Hydrothermal synthesis, crystal structure, and spectroscopic and magnetic properties of a new organically templated mixed-anion fluoro-arsenate-phosphate iron(III) compound, (C_6H_(14)N_2) [Fe_3(HAsO_4)_(1.33)(HPO_4)_(0.67)(AsO_4)_(0.84)(PO_4]_(PO_4)

摘要

The new organically templated mixed-anion fluoro-arsenate-phosphate iron(III) compound, with formula(C_6H_(14)N_2) [Fe_3(HAsO_4)_(1.33)(HPO_4)_(0.67)(AsO_4)_(0.84)(PO_4]_(PO_4)_(0.16)F_4]0.5(H_2O), has been synthesized by using mild hydrothermal conditions under autogeneous pressure. The crystal structure has been solved from X-ray single crystal data. The unit-cell parameters are a = 18.267(1), b = 10.085(1), c = 20.436(2) A, β = 105.97(1)°. Monoclinic, C2/c with Z = 8. The structure consists of a three-dimensional inorganic framework formed by [Fe_3(HAsO_4)_(1.33)(HPO_4)_(0.67)(AsO_4)_(0.84)(PO_4]~(2-) inorganic layers linked by hydrogen-arsenate/phosphate anions. There are three iron atoms crystallographically independent per unit-formula. The sheets are constructed from Fe(1)Fe(3)O_6F_4 and Fe(2)_2O_8F_2 diametric units with edge-sharing octahedra. The 1,4-diazabicyclooctane dications are located inside the cavities of the inorganic skeleton. The IR and Raman spectroscopies conform the simultaneously existence of both the arsenate/hydrogenarsenate and phosphate/hydrogenphosphate anions. From the diffuse reflectance spectrum the Dq = 1080 and Racah parameters B = 1040 and C = 2620 cm~(-1) for the d~5-high spin iron(III) cation in octahedral geometry have been calculated. The Mossbauer spectrum at room temperature is characteristic of high spin iron(III) cations. The ESR spectra are isotropic with a g-value of 1.99(1), which remains unchanged with variation in temperature. Magnetic measurements indicate the presence of antiferromagnetic interactions with a maximum in the susceptibility at around 6.0 K.