Synthesis and anion recognition studies of novel bis (4-hydroxycoumarin) methane azo dyes

• New bis (4-hydroxycoumarin) methane azo dyes were synthesized for anion sensor evaluation.
• It is a very good naked eye detection sensor.
• Naked-eyes detectable color changes for acetate and fluoride were realized successfully in aqueous solution.

Four new bis (4-hydroxycoumarin) methane azo dyes were synthesized by the condensation of 4-hydroxycoumarin with four different azo salicylaldehydes and their structures were characterized by FT-IR, 1H NMR, 13C NMR, HRMS. Anion binding ability in dimethyl sulfoxide (DMSO) solutions with tetrabutylammonium (TBA) salts (F−, Cl−, Br−, I−, AcO− and H2PO4−) was investigated by the naked eye, as well as UV–visible spectroscopy. The sensor shows selective recognition towards fluoride and acetate. The binding affinity of the sensors with fluoride and acetate was calculated using UV–visible spectroscopic technique.

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