Pyrazino[2,3-f][1,10]phenanthroline Derivatives for Oxygen-Tolerant Dual Photoredox/Copper Catalyzed Atom Transfer Radical Polymerization with Ultra-low Catalyst Dosage

Abstract

Substantial progress has been made over recent years in visible light-driven dual photoredox/copper catalyzed atom transfer radical polymerization (photo-ATRP) through the design of photocatalysts (PCs) and the optimization of reaction conditions. However, it remains challenging to achieve efficient photo-ATRP with low loadings of both photocatalyst and copper(II). In this study, two donor-acceptor organic PCs based on pyrazino[2,3-f][1,10]phenanthroline were successfully used to achieve efficient Cu(II)-mediated photo-ATRP. These organic PCs exhibit excellent visible light absorption capabilities and thermally activated delayed fluorescence (TADF) properties. Under blue light irradiation, the PCs facilitated highly efficient and oxygen-tolerant polymerization with an extremely low catalyst loading (50 ppb). This system demonstrated a broad applicability to various monomers, achieving successful polymerization of methacrylates, acrylates, and styrene. Additionally, efficient photo-ATRP on a large scale (250 mL) was achieved, resulting in narrow molecular weight polymers with high monomer conversions and high chain-end fidelity. This work provides an in-depth investigation into the regulatory process of photo-ATRP, offering new insights into the intricate mechanism of oxygen tolerance.