A ditopic colorimetric sensor for fluoride ion based on thiourea mercury complex

A novel ditopic chromogenic receptor, N-5-(8-hydroxy)quinoline-N′-4′-nitro-phenyl thiourea (1), was synthesized. The metal complex 1-Hg2+ showed sensitive and highly selective responses to F− over other anions such as CH3CO2−, H2PO4−, HSO4− and Cl−. 1-Hg2+–F− complex formed, which promoted the intramolecular charge transfer and led to a dramatic spectral change. The color of 1-Hg2+ solution changed from colorless to red upon addition of F−. Thus, a colorimetric assay of F− was developed in acetonitrile by naked-eye detection. F− behaved linearly in the 8.0 × 10−6 to 2.0 × 10−5 mol L−1 concentration range with LOD as 1.4 × 10−6 mol L−1.