Reversible reduction drives anion ejection and C(60) binding within an Fe(II)(4)L(6) cage

Fe(II)(4)L(6) tetrahedral cage 1 was prepared from a redox-active dicationic naphthalenediimide (NDI) ligand. The +20 charge of the cage makes it a good host for anionic guests, with no binding observed for neutral aromatic molecules. Following reduction by Cp(2)Co, the cage released anionic guests; subsequent oxidation by AgNTf(2) led to re-uptake of anions. In its reduced form, however, 1 was observed to bind neutral C(60). The fullerene guest was subsequently ejected following cage re-oxidation. The guest release process was found to be facilitated by anion-mediated transport from organic to aqueous solution. Cage 1 thus employs electron transfer as a stimulus to control the uptake and release of both neutral and charged guests, through distinct pathways.