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 H-1 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- (K-a = 5.96 x 10(3) 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. (C) 2010 Elsevier B.V. All rights reserved.