Fluoride ion detection with heterocyclic chromogenic and fluorogenic probes: Molecular design and response pathways

Abstract

Fluoride ions exhibit a dual nature as essential trace elements and potential toxicants, demanding sensitive and selective detection methods. Chromogenic and fluorogenic chemosensors have emerged as effective tools due to their simplicity, rapid response, and visual readout. In this context, heterocycle-based molecular probes have attracted increasing attention for fluoride sensing owing to their tunable electronic properties, strong anion–receptor interactions, and versatile signal transduction mechanisms. This review summarizes recent advances in heterocyclic chromogenic and fluorogenic probes for toxic fluoride ion detection, with emphasis on molecular design strategies such as hydrogen bonding, deprotonation, Lewis acid–base interactions, and reaction-based sensing. Key photophysical pathways, including ICT, PET, ESIPT, and AIE, are discussed to elucidate structure–property–function relationships. Challenges such as interference from basic anions, solvent effects, and limited aqueous compatibility are highlighted, along with future perspectives to guide the development of robust heterocycle-based probes for reliable fluoride monitoring.