Design and Structural Transformations of Zinc(II) Knotted Cage Frameworks

Interwoven architectures feature in biomolecules such as proteins, DNA, and RNA. However, the high-yielding syntheses and controlled structural transformations of artificial interwoven structures, particularly those exhibiting intricate topologies and bifurcated strands, remain a challenge. In this study, we present a rational design strategy that harnesses the rigidity of tailored ligands in combination with zinc coordination to direct the self-assembly process, thus enabling the controlled synthesis of covalently linked trefoil perplexane and trefoil tetrahedral knotted cage frameworks. We further elucidate the role of structural rigidity in governing framework transformations, demonstrating two-way interconversion between interwoven and non-interwoven architectures, accompanied by tunable guest encapsulation and release. Notably, the incorporation of peripheral crosslinkers was found to lock the cage conformation, thereby regulating its guest binding properties. In addition, the sequence of subcomponent addition was found to be critical to the product outcome: Initial construction of a covalently-linked knotted cage framework stabilizes kinetic intermediates during self-assembly, providing access to distinct products.