A colorimetric Schiff base chemosensor for CN− by naked-eye in aqueous solution

A highly selective colorimetric chemosensor (1) based on the combination of hydrazine and 3,5-dichloro-2-hydroxybenzaldehyde was designed and synthesized. Receptor 1 showed exclusive response toward cyanide by a color change from colorless to yellow in aqueous solution. The binding mode of 1-CN− species was determined to be a 1:1 stoichiometry through Job plot, 1H NMR titration, and ESI-mass spectrometry analysis.