Hierarchical Assembly of an Interlocked M₈L₁₆ Container

The self-assembly of eight Pd^II cations and sixteen phenanthrene-derived bridging ligands with 60° bite angles yielded a novel M₈L₁₆ metallosupramolecular architecture composed of two interlocked D_4h-symmetric barrel-shaped containers. Mass spectrometry, NMR spectroscopy, and X-ray analysis revealed this self-assembled structure to be a very large “Hopf link” catenane featuring channel-like cavities, which are occupied by NO₃⁻ anions. The importance of the anions as catenation templates became imminent when we observed the nitrate-triggered structural rearrangement of a mixture of M₃L₆ and M₄L₈ assemblies formed in the presence of BF₄⁻ anions into the same interlocked molecule. Furthermore, the densely packed structure of the M₈L₁₆ catenane was exploited in the preparation of a hexyloxy-functionalized analogue, which further self-assembled into vesicle-like aggregates in a reversible manner.