Influence of dipicolinate ligands on the spectroscopic properties of europium(III) in solution

Absorption spectra of complexes between Eu3+ and the dipicolinate (2,6-pyridinedicarboxylate) ligand are recorded for several metal-to-ligand ratios. The influence of complexation on the spectroscopic properties of Eu3+ is studied. The complexation is reflected in the spectrum by an increase of the spectral intensities of the induced electric dipole transitions, by distinct crystal field fine structure of 2S + 1LJ manifolds with small J quantum number and by a red shift of the absorption bands. The Judd-Ofelt intensity parameters Ωλ (λ = 2, 4, 6) are determined. Special attention is given to symmetry effects in the spectra. It is illustrated how the presence or absence of the 5D0 ← 7F0 transition provides information about the site symmetry of the Eu3+ ion.