Selective and Sensitive Fluorescent Detection of Cyanide by 8-hydroxyquinoline-based Chemodosimeter: Spectral and TD-DFT Studies.

Rapid and reliable detection of cyanide ions (CN−) in aqueous environments remains a pressing analytical challenge due to the significant influence of water on sensor-analyte interactions. In this work, a fluorometric turn-on chemodosimeter MMD1 has been designed and synthesized for selective recognition of CN− that operates effectively in an aqueous solution. The distinct turn-on emission of MMD1 in the presence of CN− without the interference from any of the environmentally significant anions and lower detection capability (0.2 µM) discloses its selectivity and suitability for real-time monitoring. The 1:1 stoichiometry between MMD1 and CN− was revealed from Job’s plot, and robust binding interaction was expounded from the magnitude of the binding constant (2.2962 × 10⁴ M⁻¹). The fluorometric responses of MMD1 to CN− are due to the deprotonation combined with nucleophilic addition of CN− at the alkene C-atom, as validated by 1H and 13C-NMR and HR-MS analyses. DFT/TD-DFT studies reveal the optical property of the probe and the signaling mechanism as intramolecular charge transfer (ICT) modulation. The superior fluorescent colour alteration of MMD1-coated test buds in the presence of CN− guarantees its on-site monitoring. The probe’s performance was further validated in real water samples with good recovery and low variation, demonstrating its practical applicability.