Calix[4]arenes as selective extracting agents. An NMR dynamic and conformational investigation of the lanthanide(III) and thorium(IV) complexes

Lambert, Bernard, Jacques, Vincent, Shivanyuk, Alexander, Matthews, Susan E., Tunayar, Abdi, Baaden, Marc, Wipff, Georges, Böhmer, Volker and Desreux, Jean F. (2000) Calix[4]arenes as selective extracting agents. An NMR dynamic and conformational investigation of the lanthanide(III) and thorium(IV) complexes. Inorganic Chemistry, 39 (10). pp. 2033-2041. ISSN 0020-1669

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Abstract

The lanthanide and Th4+ complexes with calix[4]arene 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.

Item Type: Article
Uncontrolled Keywords: actinides,rare example,calixarenes,behavior,nitrates,metal perchlorates,acetamide,ions,macrocycle,molecular mechanics
Faculty \ School: Faculty of Science > School of Pharmacy
Depositing User: Rachel Smith
Date Deposited: 26 May 2011 12:06
Last Modified: 21 Apr 2020 21:17
URI: https://ueaeprints.uea.ac.uk/id/eprint/31440
DOI: 10.1021/ic990683n

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