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Ruthenium-Manganese Complexes for Artificial Photosynthesis: Factors Controlling Intramolecular Electron Transfer and Excited-State Quenching Reactions

In English

Författare

  • Malin L A Abrahamsson
  • Helena Berglund
  • Anh Tran
  • Christian Philouze
  • Katja E. Berg
  • Mary Katherine Raymond-Johnsson
  • Licheng Sun
  • Björn Åkermark
  • Stenbjörn Styring
  • Leif Hammarström

Summary, in English

Continuing our work toward a system mimicking the electron-transfer steps from manganese to P680+ in photosystem II (PS II), we report a series of ruthenium(II)-manganese(II) complexes that display intramolecular electron transfer from manganese(II) to photooxidized ruthenium(III). The electron-transfer rate constant (kET) values span a large range, 1 × 105-2 × 107 s-1, and we have investigated different factors that are responsible for the variation. The reorganization energies determined experimentally ( = 1.5-2.0 eV) are larger than expected for solvent reorganization in complexes of similar size in polar solvents (typically 1.0 eV). This result indicates that the inner reorganization energy is relatively large and, consequently, that at moderate driving force values manganese complexes are not fast donors. Both the type of manganese ligand and the link between the two metals are shown to be of great importance to the electron-transfer rate. In contrast, we show that the quenching of the excited state of the ruthenium(II) moiety by manganese(II) in this series of complexes mainly depends on the distance between the metals. However, by synthetically modifying the sensitizer so that the lowest metal-to-ligand charge transfer state was localized on the nonbridging ruthenium(II) ligands, we could reduce the quenching rate constant in one complex by a factor of 700 without changing the bridging ligand. Still, the manganese(II)-ruthenium(III) electron-transfer rate constant was not reduced. Consequently, the modification resulted in a complex with very favorable properties.

Publiceringsår

2002

Språk

Engelska

Sidor

1534-1544

Publikation/Tidskrift/Serie

Inorganic Chemistry

Volym

41

Issue

6

Dokumenttyp

Artikel i tidskrift

Förlag

The American Chemical Society (ACS)

Ämne

  • Biological Sciences
  • Ecology

Status

Published

ISBN/ISSN/Övrigt

  • ISSN: 1520-510X