Complexes of lanthanoid salts with macrocyclic ligands. Part 25. Lanthanoid trifluoroacetate complexes with 12-crown-4, 15-crown-5, and 18-crown-6 ethers |
| |
| Authors: | Jean-Claude G Bunzli Aldo Giorgetti |
| |
| Institution: | Université de Lausanne, Institut de Chimie Minérale et Analytique, Place du Château 3, CH-I O05 Lausanne, Switzerland |
| |
| Abstract: | The lanthanoid trifluoroacetates, Ln(TFA)3, react with 12-crown-4, 15-crown-5, and 18-crown-6 ethers to give complexes with various metal:ligand ratios, 1:1, 3:2, and 2:1. The following complexes have been isolated and characterized: Ln(CF3CO2)3· (C8He16O4), Ln = La, Ce, Pr; Ln(CF3CO2)3]3· (C8H16O4)2, Ln = Pr, Eu, Er; Ln(CF3CO2)3]2· (C8H16O4), Ln = Pr, Nd, Sm; Ln(CF3CO2)3]2· (C10H20O5), Ln = La---Eu; Ln(CF3CO2)3·(C12H24O6), Ln = La---Eu; Ln(CF3CO2)3]2·(C12H24O6), Ln = Y, Eu---Er, Yb. Thermogravimetric data show that the 2:1 complexes are usually thermally more stable. The 2:1 complexes with the 15-membered polyether undergo a slow hydrolysis in the presence of traces of water, which yields the hydroxo complex Ln2(CF3CO2)3(OH)(C10H20O5)2] Ln2(CF3CO2)8]. The vibrational spectra confirm the coordination of the coronands; the Δνas(CCO) shifts are not large, which point to a moderate interaction between the polyethers and the metal ions. Magnetic susceptibilities and X-ray powder diagrams have been measured.High-resolution excitation and emission spectra have been analysed for the europium-containing compounds. The spectrum of Eu(CF3CO2)3·3H2O indicates the presence of a single species with low symmetry, in agreement with the crystal structure data for the isostructural Pr-salt. The anhydrous salt Eu(CF3CO2)3 generates an emission spectrum with broad bands and probably contains several, closely related polymeric species. The spectrum of Eu(CF3CO2)3]2(C10H20O5) is consistent with the presence of two chemically different sites for Eu(III); the emission bands are broad. The double salt AgEu(CF3CO2)4·3CH3CN has also been investigated; the observed transitions point to the presence of a species with idealized D2d symmetry. The emission spectrum of Eu(CF3CO2)3]2(C12H24O6) displays sharp bands and reveals the presence of two different sites for the metal ion with efficient energy transfers between them. One of the species may have a relatively high symmetry.In solution, all the complexes are non-electrolytes in acetonitrile and propylene carbonate and close to 1:1 electrolytes in methanol. Some dissociation occurs in acetonitrile for the 2:1 complexes with 18-crown-6 ether. On the other hand, 1H NMR spectra of the lanthanum 1:1 complexes with 12- crown-4 and 18-crown-6 ethers indicate no dissociation of the complexed polyether. Log β1 is greater than 6 for both complexes; it is equal to 4.4 for the samarium 1:1 complex with 18-crown-6 ether. |
| |
| Keywords: | Author to whom correspondence should be addressed |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
