Crystal structures of two SmIII complexes with dipicolinate [DPA]2− ligands: comparison of luminescent properties of products obtained at different pH values

The formation of the two title compounds, Na3[Sm(DPA)3]·14H2O trisodium tris(pyridine-2,6-dicarboxylato-κ3O2,N,O6)samarate(III) tetradecahydrate, Na3[Sm(C7H3NO4)3]·14H2O, and catena-poly[[[diaqua(6-carboxypyridine-2-carboxylato-κ3O2,N,O6)samarium(III)]-μ-pyridine-2,6-dicarboxylato-κ4O2,N,O6:O2] tetrahydrate], {[Sm(C7H3NO4)(C7H4NO4)(H2O)2]·4H2O}n, depends on the pH value adjusted with NaOH solution. In both crystal structures, the coordination spheres of the SmIII cations were found to be best described by a tricapped trigonal prism (TTP), with a more regular O6N3 donor set for Na3[Sm(DPA)3]·14H2O than that of O7N2 for [Sm(DPA)(HDPA)(H2O)2]·4H2O. The supramolecular features of both crystal structures are dominated by O—H...O hydrogen bonds between water molecules and the O atoms of the dipicolinato ligands. Samples were made from solutions at pH = 2, pH = 5, pH = 7, and pH = 10, and the crystals present in each sample were ground to a powder. The powder samples were analyzed with powder X-ray diffraction and luminescence spectroscopy. The splitting of the bands in the luminescence spectra recorded on powders at 77 K was observed to vary with the pH

Impact of Symmetry and Donor Set on the Electronic Energy Levels in Nine-coordinated Eu(III) and Sm(III) Crystals Structures Determined from Single Crystal Luminescence Spectra

Lanthanide luminescence is characterised by “forbidden” 4f-4f transitions and a complicated electronic structure. Our understanding of trivalent lanthanide(III) ions luminescence is centered on Eu3+ because absorbing and emitting transition in Eu3+ occur from a single electronic energy levels. In Sm3+ both absorpbing and emitting multiplets have a larger multiplicity. A transition from the first emitting state multiplet to the ground state multiplet will result in nine lines for a Sm3+ complex. In this study, high resolution emission and excitation spectra were used to determine the electronic energy levels for the ground state multiplet and first excited state multiplet in four Sm3+ compounds with varying donor set and site symmetry. This was achieved by the use of Boltzmann distribution population analysis and experimentally determined transition probabilities from emission and excitation spectra. Using this analysis it was possible to show the effect of changing three oxygen atoms with three nitrogen atoms in the tricapping donor set for compounds with the same Trigonal Tricapped Prism (TTP) site symmetry on the crystal field splitting in both Eu3+ and Sm3+ crystals. This work celebrates the 40 year annivesary for the first report of [Eu(ODA)3]3- luminescence by Kirby and Richardson

Electronic Energy Levels and Optical Transitions in Samarium(III) Solvates

Lanthanide luminescence fascinates with complicated electronic structure and ’forbidden’ transitions. By studying the photophysics of lanthanide(III) solvates, a close to ideal average coordination geometry can be used to map both electronic energy levels and transition probabilities. Some lanthanide(III) ions are simpler to study than others, and samarium(III) belongs to the more difficult ones. The 4f5 system has numerous absorption and emission lines in the visible and infrared part of the spectrum, and in this work the energy levels giving rise to these transitions were mapped, the transition probability between them was calculated, and it was shown that the electronic structure of the samarium(III) solvates in DMSO, MeOH and water are different