Design and synthesis of phenothiazine-based D-A molecules with ICT characteristics as efficient fluorescent probes for detecting hypochlorite in water.

Phenylthiazide compounds are frequently utilized to construct electron donor-acceptor (D-A) dyes, exhibiting excellent fluorescence and colorimetric analysis performance due to their electron-rich properties. Three D-A type compounds 5a-c, featuring intramolecular charge transfer (ICT) characteristics, were designed and synthesized using phenothiazine as the donor and various aryl-substituted imidazoles as acceptors for the detection of hypochlorite. Additionally, the ICT properties of the compounds can be fine-tuned by introducing various substituents to achieve a more sensitive optical response to HClO/ClO. Among these, compound 5c, which contains the electron-withdrawing group -CN, demonstrated high sensitivity (3.5 nM), high selectivity, and a rapid response to HClO/ClO. Experimental results indicated that the strategy based on structural tuning presents a promising approach for optimizing fluorescent probes. To broaden practical applications, compound 5c was fabricated into paper test strips and thin-layer chromatography (TLC) plates for on-site analysis and detection of HClO/ClO. The compound was capable of detecting HClO/ClO not only in actual water samples but also in complex environmental water samples, thereby providing a convenient tool for real-time HClO/ClO detection.