Ab Intio Studies On The Electronic Structure And Electronic Spectra Of "Res₆(μ₃-S)₈X₆"～(4-)(X=Cl,Br,I) And Re₂(edt)₄

The atomic cluster compounds with cubic core [Re6(u 3-Q)g]2+(Q=S Se) have special fluorescence. Nearly all of atomic cluster compounds with cubic core [Re& (n 3-Q)8]2+(Q=S Se) have luminescent behavior. |Re6(H 3-S)8X6]4-(X=CK Br,I ) show strong red emission,either in solid state or in soluble state. In this studies,geometry optimizations for [Re&( " 3-S)gX6j4-(X=CK Br> I) were carried out with HF method. On the basis of optimizated geometries .molecular orbitals and excited states of the three ions were caculated with single excitation configuration interactions (CIS) method.The electronic absorbsion spectra and the mechanism of phosphorescence of [Re&( u 3-S)gX6J4-(X=Cl Br I ) were explained very well,which,in some extent,is favor to the photochemical investigation of atomic cluster compounds with cubic core [Re6(P3-Q)8]2+(Q=S,Se).It is showed that the frontier orbitals of [Re6( u3-S)8X6]4-(X=Cl Br I) are heavy metal rhenium based (the percentage of rhenium in the frontier orbitals is about 80%). Thus,aiter the three cluster ions absorb photon and singlet groud state is turned into singlet excited state.the electron in excited energy level can change its direction because of the spin-orbit coupling of heavy metal rhenium,which converts singlet excited state into triplet excited state.And then,the cluster ions return to singlet groud state by means of radiate transiton. This is essential reason why [Re&( u 3-S)8X6]4-(X==Cl Br I ) have vivid red emission. The low oscillatory energy levels both in ground state and in excited state of [Re&( u3-S)8X6]4- (X=Cl Br I ) is another important reason.By comparison,geometry optimization and natural bond orbital analysis for Re2 (edt)4 were carried out with B3LYP method. Molecular orbitals and excited states for Re2(edt)4 were calculated with CIS method . The results show that there is not obvious triplet metal-metal bond between two Re atoms in Re2 (edt)4 and that the electronic absorption spectra of Re2(edt)4 was explained very well by theoretical calculation results.