Synthesis and characterization of dinuclear ruthenium complexes covalently linked to RuII Tris-bipyridine: An approach to mimics of the donor side of photosystem II

Yunhua Xu, Gerriet Eilers, Magnus Borgström, Jingxi Pan, Maria Abrahamsson, Ann Magnuson, Reiner Lomoth, Jonas Bergquist, Tomáš Polívka, Licheng Sun, Villy Sundström, Stenbjörn Styring, Leif Hammarström, Björn Åkermark

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Abstract

To mimic the electron-donor side of photosystem II (PSII), three trinuclear ruthenium complexes (2, 2a, 2b) were synthesized. In these complexes, a mixed-valent dinuclear Ru2II,III moiety with one phenoxy and two acetato bridges is covalently linked to a RuII tris-bipyridine photosensitizer. The properties and photoinduced electron/energy transfer of these complexes were studied. The results show that the Ru 2II,III moieties in the complexes readily undergo reversible one-electron reduction and one-electron oxidation to give the Ru 2II,III and Ru2III,III states, respectively. This could allow for photo-oxidation of the sensitizer part with an external acceptor and subsequent electron transfer from the dinuclear ruthenium moiety to regenerate the sensitizer. However, all trinuclear ruthenium complexes have a very short excited-state lifetime, in the range of a few nanoseconds to less than 100 ps. Studies by femtosecond time-resolved techniques suggest that a mixture of intra-molecular energy and electron transfer between the dinuclear ruthenium moiety and the excited [Ru(bpy)3] 2+ photosensitizer is responsible for the short lifetimes. This problem is overcome by anchoring the complexes with ester- or carboxyl-substituted bipyridine ligands (2a, 2b) to nanocrystalline TiO 2, and the desired electron transfer from the excited state of the [Ru-(bpy)3]2+ moiety to the conduction band of TiO 2 followed by intramolecular electron transfer from the dinuclear Ru2II,III moiety to photogenerated RuIII was observed. The resulting long-lived Ru2III,III state decays on the millisecond timescale.

Original languageEnglish
Pages (from-to)7305-7314
Number of pages10
JournalChemistry - A European Journal
Volume11
Issue number24
DOIs
Publication statusPublished - Dec 9 2005

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Keywords

  • Electrochemistry
  • Electron transfer
  • Mixed-valent compounds
  • Ruthenium cluster
  • Sensitizers

ASJC Scopus subject areas

  • Catalysis
  • Organic Chemistry

Cite this

Xu, Y., Eilers, G., Borgström, M., Pan, J., Abrahamsson, M., Magnuson, A., Lomoth, R., Bergquist, J., Polívka, T., Sun, L., Sundström, V., Styring, S., Hammarström, L., & Åkermark, B. (2005). Synthesis and characterization of dinuclear ruthenium complexes covalently linked to RuII Tris-bipyridine: An approach to mimics of the donor side of photosystem II. Chemistry - A European Journal, 11(24), 7305-7314. https://doi.org/10.1002/chem.200500592