Electrochemical investigation of Mn4O4-cubane water-oxidizing clusters

Robin Brimblecombe, Alan M. Bond, G Charles Dismukes, Gerhard F. Swiegers, Leone Spiccia

Research output: Contribution to journalArticle

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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, [Mn4O4L 6] (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.

Original languageEnglish
Pages (from-to)6441-6449
Number of pages9
JournalPhysical Chemistry Chemical Physics
Volume11
Issue number30
DOIs
Publication statusPublished - 2009

Fingerprint

cubane
Manganese
Water
Methylene Chloride
electrolysis
Photocurrents
Electrolysis
Oxidation
water
oxidation
Electrodes
photocurrents
electrodes
Electrons
manganese
Ligands
catalysts
manganese ions
ligands
Catalysts

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Physics and Astronomy(all)

Cite this

Electrochemical investigation of Mn4O4-cubane water-oxidizing clusters. / Brimblecombe, Robin; Bond, Alan M.; Dismukes, G Charles; Swiegers, Gerhard F.; Spiccia, Leone.

In: Physical Chemistry Chemical Physics, Vol. 11, No. 30, 2009, p. 6441-6449.

Research output: Contribution to journalArticle

Brimblecombe, Robin ; Bond, Alan M. ; Dismukes, G Charles ; Swiegers, Gerhard F. ; Spiccia, Leone. / Electrochemical investigation of Mn4O4-cubane water-oxidizing clusters. In: Physical Chemistry Chemical Physics. 2009 ; Vol. 11, No. 30. pp. 6441-6449.
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