Selective host-guest interactions of a transformable coordination capsule/tube with fullerenes

Area of Science:

• Supramolecular Chemistry
• Coordination Chemistry
• Materials Science

Background:

• Dynamic covalent chemistry enables the construction of adaptable molecular architectures.
• Coordination capsules and tubes offer unique environments for host-guest chemistry.
• Controlling interconversion between different supramolecular structures is a key challenge.

Purpose of the Study:

• To selectively synthesize M2L4 coordination capsules and M2L2 coordination tubes.
• To investigate the reversible interconversion between these structures.
• To explore the distinct host-guest properties of the capsule and tube.

Main Methods:

• Utilized mercury(II) ions as hinges and bent bispyridine ligands for self-assembly.
• Manipulated the metal-to-ligand ratio to control structural formation and interconversion.
• Studied host-guest interactions using fullerenes (C60 and C70) as model guests.

Main Results:

• Achieved selective formation of M2L4 coordination capsules and M2L2 coordination tubes.
• Demonstrated reversible structural interconversion at room temperature.
• Observed selective encapsulation of large spherical molecules (fullerenes) by the capsule.
• Showed that guest release is triggered by capsule-to-tube transformation via metal ion addition.

Conclusions:

• The Hg(II)-bispyridine system allows for the dynamic formation and interconversion of coordination cages and tubes.
• The distinct architectures exhibit differential host-guest behavior, with the capsule selectively binding fullerenes.
• This work provides a responsive platform for molecular encapsulation and guest release.