Fluorinated Twists: A Pathway to a Stable Pd₈L₁₆ Square Antiprism

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Organic Synthesis

Background:

• The synthesis of palladium-organic cages (Pd_nL_2n) is well-established for small (Pd₂L₄-Pd₆L₁₂) and large (≥Pd₁₂L₂₄) structures.
• Intermediate-sized cages (e.g., Pd₈L₁₆) are challenging to access due to the difficulty in creating ligands with specific metal-ligand coordination angles (90-120°).

Purpose of the Study:

• To report the synthesis and characterization of a novel Pd₈L₁₆ square antiprism metal-organic cage.
• To demonstrate a new ligand design strategy for accessing intermediate-sized metallosupramolecular structures.

Main Methods:

• Design and synthesis of a novel ligand incorporating a perfluorobiphenyl backbone.
• Characterization of the resulting Pd₈L₁₆ cage using spectroscopic and crystallographic techniques.
• Thermodynamic stability studies in solution and solid state.

Main Results:

• A stable Pd₈L₁₆ square antiprism cage was successfully synthesized and characterized.
• The perfluorobiphenyl ligand backbone induces a dihedral twist, achieving the ideal 105.1° angle for square antiprism formation.
• The ligand's rigidity prevents the formation of mixed structural products, ensuring high structural fidelity.

Conclusions:

• The development of the Pd₈L₁₆ square antiprism represents a significant advancement in the synthesis of intermediate-sized palladium-organic cages.
• The use of fluorinated backbones in ligands offers a versatile strategy for controlling coordination angles and accessing complex metallosupramolecular architectures.
• This approach is expected to have broad applicability in the field of (metallo)supramolecular chemistry.