Reduced-Symmetry Homoleptic Pd2L4 Cages Stabilized by Noncovalent π-Interactions.

Low symmetry molecular cages are synthetically challenging yet may have important applications. Symmetry in coordination cages is typically broken by repulsive design leveraging steric clashes, geometric mismatches, or orthogonal ligands. Here, we demonstrate a contrasting strategy exploiting attractive π-interactions from a sole symmetric bipyridyl ligand LF bearing an endohedrally-pendant pentafluorobenzyl ether to guide the self-assembly of low-symmetry, homoleptic cages. Ligand LF formed lantern-type Pd2L4 cages that adopt a single, low-symmetry conformer-stabilized by both π-stacking and tetrafluoroborate encapsulation-demonstrated by crystallographic and spectroscopic characterization. Cage assembly with LF contrasted the control assembly lacking fluorination (LH), which formed dynamic, less-defined structures, underscoring the essential role of π-interactions in both structural selection and kinetic stability. These findings introduce a new design paradigm: using minimal, attractive forces to direct symmetry and dynamics of supramolecular architectures.