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. ORCID: https://orcid.org/0000-0001-8821-0851, 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: 03 Oct 2022 04:22
URI: https://ueaeprints.uea.ac.uk/id/eprint/31440
DOI: 10.1021/ic990683n

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