Theoretical Studies On The Nature Of Some Moderate Metal…π-type Interactions

The metal π-type interaction is one of the intermolecular interactions and exists inmany complexes. The studies on cation-π interaction have very important significances.Dinuclear metallocenes are widely used in the field of photochemistry, thermodynamics,kinetics and biochemistry, etc. The nature of chemical bonding in dinuclear metallocenes alsohas been one of the hottest issues of the current chemistry science.In this thesis, the nature of π-type interactions in Copper(I)···thiophene and the influencesof metal doping on π-type Copper(I)···thiophene interactions are investigated. The nature ofchemical bond in homodinuclear carbonyl metallocenes [CpM(CO)3]2(M=Cr, Mo, W; Cp=C5H5) and heterodinuclear donor–acceptor sandwiches CpE–MCp (E=B, Al, Ga; M=Li, Na,K; Cp=η5-C5H5) are also studied. All the works have been done within the framework of the‘atoms in molecules’(AIM) theory and using ‘electron localization function’(ELF) analysis.All calculations are carried out using the Gaussian03program package. The topologicalanalyses of electron density of molecule have been studied using AIMALL program,TOPMOD program and MULTIWFN program. The main contents are the following aspects:1. The nature of Copper(I)···thiophene interactions and the influences of metal doping onπ-type Copper(I)···thiophene interactions are investigated at the MP2(full)/6-311+G(2df) levelusing the atoms in molecules (AIM) theory, electron localization function (ELF), molecularelectrostatic potential analysis (WFA) methods and energy decomposition analysis (EDA).The calculated results show that the copper(I)···thiophene bondings belong tomoderate-strength interactions. They display partly covalent characters. The Li, K, Ca, and Scatom doping on thiophene enhance the π-type copper(I)···thiophene interactions. Theenhancement is determined by the atomic radius and the electronegativity of doping metal.The larger atomic radius and the larger electronegativities atoms have more influences onenhancing the copper(I)···thiophene bondings. Moreover, Perfect linear relationships existbetween the bond length d(Cu···π) and the topological properties at the BCP (ρ(rc),2ρ(rc),Hcand δ(A, B)) of Cu···thiophene. The shorter the Cu···π bond length, the larger ρ(rc) and thestronger the Cu···π bonding. The shorter the Cu···π bond length, the larger positive2ρ(rc),δ(A, B) and the smaller value of Hc, and the greater the covant character of the Cu···π bond.2. The nature and variation of metal–metal bonding in a series of dinuclear carbonylmetallocenes [CpM(CO)3]2(M=Cr, Mo, W; Cp=C5H5) have been characterized within theframework of the atoms in molecules theory, electron localization function, and molecular formation density difference. Calculated results show that the strength of the M–M bondsincreases in the order Cr–Cr <Mo–Mo <W–W. Among these, the Cr–Cr bond has theweakest interaction, whereas Mo–Mo and W–W bonds have interactions of moderate strength.The M–M (M=Cr, Mo, W) bonds form mainly by “closed shell” interactions, therefore, theyare not belong to covalent single bonds. The M–M bonds have partially covalent characters.The covalent characters increase in the sequence Cr <Mo <W.3. The nature of the chemical bonds in the dinuclear donor–acceptor sandwichesCpE–MCp (E=B, Al, Ga; M=Li, Na, K; Cp=η5-C5H5) has been studied using the atoms inmolecules (AIM) theory, electron localization function (ELF), natural bond orbital analysis(NBO) methods and energy decomposition analysis (EDA). Both the topological and theorbital analysis show that the E atom determines the bond strength of the E–M bonds, whilethe M atom has little influence on it. The E–M strength decreases in the sequence E=B, Al,Ga. The E–M bond is a double-electron bond for E=B, while it decreases to a single-electronbond for E=Ga. The electrostatic character of the E–M bond decreases in the order E=B>Al> Ga, while the covalent character shows the opposite trend. As a consequence, not onlythe s orbital, but also the p orbital of the E/M atom participate in the formation of the E–Mbond. The orbital interactions consist of σ and π two types. The σ interactions come from theoverlap of the hybrid orbitals, whilst the π interactions are due to the overlap of the p orbitalsof the E/M atoms. The σ-type interactions play more important roles than the π-typeinteractions. Moreover, the interactions of E and M with Cp are different. The M–Cpinteraction is purely electrostatic while the E–Cp interaction has a partly covalent character.The innovations in the thesis:1. The M–M bonds in [CpM(CO)3]2(M=Cr, Mo, W) are belong to “closed shell”interactions, not covalent single bonds.2. The influences of metal doping on π-type Copper(I)···thiophene interactions have beenstudied, the calculated results can be used in the material design.