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(CF 3CO 2) 3· (C 8He 16O 4), Ln = La, Ce, Pr; [Ln(CF 3CO 2) 3] 3· (C 8H 16O 4) 2, Ln = Pr, Eu, Er; [Ln(CF 3CO 2) 3] 2· (C 8H 16O 4), Ln = Pr, Nd, Sm; [Ln(CF 3CO 2) 3] 2· (C 10H 20O 5), Ln = LaEu; Ln(CF 3CO 2) 3·(C 12H 24O 6), Ln = LaEu; [Ln(CF 3CO 2) 3] 2·(C 12H 24O 6), Ln = Y, EuEr, 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 [Ln 2(CF 3CO 2) 3(OH)(C 10H 20O 5) 2] [Ln 2(CF 3CO 2) 8]. The vibrational spectra confirm the coordination of the coronands; the Δν as(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(CF 3CO 2) 3·3H 2O 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(CF 3CO 2) 3 generates an emission spectrum with broad bands and probably contains several, closely related polymeric species. The spectrum of [Eu(CF 3CO 2) 3] 2(C 10H 20O 5) is consistent with the presence of two chemically different sites for Eu(III); the emission bands are broad. The double salt AgEu(CF 3CO 2) 4·3CH 3CN has also been investigated; the observed transitions point to the presence of a species with idealized D 2 d symmetry. The emission spectrum of [Eu(CF 3CO 2) 3] 2(C 12H 24O 6) 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 β 1 is greater than 6 for both complexes; it is equal to 4.4 for the samarium 1:1 complex with 18-crown-6 ether.