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

Abstract

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.

Mapping the distribution of electronic states within the 5D4 and 7F6 levels of Tb3+ complexes with optical spectroscopy

“…Over the last decade, we have used molecular photophysics to revisit the electronic structure of several lanthanide ions. 23,[29][30][31][32][33][34][35][36][37][38][39][40] Due to the reasons laid out above, the focus has been on Eu(III) in particular, where the correlation between molecular structure and photophysics has been investigated in detail for both sensitized europium luminescence, 31,41,42 and direct excitation. 29,36,37 While others have aimed to optimize e.g.…”

“…23,33,[35][36][37]39 We have revisited complexes of Eu(III) with dipicolinate. 36,40,48 We have determined quantum yields of luminescence and the radiative rate constants. 23,29,37 We have investigated the relationship between electronic structure and molecular structure of Dy(III), Sm(III), Yb(III), and Nd(III), 33,35,37,39 and now we turn to Tb(III).…”