Cyclic triimidazole derivatives: An intriguing family of multifaceted emitters

The search of organic materials displaying room temperature phosphorescence (RTP) and ultralong phosphorescence (RTUP) has attracted considerable attention in recent years due to the increased biocompatibility and reduced costs of metal-free compounds with respect to their organometallic counterparts. On this regard, we have recently identified a simple organic molecule, i.e. triimidazo[1,2- a :1',2'- c :1?,2?- e ][1,3,5]triazine or cyclic triimidazole, showing crystallization-induced emission and RTUP (lifetime up to 1 s) behavior, this latter feature being attributed to the presence of H-aggregation in its crystal structure. Starting from this organic scaffold, introduction of one, two or three halogen atoms as well as of chromophoric groups, and assembling of hybrid organic/inorganic compounds allow to get emissive materials with an extraordinary variety of photophysical properties, spanning from Kasha and anti-Kasha fluorescence, to molecular and supramolecular phosphorescences, in addition to H-aggregation RTP. The results obtained so far and possible future developments on this family are here reported.