A naphthol hydrazone Schiff base bearing benzothiadiazole unit for fluorescent detection of Fe3+ in PC3 cells.

[Display omitted] • A probe is designed with naphthol and benzothiadiazole at both ends linked by a hydrazone. • Theoretical study suggests a key role of Fe3+ in affecting the electron localization. • Sensing mechanism is proved to be a combination of two processes. • The probe exhibits an excellent sensitivity and a short response time. • Discriminative turn-off emission is observed in paper strips and bioimages. Naphthol hydrazone derivatives are recognized as efficient chelating agents for both qualitative and quantitative detection of metal ions. Here we design a naphthol hydrazine-based chemosensor with covalently linking a strong electron-withdrawing benzothiadiazole group to modulate the molecular electronic structure, nominated as NtHzBtd. The fluorescent probe performs excellent selectivity and sensitivity towards Fe3+ with 1:1 binding stoichiometry, while exhibiting a quick response at 55 s with a relatively low limit of detection of 0.036 µM. A series of spectroscopic measurements in tandem with theoretical calculations suggest that the probe undergoes both intramolecular charge transfer (ICT) and chelation enhanced quenching (CHEQ) processes. Successful color rendering of paper strips and bioimaging in PC3 cells demonstrate the promising applicability of NtHzBtd for portable Fe3+ detection in real samples and biosystems. [ABSTRACT FROM AUTHOR]