Structural Effects in the Iridium Complex Series: Photoredox Catalysis and Photoinitiation of Polymerization Reactions under Visible Lights

Abstract

A series of 18 iridium complexes ( Ir ) have been prepared and studied. Their abilities to initiate both a ring‐opening cationic polymerization (CP) using an Ir /iodonium salt couple and a free radical polymerization (FRP) in the presence of an Ir /amine/alkyl halide system under very soft irradiation (i.e., halogen lamp) or upon exposure to laser diodes @457 nm and @532 nm are investigated. Interestingly, these photoinitiating systems operate through an oxidative or a reductive photoredox catalytic cycle, respectively. Excellent polymerization profiles are obtained (reactive function conversions >70% for the CP of an epoxide and >60% for the FRP of low viscosity triacrylate). The photochemical mechanisms are studied by fluorescence, steady state photolysis, cyclic voltammetry, and electron spin resonance spin trapping experiments.