Vibration‐Induced Emission (VIE) of N,N′‐Disubstituted‐Dihydribenzo[a,c]phenazines: Fundamental Understanding and Emerging Applications

Organic fluorophores with dual‐emission and large Stokes shifts are attracting great attention due to their importance in fundamental research and technique applications. This Progress Report gives an account on how a novel luminescence mechanism termed vibration‐induced emission (VIE) is established. The VIE mechanism is coined for the rationalization of an alterable dual emission of V‐shaped N,N′‐disubstituded‐dihydribenzoa,c]phenazines (DHPs), which are originated from a bent‐to‐planar vibration and the reverse in the excited state. The validation of the VIE mechanism is highlighted, such as the work reporting the utilization of chemically‐locked strategy to snapshot the excited‐state planarization of DHPs, and the application of the approach of steric hindrance‐induced planarization to tune the ground‐state geometry of DHPs. Moreover, the emerging applications of this VIE concept in photoelectric and biomedical disciplines are summarized. Additionally, further development of the VIE systems as well as the remaining challenges are prospected. This report could arouse wide interest from various fields to the specific area of VIE, which would not only broaden the VIE territory but also enlarge the scope of advanced functional materials.