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

• Published in: Journal of the American Chemical Society Vol. 144; no. 16; pp. 7043 - 7047
• Main Authors: Zhao, Zijian, Niu, Fushuang, Li, Pengju, Wang, Hanqi, Zhang, Zhenghao, Meyer, Gerald J, Hu, Ke
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 27.04.2022
• Subjects: Catalysis; Electron Transport; Electrons; Light; Reducing Agents
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.2c00422

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•– anchored to a ZrO2 insulator yields a ZrO2(e–)|PDI charge separated state with an ∼10 μs 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.