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

Comprehensive Summary 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.