Emerging perylene diimide-based photocatalysts: status and trends in organic synthesis

Perylenediimide (PDI)-based photocatalysts constitute a transformative breakthrough in synthetic chemistry, distinguished by their unique dual-photon activation mechanism that surpasses conventional single-photon systems. Through consecutive photoinduced electron transfer (conPET), PDI radical anions (PDI˙-) can absorb a second visible photon to generate excited radical anions (PDI˙-*) with extraordinarily negative oxidation potentials reaching -2.0 V vs. SCE, enabling challenging activation of chemically inert bonds. The strategic three-axis functionalization approach targeting imide, bay, and ortho positions provides unprecedented control over photophysical properties, redox behavior, and catalytic performance, establishing definitive structure-activity relationships. This mini-review demonstrates exceptional synthetic utility across a broad spectrum of transformations, encompassing aryl halide reductions, fluoroalkylation processes, electrophotocatalytic C-F bond functionalization, sulfoxide reduction, controlled radical polymerization, and radical cyclization reactions, while comprehensively addressing fundamental concepts, PDI design principles, mechanistic frameworks, and future research directions in this rapidly advancing field.