Reversible Red‐/Blue‐Shifted Mechanofluorochromic Properties of Indole‐Based Difluoroboron Compounds with Aggregation‐Induced Emission

To further explore the relationship between structure and property of the mechanofluorochromic materials, two indole‐based aggregation‐induced emission compounds ( I−Ph−BF 2 and I−PhNp−BF 2 ) with BF 2 ‐core were designed and synthesized. They displayed intramolecular charge transfer characteristics and dissimilar reversible mechanofluorochromic behaviors (red‐shift for I−Ph−BF 2 and blue‐shift for I−PhNp−BF 2 ). Based the powder X‐ray diffraction patterns and quantum chemical calculation results, it was responsible for the blue‐shift mechanofluorochromic behavior of I−PhNp−BF 2 that the reduced molecular polarity of the excited state and the undermined partially ordered structure. In contrast, the phase change between an ordered arrangement state and a disordered amorphous state of I−Ph−BF 2 solid powder, as well as the appropriate molecular polarity, brought out red‐shift mechanofluorochromic effect. It provided a foundation for further exploration of the mechanofluorochromic property.