Constructing Stimuli‐Responsive Luminescent Systems with High‐Contrast Fluorescence and Phosphorescence Through a Host‐Guest Strategy

Organic room-temperature phosphorescence (RTP) materials have attracted significant attention because of their potential applications in information storage, bioimaging, sensors, among others. However, the design of high-performance stimulus-responsive RTP materials remains challenging. In this work, multi-stimuli-responsive RTP systems are constructed by utilizing the acid-base responsive properties of the pyridine group, the heavy-atom effect of halogen and sulfur atoms, and d-pπ bonds. Six phenothiazine derivatives are designed and synthesized. A systematic investigation is conducted on the effects of molecular structure, molecular conformation, stacking arrangements, and intermolecular interactions on their luminescence properties. Employing phenothiazine derivatives as the guest and their corresponding 5,5-dioxide phenothiazine derivatives as the host, host-guest doping is achieved through the slow solvent evaporation and the melting-blending methods. The host-guest doping system exhibits highly efficient and long-lifetime phosphorescence through the formation of triplet exciplexes, with a phosphorescence quantum yield of up to 63.6%. The doping systems exhibit higher-contrast acid-base, acid-thermal, and multi-stimulus responsive luminescence characteristics than the single compounds. The potential applications of these systems in sensors, multicolor patterning, and multi-information encryption are explored.