Synthesis of novel colorimetric probe molecules and their application in anion recognition based on strong hydrogen bond

A novel pair of ferrocene-containing azobenzene-based probe molecules, which behave as a selective probe for sensing fluoride and dihydrogen phosphate in colorimetric systems (even by naked eye), were designed. The probe 2 (N ,N ′-bisamideazophenyl-ferrocene) showed a high selectivity toward F− and −H24POH2PO4− with a color change from yellow to salmon pink without any interference from other ions. Meanwhile, the probe 1 (4-amideferrocenylazobenzene) showed only high selectivity for F− with a color change from yellow to salmon pink without any interference from other ions.