Simple azo-based salicylaldimine as colorimetric and fluorescent probe for detecting anions in semi-aqueous medium

A series of novel, highly sensitive, and selective azo-based anion sensors 13 have been designed and synthesized from the condensation reaction between 4-amino azo benzene and three different aldehydes. The structure of the sensors 13 were confirmed by IR, HRMS, 1H NMR, and 13C NMR spectroscopic methods. Colorimetric naked-eye analysis revealed the anion detection by receptors 2 and 3 as color changes from yellow to pink and yellow to orange, respectively. Anion sensing ability of all receptors was further investigated by 1H NMR titration, UV-vis experiment, and fluorescence titration. UV-vis measurements highly indicate the selective recognition of fluoride and acetate ions in 9:1 dimethyl sulfoxideH2O (v/v) for receptors 2 and 3. Binding constant value showed among all receptors, receptor 3 has strong affinity toward F and AcO in semi-aqueous medium, which is due to the presence of chromogenic signaling unit in it. The F ion detection property of receptor 2 in organic medium was also extended in the real sample like toothpaste. Copyright (c) 2013 John Wiley & Sons, Ltd.