[FE-4(PO4)(4)F-2(H2O)(3)]CENTER-DOT[C6H14N2] OR ULM-12, THE FIRST MAGNETIC FERRIC PHOSPHATE WITH AN OPEN STRUCTURE - HYDROTHERMAL SYNTHESIS, STRUCTURE, AND MAGNETIC-PROPERTIES
M. Cavellec et al., [FE-4(PO4)(4)F-2(H2O)(3)]CENTER-DOT[C6H14N2] OR ULM-12, THE FIRST MAGNETIC FERRIC PHOSPHATE WITH AN OPEN STRUCTURE - HYDROTHERMAL SYNTHESIS, STRUCTURE, AND MAGNETIC-PROPERTIES, Zeolites, 17(3), 1996, pp. 250-260
The first three-dimensional magnetic ferric phosphate with an open str
ucture [Fe-4(PO4)(4)F-2(H2O)(3)].[C6H14N2] has been hydrothermally syn
thesized (453 K, 24 h, autogeneous pressure) from a mixture of Fe2O3,
H3PO4, HF, 1,4-diazabicyclo [2.2.2] octane (DABCO), and H2O in the rat
io 1:2:2:0.5:80. The structure was determined by single crystal X-ray
diffraction. It is monoclinic (space group P2(1)/n (n degrees 14)) wit
h a = 9.987(1) Angstrom, b = 12.275(1) Angstrom, c = 17.462(1) Angstro
m, beta = 102.78(1)degrees, V = 2088(1) Angstrom(3), Z = 4. The struct
ure, refined to wR(2)(F-2) = 0.062, R(F) = 0.026 from 5,286 reflection
s (I> 2 sigma(I), is three-dimensional. The complex framework is built
up from two types of secondary building units. In the hexamer [Fe-3(P
O4)(3)F-2(H2O)(2)],Fe3+ octahedra form via fluorine atoms corner shari
ng trimers that are capped by three PO4 tetrahedra. These hexamers sha
re four vertices along [010] and form infinite columns. These columns
are linked together along [100] and [001] by dimers [FePO7(H2O)] forme
d by the O linkage between a Fe3+ square pyramid and a PO4 tetrahedron
. The resulting framework leaves large cages limited by 3-, 4-, 6-, an
d 8-membered windows in which the diprotonated amines are located. Upo
n heating, water molecules are lost between 150 and 260 degrees C. At
350 degrees C, the decomposition is achieved and leads to FePO4. The t
itle compound orders antiferromagnetically at T-N = 10.7(1) K. Mossbau
er spectroscopy confirms the presence of four distinct Fe3+ sites in t
he structure.