Water‐Gated Allosteric Reconfiguration of a Lanthanide–Organic Cage Dynamically Modulates Fullerene Chiroptical Response and Radical Persistence

Dynamic control over both the chiroptical response and radical persistence of fullerene within a single adaptive host remains challenging. Here we report that a trace amount of water serves as a key to gate a fullerene‐assisted vertex‐chirality inversion in an allosteric lanthanide coordination cage, converting C 60 ⊂ Δ 4 P 4 into C 60 ⊂ Λ 4 P′ 4 . The switch proceeds via a concerted architectural reset, featuring ∼20% cavity contraction, near‐closure of the cage windows, and strengthened host‐guest contacts, yielding a thermodynamically more stable complex under aqueous perturbation. Confinement within the compact Λ 4 P′ 4 cavity inverts and amplifies the induced chiroptical response of encapsulated C 60 (×3.5, | g abs | = 1.62 × 10 −2 ), the highest value reported for noncovalent chiral induction of C 60 in solution, while switching C 60 •− from a short‐lived state (<4 min) in the pre‐inversion cage to a substantially more persistent state (∼2 h) in the post‐inversion cage. These effects arise from enhanced concave‐convex π‐π/dispersion interactions that stabilize the post‐inversion host‐guest state. By linking water‐triggered allosteric reconfiguration to both chiral information transfer and radical persistence, this work establishes adaptive coordination cages as active regulators of fullerene electronic and chiroptical states, providing a strategy for programming coupled chirality and redox functions in carbon nanostructures.