Synthesis of covalently linked knotted cage frameworks

Area of Science:

• Supramolecular Chemistry
• Organic Synthesis
• Materials Science

Background:

• Interwoven molecular structures are crucial for biomolecule function.
• Synthesizing artificial topologically complex structures efficiently is a significant challenge.
• Existing methods often lack high yields and simplicity.

Purpose of the Study:

• To develop a streamlined, high-yield one-pot synthesis for knotted cage frameworks.
• To create novel topologically chiral perplexane and trefoil tetrahedron architectures.
• To investigate the guest-locking properties and stability of these interwoven structures.

Main Methods:

• Employed a subcomponent strategy to bridge over predesigned cage frameworks.
• Utilized one-pot subcomponent self-assembly using a trialdehyde, bridging triamine, and zinc(II) salt.
• Synthesized Zn(II)4L3 and Zn(II)4L4 cages, followed by reduction and demetallation.

Main Results:

• Achieved high-yield synthesis of knotted perplexane and trefoil tetrahedron cages.
• The trefoil tetrahedron demonstrated exceptional mechanical guest-locking, with a 17,000-fold increase in guest exchange half-life compared to the original cage.
• Metal-free interwoven structures were obtained, with the trefoil tetrahedron retaining topological chirality.

Conclusions:

• The developed one-pot subcomponent self-assembly strategy enables efficient synthesis of complex knotted molecular cages.
• This method enhances the robustness and guest-binding capabilities of cage frameworks.
• The strategy holds potential for knotting various existing cage frameworks, expanding their applications.