Sequential and Time-Controlled Sol-Gel Transitions by Mechanical Switching of Molecular Tweezers

Controlling the motion of molecular machines to influence higher-order structures is well-established in biological systems but remains a significant challenge for synthetic analogs. Herein, we aim to harness the mechanical switching of switchable molecular tweezers to modulate their self-assembly and produce stimuli-responsive organogels. We report a series of terpy(Pt-salphen)₂ molecular tweezers functionalized with alkyl chains that act as low-molecular-weight gelators (LMWGs) in their open conformation. The resulting organogels were thoroughly characterized by SEM, cryo-TEM, SAXS, and rheology. The macroscopic transition from gel to solution was achieved by the cation-induced closing of the tweezers, which triggers their substantial structural reorganization. Reversible sol-gel transitions were achieved through the sequential addition of chemical stimuli or by a decomposable acid in a time-controlled operation. Such transient disassembly process regulated by a chemical fuel enables multiple gelation cycles with minimal waste while maintaining stable rheological properties. These results underscore the potential of switchable molecular tweezers in creating advanced stimuli-responsive materials.