₃.The charge transfer from the lone-pair orbital on the oxygen aotm into the C-T and T-H antibonding orbitals makes these complexes stable.Complexation of PhTH₃/Ph SiF₃ with H₃ ZO makes the T···O bond with a significant degree of covalency,and a pentacoordinate silicon complex is formed in Ph SiF₃···H₃NO with the almost equivalent C-Si and Si-O bond lengths.