ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

New complexanes. VI. Determination of the stability constants of the lanthanide complexes of racemic 2,3-diaminobutane-N,N,N',N'-tetraacetic acid by polarographic investigation of the exchange equilibria

V. Novák, M. Svičeková, and J. Majer

Komenský University, Bratislava

Abstract: cf. preceding abstrs. The following stability consts. were obtained at 20° and ionic strength 0.1 (KNO₃) (M³⁺ and log KML given): La, 16.68; Ce, 17.21; Pr, 17.49; Nd, 17.70; Sm, 18.32; Eu, 18.61; Gd, 8.84; Tb, 19.45; Dy, 19.93; Ho, 20.27; Er, 20.68; Tm, 20, 96; Yb, 21.29; Lu, 21.33. The title ligand (I) forms more stable complexes with trivalent lanthanide ions than meso-acid (II) (CA 64, 6071g). The difference in stability of complexes of I and II raises from 2 to 3 log units on going from La to Lu. It is caused by the presence of CH₃ groups which influences the steric arrangement, the N-N distance, and basicity of N atoms and COOH groups. Both stability consts. and the log KML vs. at. no. (Z) plots for I are very similar to those of cyclo-hexanediaminetetraacetic acid. When compared to II, the log KML vs. Z plot is steeper and the Gd break is less pronounced with I.

Full paper in Portable Document Format: 204a252.pdf (in Slovak)

Chemical Papers 20 (4) 252–260 (1966)