Visible Light Generation of a Microsecond Long-Lived Potent Reducing Agent

Area of Science:

• Photochemistry
• Materials Science
• Catalysis

Background:

• Photoexcitation of molecular radicals generates potent reducing agents.
• Short lifetimes of excited states limit practical applications of these radicals.

Purpose of the Study:

• To develop a general strategy for stabilizing energetic electrons from excited molecular radicals.
• To maintain the strong reducing potential of these electrons for catalytic applications.

Main Methods:

• Anchoring salicylic acid-modified perylene diimide radical anion (PDI•-) to a zirconium dioxide (ZrO2) insulator.
• Exciting the PDI•- with red light to induce photoexcitation.
• Characterizing the resulting charge-separated state (ZrO2(e-)|PDI) and its lifetime.

Main Results:

• A ZrO2(e-)|PDI charge-separated state with a lifetime of approximately 10 μs was achieved, a 6-order-of-magnitude increase.
• The stabilized electrons maintained a reducing potential below -2.4 V vs SCE.
• The ZrO2(e-) species effectively drove CO2 to CO reduction in the presence of a rhenium (Re) catalyst.

Conclusions:

• The strategy of transferring energetic electrons to ZrO2 insulators significantly enhances their lifetime.
• This method allows for the use of highly energetic electrons as reducing agents at low catalyst concentrations.
• This approach opens new avenues for reducing various chemical species and catalysts via diffusional electron transfer.