Ab initio investigation on the excited-state properties and aurophilic interaction of the eight-membered ring complex [Au_2(dpm)(HSCH_2SH]~(2+) (dpm=bis(diphosphino)methane)

摘要

Au~I–Au~I aurophilicity and excited-state properties of the eight-membered ring complex, [Au_2(dpm)(HSCH_2SH)]~(2+) (dpm=bis(diphosphino)methane), were studied by ab initio methods. The weakly solvated [Au_2(dpm)(HSCH_2SH)]~(2+)·(MeCN)_2 accounting for the solvent effect of acetonitrile was applied to reveal the electronic structure and luminescent properties of the title complex in solution. The various possible geometries of [Au_2(dpm)(HSCH_2SH)]~(2+) and [Au_2(dpm)(HSCH_2SH)]~(2+)·(MeCN)_2 were fully optimized using the MP2 method for the ground-state and the CIS method for the excited-state, in which the boat-conformation ones as an example were discussed in details. We obtained a high-energy emission of 346 nm for [Au_2(dpm)(HSCH_2SH)]~(2+) arising from ~3A" → ~1A' transition, which has the nature of MCCT (metal-centered charge transfer). In acetonitrile solution, the lowest-energy emission was calculated at 677 nm and assigned as the ~3A"(S_σ) → ~1A'(d_σ*) transition, The Au~I–Au~I aurophilicity is very weak in the ~1A' ground-state, but is strongly enhanced in the ~3A" excited-state for [Au_2(dpm)(HSCH_2SH)]~(2+) in both the solid state and the solution, which clearly correlates with the luminescent properties of MCCT of the Au(I) complex. Our calculations show that both AuI–AuI aurophilic attraction and the solvent effect for [Au_2(dpm)(HSCH_2SH)]~(2+) complex result in a large red shift in emissive wavelength.