N,N′-Ethylenediaminobis(benzylphosphonic acids) as a potent class of chelators for metal ions

Aminophosphonates were found to be effective metal ion chelators. Ethylenediamine (EN) itself binds strongly to a series of metal ions forming efficient five-membered chelate ring using two nitrogen donors. Combination of EN with phosphonate function results in the family of low molecular chelating agents. Introduction of a pyridine moiety into EN–phosphonate structure results in the very effective ligands involving a four-nitrogen donor set to coordinate the metal ion. In this work, the potentiometric and spectroscopic data for two analogues 2,2′-(ethylenedi-imino)bis(3-pyridylphosphonic-acid) – L2 and 2,2′-(ethylenedi-imino)bis(2-pyridyl-phosphonic-acid) – L3, comprising EN, two phosphonates and two pyridines with Cu(II), Ni(II) and Zn(II) ions are presented showing very high efficacy of one of the ligands studied.