The optical and colorimetric properties of a new chemosensor 4-((2,4-dichlorophenyl) diazenyl)-2-(3-hydroxypropylimino)methyl)phenol (L) for cyanide ions were investigated by the naked-eye detection and UVevis spectroscopy. This receptor reveals visual changes toward CN anions in aqueous media. No significant color changes were observed upon the addition of any other anions. The cyanide recognition properties of the receptor through proton-transfer were monitored by UVevis titration and 1H NMR spectroscopy. The binding constant (Ka) and stoichiometry of the formed hosteguest complex were calculated by the BenesieHildebrand (BeH) plot and Job's plot method, respectively. The detection limit of the probe towards CN was 1.03 106 mol L1, which is lower than the maximum value of cyanide (1.9 106 mol L1) permitted by the World Health Organization in drinking water. Thus, this chemosensor was sensitive enough to detect cyanide in aqueous solutions. 1H NMR experiments were conducted to investigate the nature of interaction between the receptor and CN anions. Notably, the designed sensor can be applied for the rapid detection of cyanide anions in the basic pH range and also under physiological conditions, for practical purposes for a long duration. The sensing behavior of the receptor was further emphasized by computational studies. Quantum-chemical calculations and molecular studies via Density Functional Theory (DFT) were carried out to supplement the experimental results.
