Molecular engineering of bis(triphenylamine)-modified fluorene luminophore for immensely enriching anisotropic force-triggered high-contrast tricolor fluorescent molecular switches library

The preparation of anisotropic mechanical force-triggered high-contrast tricolor fluorescent solid switches is both significant and extremely challenging. Herein, we report a high-efficiency molecular engineering strategy for developing mechanochromic compounds that exhibit an infrequent yet contrasting three-color fluorescence switching feature. Notably, 14 new symmetric fluorescent molecules by introducing a variety of substituents on either side of the central organic moiety involving 4,4'-((9<i>H</i>-fluoren-9-ylidene)methylene)bis(<i>N</i>,<i>N</i>-diphenylaniline) are successfully obtained, and 10 new fluorogenic compounds have been discovered to exhibit seldom-observed tricolored mechanofluorochromic phenomena. Impressively, among them, 8 luminogens demonstrate exceptionally scarce anisotropic force-triggered high-contrast three-color fluorescence responses, which is a commendable achievement, fully verifying the effectiveness of our molecular engineering strategy presented in this study. Furthermore, based on two newly developed representational mechanically responsive tricolor fluorescence switches, three advanced information anticounterfeiting systems are skillfully constructed.