I.R. and Raman spectra of europium(III) β-diketonates

Abstract

The i.r. and Raman spectra of several complexes of europium(III) β-diketonates have been observed. The β-diketones used for the preparation of the complexes include acetylacetone, trifluoroacetylacetone, benzoyltrifluoroacetone, halogen substituted benzoyltrifluoroacetones (F, Cl, and Br mono-substituted into the benzene ring at various positions), benzoylacetone, dibenzoylmethane, and some of their deuterated analogs. Interpretations of the spectra have been attempted. It has been found that all the spectra can be interpreted, to a good approximation, by considering a single chelate ring withy a local C 2 v symmetry. However, some bands observed in the i.r. and Raman spectra of europium acetylacetonate have to be interpreted with a D 3 symmetry for the configuration of the three chelate rings attached to a europium atom. Possible symmetries suggested in the literature for the configuration of four chelate rings attached to a europium atom have been considered. From the i.r. and Raman spectra of the four-ligand complexes studied, it has been found that it is quite unlikely that the four-ligand anions belong to any one of the symmetry groups C 1 h , D 4 h , D 2 d , C 4 v , and C 2 v , but they may belong to the symmetry group S 4 or C 1. Samples of europium benzoyltrifluoroacetonate have been prepared in the three-ligand and four-ligand forms. The similarity of the i.r. spectra of these samples suggests the applicability of the single chelate ring analysis. However, the Raman spectra of these samples showed striking differences indicating an approximate D 3 symmetry for the three-ligand anion. The i.r. spectra of several complexes prepared from some rare earth metals other than europium have also been studied and it has been found that the spectra are almost identical to their europium analogs.