Spin coupling in distorted high-valent Fe(IV)-porphyrin radical complexes |
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Authors: | M Müther E Bill A X Trautwein D Mandon R Weiss A Gold K Jayaraj R N Austin |
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Institution: | (1) Institut für Physik, Medizinische Universität zu Lübeck, 23538 Lübeck, Germany;(2) Institut Le Bel, Université Louis Pasteur, 67070 Strasbourg, France;(3) Department of Environmental Sciences and Engineering, University of North Carolina, Chapel Hill, NC, USA |
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Abstract: | In order to study structural influences on the interaction of Fe(IV) (S=1) and porphyrin cation radical (S=1/2) in high-valent iron porphyrin complexes of the type ¦X-(TMP)Fe=O¦+(Cl–), X=I, Br2, Br4 were generated by mCPBA oxidation of corresponding Fe(III) porphyrins. The halogen substitution at the peripheral positions of the porphyrin leads to distortion of the planar porphyrin ring of ¦(TMP)Fe=O¦+. The new species have beeen investigated by temperature-dependent EPR and field-dependent Mössbauer spectroscopy; for the evaluation of spectra, we adopted the spin-Hamiltonian formalism including exchange interaction explicitly. As in ¦(TMP)Fe=O¦+, strong ferromagnetic spin coupling was observed with|J0|D=0.9–1 and a zero-field spltting ofD32 cm–1. For consistent parametrization of EPR and Mössbauer results, anisotropic coupling had to be introduced. Compared to ¦(TMP)Fe=O¦+ 1], analysis of the spectroscopic data shows that zero-field splitting and spin coupling is only slightly affected by the halogen distortion of the porphyrin structure. |
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