Coordination compounds of divalent lanthanides with crown ethers

Abstract

New complexes LnI 2·18-crown-6 (Ln-Sm, Tm, Dy, Nd) and LnJ 2·dibenzo-18-crown-6 (Ln-Sm, Tm) were synthesized using the solutions of LnI 2 in THF. The compounds obtained oxidize quickly in air, but are relatively stable in an inert atmosphere. The Tm 2+ complex is decomposed by light. The compounds obtained are poorly soluble in THF, the Sm 2+ and Tm 2+ compounds are soluble in CH 3CN, forming solutions with a period of half oxidation of 170 h and 6 min, respectively. Iodide ions of the complexes can be substituted for Cl − during treatment of the compounds by solution of LiCl in THF. The reflection spectra of the compounds synthesized are similar to the absorption spectra of Ln 2+ in THF, although a shift of bands towards the short wave region is observed. The study of the Ln 2+ oxidation kinetics in H 2O, CH 3CN, THF in the presence of crown ethers has shown that their stability is influenced not only by the type of solvent, relative solubility and stability of complexes Ln 2+ and Ln 3+, but also by phenyl groups, and by decreasing stability of Dy 2+ and Nd 2+.