Determination of electron paramagnetic resonance parameters for osmium(III) low-spin systems using graphical solutions

Abstract
Optical absorption and electron paramagnetic resonance (EPR) results for the low-spin compounds [Os(NH 3 ) 5 L][O 3 SCF 3 ] n [L = 4,4′-dithiodipyridine (dtdp) or H 2 O, n = 3; L = O 3 SCF 3 , 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(NH 3 ) 5 (dtdp)][O 3 SCF 3 ] has been interpreted to be the result of an Os III → 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.

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