Two New Three-Dimensional Vanadium(III) and Iron(III) Phosphites Templated by Ethylenediamine: (C₂H₁₀N₂)_0.5[M(HPO₃)₂]. Ab Initio Structure Determination, Spectroscopic, and Magnetic Properties

Abstract

The (C2H10N2)0.5[M(HPO3)2] (M = V, Fe) inorganic−organic hybrid compounds have been synthesized under mild hydrothermal conditions. The crystal structure determination of the vanadium phase has been carried out from X-ray powder diffraction data by using the ab initio method. A Rietveld full-profile refinement has been performed on the isostructural iron compound. The unit-cell parameters are a = 9.243(1), b = 8.817(1), c = 9.684(1) Å, and β = 120.92(2)° and a = 9.247(1), b = 8.824(1), c = 9.693(1) Å, and β = 120.72(1)° for the vanadium and iron compounds, respectively. Both compounds are monoclinic, P2/c with Z = 4. The crystal structure consists of a three-dimensional framework with channels along the c axis where the ethylenediammonium cations are located. The metallic ions are interconnected by the pseudopyramidal (HPO3)2- phosphite anions and adopt a tetrahedral-like−diamond distribution. The IR and Raman spectra of both phases show the bands corresponding to the phosphite oxoanions and ethylenediammonium cations. The diffuse reflectance spectra in the visible region are consistent with the existence of vanadium(III) and high-spin iron(III) cations in slightly distorted octahedral coordination. Magnetic measurements indicate the existence of antiferromagnetic interactions being stronger in the iron compound.