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

A new three-dimensional europium-doped Yttrium(III) tricarboxylate, MIL-92LT1 or Y1−xEux(H2O)2{C6H3(CO2)3} (x∼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-92HT or Y1−xEux{C6H3(CO2)3} (x∼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-92LT: monoclinic space group C2/c (n° 15) with a=16.428(1) Å, b=6.071(1) Å, c=20.404(1) Å, β=95.31(3)° and Z=2. Crystal data for MIL-92HT: monoclinic space group C2/c (n° 15) with a=17.390(1) Å, b=5.521(1) Å, c=19.487(1) Å, β=105.35(2)° and Z=2.