Mechanism of Ferric Oxalate Photolysis

David M. Mangiante, Richard Daniel Schaller, Piotr Zarzycki, Jillian F. Banfield, Benjamin Gilbert*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

54 Scopus citations


Iron(III) oxalate, Fe3+(C2O4)3 3-, is a photoactive metal organic complex found in natural systems and used to quantify photon flux as a result of its high absorbance and reaction quantum yield. It also serves as a model complex to understand metal carboxylate complex photolysis because the mechanism of photolysis and eventual production of CO2 is not well understood for any system. We employed pump/probe mid-infrared transient absorption spectroscopy to study the photolysis reaction of the iron(III) oxalate ion in D2O and H2O up to 3 ns following photoexcitation. We find that intramolecular electron transfer from oxalate to iron occurs on a sub-picosecond time scale, creating iron(II) complexed by one oxidized and two spectator oxalate ligands. Within 40 ps following electron transfer, the oxidized oxalate molecule dissociates to form free solvated CO2(aq) and a species inferred to be CO2 - based on the appearance of a new vibrational absorption band and ab initio simulation. This work provides direct spectroscopic evidence for the first mechanistic steps in the photolysis reaction and presents a technique to analyze other environmentally relevant metal carboxylate photolysis reactions.

Original languageEnglish (US)
Pages (from-to)270-276
Number of pages7
JournalACS Earth and Space Chemistry
Issue number5
StatePublished - Jul 20 2017


  • carbon dioxide radical anion
  • metal cycling
  • mid-infrared vibrational spectroscopy
  • photochemistry
  • ultrafast spectroscopy

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Atmospheric Science
  • Space and Planetary Science


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