Architecting Anisotropic Force-Responsive Bidirectional High-Contrast Three-Color Fluorescence Switches via Effective Molecular Modulation for High-Security Information Storage.

Although bidirectional three-color fluorescent molecular switches triggered by anisotropic force are promising for enhancing the security of information storage, the engineering and development of such force-responsive smart emissive materials face significant challenges, rendering them extremely rare. Here, 13 uncommon tricolored mechanofluorochromic luminogens were obtained through efficient molecular engineering strategies synergistically integrating substituent variation and positional isomeric approaches, three of which exhibited exceedingly scarce force-induced hypsochromic and bathochromic bidirectional fluorescence responses. More specifically, employing dibenzofulvene as the core scaffold, a family of 20 fluorene-based fluorogenic compounds was elaborately constructed by incorporating pyrene, tetraphenylethene, and three isomeric carbazole moieties at the conjugated extension sites, with phenyl and regioisomeric trifluoromethylphenyl groups respectively attached to the two flanking positions. Next, a three-step high-efficiency screening protocol was devised for these luminogens: first assessing mechanoresponsive fluorescence behaviors, then evaluating the three-color mechanofluorochromic capabilities, and finally determining whether the selected force-responsive tricolored fluorescence switches could realize bidirectional three-color fluorescence switching after sequential grinding from gentle to vigorous. Ultimately, 3 luminogens featuring ultra-rare bidirectional three‑color mechanofluorochromism were identified. Impressively, based on the screened force-triggered bidirectional high-contrast tricolor fluorescent switch TPE-o-CF