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

Photoexcitation of molecular radicals can produce strong reducing agents; however, the limited lifetimes of the doublet excited states preclude many applications. Herein, we propose and demonstrate a general strategy to translate a highly energetic electron from a doublet excited state to a ZrO2 insulator, thereby increasing the lifetime by about 6 orders of magnitude while maintaining a reducing potential less than -2.4 V vs SCE. Specifically, red light excitation of a salicylic acid modified perylene diimide radical anion PDI center dot- anchored to a ZrO2 insulator yields a ZrO2(e(-))vertical bar PDI charge separated state with an similar to 10 mu s lifetime in 23% yield. The ZrO2(e(-))s were shown to drive CO2 -> CO reduction with a Re catalyst present in micromolar concentrations. More broadly, this strategy provides new opportunities to reduce important reagents and catalysts at low concentrations through diffusional electron transfer.

Automated summary

A general strategy to transfer highly energetic electrons from doublet excited states to a ZrO2 insulator is proposed and demonstrated, resulting in a significant increase in lifetime and the ability to catalyze reduction of important reagents and catalysts at low concentrations.