Reversible Mechanical Interlocking via Stimuli-Triggered Nonhomeomorphic Topology Transformation Enables Highly...

Area of Science:

• Supramolecular Chemistry
• Organic Synthesis
• Materials Science

Background:

• Mechanically Interlocked Molecules (MIMs), particularly rotaxanes, are fundamental to supramolecular chemistry.
• Current synthesis methods for complex rotaxanes often lack efficiency, convenience, and desired features like reversibility and diverse topologies.

Purpose of the Study:

• To develop a novel, efficient, and versatile strategy for synthesizing rotaxanes and higher-order MIMs.
• To achieve quantitative synthesis of rotaxanes with specific geometries and controllable mechanical properties.

Main Methods:

• A one-pot "threading-and-shrinking" strategy was employed, utilizing UV light (365 nm) irradiation.
• The synthesis relies on reversible topology transformation between nonhomeomorphic structures, driving macrocycle shrinkage without additional reagents.
• Heat-triggered reverse topology transformation was used for mechanical unlocking.

Main Results:

• Quantitative preparation of [2]rotaxane ( >99% conversion, 92% isolated yield) and bis[2]rotaxane (96% conversion, 80% isolated yield).
• Synthesis of rotaxanes with chair-like and orthogonal geometries in a single step.
• Chair-like rotaxanes demonstrated heat-triggered mechanical unlocking, while orthogonal rotaxanes showed thermal stability.

Conclusions:

• The "threading-and-shrinking" strategy offers a convenient and efficient route to complex rotaxanes with high yields.
• The method allows for the synthesis of rotaxanes with tunable geometries and controllable mechanical properties (locking/unlocking).
• This approach advances the synthesis of sophisticated mechanically interlocked molecules for diverse applications.