Conductometric, spectrophotometric, ~1HNMR and quantum chemical studies of the thermodynamics complexation of some transition metal ions with aza-15-crown-5 ligands in acetonitrile solution

摘要

Inlhis paper, the complexation reactions between aza-15-crown-5 (A15C5) ligand with Zn~(2+)Hg~(2+), Co~(2+), Ag~+and Cd~(2+) ions has been studied by con-ductometric and spectrophotometric methods in acetonitrile solution at various temperatures; The formation constants of the resulting 1:1 com-plexes were calculated from the computer fitting of the molar conductance-mole ratio data at different temperatures. At 25°C, the order of stability of the 1:1 complexes of the A15C5 ligand with different cations are as Hg~(2+)> Co~(2+)> Cd~(2+)> Zn~(2+)> Ag~+. The enthalpy and entropy changes of the complexation reactions were evaluated from the temperature dependence of formation constants. In addition, 'HNMR study of complexes of nitrate salt of Cd+2 in acetonitrile with A 15C5 ligand at 25°C has been also undertaken to compare the results with those obtained by conductivity and UV measurements, which have been found to be in good agreement with each other. Finally, ab initio studies of the level of HF/lanl2dz have been done to investigate the binding energies of the ligand with Ag~+ and Hg~(2+). All theoretical data are in line with the experimental ones.