Tunable Circularly Polarized Luminescence of Excited-State-Proton-Transfer-Based Chiral Guanidine

Circularly polarized luminescence (CPL) of chiral materials responsive to external stimuli has drawn widespread attention due to their important applications in smart photonic materials. Here, a CPL-active chiral emitter derived from guanidine-substituted 1,8-naphthalimide ( R/ S-1) is reported, which could emit tunable circularly polarized light through regulating the situation of protonation/ deprotonation in aqueous, as well as the solvent polarity. Tunable fluorescence emission from the protonated compound can be observed, which is contributed to excited-state proton transfer of guanidine moiety, as well as the intramolecular charge transfer of naphthalimide group. Subsequently, color-tunable CPL is obtained, enabling a single-molecule-white-color circularly polarized light emission. Additionally, by introducing R/ S-1 into chiral nematic liquid crystal film, CPL emission is adjusted by exposing to acid/alkaline environment, which can be directly distinguished by naked eyes due to the extremely large dissymmetry factor (| g(lum)| = 1.1). This work opens new venues for photonic applications of CPL active materials.