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Computation of Hyperfine Tensors for Dinuclear Mn III Mn IV Complexes by Broken‐Symmetry Approaches: Anisotropy Transfer Induced by Local Zero‐Field Splitting
Author(s) -
Schraut Johannes,
Arbuznikov Alexei V.,
Schinzel Sandra,
Kaupp Martin
Publication year - 2011
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201100443
Subject(s) - hyperfine structure , anisotropy , symmetry (geometry) , zero (linguistics) , chemistry , field (mathematics) , manganese , physics , computation , zero field splitting , atomic physics , crystallography , quantum mechanics , geometry , organic chemistry , spin polarization , electron , linguistics , philosophy , mathematics , algorithm , computer science , pure mathematics
Based on broken‐symmetry density functional calculations, the 55 M n hyperfine tensors of a series of exchange‐coupled, mixed‐valence, dinuclear Mn III Mn IV complexes have been computed. We go beyond previous quantum chemical work by fully including the effects of local zero‐field splitting (ZFS) interactions in the spin projection, following the first‐order perturbation formalism of Sage et al. [ J. Am. Chem. Soc. 1989 , 111 , 7239]. This allows the ZFS‐induced transfer of hyperfine anisotropy from the Mn III site to the Mn IV site to be described with full consideration of the orientations of local hyperfine and ZFS tensors. After scaling to correct for systematic deficiencies in the quantum chemically computed local ZFS tensors, good agreement with experimental 55 M n anisotropies at the Mn IV site is obtained. The hyperfine coupling anisotropies on the Mn III site depend sensitively on structural distortions for a d 4 ion. The latter are neither fully reproduced by using a DFT‐optimized coordination environment nor by using experimental structures. For very small exchange‐coupling constants, the perturbation treatment breaks down and a dramatic sensitivity to the scaling of the local ZFS tensors is observed. These results are discussed with respect to ongoing work to elucidate the structure of the oxygen‐evolving complex of photosystem II by analysis of the EPR spectra.