Magnetic and high-frequency EPR studies of an octahedral Fe(III) compound with unusual zero-field splitting parameters.
Temperature-dependent magnetic susceptibility and multi-frequency EPR (9.4, 34.5, 94 and 188 GHz) spectroscopic measurements have been carried out together with an X-ray study at 100 K to study [Fe(DMSO)(6)](NO(3))(3). The iron(III) ion remains high-spin (S = 5/2) in the temperature range studied, therefore, the EPR data were interpreted using the conventional S = 5/2 spin Hamiltonian. A full analysis of EPR spectra at 95 GHz of a powdered sample at 290 K revealed that they are extremely sensitive to D and E values. The zfs parameters were precisely determined: D = + 0.1730 cm(-1), E = 0.00 cm(-1) and lambda = |E/D| = 0.00. A sequence of the spectra neatly shows that the compound has a clear magnetic dependence on temperature. The study at 5 K, showed that the zfs parameters increase: D = + 0.1970 cm(-1), E = 0.017 cm(-1) and lambda = |E/D| = 0.086. These data indicate that as the temperature decreases the D tensor increases slightly showing an increase in the rhombicity. These results confirm that |2D| is congruent to h nu at X-band in this case. Additionally, it has been shown by X-ray crystal analysis of [Fe(DMSO)(6)](NO(3))(3) at 100 K that this is involved in a hydrogen bonding network, consisting of C-H...O interactions between the nitrate anions and the methyl groups of the coordinated DMSO molecules, thus suggesting that the differences found in the spectroscopic parameters D and E at different temperatures must be due to these supramolecular interactions.
Departamento de Química Inorgánica y Nuclear, Facultad de Química, Universidad Nacional Autónoma de México, México D.F., 04510, México.
Alejandro
A
Solano-Peralta
Juan P
JP
Saucedo-Vázquez
Roberto
R
Escudero
Herbert
H
Höpfl
Hassane
H
El-Mkami
Graham M
GM
Smith
Martha E
ME
Sosa-Torres
D002412:Cations; D018360:Crystallography, X-Ray; D004121:Dimethyl Sulfoxide / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D005290:Ferric Compounds / Q000737:chemistry*; D008280:Magnetics; D008958:Models, Molecular; D009566:Nitrates / Q000737:chemistry*
D002412:Cations; D005290:Ferric Compounds; D009566:Nitrates; D004121:Dimethyl Sulfoxide