Several hemicyanine dyes as fluorescence chemosensors for cyanide anions.

Four hemicyanine dyes as chemosensors for cyanide anions were synthesized easily. Their photophysical properties and recognition properties for cyanide anions were investigated. The results indicate that all the dyes can recognize cyanide anions with obvious color, absorption and fluorescence change. The recognition mechanism analysis basing on in situ 1H NMR and Job plot data indicates that to the compounds with hydroxyl group, the recognition mechanism is intramolecular hydrogen bonding interaction. However, to the compounds without hydroxyl group, cyanide anion is bonded to carbon–carbon double bond in conjugated bridge and induces N+CH3 to neutral NCH3. Fluorescence of the compounds is almost quenched upon the addition of cyanide anions.