Synthesis and recognition properties of a class of simple colorimetric anion chemosensors containing OH and CONH groups

Two simple colorimetric anion chemosensors 1 and 2 containing OH and CONH groups were synthesized and their recognition properties toward various anions were investigated by naked-eye observation, UV–vis and 1H NMR titration spectra. The experiment results showed that compound 1 was able to selectively recognize F− and AcO− through the formation of 1:1 hydrogen bonding complex, concomitant with a detectable color change (from colorless to pale yellow) during the recognition process. For compound 2, a noticeable color change was seen only in the case of F−, which was very similar to compound 1 in the molecular structure merely lack of a salicyloyl OH group. Additionally, compound 1 displayed a moderate binding affinity to H2PO4− (Ka = 5.96 × 103 M−1). In contrast, there were no detectable interactions between compound 2 and H2PO4−. In a word, the current studies suggested that a subtle change to receptor structure may lead to large and unpredictable differences to recognition behavior of receptor compound.