Manipulating the AIE and low-temperature phosphorescence properties of o-carborane-imidazole derivatives via fine tuning their structural features

Four D−π−A dyads based on various imidazole derivatives donor and o-carborane acceptor moiety have been designed and synthesized for efficient tunable solid-state fluorescence and low-temperature phosphorescence. The results showed that four dyads are all AIEgens with dual emission properties in solution, highly solid-state emission, and low-temperature phosphorescence. The dual emissions were attributed to the locally excited (LE) and twisted intramolecular charge transfer (TICT) emission. The crystallographic measurements and theoretical calculations demonstrated that the strong phosphorescence with a long lifetime up to 2.18 s at low temperature may be attributed to the C–H⋅⋅⋅N, C–H⋅⋅⋅π interactions, strong TICT effect and the reduced vibration coupling by attaching a bulky carborane moiety to the chromophore. Four o-carborane-imidazole derivatives have been successfully synthesized with AIE and ultra-long lifetime low-temperature phosphorescence properties up to 2.18 s. [Display omitted] •Four D−π−A dyads based on various imidazole derivatives and o-carborane moiety have been designed and synthesized.•Four dyads are all AIEgens with dual emission properties in solution, highly solid-state emission, and ultra-long lifetime low-temperature phosphorescence.•The strong phosphorescence with a long lifetime up to 2.18 s at low temperature may be attributed to the C–H⋅⋅⋅N, C–H⋅⋅⋅π interactions and strong TICT.