Theoretical Study On The Structure And Properties Of Two Kinds Of Planar Four - Coordination Carbon Complexes

Two kinds of complexes with planar tetracoordinate carbon (ptC) were designed in this thesis, one is that stable metallacyclic complexes with ptC formed by 6 group metals (Cr, Mo and W) and the radicals and another is that poly-membered macrometallacyclic complexes fomed by Ag and Au bearing functionalized N-Heterocyclic carbine (NHC) and functionalized 2-borabicyclo[1.1.0]but-1(3)-ene (2BT) ligands. The structures and stability of these complexes have been investigated using density functional theory (DFT). The lowest energy structures of these complexes have been obtained theoretically. The chemical bonding of these complexes have been analysized by the natural bond orbital (NBO) and atoms in molecules (AIM) methods. The NICS values of all rings and their electronic spectra properties of the stable complexes have been calculated. The main content of this thesis includes two parts as follows:1, The lowest-energy structures of the VIB group metallacyclic complexes M(OMe)3η3-R(M=Cr, Mo and W; R=C3H3, C5H5, C7H5, C9H7, C11H7, C13H9, C13H7 and C15H9) were obtained. Analysis of the chemical bonding of these complexes indicated that the 1,3-metal-carbon bond is formed in the twenty-four complexes, thus these complexs contain planar tetracoordinate carbon (ptC). The NICS(O) values of the six-membered rings of the lowest energies structures of M(OMe)3η3-R(M=Cr, Mo and W) have relationship with their positions. According to [2+2]cycloaddition reactions, we have predicted the variation of the energies and free energies of the reactions to give the stable M(OMe)3η3-R complexes, which indicated that M(OMe)3η3-R (M=Cr and Mo; R=C7H5, C11H7, C13H7 and C15H9) and W(OMe)3n3-R(R=C3H3, C5H5, C7H5, C9H7, C11H7, C13H9, C13H7and C15H9) are thermodynamically favorable. However, other reactions are thermodynamically unfavorable.The first vertical transition energies of Cr(OMe)3η3-R, Mo(OMe)3η3-R and W(OMe)3η3-R are in the range of 492-1020 nm,490-741 nm and 401-624 nm,respectively.2,The stable structures of eight-, ten- and twelve-membered macrometallacyclic complexes of silver and gold bonded to functionalized N-Heterocyclic carbene (NHC) ligands and functionalized 2-borabicyclo[1.1.0]but-1(3)-ene (2BT) ligands were obtianed in this thesis. Calculated results indicated that the lowest-energy structures of the twleve-membered macrometallacyclic complexes of silver and gold coordinated with the functionalized NHC ligands, and their first vertical transition and the maximal emission wavelengths are consistent with the experimental results of the similar complexes. Moreover, the lowest-energy structures of the poly-membered macrometallacyclic complexes of silver and gold coordinated with the functionalized 2BT ligands indicated that these complexes contain ptCs, thus a kind of novel method to construct poly-membered macrometallacyclic complexes containing ptC was obtained. The electronic absorption spectra of the eight-membered macrometallacyclic complexes of silver and gold with the functionalized 2BT ligands have a blue shift compared to that of with the functionalized NHC ligands. In contrast, the electronic absorption spectra of the ten-and twelve-membered macrometallacyclic complexes coordinated with the functionalized 2BT ligands have a significant red shift compared to that of with the functionalized NHC ligands. The electron emission maximum wavelengths of the macrometallacyclic complexes of silver and gold bonded to the functionalized NHC ligands and the functionalized 2BT ligands are in the range of 414-612 nm and 468-854 nm, respectively. The centers of the three- and five-membered rings of the poly-membered macrometallacyclic complexes have strong acromaticity.