Skip to main content

Electrochemical investigation of Mn4O4-cubane water oxidizing clusters

Journal Article


Abstract


  • High valence states in manganese clusters are a key feature of the function of one of the most important catalysts found in nature, the water-oxidizing complex of photosystem II. We describe a detailed electrochemical investigation of two bio-inspired manganese-oxo complexes, [Mn4O4L6] (L = diphenylphosphinate (1) and bis(p-methoxyphenyl)phosphinate (2)), in solution, attached to an electrode surface and suspended within a Nafion film. These complexes contain a cubic [Mn4O4](6+) core stabilized by phosphinate ligands. They have previously been shown to be active and durable photocatalysts for the oxidation of water to dioxygen. A comparison of catalytic photocurrent generated by films deposited by two methods of electrode immobilization reveals that doping of the catalyst in Nafion results in higher photocurrent than was observed for a solid layer of cubane on an electrode surface. In dichloromethane solution, and under conditions of cyclic voltammetry, the one-electron oxidation processes 1/1(+) and 2/2(+) were found to be reversible and quasi-reversible, respectively. Some decomposition of 1(+) and 2(+) was detected on the longer timescale of bulk electrolysis. Both compounds also undergo a two-electron, chemically irreversible reduction in dichloromethane, with a mechanism that is dependent on scan rate and influenced by the presence of a proton donor. When immersed in aqueous electrolyte, the reduction process exhibits a limited level of chemical reversibility. These data provide insights into the catalytic operation of these molecules during photo-assisted electrolysis of water and highlight the importance of the strongly electron-donating ligand environment about the manganese ions in the ability of the cubanes to photocatalyze water oxidation at low overpotentials.

Authors


  •   Swiegers, Gerhard (Gerry)
  •   Spiccia, Leone (external author)
  •   Brimblecombe, Robin (external author)
  •   Dismukes, Charles (external author)
  •   Bond, Alan M. (external author)

Publication Date


  • 2009

Citation


  • Swiegers, G., Spiccia, L., Brimblecombe, R., Dismukes, C. & bond, a. (2009). Electrochemical investigation of Mn4O4-cubane water oxidizing clusters. Physical Chemistry Chemical Physics, 11 (30), 6441-6449.

Scopus Eid


  • 2-s2.0-68849106316

Ro Metadata Url


  • http://ro.uow.edu.au/aiimpapers/400

Has Global Citation Frequency


Number Of Pages


  • 8

Start Page


  • 6441

End Page


  • 6449

Volume


  • 11

Issue


  • 30

Abstract


  • High valence states in manganese clusters are a key feature of the function of one of the most important catalysts found in nature, the water-oxidizing complex of photosystem II. We describe a detailed electrochemical investigation of two bio-inspired manganese-oxo complexes, [Mn4O4L6] (L = diphenylphosphinate (1) and bis(p-methoxyphenyl)phosphinate (2)), in solution, attached to an electrode surface and suspended within a Nafion film. These complexes contain a cubic [Mn4O4](6+) core stabilized by phosphinate ligands. They have previously been shown to be active and durable photocatalysts for the oxidation of water to dioxygen. A comparison of catalytic photocurrent generated by films deposited by two methods of electrode immobilization reveals that doping of the catalyst in Nafion results in higher photocurrent than was observed for a solid layer of cubane on an electrode surface. In dichloromethane solution, and under conditions of cyclic voltammetry, the one-electron oxidation processes 1/1(+) and 2/2(+) were found to be reversible and quasi-reversible, respectively. Some decomposition of 1(+) and 2(+) was detected on the longer timescale of bulk electrolysis. Both compounds also undergo a two-electron, chemically irreversible reduction in dichloromethane, with a mechanism that is dependent on scan rate and influenced by the presence of a proton donor. When immersed in aqueous electrolyte, the reduction process exhibits a limited level of chemical reversibility. These data provide insights into the catalytic operation of these molecules during photo-assisted electrolysis of water and highlight the importance of the strongly electron-donating ligand environment about the manganese ions in the ability of the cubanes to photocatalyze water oxidation at low overpotentials.

Authors


  •   Swiegers, Gerhard (Gerry)
  •   Spiccia, Leone (external author)
  •   Brimblecombe, Robin (external author)
  •   Dismukes, Charles (external author)
  •   Bond, Alan M. (external author)

Publication Date


  • 2009

Citation


  • Swiegers, G., Spiccia, L., Brimblecombe, R., Dismukes, C. & bond, a. (2009). Electrochemical investigation of Mn4O4-cubane water oxidizing clusters. Physical Chemistry Chemical Physics, 11 (30), 6441-6449.

Scopus Eid


  • 2-s2.0-68849106316

Ro Metadata Url


  • http://ro.uow.edu.au/aiimpapers/400

Has Global Citation Frequency


Number Of Pages


  • 8

Start Page


  • 6441

End Page


  • 6449

Volume


  • 11

Issue


  • 30