Theoretical Study On Some New Non-covalent Interactions

Intermolecular interactions have been the focus of theoretical research due to their important roles in the construction of new functional materials,supramolecular self-assembly,and biological system.With the continuous development of research,people gradually shifted their focus from the study of weak interactions such as hydrogen bonds and halogen bonds to the study of new-type non-covalent interactions.Based on the previous research,the new-type halogen bonds formed by superalkalies M2OCN/M2NCO with dihalogen molecules,the supervalent halogen bonds formed by hypervalent At halides with CO,and the regium bonds formed by phosphinic acid with AuX are systematically theoretical studied on MP2/aug-cc-pVTZ(PP)level.The main contents are as follows:(1)Theoretical researches on the dimers formed by CO with halides of the multivalent astatine as a Lewis-acid center are conducted to examine the typical characteristics of supervalent halogen bond.Calculation on MP2/aug-cc-pVTZ level reveals that the multiple nucleophilic sites of multivalent halide monomers can promote the formation of various types of halogen bonds,among which the most stable ones are At-halogen bond complexes with the multivalent astatine as Lewis acid center,followed by the ?-halogen bond dimers,and the weakest are the X-halogen bonds.Compared with multivalent Cl-,Br-,and I-center,At,as the heaviest halogen,exhibits the highest halogen-bond donating ability.We found that the electrostatic term and the dispersion term playing an important role in the overall attractive interaction energy,and the smallest attraction term for all complexes is the polarization term(?Epol).Moreover,the tri and pentavalent halides analyzed here possess the very "flexible"tautomerism that the transformation occurs during the formation of the dimers.AIM theory and NBO analysis are also applied here.(2)A new type of halogen bond formed by supermetals or superalkalies with dihalogen molecules were analyzed by means of ab initio at MP2/aug-cc-pVTZ level.The results reveal that the two configurations are found in the complexes M2OCN/M2NCO with dihalogen molecule,i.e.a linear structure made stable by halogen bond and a curved structure made stable by the cooperation of halogen bond and metal bond.The interaction energies and the NBO analysis indicates that the curved structures are more stable than the linear structures.To provide further insight into the nature of the intermolecular interaction,energies decomposition analysis was carried out,which implies that the electrostatic energy is the major source of the attraction for most complexes,except for Li2NCO/Na2NCO…F2 where the main contribution is dispersion energy.In addition,atoms in molecules and molecular electrostatic potential were also used to probe halogen bonding and metal bonding strength.RDG graphical analysis reveals the spatial location and the strength of the weak interactions.(3)Ab initio MP2/aug-cc-pVTZ(PP)has been carried out on the regium bonding intermolecular interaction between AuX(X=F,Cl,Br)and RPHOH(R=CH3,F,CF3,NH2,CN).For the AuX-·RPHOH complexes,four types of configurations(trans-P,trans-O,cis-P and cis-O)are observed.The magnitude of molecular interaction energies is in the order of NH2>CH3>F>CF3>CN,F>C1>Br with the nature of the substituent directly affecting the strength of the interaction.The transition structures which present the energy barriers to the inter-conversion between the trans-type and the cis-type structures and the Boltzmann distribution to quantitatively determine the proportion of the cis-type and the trans-type geometries have been obtained.The natural resonance theory confirms the presence of the Au…O and the Au…P regium bonds with two major secondary resonance structures X-Au:RPHOH(??)(?)X:Au-RPHOH(??).In addition,LMO-EDA energy decomposition analysis is performed on the regium bonded complexes to predict the dominant energy component and the nature of the Au…O and the Au…P regium bonded interaction.