D-A-A′ type acridine-based isomeric luminogens: concentration-dependent white light emission, high-contrast mechanofluorochromism and its application in rewritable medium

Three D-A-A′ architecture isomeric luminogens ( o -, m -, p -DMAc-Ph 2 CO-BT ) were designed and synthesized, comprising acridine (donor, D), benzophenone (acceptor, A), and trifluoromethylphenol (acceptor, A′) units. Impressively, all three prepared compounds achieved concentration-dependent high-quality white-light emission, which resulted from the integration of bluish-violet single molecules and yellow excimers. Furthermore, solid p -DMAc-Ph 2 CO-BT exhibited reversible mechanofluorochromism (MFC), with a high-contrast fluorescence shift from blue-green to yellow-green upon grinding, rendering it suitable for a rewritable medium. Single-crystal structural analysis revealed the underlying mechanism of force-responsiveness among the isomers that only o -DMAc-Ph 2 CO-BT possessed C–H⋯F interactions, accompanied by diverse and shorter intermolecular contacts, leading to rigid stacking and MFC passivity. In contrast, p -DMAc-Ph 2 CO-BT showed the weakest intermolecular interactions and the most loosely packed structure, endowing it with high sensitivity to mechanical force. This study demonstrated the critical role of intermolecular interactions in modulating the MFC, providing valuable insights for the rational design of intelligent fluorescent materials.