Redox-Induced Structural Rearrangement in an M₈L₂ Self-Assembly

Due to the reversible nature of the metal-ligand bond, coordination cages are inherently dynamic architectures which can undergo structural transformations upon appropriate external stimulations. This adaptability has been widely explored in various fields. Herein, we report the preparation of a redox-responsive discrete (Ru₂)₄L₂ architecture through a coordination-driven self-assembly approach, where Ru₂ is a bis(ruthenium(II)) complex and L a tetrapyridyl ligand. Importantly, ligand L is designed around the π-extended tetrathiafulvalene framework (exTTF), whose geometry is highly sensitive to its redox state. The resulting (Ru₂)₄L₂ assembly was fully characterized, revealing a twisted configuration with two orthogonally oriented L units in close spatial proximity. Remarkably, this assembly undergoes an oxidation-induced transformation into a (Ru₂)₄L^ox₂ structure, in which the two dicationic ligands are now spatially separated and aligned according to a face-to-face arrangement, affording a cage-like structure. This reorganization is driven by the redox-induced geometric and electronic changes of the exTTF cores and the resulting electrostatic repulsions occurring between both oxidized ligands. The process is fully reversible upon chemical reduction, restoring the original (Ru₂)₄L₂ structure.