Highly Emissive Boron Ketoiminate Derivatives as a New Class of Aggregation‐Induced Emission Fluorophores

A series of boron ketoiminate derivatives that exhibited clear aggregation-induced emission (AIE) characteristics (in THF: Φ(PL)≤0.01; in the solid state: Φ(PL)=0.30-0.76) were prepared by the reactions of 1,3-enaminoketone derivatives with boron trifluoride-diethyl etherate. The structures and optical properties were investigated by UV-visible spectroscopy, photoluminescent (PL) spectroscopy, and X-ray single-crystal measurements. These results indicate that the AIE characteristics were derived from molecular motions of the boron-chelating rings with a boron-nitrogen (B-N) bond. Furthermore, the optical properties were controllable by steric hindrance of the substituted groups on the nitrogen atom.