Temperature-Responsive Supramolecular Chiral Switch Achieved by Macrocyclic Confinement

A series of tunable morphological nanoaggregates are constructed by hydroxypropyl-β/γ-cyclodextrin (HPβ/γCD) and cucurbit[8]-uril (CB[8]), respectively, encapsulating phenylalanine dipeptide-modified pyrene (PFF) based on host-guest complexation, which not only exhibits a topological transformation from helical nanofibers of PFF to supramolecular nanoparticles, nanotubes, and nanosheets but also induces chiral transmission from phenylalanine dipeptide to pyrene moiety achieving temperature-controlled supramolecular chiral switches. Unlike the encapsulation of HPβCD to PFF at a 1:1 stoichiometric ratio, HPγCD with larger cavity can encapsulate two PFFs, achieving enhanced fluorescence behavior with quantum yield increasing from 1.66% to 32.14% and circular dichroism (CD) with a negative Cotton effect peak at 440 nm with an asymmetric factor (<i>g</i> _abs) of -1.44 × 10^-4. Compared with HPβ/γCD, CB[8] gives a stronger binding affinity of up to 5.99 × 10⁵ M^-1 and a significant positive CD peak at 450 nm. Molecular dynamics and density functional theory calculations reveal that HPγCD and CB[8] could effectively disrupt the symmetric aggregates and restrict the conformations of PFF to realize the efficient chiroptical transmission. Moreover, PFF-HPγCD and PFF-CB[8] supramolecular chiral switches exhibit reversible thermal responsiveness (20-75 °C) and positive circularly polarized luminescence, which are successfully applied to chiral logic gate and polarization-dependent encryption.