Dynamic Regulation of Radical Photochromism and Photoluminescence via Polymer Polarity

While polymer matrices are widely used to protect excited-state phosphors from oxygen and moisture quenching by providing a network that enables long-lived room-temperature phosphorescence (RTP), the influence of polymer polarity on phosphors for stable free radicals with radical luminescence (RL) has not been well studied. In this work, naphthalene diimide (NDI) derivatives, denoted as NDI-XC-OH (X = 2-6), featuring different alkyl alcohol chains, exhibit multi-responsive and tunable RTP and RL properties through polymer matrix polarity regulation. Experimental results reveal that NDI-XC-OH^•- anion radicals are generated via not only photoinduction in the excited state but also intermolecular interactions of polar matrix in the ground state. Theoretical simulations demonstrate that polar polymers rich in hydrogen-bonding donors (e.g., ─NH₂, ─NH─, and ─OH), where electrostatic interactions dominate over dispersion (E/D > 1), more readily induce anion radicals compared to polar polymers rich in acceptors (e.g., ─CN and ─CO─), where dispersion interactions outweigh electrostatic effects (E/D < 1). These derivatives exhibit potential applications in information encryption and volatile amine detection due to their chromic and luminescent properties. These findings offer perspectives on the role of polymer matrix polarity in modulating anion radical behavior, and mechanistic insights into the balance between RTP and RL properties.