Synthesis and anion recognition studies of a dipodal thiourea-based sensor for anions

A new dipodal thiourea-based sensor (L) has been synthesized and its binding affinity toward a variety of anions has been investigated in solution and solid state. The colorimetric studies show a significant color change of L in the presence of fluoride, dihydrogen phosphate, and acetate in DMSO. The data obtained from UV–vis titrations is consistent with the results of the colorimetric observations. As investigated by 1H NMR titrations, the sensor binds an anion in a 1:1 binding mode showing the binding trend in the order of F− > Cl− > Br− > I− for halides and H 2 PO 4 - > CH 3 COO - , SO 4 2 - > HSO 4 - > NO 3 - , ClO 4 - for oxoanions. The data demonstrates that the binding is primarily influenced by the basicity of anions.