Fluoride ion probe based on 2-thiohydantoin

Abstract

2-Thiohydantoin derivatives 1 and 2 were synthesized by the reaction of isoleucine methyl ester hydrochloride with 4-nitro-phenyl isothiocyanate or 4-cyano-phenyl isothiocyanate. The anion sensing ability of 1 and 2 was estimated via tetra-n-butylammonium (TBA) salts of a series of anions in N, N-dimethyl formamide (DMF). After the addition of F-, the color of the DMF solution of 1 and 2 immediately changes from colorless to yellow, while the color of solution changes slightly by the addition of Cl-, HSO4-, Br-, NO3- and CH3CO2-. The experimental facts indicate that 1 and 2 exhibit high selectivity sensing ability to F-. The 1H NMR titrations of 1 and 2 reveal that the colorimetric response of 1 and 2 are triggered by the hydrogen bonding interaction between 2-thiohydantoin and F-. Binding constants confirmed that 1 is more sensible to F- than 2. Furthermore, 1 can also be used as a chemosensor for the detection of F- in test paper. © 2014 Chinese Chemical Society & SIOC, CAS.