Red-light operable photosensitizer with symmetry-breaking charge transfer induced intersystem crossing for polymerization of methyl methacrylate

Abstract

We present a red light-activated zinc^II bis(dipyrrin) symmetry breaking charge transfer (SBCT) architecture, showing a large molar absorption coefficient (ε = 15.4 × 10⁴ M⁻¹ cm⁻¹), high reactive singlet oxygen generation efficiency (Φ_Δ ≈ 0.8) and long-lived triplet state (τ_T = 150 μs) compared to the donor–acceptor analogue dipyrrin-BF₂ complex, highlighting the superiority of the SBCT approach. For the first time, we demonstrated the potential of a SBCT scaffold in red-light-induced methyl methacrylate (MMA) polymerization, using a dual photocatalyst excitation approach.