J. Phys. IV France 7 (1997) C2-641-C2-642
Temperature and pH Dependence of Gd-DOTA and Gd-DTPA Complexes Dissociation Studied by EXAFSS. Bénazeth1, 2, M.C. Chalbot1, J. Purans2, 3, K. Nguyen4, L. Nicolas4, C. Souleau2 and A. Gaudemer4
1 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
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