Redox-switchable self-assembly of a thia-cage with Bipyridiniums

We report a redox-active molecular cage 1 incorporating two dibenzo[24]-crown-8 ether (DB24C8) units and two thianthrene (TA) moieties, which enables reversible complexation with pyridinium guests. Cage 1 forms stable 1:1 complexes with methyl viologen (MV²⁺) and 1,2-bis(4-pyridinium)ethane (DPE²⁺), as confirmed by NMR spectroscopy, UV – vis analysis, and single-crystal X-ray diffraction. The association constants were determined to be (4.2 ± 0.8) × 10⁵ M^{− 1} for MV²⁺ and (3.0 ± 0.6) × 10⁵ M^{− 1} for DPE²⁺. Cyclic voltammetry revealed that 1 undergoes reversible two-electron oxidation (<i>E</i>_₁/₂ = 0.384 V) and reduction, with guest release occurring upon oxidation to 1²⁺ and re-encapsulation upon reduction to the neutral state. Redox-switchable complexation was observed for both MV²⁺ and DPE²⁺, evidenced by characteristic shifts in redox potentials and restoration of binding. These results highlight cage 1 as a versatile redox-responsive host, providing a promising platform for the design of stimuli-controlled molecular devices and adaptive supramolecular systems.