Blue-Green-Yellow Thermochromic Fluorescence and Bubble-Propelled Crystal Motion Driven by Molecular Gear Rotations

Guest-release induced responsive behaviors in nonporous organic solvate crystals remain elusive due to the lack of well-defined diffusion pathways and the rarity of crystal-to-crystal transitions. Here, we report a pentiptycene-derived nonporous organic solvate (1B) that exhibits a striking blue → green → yellow thermochromic fluorescence sequence through a two-stage crystal-to-crystal transformation. In the first stage, subtle gear-like rotations transiently open a zigzag diffusion pathway, releasing dichloromethane (DCM) and generating a green-emissive phase (1G). In silicone oil, asymmetric bubble evolution during DCM release drives directional crystal propulsion. A second heating step triggers a ∼90° correlated gear rotation that reconfigures alkyl conformation and anthracene packing, producing excimer-based yellow emission (1Y). These coupled sequential optical, mechanical, and structural responses reveal a unique paradigm of guest-driven dynamics in nonporous solvate crystals.