Design, Synthesis, and Photophysical Characterization of Biocompatible Thermally Activated Delayed Fluorescent Carbazole-Coumarins for Sensing Applications

A series of fluorescent carbazole-coumarins exhibiting good photoluminescence quantum yields and thermally activated delayed fluorescence (TADF) properties have been designed and synthesized using computer-aided density functional theory calculations. The TADF characteristics of the carbazole-coumarins were systematically explored both in solution and in the solid state, utilizing poly(methyl methacrylate) (PMMA) as a matrix. The study revealed that introducing carbazole units onto the coumarin benzene ring led to compounds with thermally induced reverse intersystem crossing and delayed fluorescence. The study further demonstrated the potential utility of these compounds in practical applications by incorporating them into a Cmr-PMMA-based sensor for molecular oxygen detection. The resulting sensor exhibited promising performance, highlighting the adaptability and efficacy of the synthesized TADF-carbazole-coumarin compounds for reversible molecular oxygen sensing.