Synthesis, characterisation and properties of a new three-dimensional Yttrium-Europium coordination polymer

A new three-dimensional europium-doped Yttrium(III) tricarboxylate, MIL-92LT(1) or Y1-xEux (H2O)(2) {C6H3-(CO2)(3)} (x similar to 0.03) (LT: Low Temperature) has been synthesised hydrothermally. Its three-dimensional structure, determined using X-ray powder diffraction data, is built-up from isolated eight coordinated Ln(III) monocapped square antiprisms (Ln = Y, Eu) linked through carboxylate moieties. Its thermal behaviour, investigated using TGA and X-ray thermodiffractometry indicates that dehydration is irreversible giving the solid MIL-92(HT) or Y1-xEux {C6H3-(CO2)(3)} (x similar to 0.03) (HT: High Temperature). It induces a change in the connection mode of the carboxylate and a decrease in the coordination number of the rare-earth leading to an unusual octahedral environment for the rare-earth cation. After a structural analysis of the reconstructive phase transition, the optical properties of these solids have been investigated and show that dehydration leads to a strong increase in the optical output. Crystal data for MIL-92(LT): monoclinic space group C2/c (n degrees 15) with a = 16.428 (1) angstrom, b = 6.071 (1) angstrom, c = 20.404(l) angstrom, beta = 95.31(3)degrees and Z = 2. Crystal data for MIL-92(HT): monoclinic space group C2/c (n degrees 15) with a = 17.390(1) angstrom, b = 5.521 (1) angstrom, c = 19.487(1) angstrom, beta = 105.35 (2)degrees and Z = 2. (c) 2005 Elsevier SAS. All rights reserved.