A Robust Heterometallic Pt₂Pd₂L₈ Double Cage Catenane

The combination of different metal ions in supramolecular structures can lead to the emergence of new features, such as enhanced stability, reduced symmetry, and peculiar reactivity. Mechanically interlocked architectures containing dissimilar metal ions are still scarce. Herein, we report the first example of a heterometallic, quadruply interlocked Pt₂Pd₂L₈ cage catenane, assembled via a combination of metal-mediated self-assembly and dynamic covalent chemistry. While direct complexation of the used asymmetric ligand with a mixture of Pt(II) and Pd(II) ions could yield 14 different monomeric and 576 interlocked cage products, the chosen approach allowed us to selectively obtain one PtPdL₄ monomeric cage and a single Pt₂Pd₂L₈ double cage isomer as major products, respectively, depending on the reaction conditions. In the obtained interlocked Pt₂Pd₂L₈ structure, the kinetically inert Pt(II) ions are positioned peripherally, while the more labile Pd(II) ions are buried and interlocked within the cage interior, as confirmed by NMR spectroscopy, trapped ion mobility spectrometry (TIMS), and single-crystal X-ray diffraction. The resulting catenane structure exhibits an enhanced kinetic stability, resisting disassembly in the presence of excess competitive ligands such as halide anions, unlike previously reported Pd(II) cage catenanes. Furthermore, the Pt₂Pd₂L₈ cage binds halide anions with high affinity, enabling efficient sequestration of halides from organic substrates.