Etude de la complexation des lanthanides trivalents par les six isomeres de l'acide diaminocyclohexanetetraacetique: Partie 1: synthèses et détermination des constantes d'acidité et des constantes de formation des complexes 1:1 avec les lanthanides trivalents de l'acide trans-1,2-diaminocyclohexane- N,N,N′,N′-tétraacétique

Abstract

( Study of the complexation of trivalent lanthanides by the six isomers of diaminocyclohexanetetraacetic acid. Part 1. Syntheses, acidity constants of trans- 1,2-diaminocyclohexane-N,N,N′,N′-tetraacetic acid, and formation constants of its 1:1 complexes.) The syntheses of five isomers (1,2 cis, 1,3 cis, 1,3 trans, 1,4 cis, 1,4 trans) of diaminocyclohexanetetraacetic acid which are not commercially available are described. For comparison with literature vlaues, potentiometric measurements of the acidity constants of the sixth isomer (1,2 trans) and of the stability constants of its 1:1 complexes with trivalent lanthanides are reported for an ionic strength of 1 (KCl) at 25°C. In contrast to some literature data, the stability constants found, plotted as a function of Z, display only one discontinuity at the level of gadolinium.