Synthesis of 4-Nitrophenylthiosemicarbazone of Salicylaldehyde and its Colorimetric Anion Recognition Properties

An efficient colorimetric anion sensor, N 4 -nitrophenylthiosemicarbazone of salicylaldehyde, behaves with a good selectivity and sensitivity in the recognition for F - anions by naked eye observations and UV–Vis spectral changes in DMSO. The colour of the solution containing the sensor had an obvious change from colourless to purple only after the addition of F - in DMSO while other anions did not cause obvious colour changes. The sensor reacted with F - to form a stable complex and the association constant K a is calculated as 1.415×10 4 M −1 .