Hydrothermal synthesis, structure, and magnetic characterization of a new ferrimagnetic open framework phosphate:: MIL-21 or [Fe5-xIIIVxIII(H2PO4)4(HPO4)4F4(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. 114, 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 connection via phosphate tetrahedra of infinite corner-sharing cis-trans octahedral 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 structure exhibits small tunnels and cages in which the ethylenediamine molecules are located. Moreover, MIL-21 shows a ferrimagnetic behavior below 13 K, (C) 1999 Academic Press.