Mild hydrothermal synthesis, crystal structure, spectroscopic and magnetic properties of the [MxIIM2.5-xIII(HO(HPO)(PO)F] [M=Fe, x=2.08, y=1.58; M=Co, Ni, x=2.5, y=2] compounds
Abstract
The [MxIIM2.5-xIII(HO(HPO)y(PO)F] [ M=Fe ( 1), x=2.08, y=1.58; M=Co ( 2), x=2.5, y=2; Ni ( 3), x=2.5, y=2] compounds have been synthesized using mild hydrothermal conditions at 170 °C during five days. Single-crystals of ( 1) and ( 2), and polycrystalline sample of ( 3) were obtained. These isostructural compounds crystallize in the orthorhombic system, space group Aba2, with a=9.9598(2), b=18.8149(4) and c=8.5751(2) Å for (1), a=9.9142(7), b=18.570(1) and c=8.4920(5) Å for (2) and a=9.8038(2), b=18.2453(2) and c=8.4106(1) Å for ( 3), with Z=8 in the three phases. An X-ray diffraction study reveals that the crystal structure is composed of a three-dimensional skeleton formed by [ MO 5F] and [ MO 4F 2] ( M=Fe, Co and Ni) octahedra and [HPO 3] tetrahedra, partially substituted by [PO 4] tetrahedra in phase ( 1). The IR spectra show the vibrational modes of the water molecules and those of the (HPO 3) 2- tetrahedral oxoanions. The thermal study indicates that the limit of thermal stability of these phases is 195 °C for ( 1) and 315 °C for ( 2) and ( 3). The electronic absorption spectroscopy shows the characteristic bands of the Fe(II), Co(II) and Ni(II) high-spin cations in slightly distorted octahedral geometry. Magnetic measurements indicate the existence of global antiferromagnetic interactions between the metallic centers with a ferromagnetic transition in the three compounds at 28, 14 and 21 K for ( 1), ( 2) and ( 3), respectively. Compound ( 1) exhibits a hysteresis loop with remnant magnetization and coercive field values of 0.72 emu/mol and 880 Oe, respectively.
- Publication:
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Journal of Solid State Chemistry France
- Pub Date:
- August 2009
- DOI:
- 10.1016/j.jssc.2009.05.041
- Bibcode:
- 2009JSSCh.182.2191O