Synthesis, structure and metamagnetic behaviour of a three-dimensional Fe(II) carboxyethylphosphonate:: [Fe3(OH)2(H2O)4(O3P-(CH2)2-CO2H)2] or MIL-38

[Fe-3(II)(OH)(2)(H2O)(4)(O3P-(CH2)(2)-CO2H)(2)] labelled MIL-38 was hydrothermally synthesized (170 degreesC, 48 h, autogeneous pressure). Its three-dimensional open structure was solved by single crystal X-ray diffraction (monoclinic, space group P2(1)/c (No. 14), a = 4.6308 (5), b = 10.4322(10), c = 17.711(2) Angstrom, beta = 96.051(2)degrees, Z = 2, V = 850.8(2) Angstrom(3)). It is built up from linear trimers of edge-sharing iron(H) octahedra linked by organic moieties thus delimiting empty channels along [10 0]. This new compound was characterized by Fe-57 Mossbauer spectrometry and magnetic measurements: it adopts a metamagnetic behaviour below 10 K, antiferromagnetic at low fields and ferromagnetic above 1.5 T. (C) 2002 Editions scientifiques et medicales Elsevier SAS. All rights reserved.