The development of single molecule white light emitters is extremely challenging for pure phosphorescent metal-free system at room temperature. Here we report a single pure organic phosphor, namely 4-chlorobenzoyldibenzothiophene, emitting white room temperature phosphorescence with Commission Internationale de l’Éclair-age coordinates of (0.33, 0.35). Experimental and theoretical investigations reveal that the white light emission is emerged from dual phosphorescence, which emit from the first and second excited triplet states. We also demonstrate the validity of the strategy to achieve metal-free pure phosphorescent single molecule white light emitters by intrasystem mixing dual room temperature phosphorescence arising from the low- and high-lying triplet states.

Chromophores containing olefinic double bonds are the core components of many important luminogen systems that show the novel photophysical effect of aggregation-induced emission (AIE). The role and extent of E–Z isomerization (EZI) of the double bond in affecting the solution emissions of the AIE luminogens (AIEgens), however, have not been fully understood. In this work, we verified the occurrence of EZI in the dilute solutions of TPE-cored AIEgens by NMR spectroscopy using elaborate experimental procedures. We further designed a TPE-fluorescein adduct to quantify that EZI plays a minor role whereas intramolecular rotation plays a major role in the emission quenching processes of the AIEgen solutions. This study fills the gap in the research on the restriction of the intramolecular rotation (RIR) mechanism for the AIE effect and provides a useful tool for the mechanistic investigation of photoluminescence processes.