Intercalation-Directed Programming of Nanomechanics and Mesoscale Topology.

Creating topologically complex structures beyond the molecular scale remains a long-standing challenge in chemistry and materials science. Here, we introduce a self-assembly strategy using snowflake-shaped molecular building blocks, coupled with a molecular intercalation approach that finely tunes fibril-fibril interactions within the assemblies. This dual strategy enables concurrent control over topology, mechanical stiffness, and chiroptical response. Remarkably, the elastic modulus of the assemblies can be modulated across more than 2 orders of magnitude─from a few gigapascals to tens of megapascals─allowing the structures to fold and writhe under geometric confinement into diverse topologies, including faceted and rounded toroids, figure-eight, and supercoiled architectures. These topological transformations are accompanied by distinct excitonic coupling among the snowflake chromophores, leading to continuous tuning of chiroptical properties and even chirality inversion. Extending beyond molecular systems, this strategy offers a universal pathway to design topologically intricate architectures in hybrid and inorganic materials.