A Naphthalimide–Sulfonylhydrazine Conjugate as a Fluorescent Chemodosimeter for Hypochlorite

Hypochlorite anion (ClO−) is a widely-used disinfectant and a microbicidal agent in the immune system. Accurate detection of ClO− in environmental and biological samples by simply prepared chemosensors/chemodosimeters is important. Herein, we report that a naphthalimide–sulfonylhydrazine conjugate with an imine (C=N) linker, prepared via simple condensation, acts as an effective fluorescent chemodosimeter for ClO−. The molecule exhibits a weak emission, but ClO−-selective cleavage of its C=N bond creates a strong green emission. Ab initio calculation showed that the emission enhancement by ClO− originates from the suppression of intramolecular electron transfer from the photoexcited naphthalimide through the C=N linker. This response enables selective and sensitive detection of ClO− at physiological pH range (7–9) and allows fluorometric ClO− imaging in the presence of cells.