Fluorinated Twists: A Pathway to a Stable Pd8L16 Square Antiprism

Within the extensive family of PdnL2n metal-organic cages, some structures are much easier to access than others. Ligands are generally constructed from planar aromatic linkers. While small structures (Pd2L4 to Pd6L12) and large pseudospherical structures (≥Pd12L24) can be readily obtained from these flat aryl-based ligands, strategies to intermediate-sized structures have remained elusive as the required angle between metal-ligand coordination vectors (90-120°) is hard to construct from the common toolkit of organic molecules. Herein, we report the Pd8L16 square antiprism as a new addition to the PdnL2n family, a structure shown as thermodynamically stable in both solution and the solid state, for the first time. The ligand achieves close to the ideal angle of 105.1° needed for the square antiprism through the incorporation of a perfluorobiphenyl backbone. The substantial dihedral twist induced by the fluorines diverges the coordination vectors compared to nonfluorous examples while crucially maintaining ligand rigidity to avoid the formation of mixtures of structuresa strategy we believe will have widespread applications in (metallo)-supramolecular chemistry.