Colorimetric detection of anions in aqueous media using N-monosubstituted diaminomaleonitrile-based azo-azomethine receptors: Real-life applications

• New unsymmetrical diaminomaleonitrile-based azo-azomethine dyes have been synthesized.
• The dyes can be considered as practical sensors for qualitative and quantitative detection of F− in real samples.
• The detection limit of inorganic F− in aqueous media is lower than WHO permissible level for safe drinking.

New N-monosubstituted diaminomaleonitrile-based azo-azomethine dyes have been synthesized in order to develop colorimetric sensors for detection of biologically important anions in aqueous media. Importantly, the reported sensor decorated with strong electron-withdrawing group can detect inorganic fluoride in water even at 0.037 ppm level, which is lower than WHO permissible level (below 1 ppm). Successfully, the prepared dyes were used for qualitative and quantitative detection of inorganic fluoride in toothpaste and mouthwash. The anion recognition mechanism was also investigated by detailed UV–Vis and 1H NMR experiments. The detailed 1H NMR experiments corroborated that anion recognition is based on the deprotonation phenomenon.

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