Efficient and Simple Colorimetric Fluoride Ion Sensor Based on Receptors Having Urea and Thiourea Binding Sites^†

Novel colorimetric receptors for selective fluoride ion sensing containing anthraquinone as chromogenic signaling subunit and urea (N,N‘ ‘-(9,10-dihydro-9,10-dioxo-1,2-anthracenediyl)bis[N‘-phenyl])/thiourea (N,N‘ ‘-(9,10-dihydro-9,10-dihydro-9,10-dioxo-1,2-antrhacenediyl)bis[N-phenyl]) binding sites have been reported. These receptors have shown no affinity for other halide ions (Cl^-, Br^-, and I^- ions). Well-defined color change in the visible region of the spectrum was observed upon addition of fluoride ion in DMSO/CH₃CN solution of the receptors 1 and 2.