Force-Induced Ring Flipping in a Threaded Pillar[5]Arene.

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Mechanochemistry

Background:

• Pillar[n]arenes are versatile macrocycles with unique host-guest properties and planar chirality due to their specific conformations.
• Controlling intermediate conformations, like a single inverted ring, in pillar[n]arenes is synthetically challenging.

Purpose of the Study:

• To investigate the use of mechanical force to control pillar[n]arene conformations.
• To explore the force-induced flipping of a single hydroquinone ring in pillar[5]arene-based rotaxanes.
• To understand the influence of rotaxane components and pillararene substituents on this flipping motion.

Main Methods:

• Utilized mechanochemistry to apply controlled force to pillar[5]arene-based rotaxanes.
• Investigated the effect of stopper and axle design on the flipping dynamics.
• Analyzed the impact of pillar[5]arene substituents on the conformational changes.

Main Results:

• Demonstrated force-induced flipping of a single hydroquinone ring in pillar[5]arene rotaxanes, accessing elusive conformations.
• Showcased control over this flipping motion by varying rotaxane architecture and pillararene substituents.
• Identified the flipping behavior as a mechanical damping mechanism that slows polymer scission under tension.

Conclusions:

• Mechanical force provides a novel route to synthetically challenging supramolecular architectures.
• The force-induced flipping mechanism acts as a mechanical damper, offering potential for creating tougher materials.