Unravelling the nucleation-elongation mechanism of one-pot catenation.

The formation of catenanes through dynamic covalent reaction of self-assembling precursors in one pot offers a powerful route to complex interlocked architectures, yet the mechanistic insight remains underexplored. Here, we elucidate the nucleation-elongation mechanism in the one-pot synthesis of topologically distinct catenanes, using dimeric (DCC) and trimeric cage-catenanes (TCC) as model systems. Unlike conventional supramolecular polymerization, catenation exhibits topology-dependent pathways: DCC formation is driven by the strong templating effect of its monomeric unit MC-1, while TCC assembly proceeds with several pathways in parallel, via cooperative binding of partially catenated intermediates. Kinetic profiling of the catenation reveals sigmoidal growth with distinct induction periods, where longer induction period correlates with more challenging nucleation. Seeded growth experiments demonstrate that preformed nuclei (e.g., MC-1 for DCC) bypass kinetic barriers, remarkably reducing its induction period, akin to seeded supramolecular polymerization. Our work bridges the gap between supramolecular polymerization and mechanical bonding for interlocked structures, offering a hint for the rational synthesis of structures with sophisticated topology.