Proceedings of the 9th International Conference on X-Ray Absorption Fine Structure

J. Phys. IV France 7 (1997) C2-641-C2-642
DOI: 10.1051/jp4/1997127

Temperature and pH Dependence of Gd-DOTA and Gd-DTPA Complexes Dissociation Studied by EXAFS

S. Bénazeth^{1, 2}, M.C. Chalbot¹, J. Purans^{2, 3}, K. Nguyen⁴, L. Nicolas⁴, C. Souleau² and A. Gaudemer<sup>4

1</sup>  LURE, Bât. 209D, Université Paris Sud, 91405 Orsay, France
²  Laboratoire de Chimie Inorganique, UFR Pharmacie-Université Paris XI, 92296 Paris, France
³  Institute of Solid State Physics, University of Latvia-Kengaraga 8, 1063 Riga, Latvia
⁴  Laboratoire de Chimie Bioorganique et Bioinorganique, Bât. 420, Université Paris Sud, 91405 Orsay, France

Abstract
The Gd L3-edge of Gd(DTPA)^2- and Gd(DOTA)^- complexes, in crystalline state and aqueous solutions presenting various pH (0.15-8) at different temperatures (25-90 °C), are investigated by XAFS experiments. For the Gd(DTPA)^- complexes we observe a strong pH (0.15-1.5) dependence of XAFS signals. On the other hand, the XAFS signals of Gd(DOTA)^- complexes exhibit a light pH (1-1.5) dependence and for pH<l we observe a ligand decomposition. Concerning both complexes, we note just a light temperature dependence. To obtain information about the short and medium range order (up to 5 Å), multiple scattering calculation is performed. For the first coordination shell, we apply multi-shell fitting and RDF reconstruction. The comparative XAFS and XRD results are discussed, and some discrepancies with previous RMN experiments are underlined.

© EDP Sciences 1997