Mechanically Interlocked Indigo Photoswitches.

Area of Science:

• Supramolecular Chemistry
• Photochemistry
• Materials Science

Background:

• Photoswitches enable precise remote control of matter at the nanoscale.
• Long-wavelength photoswitches are crucial for materials and biological applications, but few respond to red/near-infrared light.
• Previous methods using intermolecular interactions to redshift photoswitch activation wavelengths are limited by bimolecularity, restricting their use in dilute or complex environments.

Purpose of the Study:

• To develop a photoswitch with improved properties, specifically response to longer wavelengths and enhanced stability.
• To overcome the limitations of previous supramolecular strategies for photoswitch optimization.
• To explore the use of topologically constrained supramolecular interactions for photoswitch design.

Main Methods:

• Incorporation of an indigo photoswitch into a [2]-rotaxane structure.
• Utilizing topologically constrained supramolecular interactions to modify photoswitch properties.
• Characterization of photoswitching behavior, thermal half-life, and metastable state population under irradiation.

Main Results:

• Achieved photoswitching using 730 nm light, a significant red-shift.
• Demonstrated a 100-fold increase in thermal half-life compared to previous methods.
• Observed a doubling of the metastable state population under constant irradiation.
• Exceeded previous supramolecular interaction strategies for enhancing thermal half-life by over 10-fold.

Conclusions:

• Topologically constrained supramolecular interactions offer a powerful strategy for redshifting and fine-tuning molecular photoswitches.
• This novel approach significantly improves photoswitch stability and response range.
• The findings have broad implications for the design of molecular machines and applied switching technologies, particularly within the field of mechanically interlocked molecules.