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

The formation of the two title compounds, Na(3)[Sm(DPA)(3)]·14H(2)O tris­odium tris­(pyridine-2,6-di­carboxyl­ato-κ(3) O (2),N,O (6))samarate(III) tetra­deca­hydrate, Na(3)[Sm(C(7)H(3)NO(4))(3)]·14H(2)O, and catena-poly[[[di­aqua­(6-carb­oxy­pyridine-2-carb­oxyl­ato-κ(3) O (2),N,O (6))samarium(III)]-μ-pyridine-2,6-di­carboxyl­ato-κ(4) O (2),N,O (6):O (2)] tetra­hydrate], {[Sm(C(7)H(3)NO(4))(C(7)H(4)NO(4))(H(2)O)(2)]·4H(2)O}( n ), depends on the pH value adjusted with NaOH solution. In both crystal structures, the coordination spheres of the Sm(III) cations were found to be best described by a tricapped trigonal prism (TTP), with a more regular O(6)N(3) donor set for Na(3)[Sm(DPA)(3)]·14H(2)O than that of O(7)N(2) for [Sm(DPA)(HDPA)(H(2)O)(2)]·4H(2)O. 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.