Synergistic Effects And Group Transfer In Several Important Intermolecular Interactions

This dissertation focuses mainly on the group transfer and synergistic effects in several important intermolecular interactions.The main results of this dissertation are summarized as follows:（1）The Cl···N halogen bond（XB）in FCl···NH₃ is tuned from a traditional one to a chlorine-shared or an anion-pair one with three methods.The first method is to put this complex into different clusters of（FCl···NH₃）（H₂O）₆.The second one is to add solvents with different dielectric constants around this complex.The third one is to impose a proper external electric field on this complex.The traditional XB has the negative quantity[r₁（F–Cl）-r₂（Cl–N）],while the chlorine-shared and ion-pair XBs exhibit the positive[r₁-r₂],both having the ion-pair character of smaller and larger than 85%,respectively.（2）HOX（X=Cl,Br,I,and At）can engage in either a H-bond（HB）or halogen bond（XB）with a base like HCN,NH₃,and imidazole.While the former is energetically preferred for X=Cl and Br,it is the XB that is more stable for At,with I showing little preference.In addition,MgY₂ forms a Mg-bond with the O atom of HOX,which grows stronger in the order X=Cl<Br<I<At and Y=F<Cl<Br.There is a synergistic effect between MgB and XB/HB,and the synergy makes the two effects mutually reinforce each other.However,the effect of MgB on the intensity of XB and HB is more pronounced,the competition between XB and HB is reversed,and MgB causes the halogen/proton transfer in XB/HB,which changes from O···Cl/H to Cl/H···N effect.We also chose to compare with BeB’s impact on XB and HB competition studies.（3）The M···PhTX₃···N-base(M=Li⁺,Be²⁺,Mg²⁺;T=Si and Ge;X=H and F;N-base=NH₃,NHCH₂,HNC)systems have been used to study the regulation of a tetrel bond by a cation-πinteraction.It was found that there is a synergistic effect between the cation-πinteraction and the tetrel bond,and the cation-πinteraction enhances the tetrel bond.At the same time,the synergistic effect may lead to TX₃ group transfer from the C end of PhTX₃to the N-base.The group transfer is favorable in the order of M=Li⁺<Mg²⁺<Be²⁺,X=H<F,and T=Ge<Si,and it is more prominent in the presence of a strong N-base,such as in Be²⁺···PhSiH₃···HNC system.（4）The 4-halopyridine contains a Lewis acid site and a Lewis base site.Its halogen atom participates in the formation of a halogen bond as a Lewis acid,while the nitrogen atom can form aσ-hole tetrel bond as a Lewis base.The ternary complexes PhSiF₃···4-iodopyridine···N-base（N-base=HCN,NH₃,NHNH₂,and NH₂CH₃）,PhTF₃···4-iodopyridine···NH₃（T=C and Ge）,PhSiX₃···4-iodopyridine···NH₃（X=H and Cl）,PhSiF₃···4-bromopyridine···NH₃ have been utilized to investigate synergistic effect between the halogen bond and the tetrel bond.Most complexes display positive cooperative effect between the halogen bond and the tetrel bond,while PhCF₃···4-iodopyridine···NH₃ shows negative cooperative effect between the halogen bond and the hydrogen bond.（5）Pyrazine and 1,4-dicyanobenzene can ont only form aπ-hole tetrel bond with F₂TO（T=C,Si）but also engage in aσ-hole tetrel bond with TH₃F（T=C and Si）.Theπ-hole tetrel bond has greater interaction energy,electron density,and charge transfer,so it is stronger than theσ-hole tetrel bond.Compared with 1,4-dicyanobenzene,the negative electrostatic potential on the pyrazine N atom is smaller,but it is incline to participate in the tetrel bond.Pyrazine and 1,4-dicyanobenzene haveπelectrons,thus anions can form ananion-πinteractionwithitsπelectrons.InX^–···1,4-dicyanobenzene/pyrazine···TH₃F/F₂TO（X=F,Cl,and Br）,anion-πinteraction andσ-hole/π-hole tetrel bond display positive cooperativity.Anion-πinteraction strengthens the tetrel bond,which is stronger in the order of Br^–<Cl^–<F^–and varies from a purely closed-shell interaction to a partially covalent interaction.The anion-πinteraction is also significantly enhanced with binding energy up to-38 kcal/mol.