| Abstract: The parent azacrown ether 1,10 -dioxa-4,7,13,16-tetraaza-18-crown-6(1) and its derivative 4,7,13,16-tetra(2-hydroxy-5-nitrobenzyl)-1,10-dioxa-4,7,13,16-tetraaza-18-crown-6(2) were synthesized and characterized via elemental analysis and 1H NMR spectroscopy. The cation binding behavior of 2 with H+, Mn2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+ and Hg2+ was evaluated by UV-Vis method in H2O-DMSO (V/V=1/4) mixed solvent, and the stability constants of the complexes were determined. The results indicate that azacrown ether 2 has strong absorption peak alone in the vicinity of 316 nm at pH<7.96. While pH>7.96 in the system, a new absorption band can be observed around 400 nm which is probably a charge transfer band, and its peak position is shifted toward longer wavelength, the absorption intensity is increased gradually with increasing pH value. The peak position of 2 around 400 nm is shifted appreciably toward shorter wavelength when a transition metal ion addition to 2. Thus the formation of the complex is verified at a range of pH values(for example Ni2+, 5.62 selectively binds Mn2+ over other transition metals. The ligand also forms more stable complexes with Co2+, Ni2+, Cu2+ and Zn2+ than with Cd2+and Hg2+. |
