[00.2] INORGANIC CHEMISTRY 39: (10) 2033-2041 MAY 15 2000
Calixarenes as selective extracting agents. An NMR dynamic and conformational investigation of the lanthanide(III) and thorium(IV) complexes
B. Lambert, V. Jacques, A. Shivanyuk, S. E. Matthews, A. Tunayar, M. Baaden, G. Wipff 2,*, V. Böhmer 3,*, J.-F. Desreux1,*
The lanthanide and Th4+ complexes with calixarene ligands substituted either on the narrow or at the wide rim by four coordinating groups behave totally differently as shown by an NMR investigation of the dia- and paramagnetic complexes. Solutions of complexes were prepared by reacting anhydrous metal perchlorate salts with the ligands in dry acetonitrile (CAUTION). Relaxation time T-1 titrations of acetonitrile solutions of Gd3+ by calixarenes indicate that ligands substituted on the narrow rim form stable 1:1 complexes whether they feature four amide groups (1) or four phosphine oxide functions. In contrast, a ligand substituted by four (carbamoylmethyl)diphenylphosphine oxide moieties on the wide rim (3) and its derivatives form polymeric species even at a 1:1 ligand/metal concentration ratio. Nuclear magnetic relaxation dispersion (NMRD) curves (relaxation rates 1/T-1 vs magnetic field strength) of Gd3+, Gd3+.1 and Gd3+.3 perchlorates in acetonitrile are analyzed by an extended version of the Solomon-Bloembergen-Morgan equations. A comparison of the calculated rotational correlation times tau(r) shows that ligand 3 forms oligomeric Gd3+ species. The chelates of ligand 1 are axially symmetric (C-4 symmetry), and the paramagnetic shifts induced by the Yb3+ ion are accounted for quantitatively. The addition of water or of nitrate ions does not modify the geometry of the complex. The metal chelates of 3 and its derivatives adopt a C-2 symmetry, and the paramagnetic shifts are interpreted on a semiquantitative basis only. Water and NO3- ions completely labilize the complexes of the heavy lanthanides. The very high selectivity of ligand 3 through the lanthanide series stems from a complex interplay of factors.
|Article 2000.2 (Inorg. Chem. 39, 2033)|
Correspondence should be addressed to Prof. J.-F. Desreux.
- Univ Liege, B6, B-4000 Liege, Belgium.
- CNRS, UMR 7551, Inst Chim, Lab MSM, F-67000 Strasbourg, France
- Univ Mainz, Inst Organ Chem, D-55099 Mainz, Germany.
7 times cited on 20/8/2003 (Ref. ISI Web Of Science)