Valence Photoemission Spectra of Aqueous Fe2+/3+ and [Fe(CN)6]4鈥?3鈥?/sup> and Their Interpretation by DFT Calculations
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- 作者：Robert Seidel ; Stephan Th眉rmer ; Jan Moens ; Paul Geerlings ; Jochen Blumberger ; Bernd Winter
- 刊名：Journal of Physical Chemistry B
- 出版年：2011
- 出版时间：October 13, 2011
- 年：2011
- 卷：115
- 期：40
- 页码：11671-11677
- 全文大小：860K
- 年卷期：v.115,no.40(October 13, 2011)
- ISSN：1520-5207
文摘
Aqueous solutions of ferrous and ferric iron (Fe2+/3+) and of the iron鈥揾exacyano complexes [Fe(CN)6]4鈥?3鈥?/sup> are studied by photoelectron spectroscopy using a liquid microjet in conjunction with synchrotron soft X-rays for ionization. For Fe2+(aq) we observe two well-resolved peaks at 7.09 and 9.16 eV electron binding energy (BE) that can be assigned to the iron鈥揾exaaquo complex. For Fe3+(aq) we observe only one peak above the highest valence band of liquid water, at 10.08 eV BE. Interpreting the spectra in terms of the one-electron levels of Kohn鈥揝ham density functional theory, we find that the two peaks for Fe2+(aq) originate from the energy splitting between the highest occupied 尾 (= minority) spin level (Fe d(t2g)) and the five highest occupied 伪 (= majority) spin levels (Fe d(t2g) and d(eg)). The peak for Fe3+(aq) arises from d-levels that are strongly mixed with the solvent. The spectra of the aqueous hexacyano complexes show a single strong peak at 6.11 and 7.52 eV BE for [Fe(CN)6]4鈥?/sup> and [Fe(CN)6]3鈥?/sup>, respectively, originating from the highest occupied Fe d(t2g) levels, and two further peaks at higher BE originating from the cyano ligands. The PE spectra of the reduced aquo and cyano ions are then used to obtain鈥搒olely on experimental grounds鈥搗alues for the reorganization free energy of the oxidized ions. DFT/continuum calculations of this important parameter in the Marcus theory of oxidation reactions are in fairly good agreement with experiment.