Light-harvesting in multichromophoric rotaxanes

Area of Science:

• Supramolecular Chemistry
• Organic Chemistry
• Photochemistry

Background:

• Mechanically interlocked molecules (MIMs) offer unique platforms for energy transfer studies.
• Rotaxanes, a class of MIMs, can be designed with specific chromophores for light-harvesting applications.
• Controlling energy transfer pathways within MIMs is crucial for developing advanced functional materials.

Purpose of the Study:

• To synthesize two distinct rotaxanes featuring naphthalene and pyrene chromophores.
• To investigate the light-harvesting properties and energy transfer efficiencies in these rotaxanes.
• To demonstrate light-harvesting function within the mechanically interlocked components of rotaxanes.

Main Methods:

• Anion template effect synthesis of rotaxanes with benzyl ether axles and tetralactam wheels.
• Incorporation of naphthalene chromophores on stopper groups and a pyrene chromophore on the wheel.
• Photophysical characterization to assess energy transfer efficiency from naphthalene to pyrene.

Main Results:

• Successful synthesis of two rotaxanes differing in the linker (triazole or alkynyl) between the naphthalene chromophore and the axle.
• Both rotaxanes demonstrated efficient light-harvesting, with over 90% energy transfer efficiency from naphthalene to pyrene.
• The study confirmed efficient energy transfer between chromophores integrated into the axle and wheel components.

Conclusions:

• Rotaxanes can be effectively designed to exhibit efficient intramolecular energy transfer.
• The anion template effect is a viable method for synthesizing complex MIMs for photophysical studies.
• These findings highlight the potential of MIMs as functional light-harvesting systems.