Functionalization of boron diiminates with unique optical properties: multicolor tuning of crystallization-induced emission and introduction into the main chain of conjugated polymers.

In this article, we report the unique optical characteristics of boron diiminates in the solid states. We synthesized the boron diiminates exhibiting aggregation-induced emission (AIE). From the series of optical measurements, it was revealed that the optical properties in the solid state should be originated from the suppression of the molecular motions of the boron diiminate units. The emission colors were modulated by the substitution effects (λPL,crystal = 448–602 nm, λPL,amorphous = 478–645 nm). Strong phosphorescence was observed from some boron diiminates deriving from the effects of two imine groups. Notably, we found some of boron diiminates showed crystallization-induced emission (CIE) properties derived from the packing differences from crystalline to amorphous states. The 15-fold emission enhancement was observed by the crystallization (ΦPL,crystal = 0.59, ΦPL,amorphous = 0.04). Next, we conjugated boron diiminates with fluorene. The synthesized polymers showed good solubility in the common so...