Spectroscopic and Theoretical Studies on the Selective Detection of Cyanide Ions by a Turn-On Fluorescent Chemo-Dosimeter and its Application in Living Cell Imaging.

A new chemo-dosimeter AK4 containing quinoline fluorophore has rationally been designed, synthesised and characterized using H and C NMR and mass spectral techniques. The probe senses explicitly CN ion through a dramatic enhancement in fluorescence over other commonly coexistent anions in HO:DMSO (9:1 v/v) medium over a broad pH range (4-10). H NMR titration revealed the deprotonation followed by nucleophilic addition reaction of CN, which was supported by C NMR and mass spectral examinations. The Job's continuous variation method indicated the formation of a 1:1 adduct between AK4 and CN with a binding constant of 1.62 × 10 M. A limit of detection (LOD) towards CN of 0.69 µM has been determined, which is much lower than the World Health Organization (WHO) recommended limit of CN in drinking water (1.9 µM). The changes in the optical properties of AK4 upon reaction with CN were delineated using Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TD-DFT) calculations. Moreover, fluorescence microscopic studies established that AK4 could be an effective probe for imaging intracellular CN in HeLa cells.