Naphthalene based colorimetric sensor for bioactive anions: Experimental and DFT study

A simple anion selective colorimetric sensor L has been designed by combining 2-hydroxy-1-naphthaldehyde with 2-aminothiophenol. Sensor L portrayed a necked-eye detectable color change from light green to red upon addition of AcO−, F− and H2PO4- anions in CH3CN, where as no significant color change was observed upon addition of other anions such as Cl−, Br−, I− and HSO4-. Sensor L showed selectivity towards AcO− under competitive environment, with a detection limit (3σ/S) down to 1.1 × 10−7 M. In addition, the anion sensing ability of L was explored in mixed H2O/CH3CN (v/v) medium. Further, the nature of interactions between the sensor L and AcO− was investigated by 1H NMR and the probable structure of the L-AcO− complex was predicted by B3LYP/6-31G(d,p) method.