A Comparative Study of Nitrate and Iodide of the Spin-Variable Iron(III) Cation with the N4O2 Coordination Sphere by Mössbauer Spectroscopy

The spin state of the magnetic center for a spin-variable cation with nitrate [FeIII(3-OMe-Sal2trien)]NO3⋅H2O(I) and iodide [FeIII(3-OMe-Sal2trien)]I (II) anions is studied by Mössbauer spectroscopy on 57Fe nuclei (3-OMe-Sal2trien is the condensation product of triethylenetetramine with 3-methoxy salicylaldehyde) in the temperature ranges of 5 to 305 and 85 to 296 K, respectively. It was shown that, for both complexes, only one low-spin (S = 1/2) doublet from iron(III) ions appears in the spectra, despite significant differences (up to ~10%) in the length of the iron(III)–ligand bonds in the N4O2 coordination octahedron of the salt II compared with I, according to X-ray diffraction data at 293 K. The Debye temperatures were determined for both compounds, Θ = 157 and 153 K.