Internal Heavy-Atom Effect on Visible-Light-Induced Cyclization Reaction in Diarylethene-Perylenebisimide Dyads

Area of Science:

• Materials Science
• Organic Chemistry
• Photochemistry

Background:

• Diarylethene-perylenebisimide (DAE-PBI) dyads are known molecular switches.
• Previous studies indicated that heavy atoms enhance photocyclization reactions via an external heavy-atom effect.
• Visible-light-induced reactions are desirable for practical applications.

Purpose of the Study:

• To design and synthesize novel DAE-PBI dyads with bromine heavy atoms integrated into the molecular structure.
• To investigate the effect of intramolecular heavy atoms on the visible-light-induced photocyclization efficiency.
• To explore the potential for developing highly efficient all-visible-light-activatable molecular switches.

Main Methods:

• Synthesis of novel DAE-PBI dyads containing bromine atoms at various positions.
• Photophysical characterization including absorption and emission spectroscopy.
• Quantum yield measurements for photocyclization and cycloreversion reactions under visible light irradiation.
• Computational analysis to correlate molecular orbital contributions with reactivity.

Main Results:

• The synthesized DAE-PBI dyads with internal bromine atoms exhibited significantly higher photocyclization quantum yields under visible light compared to non-brominated analogues.
• The enhanced reactivity was observed even in solvents lacking heavy atoms, indicating an internal heavy-atom effect.
• The degree of enhancement correlated with the contribution of bromine's atomic orbitals to the lowest unoccupied molecular orbitals (LUMOs).

Conclusions:

• The incorporation of bromine heavy atoms directly into the DAE-PBI molecular structure effectively enhances visible-light-induced photocyclization.
• This internal heavy-atom effect provides a powerful strategy for designing efficient molecular switches activated by visible light.
• These findings open new avenues for molecular design in the field of light-responsive materials and molecular devices.