Reversible C 60 Ejection from a Metallocage through the Redox‐Dependent Binding of a Competitive Guest

The reversible encapsulation of a tetrapyridyl extended‐tetrathiafulvalene (exTTF)‐based ligand ( m ‐Py)exTTF by a tetragonal Zn‐porphyrin‐based prismatic nanocage ( 1 ) is described. The reversible uptake and release of the ( m ‐Py)exTTF guest proceeds through drastic electronic and conformational changes occurring upon oxidation of the latter. This reversible system has been explored in a guest‐exchange process, by addition of ( m ‐Py)exTTF to the host–guest complex [C 60 ⊂ 1 ], leading to fullerene C 60 ejection from the host cavity. Remarkably, the subsequent redox‐triggered ejection of ( m ‐Py)exTTF, leads to the recovery of the empty cage 1 , which remains available for further C 60 encapsulation. The C 60 ejection is justified by the preferable coordination of the pyridine anchors of ( m ‐Py)exTTF to the two Zn‐porphyrin units of 1 . This approach, based on the use of a switchable competitive guest, offers a promising new strategy for guest‐delivery control.