Integrative, Orientational Self-Sorting at the Four-Crossing Level in Molecular Knots and Links

Low-symmetry mechanically interlocked molecules (MIMs) remain challenging targets because of their anisotropic structures and synthetic complexity. We devised a self-sorting strategy employing two unsymmetric flexible bidentate ligands, L^ab and L^cd, which co-assemble with two size-differentiated rigid chelating building blocks and half-sandwich organometallic units. This approach yields three discrete topologies with high orientational fidelity: a Solomon link ( $4_1^2$ ), a figure-eight knot (4₁), and a trefoil (3₁) knot, enabling systematic investigation of oriented entanglements. Notably, we successfully implemented a "MIM-to-MIM" strategy that enables the transformation between fully interlocked molecular species, representing the first example in which both reactants and products are discrete MIMs. Through either this interlocked molecular fusion process or completely integrative self-sorting of mixed unsymmetric components, a heteroleptic Solomon link was constructed in a non-statistical manner. The outcome highlights how diverse noncovalent interactions, the conformational adaptability of ligands, and geometric complementarity cooperate to direct complex self-sorting behavior in unpredictable, non-rigid mixed-assembly systems.