TY - JOUR
T1 - Mechanism of Ferric Oxalate Photolysis
AU - Mangiante, David M.
AU - Schaller, Richard Daniel
AU - Zarzycki, Piotr
AU - Banfield, Jillian F.
AU - Gilbert, Benjamin
N1 - Funding Information:
This work was supported by the National Science Foundation under Grant GG-1324791. Benjamin Gilbert was supported by the Chemical Sciences, Geosciences, and Biosciences Division of the United States Department of Energy (U.S. DOE) under Contract DE-AC02-05CH11231. Use of the Center for Nanoscale Materials, an Office of Science user facility, was supported by the Office of Basic Energy Sciences, Office of Science, U.S. DOE, under Contract DE-AC02-06CH11357.
Publisher Copyright:
© 2017 American Chemical Society.
PY - 2017/7/20
Y1 - 2017/7/20
N2 - 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.
AB - 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.
KW - carbon dioxide radical anion
KW - metal cycling
KW - mid-infrared vibrational spectroscopy
KW - photochemistry
KW - ultrafast spectroscopy
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U2 - 10.1021/acsearthspacechem.7b00026
DO - 10.1021/acsearthspacechem.7b00026
M3 - Article
AN - SCOPUS:85049340283
SN - 2472-3452
VL - 1
SP - 270
EP - 276
JO - ACS Earth and Space Chemistry
JF - ACS Earth and Space Chemistry
IS - 5
ER -