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 (|glum| = 1.1). This work opens new venues for photonic applications of CPL active materials.