Study on the selectivity of anion receptors by adjusting the distance of two urea fragments and their analytical application

Three anion receptors based on urea: 1 N, N'-bis-(p-nitrophenylaminocarbonyl)-Hydrazine, 2 N, N'-bis-(p-nitrophenylaminocar-bonyl)-ethylenediamine and 3 N, N'-bis-(p-nitrophenylaminocarbonyl)-1, 3-propane-diamine are designed and synthesized. Studies of UV-vis spectra presented that 1 was an excellent sensor of F- and 2 was sensitive to H2PO4 (-). Unfortunately, 3 can not distinguish the anions investigated in this paper. The color changes of the hosts upon the addition of a variety of structurally different anions were also utilized as naked-eye detection which is very convenient. It also revealed significantly that the distance between two recognition sites of receptor had an immediate effect on the selectivity of receptor for anions, which had been confirmed by the H-1 NMR titration and IR.