Simple and efficient sensors 1 and

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.