Synergistic Tuning of Photoreduction Reactivity in Dihydrophenazine Photocatalysts via Fluorination and Annulative π-Extension

Abstract

Dihydrophenazine (DPZ) derivatives are attractive metal-free photocatalysts, but experimentally grounded structure–property relationships for small-molecule ATRC remain underdeveloped. Here, we report a synergistic locking-fluorination strategy to modify the DPZ core. A four-catalyst platform, consisting of DPZ, FDPZ, CDPZ, and FCDPZ, allows the effects of molecular locking and fluorination to be compared independently and in combination. Their impacts in a visible-light ATRC reaction between 1,6-enynes and perfluorobutyl iodide were evaluated. Molecular locking enhances light absorption and fluorescence lifetime, whereas fluorination modulates the electronic environment and excited-state polarization. The combined catalyst FCDPZ exhibits the most balanced profile in this series, delivering high yields with useful Z-selectivity and 2 h reaction completion. These results demonstrate that cooperative core engineering provides a useful strategy for tuning dihydrophenazine photocatalysts.