Electron paramagnetic resonance study of the S=1/2 ground state of a radiolysis-generated manganese(III)-trimanganese(IV) form of [Mn-IV;O-4(6)(bipy)(6)](4+) (bipy=2,2'-bipyridine). Comparison with the photosynthetic Oxygen Evolving Complex

Geneviève Blondin, Roman Davydov, Christian Philouze, Marie-France Charlot, Stenbjörn Styring, Björn Åkermark, Jean-Jacques Girerd, Alain Boussac

Research output: Contribution to journalArticlepeer-review

Abstract

gamma-Ray irradiation at liquid nitrogen temperature of a dimethylformamide solution of the tetranuclear complex [(Mn4O6)-O-IV(bipy)(6)](4+) (bipy = 2,2'-bipyridine) allowed the generation of the first mixed-valence tetranuclear system containing Mn-III and Mn-IV ions and exhibiting a S = 1/2 ground state. The X-band EPR spectrum of this tetranuclear system has been obtained. Simulations have been undertaken and the Mn hyperfine coupling tensors determined clearly show a (MnMn3IV)-Mn-III, composition for the EPR active species. A general approach for the analysis of the isotropic components of the Mn hyperfine tensors is presented in detail. This allowed the determination of the spin projection value for each Mn site. A three J coupling scheme assuming that the linear topology of the starting compound remains is able to reproduce these spin projection values if and only if the Mn-III ion is located at a terminal position in a N4O2 environment. The EPR signal of this [Mn4O6(bipy)(6)](3+) species is compared with the multiline signal observed in the S-2 state of the photosynthetic Oxygen Evolving Complex.
Original languageEnglish
Pages (from-to)4069-4074
JournalJournal of the Chemical Society. Dalton Transactions
Volume1997
Issue number21
DOIs
Publication statusPublished - 1997

Subject classification (UKÄ)

  • Biological Sciences

Free keywords

  • PLANTS
  • WATER
  • S2 STATE
  • SIMULATION
  • REDOX PROPERTIES
  • MANGANESE CLUSTER
  • MULTILINE EPR SIGNALS
  • MN-OXO CLUSTER
  • PHOTOSYSTEM-II
  • OXIDATION

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