Lanthanide luminescence fascinates with a 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 4f 5 system has numerous absorption and emission lines in the visible and infrared parts 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 structures of the samarium(III) solvates in DMSO, MeOH, and water are different.

The formation of the two title compounds, Na3[Sm(DPA)3]·14H2O trisodium tris(pyridine-2,6-dicarboxylato-κ3 O 2,N,O 6)samarate(III) tetradecahydrate, Na3[Sm(C7H3NO4)3]·14H2O, and catena-poly[[[diaqua(6-carboxypyridine-2-carboxylato-κ3 O 2,N,O 6)samarium(III)]-μ-pyridine-2,6-dicarboxylato-κ4 O 2,N,O 6:O 2] 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.

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.