A new organically templated monodimensional mixed valence (FeII/FeIII) phosphite: (C4H12N2)[FeIIFeIII(HPO3)2F3]: Solvothermal synthesis, crystal structure, spectroscopic and magnetic properties

The organically templated (C4H12N2)[FeIIFeIII(HPO3)2F3] compound has been synthesized under mild solvothermal conditions. The crystal structure has been determined from X-ray single-crystal diffraction data. The compound crystallizes in the P21/n monoclinic space group, with the unit-cell parameters a = 12.935(1), b = 6.4476(7), c = 15.693(2) Å, β = 105.630(9)° and Z = 4. The crystal structure consists of [FeIIFeIII(HPO3)2F3]2− chains formed by a central chain built of [Fe(2)O4F2] edge-sharing octahedra, and two side chains formed by alternating [Fe(1)O3F3] octahedra and [HP(1)O3] tetrahedra. The piperazinium cations are placed between the chains linked by ionic and hydrogen interactions. The IR and Raman spectra show the existence of two phosphite crystallographically independent. From the diffuse reflectance spectrum the Dq parameter for the iron(II) cations has been calculated (Dq = 820 cm−1). The Mössbauer spectrum in the paramagnetic state shows the simultaneous presence of Fe2+ and Fe3+. The magnetic measurements indicate the existence of antiferromagnetic interactions.