Synthesis, Characterization, and Properties of an Open-Framework Iron(III) Dicarboxylate:  MIL-85 or FeIII₂O{O₂C−CH₃}₂{O₂C−C₆H₄−CO₂}·2CH₃OH

A new three-dimensional iron(III) dicarboxylate, MIL-85 or Fe III 2 O{O 2 C−CH 3 } 2 {O 2 C−C 6 H 4 −CO 2 }·2CH 3 OH, has been obtained under solvothermal conditions, and its structure was determined using X-ray powder diffraction data. Its chiral framework is built up from helical chains of iron(III) octahedra linked through terephthalate dianions. This creates a three-dimensional structure with an array of 1-D small-pore channels filled with free and bound methanol moieties. The thermal behavior has been investigated using TGA, and X-ray thermodiffractometry indicates that MIL-85 is stable up to 275 °C with a fully reversible departure of solvent process. When the free and bound solvent molecules are removed, a nanoporous solid with a Langmuir surface area of 110 m 2 /g is obtained. Mössbauer spectrometry confirms the presence of high-spin-state Fe 3+ within the structure and a change in the iron environment upon solvent departure. Finally, one can conclude from magnetic data that MIL-85 exhibits a frustrated magnetic behavior in the low-temperature range. Crystal data for MIL-85: hexagonal space group P 6 1 (nο. 169) with a = 11.045 (1) Å, c = 18.823 (1) Å, and Z = 6.