Influence of outer-sphere anions in europium tetrahydrofuran-2-carboxylates on the Eu3+ luminescence center, analyzed by methods of X-ray diffraction and optical spectroscopy

• Published in: Polyhedron Vol. 56; pp. 109 - 115
• Main Authors: Zhuravlev, K.P., Vologzhanina, A.V., Kudryashova, V.A., Klemenkova, Z.S., Tsaryuk, V.I.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 12-06-2013
• Subjects: Eu3; IR spectra; Luminescence; Tb3; Tetrahydrofuran-2-carboxylate; X-ray crystal structure; Eu3; X-ray crystal structure; IR spectra; Tb3; Luminescence; Tetrahydrofuran-2-carboxylate
• ISSN: 0277-5387
• DOI: 10.1016/j.poly.2013.03.059

Crystal structures for four new Eu and Tb compounds. An increase of the distortions of the Eu coordination polyhedron with the size of the counterion. An extra splitting of the 7FJ states under distortions of the Eu3+ nearest surroundings. A growing influence of the crystal field components of the second and fourth ranks. [Display omitted]
Five new lanthanide tetrahydrofuran-2-carboxylate (THFC) complexes [Ln(THFC)2(H2O)2]·L·H2O (Ln=Eu; L=Cl−, Br−, NO3− and Ln=Tb; L=Cl−, NO3−) have been synthesized. The crystal structures of four compounds were solved by the X-ray diffraction method. The Ln3+ ions are coordinated to eight oxygen atoms: six oxygen atoms are provided by two tridentate bridging-cyclic THFC ligands, and the other two by water molecules. The Ln3+ coordination polyhedron can be described as a distorted square antiprism. The structures consist of planar layers linked by hydrogen bonds through outer-sphere L anions and H2O molecules. The influence of the L anion on the Eu3+ luminescence center is analyzed with the help of luminescence and IR vibrational spectroscopy. The distortions of the square antiprism increase with the size of the L outer-sphere anions. Consequently, the lowering of the symmetry of the crystal field around the Eu3+ ion appears as an extra splitting of the 7FJ levels under the influence of the crystal field components of the second and fourth ranks.