Stability constants of europium complexes with a nitrogen heterocycle substituted methane-1,1-diphosphonic acid

[摘要] Even in moderately acidic solutions ([H+]>0.01 M), N-piperidinomethane-1,1-diphosphonic acid (H(4)PMDPA) is a strong complexant of trivalent lanthanide ions that shows enhanced complex solubility over previously studied 1,1-diphosphonic acids. The protonation constants of PMDPA in 2.0 M H/NaClO4 were determined by potentiometric and NMR titrations, and the stability constants for the formation of complexes with Eu3+ were determined by solvent extraction. The difference in protonation equilibria induced by the addition of the nitrogen heterocycle results in an increase in the complexation strength of PMDPA. In solutions containing 0.1 M H+ and ligand concentrations greater than 0.02 M, PMDPA is the most effective 1,1-diphosphonic acid for europium complexation studied thus far.

[发布日期] 1997-03-15

[效力级别]  Proceedings Paper

[关键词] europium;phosphonic acids;stability constants;protonation constants;solvent extraction