Determination of electron paramagnetic resonance parameters for osmium(III) low-spin systems using graphical solutions
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Antonio N. Medina, Flavio G. Gandra, Mauro L. Baesso, Joacy B. Lima, Bruce R. McGarvey and Douglas W. Franco
Abstract
Optical absorption and electron paramagnetic resonance (EPR) results for the low-spin compounds [Os(NH3)5L][O3SCF3 ]n [L = 4,4′-dithiodipyridine (dtdp) or H2O, n = 3; L = O3SCF3, n = 2] are reported. The EPR powder spectrum is analysed and from the three experimental g values the crystal-field parameters and the energy levels are determined. The negative sign obtained for the axial splitting in [Os(NH3)5(dtdp)][O3SCF3] has been interpreted to be the result of an OsIII → L back-bonding interaction. The IR optical spectrum shows a broad band at 2080 nm that is compared to the estimate obtained from the EPR results. Analytical expressions for the crystal-field parameters and energy levels of the system are derived. In addition, an alternative graphical method which simplifies the estimation of ligand-field parameters from the EPR parameters is presented.