Structural, thermal, spectroscopic and magnetic studies of the (C2N2H10)0.5[FexV1-x(HPO3)2] (x=0.26, 0.52, 0.74) solid solution

The (CN2H10)(0.5)[FexV1-x(HPO3)(2)] (x = 0.26, 0.52 0.74) compounds have been obtained by mild solvothermal conditions in the form of micro-crystalline powder with brown color. The crystal structures were refined by X-ray powder diffraction data using the Rietveld method. The compounds crystallize in the monoclinic system, space group P2/c with the unit-cell parameters, a 9.262(5) angstrom, b = 8.823(5) angstrom, c 9.714(6) angstrom, beta = 120.84(3)degrees; a = 9.245(1) angstrom, b = 8.823(1) angstrom, c = 9.698(1)angstrom, beta = 120.80(1)degrees and, a 9.254(4)angstrom, b = 8.822(4)angstrom, c = 9.702(4)angstrom, beta = 120.73(3)degrees for (CNH10)(0.5)[Fe0.26V0.74 (HPO3)(2)] (1), (C2N2H10)(0.5)[Fe0.52V0.48(HPO3)(2)] (2), and (C2N2H10)(0.5)[Fe0.74V0.26(HPO3)(2)] (3). The compounds show an open crystalline structure with three-dimensional character, whose formula for the anionic inorganic skeleton is [M(HPO3)(2)](2-). The inorganic framework is formed by [MO6] octahedra inter-connected by phosphite groups. The structure of the compounds exhibits channels extended along the [100] and [001] directions and the ethylendiammonium cations are located inside these channels, linked through hydrogen bonds and ionic interactions. The infrared spectra show the bands corresponding to the stretching (P-H) vibration of the phosphite group and the band corresponding to the deformation mode of the ethylendiammonium cation, delta(NH3+). The thermal and thermodiffractometric behavior show that the compounds are stable up to approximately 300 degrees C, at higher temperatures the decomposition of the crystal structure by calcination of the organic cation starts. The diffuse reflectance spectra show bands of the V3+ ion (d(2)), and a band of the Fe3+ ion (d(5)), in a slightly distorted octahedral symmetry. The values of the Dq and Racah parameters (B and C) have been calculated for the V(111) cation. Magnetic measurements were performed on a powdered sample from 5 to 300 K at magnetic fields 1000, 500 and 100 G, in the ZFC and FC modes. At the magnetic field of 1000 G antiferromagnetic interactions were observed, but at 100 G have been detected higher values of the X-m the FC mode than those observed in the ZFC one, indicating the existence of a dominant ferromagnetic component at low temperature. The magnetization measurements show hystheresis loops at 5 K, with values of the remanent magnetization and coercive field of 1.91 emu/mol and 23 Gauss for (1), 25 emu/mol and 300 Gauss for (2), and 3 emu/mol and 50 Gauss for the compound (3). (c) 2006 Elsevier Ltd. All rights reserved.