Photonic modulation of electron transfer with switchable phase inversion

Area of Science:

• Supramolecular Chemistry
• Photochemistry
• Molecular Engineering

Background:

• Photochromes exhibit reversible photoisomerization, influencing molecular properties via energy/electron transfer.
• Molecular systems with multiple chromophores offer complex photochemical behavior.
• Controlling photoinduced electron transfer is key for advanced molecular devices.

Purpose of the Study:

• To investigate the photochemical behavior of a molecular tetrad comprising a porphyrin, fullerene, dihydroindolizine photochrome, and dithienylethene photochrome.
• To explore how photochromes modulate photoinduced electron transfer and charge separation quantum yields.
• To demonstrate emergent complexity and light-responsive behavior in a synthetic molecular system.

Main Methods:

• Covalent linkage of porphyrin, fullerene, dihydroindolizine, and dithienylethene units to form a molecular tetrad.
• Photoinduced electron transfer studies from the porphyrin excited state to the fullerene acceptor.
• Modulation of charge separation quantum yield by photochrome isomers under varying light conditions (white light, UV illumination).

Main Results:

• Photoinduced electron transfer from porphyrin to fullerene generates a charge-separated state.
• Photochrome isomers quench the porphyrin excited state, significantly reducing electron transfer quantum yield.
• An out-of-phase response of quantum yield to white light intensity was observed, which inverted to an in-phase response under UV illumination.

Conclusions:

• The molecular tetrad exhibits emergent complexity in its photochemical response to light.
• Photochromes effectively control photoinduced electron transfer, demonstrating tunable molecular behavior.
• Potential applications include molecular logic gates, photochemical labeling, drug delivery, and photoprotection in artificial photosynthesis.