A highly selective colorimetric chemosensor for cyanide and sulfide in aqueous solution: experimental and theoretical studies

A new colorimetric chemosensor 1 was developed by a combination of 4-(p-tolyl)thiazol-2-amine and 2-hydroxy-1-naphthaldehyde. Sensor 1 showed selective colorimetric responses to CN- and S2- in aqueous solution. A clear color change of 1 from yellow to colorless was observed with CN- through a nucleophilic addition mechanism, while S2- was detected through a deprotonation mechanism with a distinct color change from yellow to orange. The binding stoichiometries of 1 with CN- and S2- were proposed to be 1:1, based on the Job plot, H-1 NMR titration and ESI-mass spectrometry analysis. Additionally, the sensing mechanisms of 1 for CN- and S2- were theoretically explained by DFT and TD-DFT calculations. Moreover, 1 could be used to quantify CN- in water samples.