Cation Grease/Brake Rotation in Anionic Pillar[5]arenes and Its Application for Fluorescence Switch

Abstract The manual manipulation of motions in molecule level has always been a hot topic in the field of chemistry. Molecular rotors have wide applications in building nanomachines and functional materials, due to their controllable rotations. Hence, it is urgent to develop novel rotor systems with controllable fashions. Differential kinetic traits of planar chirality transformation in sodium carboxylate pillar[5]arene (WP5-Na) and ammonium carboxylate pillar[5]arene (WP5-NH4) were observed serendipitously, which inspired us to construct a promising rotary platform in anionic pillar[5]arenes (WP5) skeletons. Herein, we demonstrate for the first time the nonnegligible effect of counter cations on rotational barriers of hydroquinone rings in WP5, which further exhibit its utilities in establishing a novel and tunable rotor system. Finally, cation grease/brake rotations of WP5 and their applications in fluorescence switch and anti-counterfeiting ink were explored. This study should find potential applications in many aspects, including sensing, molecular devices and stimulus-responsive materials.