Programming Palladium Cage Geometry through Ligand Redox Modulation

Incorporating redox active ligands into coordination cages offers a direct way to reach architectures whose structure or composition can be modulated in response to changes in the oxidation state. An exTTF-based ditopic ligand L affords a M₂L₄ cage in presence of a palladium(II) salt (M). The resulting M₂L₄ cavity exhibits selective binding properties for medium length α,ω-dinitrile alkanes. Modifying the coordination geometry of the ligand by oxidation to its L^ox state redirects the self-assembly process toward a M₂L^ox ₂ structure. The oxidized ligand can also be combined with a dibenzothiophene linker (L') to afford a heteroleptic M₂L^oxL'₂ structure whose vacant coordination sites enable subsequent dimerization into an unprecedented M₄L₄L'₄ architecture. Key intermediates and products were structurally authenticated by single-crystal x-ray diffraction. Notably, these processes are reversible. Reduction converts the M₂L^oxL'₂ assembly back to the homoleptic M₂L₄ cage. This sequence illustrates how changes of oxidation state can reshape nuclearity and composition in metal organic assemblies.