Pyrazino[2,3-f][1,10]phenanthroline Derivatives as Robust Photocatalysts Enabling ppm-Level Organocatalyzed Photoinduced Electron/Energy Transfer Reversible Addition–Fragmentation Chain Transfer Polymerization

Abstract

Exploring high-performance organic photocatalysts (PCs) for photoinduced electron/energy transfer reversible addition− fragmentation chain transfer (PET-RAFT) polymerization represents a cutting-edge research field. In this study, six donor (D)−acceptor (A) type organic PCs based on the pyrazino[2,3-f ][1,10]phenanthroline structure were designed and synthesized, showcasing their successful application in PET-RAFT polymerization. Furthermore, diverse substituent groups were introduced to enable precise control over the photophysical and electrochemical properties of organic PCs. Timedependent density functional theory (TD-DFT) analysis further identified two organic PCs (PCs 5 and 6) that exhibit thermally activated delayed fluorescence (TADF) characteristics. PCs 5 and 6 demonstrated high molar extinction coefficients (ε max ) and long delayed fluorescence (DF) lifetimes, achieving high-efficiency photopolymerization even at catalyst loadings as low as 0.1−10 ppm. This study elucidates the structure−activity correlation of such organic PCs while underscoring the facile construction of efficient PCs with TADF characteristics through strategic structural design. These findings serve as a valuable reference for advancing the development of high-performance organic PCs capable of lightinduced reversible-deactivation radical polymerization (RDRP).