Amide-based tripodal receptors for selective anion recognition

In order to improve efficiency and reduce waste production; the microwaves offer mild methods to prepare amides based neutral tripodals receptors directly from non activated carboxylic acids and amines in the absences of coupling reagents and solvents, with high yield and very short time. The preliminary 1H NMR titration experiments revealed that tripodals receptor 1 and 2 can recognize H2PO4 − and C6H5CO2 − through a 1:1 binding-stoichiometry in preference over other anions (PF6 −, ClO4 −, HSO4 − and Br−). The tripodal receptor 2 showed higher binding to the all examined anions than the tripodal receptor 1.