Reversible C₆₀ Ejection from a Metallocage through the Redox-Dependent Binding of a Competitive Guest

Area of Science:

• Supramolecular Chemistry
• Nanocage Chemistry
• Host-Guest Chemistry

Background:

• Development of sophisticated host-guest systems for molecular recognition and encapsulation.
• Exploration of redox-responsive ligands for dynamic supramolecular assemblies.
• Need for controlled guest release mechanisms in nanocontainer systems.

Purpose of the Study:

• To describe the reversible encapsulation of a tetrapyridyl extended-tetrathiafulvalene ((m-Py)exTTF) ligand by a Zn-porphyrin nanocage (1).
• To investigate the redox-triggered guest exchange and release mechanisms within the nanocage.
• To demonstrate a novel strategy for controlled guest delivery using a switchable competitive guest.

Main Methods:

• Synthesis and characterization of a tetragonal Zn-porphyrin-based prismatic nanocage (1).
• Study of the encapsulation and release dynamics of the (m-Py)exTTF ligand.
• Investigation of guest-exchange processes involving fullerene C60 and the (m-Py)exTTF ligand.

Main Results:

• Reversible encapsulation and release of (m-Py)exTTF guest by nanocage 1, driven by redox-induced electronic and conformational changes.
• Successful guest-exchange process: addition of (m-Py)exTTF to [C60 ⊂1] complex triggered C60 ejection.
• Redox-triggered ejection of (m-Py)exTTF allowed recovery of empty cage 1 for subsequent C60 encapsulation, demonstrating recyclability.

Conclusions:

• The Zn-porphyrin nanocage system exhibits reversible host-guest behavior modulated by redox stimuli.
• The competitive guest-exchange strategy effectively controls guest release and enables selective delivery.
• This approach offers a promising platform for developing switchable supramolecular systems for targeted molecular delivery.