Electronic and spin structures of manganese clusters in the photosynthesis II system

Hiroshi Isobe, Mitsuo Shoji, Kennichi Koizumi, Yasutaka Kitagawa, Shusuke Yamanaka, Seiki Kuramitsu, Kizashi Yamaguchi

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Abstract

Electronic and spin structures of manganese clusters, Mn4O 4 (1), CaMn3O4 (2), Mn3O4 (3), MnX (4), and CaMn4O4 (5), in the photosynthesis II system are investigated using the classical and quantum Heisenberg models. The molecular orbital calculations by the use of general spin orbitals (GSO) are performed for cubane-type calcium manganese cluster 2 with noncollinear spin alignment, which has also been concluded in our previous studies of 1 and 3. The calculated results, together with available experiments, enable us to propose possible electronic states (from S0 to S4) of tetranuclear manganese cluster 5, which is the active site of oxygen evolution center (OEC). The low-spin (LS) ground states of 2-5 are consistent with the ESR and other magnetic observations. A new reaction scheme for oxygen evolution from water is resulted from both theoretical and experimental results for manganese clusters 1-5 in OEC on the basis of the newly determined X-ray structure by Ferreira et al. [Science 303 (2004) 1831]. In this mechanism, both calcium and manganese ions play important roles for formation of peroxide anion bridge, which is the precursor of molecular oxygen. Implications of computational results are discussed in relation to a key role of the high-valent manganese oxo (Mn(V)O) species in OEC for oxygen evolution from water. Our previous and present computations conclude that Mn(V)O plays a crucial role in both native and artificial OEC systems.

Original languageEnglish
Pages (from-to)2767-2777
Number of pages11
JournalPolyhedron
Volume24
Issue number16-17
DOIs
Publication statusPublished - Nov 17 2005
Externally publishedYes

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Keywords

  • Ab initio GSO calculation
  • Heisenberg model
  • Manganese clusters
  • Oxygen evolution
  • Photosynthesis II
  • Reaction mechanism

ASJC Scopus subject areas

  • Biochemistry
  • Inorganic Chemistry
  • Physical and Theoretical Chemistry
  • Materials Chemistry

Cite this

Isobe, H., Shoji, M., Koizumi, K., Kitagawa, Y., Yamanaka, S., Kuramitsu, S., & Yamaguchi, K. (2005). Electronic and spin structures of manganese clusters in the photosynthesis II system. Polyhedron, 24(16-17), 2767-2777. https://doi.org/10.1016/j.poly.2005.08.049