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

A symmetric bipyridyl ligand L^F bearing an endohedrally-pendant pentafluorobenzyl ether guides the self-assembly process to yield low-symmetry, homoleptic lantern-type Pd₂L^F₄ cages as it adopts a single, low-symmetry conformer—stabilized by both π-stacking and tetrafluoroborate encapsulation—as demonstrated by crystallographic and spectroscopic characterization.

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 L^F bearing an endohedrally-pendant pentafluorobenzyl ether to guide the self-assembly of low-symmetry, homoleptic cages. Ligand L^F 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 L^F contrasted the control assembly lacking fluorination (L^H), 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.