Targeted identification of cyanide and fluoride ions utilizing dansyl-derived fluorescent probes: a deprotonation-driven sensing mechanism

In this study, we present the detection of hazardous cyanide (CN − ) and fluoride (F − ) anions using six dansyl-derived fluorescent probes ( L1–L6 ) specifically designed for rapid and highly sensitive detection in organic media. Through a combination of UV–Vis absorption and fluorescence titrations in acetonitrile, all ligands exhibited a distinct and selective “turn-off” fluorescence response upon exposure to CN − and F − , while remaining unresponsive to common halides such as Br − and Cl − . Quantitative analysis using HypSpec confirmed a consistent 1:1 binding stoichiometry across the series, with L4 emerging as the top performer, displaying low limits of detection of 2 μM and 4 μM for CN − and F − , respectively, and association constants (Log Kass) of 6.37 for CN − and 5.66 for F − . NMR and LC–MS titration studies further revealed a deprotonation-based recognition mechanism, with CN − inducing proton abstraction at sub-stoichiometric levels, while F − required up to 10 equivalents. The high affinity and rapid responsiveness of these dansyl-based systems establish them as potent fluorescent tools for the non-invasive, real-time monitoring of the toxic anions cyanide and fluoride in organic-based samples. • Six dansyl-based fluorescent probes (L1–L6) were explored for selective CN⁻ and F⁻ detection. • “turn-off” fluorescence response to cyanide and fluoride anions was observed. • L4 shows the highest binding affinities, with Log Kass values of 6.37 (CN⁻) and 5.66 (F⁻). • NMR titrations revealed a clear deprotonation-driven recognition mechanism. • These dansyl probes enable rapid, real-time, and non-invasive detection of toxic anions in organic media.