Theoretical Study On Noncovalent Tetrel Bond And Triel Bond

Tetrel bond and triel bond,as new noncovalent interactions,play an important role in the fields of crystal building,supramolecular self-assembly and drug molecular design,etc.They are the hot and frontier issues in the research of physics,chemistry,medicine and life science.Compared with hydrogen bonds and halogen bonds,the research on tetrel bond and triel bond is in the ascendant.Based on the quantum chemistry method,we systematically studied the interaction energy,electronic structure and properties of typical tetrel bond and triel bond,especially substitution effect and synergistic effect,which provided a meaningful theoretical basis for the application of new noncovalent tetrel bond and triel bond.Firstly,we study the properties of tetrel bond.In recent years,intermolecular weak interactions have aroused widespread concern,including tetrel bond and halogen bond.However,as far as we know,the intermolecular weak interactions composed of TF₃X（T =Ge,Sn;X = F,Cl,Br and I）and H₂O molecules are rarely studied.What?s interesting is that TF₃X molecule as Lewis acid can form T（T = Ge,Sn）…O tetrel and X（X = F,Cl,Br,and I）…O halogen bonding with H₂O molecule,respectively.In this paper,a theoretical study of the complexes has been performed at the MP₂/aug-cc-pVTZ（PP）level.The results show that SnF₃X molecule can form a stronger tetrel bond than that of GeF₃X molecule,both SnF₃X and Ge F₃X molecules form the halogen bond with similar strength.Energy decomposition indicates that tetrel bonds are mainly stabilized by electrostatic interaction,while the stability of halogen bonds are determined by electrostatic interaction and dispersion.In ternary systems,T…O tetrel bond and X…O halogen bond show anti-cooperativity.Triel-bonding interactions composed of Lewis acid TrOHH₂/TrOH₂X/TrOHX₂（Tr = B,Al,Ga;X = F,Cl,Br）molecule and Lewis base HCN or CN^- molecule are of research significance in bond properties,which has been investigated at MP2/aug-cc-pVTZ theory level.It is also feasible to study the halogen atom substituent effect and influence of different Lewis bases on the formation of triel bond.AIM analyses reveal that Tr（B,Al,Ga）…N bond critical point（BCP）exists in all studied triel bond.Compared with HCN molecule,anionic CN^- can participate in a stronger triel bond.Specifically,the structural change,deformation energy,and charge transfer of CN^- complexes are more obvious and larger than that of HCN complexes.In addition,halogen atom substitution effect is also discussed.MEP value and binding energy of HCN and CN^- complexes all increase after replacing one or two hydrogen atoms by halogen atoms（F,Cl,Br）in Lewis acid.Especially,replacing two hydrogen atoms by halogen atoms in Lewis acid has more remarkable enhancement in MEP value and binding energy than that of replacing only one hydrogen atom.After replacement,binding energy can be increased by 21.77 kcal/mol.