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Title: Mechanism of Ferric Oxalate Photolysis

Iron(III) oxalate, Fe 3+(C 2O 4) 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 CO 2 is not well understood for any system. Here, we employed pump/probe mid-infrared transient absorption spectroscopy to study the photolysis reaction of the iron(III) oxalate ion in D 2O and H 2O 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 CO 2(aq) and a species inferred to be CO 2 •– based on the appearance of a new vibrational absorption band and ab initio simulation. Our 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.
 [1] ; ORCiD logo [2] ; ORCiD logo [3] ;  [4] ; ORCiD logo [1]
  1. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Energy Geosciences Division
  2. Argonne National Lab. (ANL), Argonne, IL (United States). Center for Nanoscale Materials
  3. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Energy Geosciences Division; Polish Academy of Sciences (PAS), Warsaw (Poland). Inst. of Physical Chemistry
  4. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Energy Geosciences Division; Univ. of California, Berkeley, CA (United States). Dept. of Earth and Planetary Science
Publication Date:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
ACS Earth and Space Chemistry
Additional Journal Information:
Journal Volume: 1; Journal Issue: 5; Journal ID: ISSN 2472-3452
American Chemical Society
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); National Science Foundation (NSF)
Country of Publication:
United States
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Photochemistry; metal cycling; mid-infrared vibrational spectroscopy; ultrafast spectroscopy
OSTI Identifier: