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. Whilst 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 both in 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 incorporation of a perfluorobiphenyl backbone. The substantial dihedral twist induced by the fluorines diverges the coordination vectors compared to non-fluorous examples, whilst crucially maintaining ligand rigidity to avoid formation of mixtures of structures – a strategy we believe will have widespread applications in (metallo)supramolecular chemistry.