Harnessing Fluorescence versus Phosphorescence Branching Ratio in (Phenyl)n-Bridged (n = 0–5) Bimetallic Au(I) Complexes

We have designed and synthesized a series of Au(I) complexes bearing either an alkynyl–(phenylene)n–diphosphine (A-0–A-3) or a (phenylene)n–diphosphine (B-1–B-5) bridge, among which the effective distance between Au(I) and the center of the emitting ππ* chromophore can be fine-tuned via the insertion of various numbers of phenylene spacers. We then demonstrated for the first time in a systematic manner the decrease of rate constant for S1 → T1 intersystem crossing (ISC) kisc as the increase of the effective distance. The results also unambiguously showed that the phosphorescence could be harvested via higher S0 → Sn (n > 1) electronic excitation, followed by fast Sn → Tm ISC and then the po…