Wydział Chemii

Natalia Pawlak

Grażyna Oczko

Przemysław Starynowicz

2015

Polyhedron

101

152-159

10.1016/j.poly.2015.08.037

Naukowa

Angielski

Artykuł

The complexation of trivalent lanthanides with fumaric acid was studied. Monocrystals of Ln₂(C₄O₄H₂)₃·8H₂O (Ln = Sm, Eu, Nd) and Er₂(C₄O₄H₂)₃·12H₂O were formed during the slow evaporation of appropriate aqueous solutions. The spectroscopic investigations were performed for samarium(III) fumarate, and the crystal structures were solved for the samarium(III) (1), europium(III) (2), neodymium(III) (3), and erbium(III) (4) complexes. It was found that the Nd, Eu, and Sm fumarates were isostructural (space group

), but the Er compound was different (space group P2₁/c). In the three former crystals, there is one symmetry-independent Ln(III) cation, which adopts a 9-coordinate geometry with six oxygen atoms from the carboxylate groups and three oxygen atoms from water molecules. In the Er(III) complex, the metal ion is eight-coordinated (six atoms from the fumarate carboxyl groups and two water molecules). In all four crystals, 3-dimensional polymeric structures are formed. For Sm(III) fumarate, electronic (absorption and emission) spectra were recorded at room and low temperatures. In the emission spectra at 293 K and 77 K, peaks correspond to four J levels of the ⁶H_J term (J = 5/2, 7/2, 9/2, 11/2), and these transitions split at 77 K indicating the low symmetry of the Sm³⁺ ion. The most intense transition in UV–Vis is the hypersensitive ⁴G_5/2 → ⁶H_9/2 transition, and the I(⁴G_5/2 → ⁶H_9/2)/I(⁴G_5/2 → ⁶H_5/2) (η_Sm) ratio was calculated.

The nephelauxetic ratio β and Sinha’s parameter σ, calculated on the basis of the absorption spectra, suggested the decrease in the “degree of covalency” of the Sm–O bond from Sm maleate to Sm fumarate.

samarium, fumarate complexes, crystal structure, UV-Vis spectroscopy, covalency

http://dx.doi.org/10.1016/j.poly.2015.08.037

http://www.elsevier.com