Structural and fluorescence studies of compounds with general formula [Ln(DMA) 3(H 2O) 6](CF 3SO 3) 3 (DMA ≡ N,N-dimethylacetamide, Ln ≡ La-Tb)

Abstract

Structural studies of the compounds in the title were carried out using X-ray diffraction and fluorescence spectroscopy. The Pr 3+ compound, isomorphous with the others, crystallizes in the monoclinic system, space group P2 1 with a = 8.617(3) A ̊ , b = 19.893(4) A ̊ , c = 11.440(3) A ̊ , β = 103.55 (3)°, V = 1906(2) A ̊ 3 , M = 967.57, Z = 2, D c = 1.67 g cm −3, λ(Mo Kα) = 0.71073 A ̊ ; μ = 1.45 mm −1, R = 0.092 for 2068 independent reflections with I > 3 σ( I). The Pr 3+ ion is coordinated to the oxygen atoms of six independent water molecules at a mean distance Pr-O = 2.57 A ̊ and to the oxygen atoms of three independent DMA groups at a mean distance of 2.43 Å. The coordination sphere around the central ion is approximately of D 3 h symmetry. The distortion towards a C 2 symmetry shown by the crystal structure determination does not seem to affect the fluorescence spectrum significantly.