Supramolecular host–guest modulated thermally activated delayed fluorescence for photodynamic therapy

Supramolecular host-guest chemistry can tune the photophysical behavior of organic emitters by confining them within well-defined nanoscale environments. Here we report a straightforward strategy to modulate the thermally activated delayed fluorescence (TADF) properties of organic emitters in aqueous media through complexation with the macrocyclic host cucurbit[7]uril (CB[7]). Upon formation of the TADF-CB[7] complex, the photoluminescence quantum yield is enhanced due to the suppression of non-radiative decay pathways within the rigid host cavity. Furthermore, host-guest encapsulation was found to accelerate both forward and reverse intersystem crossing, resulting in improved access to the triplet state. In the presence of molecular oxygen, this facilitates an increased generation of cytotoxic singlet oxygen, thereby boosting the efficacy of photodynamic therapy (PDT). These findings provide a promising supramolecular approach to advancing the application of TADF materials in aqueous-phase PDT systems.