Monodirectional Photocycle Drives Proton Translocation.

Area of Science:

• Molecular photochemistry
• Supramolecular chemistry
• Artificial molecular machines

Background:

• Retinal photoisomerization drives ion transport in bacteria, inspiring artificial molecular switches.
• Previous light-driven systems achieved component translocation but not unidirectional proton movement.

Purpose of the Study:

• To develop a novel system for unidirectional and repetitive proton translocation using light.
• To investigate the protonation-controlled isomerization of hemi-indigo dyes.

Main Methods:

• Synthesis of hemi-indigo dyes with N-heterocycles and intramolecular hydrogen bonds.
• Investigation of photoisomerization behavior under different protonation states (Z to E and E to Z).
• Analysis of proton displacement relative to the photoswitchable scaffold.

Main Results:

• Hemi-indigo dyes exhibit protonation-controlled photoisomerization: Z to E isomerization upon protonation, and E to Z in the neutral state.
• This controlled isomerization leads to directional displacement of associated protons.
• The system demonstrates potential for light-driven proton translocation.

Conclusions:

• Developed a unique protonation-controlled isomerization mechanism in hemi-indigo dyes.
• Achieved unidirectional proton translocation using a photoswitchable scaffold.
• Paves the way for artificial systems that generate concentration gradients with light energy.