Myriam Riou-Cavellec

Magnetic iron phosphates with an open framework

Abstract Despite the existence of many naturally occurring iron phosphate minerals exhibiting a rich and varied structural chemistry, the soft hydrothermal synthesis of organically templated iron phosphates has only recently become of particular interest. This results from the increasing quest for preparing new open-framework materials with potential applications in the fields of catalysis, adsorption and/or magnetic properties. This review will summarize the results concerning the synthesis, structural features and magnetic properties of all the organic–inorganic iron phosphates with a three-dimensional open framework.

[Fe2(C10O8H2)]: an antiferromagnetic 3D iron(II) carboxylate built from ferromagnetic edge-sharing octahedral chains (MIL-62).

The first three-dimensional iron(II) tetracarboxylate is built from the connection of chains of edge-sharing Fe(II) octahedra by 1,2,4,5-benzenetetracarboxylates; magnetic measurements show an antiferromagnetic coupling of ferromagnetic chains below TN = 25(1) K.

Microporous hybrid compounds: hydrothermal synthesis and characterization of two zinciomethylenediphosphonates with 3D structures, structure determination of their dehydrated forms

The ZnCl2–H2O3P-CH2-PO3H2–NaOH–H2O quaternary system was investigated under hydrothermal conditions as a function of pH (48 h; 443 K). Zn2(H2O){O3P-CH2-PO3} (labelled VSB-3(Zn)) and NaZn2(OH){O3P-CH2-PO3}·1.5H2O (labelled MIL-48) are obtained at pH 1 and 9 respectively. Their structures were solved from single crystal X-ray diffraction. Zn2(H2O){O3P-CH2-PO3}, isostructural with Co and Ni analogues previously described, is monoclinic (C 2/c (n° 15)) with lattice parameters a = 18.7573(3) A, b = 8.2803(2) A, c = 8.9225(1) A, β = 106.815(1)°, V = 1326.56(4) A3, Z = 8, R1(Fo) = 0.0269 and wR2(Fo2) = 0.0704 for 1735 unique reflections I ≥ 2σ(I). Its thermal evolution first leads to anhydrous Zn2{O3P-CH2-PO3} (labelled VSB-4(Zn)) whose structure was refined from XRD powder pattern, then to γ and β zinc diphosphates successively. NaZn2(OH){O3P-CH2-PO3}·1.5H2O is monoclinic (P21/c (n° 14)) with lattice parameters a = 8.9929(9) A, b = 5.5093(6) A, c = 18.025(2) A, β = 92.376(2)°, V = 892.3(2) A3, Z = 4, R1(Fo) = 0.0700 and wR2(Fo2) = 0.1078 for 2358 unique reflections I ≥ 2σ(I). Its three-dimensional structure provides a new zeotype with 10-membered channels where the Na+ cations and the water molecules are encapsulated. The elimination of water provides a new compound, NaZn2(OH){O3P-CH2-PO3} (labelled MIL-48calc), whose structure was refined from XRD powder pattern.

Hydrothermal synthesis, structural approach, magnetic and Mössbauer study of the layered Fe(III) carboxyethylphosphonate [Fe(OH)(H2O)(O3P-(CH2)2-CO2H)] or MIL-37

Abstract [Fe(OH)(H2O)(O3P-(CH2)2-CO2H)] or MIL-37 was synthesized hydrothermally (443 K, 24 h) under autogenous pressure. Its layered structure was determined by single crystal X-ray diffraction (space group Pbc21 (n°29), a=7.4364(2) A, b=9.5646(4) A, c=20.4537(7) A, V=1454.79(9) A3, Z=8). It is built up from [FeO3(OH)2(H2O)] octahedral chains linked via hydroxyl vertices; these chains are then bonded by [PO3C] tetrahedra in such a way that each octahedron shares three oxygen atoms with three different tetrahedra. This layout leads to inorganic sheets which are well-known in phosphates, for instance in the iron phosphate ULM-11. At the other end of the organic chains, carboxylic groups are dangling. A Mossbauer study and magnetic measurements reveal a canted antiferromagnetic behaviour below TN=20(1) K.