Synthesis, characterization and photophysical properties of PPh _2-C _2-(C _6H _4) _n-C _2-PPh _2 based bimetallic Au(i) complexes

摘要

A family of the diphosphines PPh _2C _2(C _6H _4) _nC _2PPh _2 (n = 0-3), which possess a dialkynyl-arene spacer between the phosphorus atoms, was used for the synthesis of a series of bimetallic gold(i) complexes 1-7. Unlike the corresponding polynuclear Au(i) clusters, which show unique phosphorescence, 1-7 reveal dual emissions consisting of fluorescence and phosphorescence. The results are rationalized, in a semi-quantitative manner, by the trace (1-3) to zero (4-7) contribution of MLCT varying with the number of conjugated phenylene rings. As a result, unlike typical polynuclear Au(i) clusters with 100% triplet state population, the rate constant of the S _1→T _1 intersystem crossing is drastically reduced to 10 ~9 s ~(-1) (4-7)-10 ~(10) s ~(-1) (1-3), so that the fluorescence radiative decay rate can compete or even dominates. The drastic O _2 quenching of phosphorescence demonstrates the unprotected nature of the emission chromophores in 1-7, as opposed to the well protected, O _2 independent phosphorescence in most multimetallic Au(i) clusters.