Towards an artificial model for Photosystem II: a manganese(II,II) dimer covalently linked to ruthenium(II) tris-bipyridine via a tyrosine derivative

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Abstract

In order to model the individual electron transfer steps from the manganese cluster to the photooxidized sensitizer P680+ in Photosystem II (PS II) in green plants, the supramolecular complex 4 has been synthesized. In this complex, a ruthenium(II) tris-bipyridine type photosensitizer has been linked to a manganese(II) dimer via a substituted l-tyrosine, which bridges the manganese ions. The trinuclear complex 4 was characterized by electron paramagnetic resonance (EPR) and electrospray ionization mass spectrometry (ESI-MS). The excited state lifetime of the the ruthenium tris-bipyridine moiety in 4 was found to be about 110 ns in acetonitrile. Using flash photolysis in the presence of an electron acceptor (methylviologen), it was demonstrated that in the supramolecular complex 4 an electron was transferred from the excited state of the ruthenium tris-bipyridine moiety to methylviologen, forming a methylviologen radical and a ruthenium(III) tris-bipyridine moiety. Next, the Ru(III) species retrieved the electron from the manganese(II/II) dimer in an intramolecular electron transfer reaction with a rate constant kET>1.0x107 s-1, generating a manganese(II/III) oxidation state and regenerating the ruthenium(II) photosensitizer. This is the first example of intramolecular electron transfer in a supramolecular complex, in which a manganese dimer is covalently linked to a photosensitizer via a tyrosine unit, in a process which mimics the electron transfer on the donor side of PS II.

Details

Authors
  • Licheng Sun
  • Mary Kartherine Raymond
  • Ann Magnuson
  • Denis LeGourriérec
  • Markus Tamm
  • Malin Abrahamsson
  • Ping Huang
  • Jerker Mårtensson
  • Gunnar Stenhagen
  • Leif Hammarström
  • Stenbjörn Styring
  • Björn Åkermark
Organisations
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Biochemistry and Molecular Biology

Keywords

  • Electron transfer, Artificial photosynthesis, Manganese dimer complexes, Ruthenium complexes, Photosystem II
Original languageEnglish
Pages (from-to)15-22
JournalJournal of Inorganic Biochemistry
Volume78
Issue number1
Publication statusPublished - 2000
Publication categoryResearch
Peer-reviewedYes