Hydrothermal synthesis, structure, and magnetic characterization of a new ferrimagnetic open framework phosphate: MIL-21 or [(Fe5-xVxIII)-V-III(H2PO4)(4)(HPO4)(4)F-4(H2O)(2), 4(H2+yN-(CH2)(2)-NH2+y)] with a partial cationic disorder

MIL-21 or [(Fe5-xVxIII)-V-III(H2PO4)(4)(HPO4)(4)F-4(H2O)(2), 4(H2+yN(CH2)(2 )-NH2+y)] was prepared hydrothermally (453 K, autogenous pressure, 3 days) in the presence of ethylenediamine. Its structure was determined by single- crystal X-ray diffraction, MIL-21 is tetragonal space group P-42(1)c, No. 1 14, with cell parameters a=17.2023(2) A, c=13.3086(2)Angstrom, V=3938.27(9) Angstrom(3), Z=4, Its three-dimensional network can be described from the c onnection via phosphate tetrahedra of infinite corner-sharing cis-trans oct ahedral chains of metallic atoms in a random distribution and isolated FeO4 (H2O)(2) octahedra. The (Fe3+, V3+) infinite chains belong to the KTP type. Mossbauer and structure refinements demonstrate this segregation. This str ucture exhibits small tunnels and cages in which the ethylenediamine molecu les are located. Moreover, MIL-21 shows a ferrimagnetic behavior below 13 K , (C) 1999 Academic Press.