Highly efficient (≈75% quantum yield), aggregation-induced phosphorescence is reported. The phosphorescence is emitted at room temperature and in the presence of air from crystals of trinuclear Au(I) complexes, accompanied by an extremely large Stokes shift of 2.2 × 10⁴ cm⁻¹ (450 nm). The mechanism of the aggregation-induced room-temperature phosphorescence from the Au complex crystals was investigated in terms of the crystal packing structure and the primary structure of the molecules. It was found that two kinds of intermolecular interactions occurred in the crystals, and that these multiple dual-mode intermolecular interactions in the crystals play a crucial role in the in-air room-temperature phosphorescence of the trinuclear Au(I) complexes.

As the luminescence from conventional organic luminophores is typically quenched in constrained environments, the aggregation-induced emission (AIE) phenomenon is of interest for the development of materials that exhibit strong luminescence in condensed phases. Herein, new bismesogenic Au complexes were developed as organogelators and their photophysical properties, including their AIE characteristics, were investigated in organogels and crystals. The crystals of the gold complexes exhibited room-temperature phosphorescence with relatively high quantum yields. Moreover, the gold complexes also showed photoluminescence in the organogels and we demonstrated that the reversible switching of the luminescence intensity was induced by the sol-gel phase transition. The intense photoluminescence in the crystal and gel was induced by the restricted internal motion of the luminophore in the molecular aggregates. However, in the sol, the network structure of the organogel was destroyed and the nonradiative deactivation of the excited states was enhanced. As a result, we can conclude that the switching of the luminescence intensity was induced by changes in the aggregated structures of the molecules. The developed Au-complex-based gelators are excellent candidates for the realization of stimuli-responsive soft and smart luminescent materials.