‘Naked-eye’ detection of fluoride and acetate anions by using simple and efficient urea and thiourea based colorimetric sensors

Simple and efficient sensors 1 and 2 possessing azo and nitrophenyl as signaling units and urea and thiourea moieties as binding sites were designed and synthesized. These sensors were characterized by combination of 1H, 13C, APT, COSY NMR, FTIR, elemental analysis, and UV–vis spectral data. The interaction and colorimetric sensing properties of receptor 1 and 2 with different anions were investigated by the naked eye, as well as UV–visible and 1H NMR experiments. It was found that the receptor 1 and 2 are highly selective toward fluoride and acetate anions in CHCl3.