【Abstract】 N,N-Bis(2-pyridylmethyl)-amine-N-ethyl-2-pyridine-2-carboxamide was synthesized and characterized according to the literature. At 25 ℃, I=0.1 mol/L KNO 3, the stability constants of the binary system formed by the ligand with metal ions in ethanol aqueous solution were studied by pH potentiometric titration and the appropriate structures with respect to the titration species were proposed. The results show that the stability order of divalent metals binding to the ligand is Co<Ni>Cu<Zn which does not conform to the order of the Irving-Williams series. Then the abnormal property of copper complex is discussed.更多还原