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Engineering of supramolecular topologies offers potential opportunities for tailoring their properties to various function and applications. However, the synthesis of interlocked or intertwined compounds, catenanes, links or knots, is a challenge. Previously, we used coordination-driven self-assembly and noncovalent interactions (NCIs) between metal-based acceptors and multipyridyl donors to create supramolecular topologies with increasing complexity. Self-assembling components of fixed length and geometry have been utilized for the production of topologies such as Borromean rings, Solomon links, Hopf's link, "rectangle in rectangle", and an 8 18 molecular knot. However, recent synthesis of a linear [3]catenane by us witnessed the importance of flexible ligands along with coordination-driven self-assembly and NCIs in self-assembling units. This flexibility provides distinctive angularity for the recognition of various NCIs and thus offers tremendous possibilities for realizing complex supramolecular topologies. This study proposed a selective and quantitative synthesis, and also the first X-ray characterization of a closed three-link chain (a prime link of [3]catenane with 6 crossings) via two component coordination-driven self-assembly. The experiments based upon concentration, guest template, and solvent effects were systematically presented. Furthermore, the experimental finding was supported by density functional theory calculations, which highlighted the necessity of the multiple NCIs along with appropriate geometry of the [2 + 2] rings.

We have shown that Aln clusters do not show any characteristics of a superatom in halogenated aluminum clusters. The enhanced stability of halogenated Al clusters can be explained by the magic nature of the clusters, not by superatom chemistry. The presence of even a few electronegative elements provides significant perturbation to the molecular orbitals of Al clusters and stabilizes the electropositive Al cluster cores, closely correlating with metal cluster-ligand chemistry. Our work provides significant chemical insights into the understanding of the structure and stability of halogenated aluminum clusters, and these new insights are applicable to other metal cluster-ligand systems.