High-resolution luminescence spectroscopy of selected EU(III) ion complex salts

The luminescence spectra of solid-state europium compounds characteristically exhibit transitions having linewidths on the order of a few wavenumbers. The position and intensity of the transitions are dependent upon the type and geometric arrangement of the coordinating ligands around the Eu(III) ion. The use of the Eu(III) ion as a structural probe in organic and inorganic host environments is based on these two attributes. In the present work, a treatment of the theoretical background necessary to use the Eu(III) ion as a luminescent probe of the chemical environment and/or crystal structure is given. From group theoretical considerations, a table of the allowed ligand-field transitions for the Eu(III) ion in various site symmetries has been developed. The syntheses of solid-state salts of a wide variety of Eu(III) complex anions have been attempted. The synthetic procedures and instrumental arrangements employed are described. The luminescence spectra of those salts which could be prepared with a high degree of spectral purity are shown and interpreted so as to assign a tentative site symmetry to the Eu(III) ion. Several salts have been synthesized and spectroscopically investigated. These salts include the alkali metal, Ag (I) , Tl(I), and Ca(II) salts of the europium(ethylenediaminetetraacetate) anion and the Ag(I) and Tl(I) salts of the europium(diethylenetriaminepentaacetate) anion. In addition, the Tl(I) and K(I) salts of the europium(triethylenetetraminehexaacetate) anion, the Tl(I) salt of the europium tris(2,6-pyridinedicarboxylate) anion, and the Li(I) salt of the europium bis(nitrilotriacetate) anion have been studied. The Ag(I) and Tl(I) salts are novel in that they permit the study of interactions between "soft" counterions and lanthanide complex anions.