Structure–reactivity correlation in selective colorimetric detection of cyanide in solid, organic and aqueous phases using quinone based chemodosimeters

Abstract

Quinone based colorimetric chemodosimeters, which could instantly detect CN⁻ in solid, organic and aqueous phases with selectivity and sensitivity are described. The results of UV-Vis, fluorescence, ¹H and ¹³C NMR spectroscopy, electrochemical studies and product analysis confirmed that the mechanism of sensing is through nucleophilic addition of CN⁻ to the CC bond of the indole ring. DFT calculations were conducted to rationalize the sensing mechanism of these sensors. Though the sensors show a different color change with F⁻ in organic medium via H-bond formation, they are highly selective towards CN⁻ as shown in the relay experiment as well as when they are added together. A novel attempt is made to explain the effect of substituents on the sensing behavior by carrying out “Structure–Reactivity Correlation” using Hammett's substituent constants (σ_p).