Study On The Pnicogen Bond Complexes By Using Ab Initio And Molecular Face Theory

As a new type of the non-covalent interaction,pnicogen bonding has garnered significant interest in recent years due to its important role in supramolecular synthesis and crystal engineering.Based on ab initio and Molecular Face theory,we have investigated the D_pbbetween P and N atoms,molecular face,MFSA and MFV,charge transfer of the X_mPH_nY_3-m-nNH₃and XPH₂NH₂Z pnicogen bond complexes.The detailed contents are as follows:1.At MP2/6-311++G（d,p）level of theory,the geometry structures of the X_mPH_nY_3-m-nNH₃（X and Y represent the substituents,m and n are the number of substituents）and XPH₂NH₂Z（X and Z represent the substituents）,their corresponding monomers and free monomers have been optimized and obtained.MP2/6-311++G（d,p）level of theory has been performed to calculate the binding energies,and the ionization energies of the pnicogen bond complexes,the corresponding monomers as well as free monomers.For the single-substituted complexes XPH₂NH₃,the binding energies increase in the order X=-CH₃<-H<-NH₂<-CF₃<-OH<-CN<-Br<-Cl<-F<-NO₂.The larger binding energy,and the stronger the pnicogen bond.2.At CISD/6-31+G（d）level of theory in the MELD package with our in-house programs has been employed to calculate the D_pbs of X_mPH_nY_3-m-nNH₃and XPH₂NH₂Z complexes along the P…N atoms.It can be found that the greater D_pbvalue,the stronger the pnicogen bond.3.CISD/6-31+G（d）has been carried out to obtain the MFSAs and MFVs of these systems mentioned above.The differences of MFSA and MFV between the complexes and their corresponding monomers have been calculated.For single-substituted complexes,the difference of MFSA has a good relations with D_pband binding energy,that is,the larger the difference,the larger D_pband binding energy.4.MP2/6-311++G（d,p）level of theory has been employed to calculate the QTAIM,Hirshfeld,Mulliken,NPA,CHELPG and MK charges of X_mPH_nY_3-m-nNH₃and XPH₂NH₂Z complexes.And the charge transfer values of these complexes have been obtained.In summary,it can be found that the larger the binding energy of the complexes,the shorter the pnicogen bond length,the greater D_pb,the stronger the pnicogen bond strength.These physical quanties can be used to characterize the pnicogen bond strength.