Geometries And Properties Of Transitional Bimetallic Bridged Complexes

Due to the uniquecoordination structure and bonding modes,bimetallictransition complexeshave some novel properties different from thoseofmononuclear complexes and are the focus of the coordination chemistry.Dinuclear polyatomic organic ligands-bridged complexes are mainly applied on the fields of mimic enzyme catalysis, medical chemistry and the design and synthesis of photoelectric materials.Another kind of dinuclear complexes with inorganic monatomic as bridging atoms,usually have metal-metal bond. They are widely used in the synthesis of catalyst,conductor and semiconductor materials. In this theme, geometry structure, molecular orbital, absorption spectrum and the effects of ligand on optical properties of complexes are calculated by the density functional theory(DFT) and time-dependent density functional theory(TDDFT). We also analyzed the bond features and mechanism of luminescence of these compounds so that these results can help us people design new luminescent materials. The results are as follows:In the two nuclear cluster anions containing M-M bond, [(M2On S4-n)(i-mnt)2]2-(M=Mo and W; i-mnt= S2 C C(CN)22-; n = 0,1,2),the distance of M-Y(O/S) shorten slightly and the bond angle of M-Sb-M also became smaller gradually with the end of the terminal sulfur atoms replaced by oxygen atoms. These results indicated that with the increase of the end sulfur atom, the degree of delocalization of(M2On S4-n)2-can be fortified. The NBO analysis showed that the delocalization of π electrons exists indeed in i-mnt ligand, and these two interaction may result in special characteristics and bond parameters for clusters. These results indicated that vacant d orbital exists in the metal thus form supermolecular compound by accepting the lone electron pair of oxygen or sulfur atoms.The ligand 1,10-phenanthroline with a larger conjugate surface than2,2’-bipyridine, could lower the energy lever of the LUMO, and decrease the energy gap of HOMO-LUMO. So it is favorable for accepting electrons. This two ligands can construct bridged complexes containing no metal-metal bond with 4-[(carboxymethyl)thio]-benzoicacid(CMTB) and Cd(II) ion. Compared with other complexes, the molecular frontier orbital and absorption spectrum of this kind of compounds, weconcluded that metal ions plays the role of a bridge and they don’t take part in the electronic transitions. It belongs to ligandtoligand charge transfer(LLCT). With the conjugate surface of 2,2’-bipyridine ligand increasing, the dissipation of vibration energy will be lowered and thus transition rates became larger, absorption wavelength showed bathochromic effect. These results indicated that the selected methods and basis setswere applicable to this system. The theoretical calculation can give support to the experimental results, and can predict complexes that haven’t been synthesized.It revealed that theoretical calculation has unique advance and independence.