Tetrad effects in mixed ligand lanthanide chelates. Part I: Lanthanide, EDTA/NTA, IMDA ternary systems

The occurrence of tetrad effects has been studied for the variations in formation constants (logK _MAL ^MA ) of the mixed ligand complexes of the type Ln(III).A.L.] (where Ln(III)=La(III), Ce(III), Pr(III), Nd(III), Sm(III), Eu(III), Gd(III), Tb(III) or Dy(III); A=EDTA or NTA; L=IMDA), with the number of 4f electrons of the tervalent lanthanides. A differential plot method has been suggested for locating the (minor) breaks at the 4f ³–4f ⁴ and 4f ¹⁰–4f ¹¹ stages in the Ln(III) series.