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

Abrahamsson, Malin L A; Berglund, Helena LU ; Tran, Anh; Philouze, Christian; Berg, Katja E.; Raymond-Johnsson, Mary Katherine; Sun, Licheng; Åkermark, Björn; Styring, Stenbjörn LU and Hammarström, Leif (2002) In Inorganic Chemistry 41(6). p.1534-1544
Abstract
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... (More)
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. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Inorganic Chemistry
volume
41
issue
6
pages
1534 - 1544
publisher
The American Chemical Society
external identifiers
  • wos:000174492300028
  • pmid:11896722
  • scopus:0037170872
ISSN
1520-510X
DOI
10.1021/ic0107227
language
English
LU publication?
yes
id
dc4e7042-f8b9-49f6-8c47-4a6c82835ab7 (old id 124757)
date added to LUP
2007-06-26 08:42:14
date last changed
2017-08-27 04:09:12
@article{dc4e7042-f8b9-49f6-8c47-4a6c82835ab7,
  abstract     = {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.},
  author       = {Abrahamsson, Malin L A and Berglund, Helena and Tran, Anh and Philouze, Christian and Berg, Katja E. and Raymond-Johnsson, Mary Katherine and Sun, Licheng and Åkermark, Björn and Styring, Stenbjörn and Hammarström, Leif},
  issn         = {1520-510X},
  language     = {eng},
  number       = {6},
  pages        = {1534--1544},
  publisher    = {The American Chemical Society},
  series       = {Inorganic Chemistry},
  title        = {Ruthenium-Manganese Complexes for Artificial Photosynthesis: Factors Controlling Intramolecular Electron Transfer and Excited-State Quenching Reactions},
  url          = {http://dx.doi.org/10.1021/ic0107227},
  volume       = {41},
  year         = {2002},
}