Bis-thiourea receptors for detection and quantification of anions and salts of biological and environmental importance

Due to the importance of the anions and diverse salts in biology and the environment, there exists a great interest for the molecular recognition of these species. Within this respect, the fluorescence technique is a good tool for their detection and quantification. In this work, we report on the synthesis and characterization of two new bisthiourea receptors, Rec1 and Rec2, as well as the molecular recognition studies in DMSO between these systems and the anions F-, Cl-, Br-, I-, NO3-, CH3COO-, HSO4- and H2PO4-, as their tetraalkylammonium salts. Additionally, the alkali metal salts NaF, NaCl, KCl, LiCl, KI, Na2HPO4 and Na2SO4 were studied in DMSO: water (95: 5 v/v). All of these studies were performed by the microplate fluorescence technique. Both receptors showed better affinities and spectral responses towards the salts of basic anions. From the fluorescence response of Rec1 and Rec2, were obtained the quantification and detection limits for NaCH3COO, Na2SO4, Na2HPO4 and NaF salts, being this latter quantifiable in similar concentrations to those established by the official Mexican standards for drinking water. Because of this, quantification of fluoride by Rec1 and Rec2 could be applied in aqueous and food samples.