Theoretical Studies Of Weak Interaction Containing Boron Group

Weak interaction has important applications in many fields.such as molecular recognition.materials science,crystal engineering and biological systems.In recent years,the scientific researchers pay more and more attention to new types of weak interactions,such as halogen bond,?-hole and ?-hole.Weak interactions have very important significance for the development of science and technology and the progress of the society.All calculations were performed using the Gaussian 09 program package.the electrostatic potentials is calculated on the 0.001 a.u.(electrons bohr3)contour of the molecule's electronic density with the WFA surface analysis suite.The AIMALL program was used for the delocalization index(DI)analysis and the electron density properties and energy density properties of weak chemical bond.The NBO6.0 program were used for the wiberg bond indices and natural orbital analysis.The integral charge and molecular density difference(MFDD)were calculated by Mulitiwfn program.This work mainly includes the following sections:1.The Cl-anion as the halogen bond acceptor,the diiodotetrafluoroethane I(CF2)2I and its derivatives I(MF2)nI(M=C,Si.Ge.Sn)as the halogen bond donor,and the strong halogen bonds could be formed.The halogen bonds between I(MF2)nI and Cl-have been designed and investigated by Moller-Plesset perturbation/aug-cc-pVDZ calculations together with the aug-cc-pVDZ-pp basis set for iodine and stannum.The halogen bonds in the I(MF2)nI…Cl-complexes are strong,which are apparently related to the group IV elements,becoming stronger along the sequence of M = Si,C,Ge,Sn.Accompanied with increasing number(n)ofMF2 unit,the halocgen bonds(M=Si.Ge.Sn)also become stronger.The energy decomposition analyses reveal that the exchange energy contributes most in forming these halogen-bonded interactions.In the meantime,the electrostatic energy is also a significant factor for the I…Cl-interactions.The halogen bonds of I(MF2)nI…Cl-(M=C,Ge,Sn)belong to partial-covalent interactions,while they are noncovalent interactions when M=Si.2.HML2(M=B,Al,Ga,In;L=CO.CN)and FY(Y=CN,NC)have been designed and optimized by MP2/aug-cc-pVTZ calculations together with the aug-cc-pVTZ-pp basis set for iodine.HML2 can form two complexes with FY:the M atom in HM(CN)2 combined with the Y atom in FY to form the HM(CN)2…YF complexs,while,the M atom in HM(CO)2 formed HM(CO)2…FY complexes with the F atom in FY.The M…Y bonds are very strong in the HM(CN)2…YF complexes which were partial-covalent interaction;The M…F bonds are weak in the HM(CO)2…FY complexes,which belong to noncovalent interaction.The exchange energy accounts for 36-44%in the total attractive energy for the HM(CN)2…YF complex and 42-47%for the HM(CO)2…FY complex.In both complexes,the exchange energy accounts for the largest proportion of the attractive energy.Comparing the interaction energy between HM(CN)2…FY and HM(CO)2…FY,we found that boron group elements are more likely to participate in forming complexes as electron acceptors.3.The geometries of M3(M=B,Al,Ga)and XCN(X=Cl,Br,I)have been optimized with the M06-2X/aug-cc-pVTZ caculations.M3 ternary ring center can interact with XCN along the direction of X-C.RCP…X interaction is very weak and belong to the noncovalent interactions.Whlie RCP…X interactions belong to partial-covalent interactions for Al3…ICN,Ga3…ICN complexs.For the M3 monomer,? electrons just exist around the M atom,rather than existing in the center of the ternary ring part.The ? electrons have little contributions to the RCP…X interactions,resulting in very weak RCP…X interactions.