A novel chromo- and fluorogenic dual responding H2PO4− receptor based on an azo derivative

A simple, novel anion receptor based on 4-hydroxy-3-(N-phenyl-thiourea-N′-nitrilo-methylidynyl)-azobenzene with hybrid –OH and thiourea binding sites was synthesized and characterized. Anion binding character was determined using visual inspection, UV–vis, fluorescence and 1H NMR analyses. The addition of F−, AcO− and H2PO4− resulted in a marked red shift of the charge-transfer absorbance band (Δλ = 140 nm, from 340 nm to 480 nm) accompanied by a color change from light yellow to orange.