Abstract: The structures of [Au(i-mnt)]₂^2- (i-mnt=i-marononitriledithiolate) were optimized by the ab initio MP2 and CIS methods for the ground state and excited state respectively. The calculated ground-state Au(Ⅰ)-Au(Ⅰ) distance of 0.282 5 nm indicates a weak attraction between the two metallic Au(Ⅰ) atoms. The IPCM(Isodensity Polarized Continuum Model) approach in the SCRF (Self-Consistent Reaction Field) method was employed to account for the solvent effect of the acetonitrile solvent, and the electronic structures, electronic absorption and emission of [Au(i-mnt)]₂^2- in acetonitrile were obtained by the CIS calculations. The calculated absorption maximum, 315.5 nm, with the oscillator strength of 1.391 is assigned as an intraligand charge transfer(ILCT) transition. The phosphorescence with the wavelength of 436.2 nm arising from B³A_u→¹Ag is attributed to ILCT and metal to ligand charge transfer (MLCT) transitions, comparable to the emissive band around 500 nm of [n-Bu₄N]₂[Au(i-mnt)]₂ in glass acetonitrile solution at 20 K in the experiment. Such a transition is described as an organ-ligand luminescent mechanism with metal decoration.

Key words: Luminescent mechanism, Ab initio calculation, Solvent effect