The luminescence mechanism of two pure organic room temperature phosphorescent isomers, mechanical force detection, 3D modeling, and dynamic data encryption

Polymethyl methacrylate (PMMA) and polyvinyl alcohol (PVA) can provide a rigid and anaerobic microenvironment for pure organic room temperature phosphorescent (ORTP) luminogens, leading to significantly enhanced room temperature phosphorescence quantum yield (Phi P) and extended lifetime. However, their brittleness and hydrophilicity limit further expansion of the application range of ORTP luminogens. Herein, two novel ORTP luminogens named as PM-BTDA and OM-BTDA were designed and synthesized based on isomerization and intramolecular charge transfer effects. Interestingly, PM-BTDA showed longer RTP and afterglow (667.19 ms and 10 s) lifetimes, as well as higher Phi P (0.26) than OM-BTDA (527.17 ms, 8 s, and 0.21) in PVA film, but with long-lived visible afterglow for OM-BTDA rather than PM-BTDA in PMMA and polyvinyl chloride (PVC) films. More importantly, OM-BTDA@PVC film demonstrated an outstanding flexibility and mechanical force responsive behaviors, with continuously decreasing room temperature phosphorescent (RTP) intensity and lifetime within the elongation ranges from 0 to 147.49 %. Based on Foerster resonant energy transfer (FRET) from RTP of OM-BTDA/PM-BTDA to Rhodamine B (RhB) in PVA matrix, light yellow and red afterglows were achieved, with emission maxima of 587-612 nm, energy transfer efficiency of 83 %, and Phi P of 0.62. Based on different fluorescence and afterglow colors and lifetimes, as well as excellent flexibility of OM-BTDA@PVC film, complex dynamic digital encryption and various 3D models were successfully constructed. This work can be expected to provide more inspirations and possibilities for ORTP luminogens in molecular design and more application areas.