Room-Temperature Phosphorescence of Crystalline 1,4-Bis(aroyl)-2,5-dibromobenzenes

There is a growing interest in metal‐free organic luminophores that exhibit phosphorescence at room temperature. We report herein that 1,4‐bis(aroyl)‐2,5‐dibromobenzenes serve as a new class of such luminophores. The bis(aroyl)benzene derivatives were not emissive either in solution or in a doped polymer thin film. In contrast, crystals of bis(aroyl)benzenes showed photoluminescence under ambient conditions, which was subsequently confirmed as phosphorescence with a luminescence lifetime measurement. The emission color ranged from blue to green, depending on the nature of the aroyl groups, and the luminescent quantum yields were 0.05–0.18 at room temperature and 0.38–0.67 at 77 K. In each crystal, several intermolecular interactions such as C=O···H, Br···Br, C=O···Br, F···F, S···H, and MeO···H were observed, which contributed to the restriction of intramolecular motions, thereby diminishing the nonradiative decay process from the triplet excited states. Crystals of 1,4‐bis(aroyl)‐2,5‐dibromobenzene exhibit phosphorescence at room temperature. The emission color of the crystals can be altered from blue to green by changing the aroyl groups. Intermolecular interactions that lead to suppression of intramolecular rotation resulting in the deactivation of the excited states were observed in the crystal lattice.