Electron transfer and dissociation mechanism of ferrioxalate: A time resolved optical and EXAFS study

Chen, Jie; Zhang, Hua; Tomov, I. V.; Ding, Xunliang; Rentzepis, P. M.

doi:10.1016/j.cplett.2007.02.005

Cited by 32 publications

(63 citation statements)

References 34 publications

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“…The Becke three-parameter hybrid functional with the LeeYang-Parr correlation corrections (B3LYP) was used in the DFT calculations. Some theoretical results for ferrioxalate have also been reported (26,28). The very good agreement between theoretical calculations and the experimental data made it possible to propose a mechanism that is consistent with these data and is also supported by additional optical and radical scavenging experimental results.…”

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confidence: 74%

“…It is also to be noted that our time-resolved optical studies were aimed only at the cage intermediates (25) and not at the study of the expected out-of-cage photochemical intermediates that were observed later by time-resolved x-ray diffraction (24). Recently, we reported on the photochemistry of ferrioxalate in water by means of ultrafast transient optical and EXAFS spectroscopy and density functional theory (DFT)/unrestricted Hartree-Fock (UHF) calculations (26)(27)(28)(29). Previously, we reported that excitation of ferrioxalate with either 267/266 nm or 400/355 nm pulses results predominantly in Fe-O bond dissociation, concurrent with photoelectron detachment followed by electron solvation as a side reaction, rather than intramolecular ET (26,27,29).…”

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confidence: 99%

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Photochemistry and electron-transfer mechanism of transition metal oxalato complexes excited in the charge transfer band

Chen

Zhang

Tomov

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

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The photoredox reaction of trisoxalato cobaltate (III) has been studied by means of ultrafast extended x-ray absorption fine structure and optical transient spectroscopy after excitation in the charge-transfer band with 267-nm femtosecond pulses. The Co-O transient bond length changes and the optical spectra and kinetics have been measured and compared with those of ferrioxalate. Data presented here strongly suggest that both of these metal oxalato complexes operate under similar photoredox reaction mechanisms where the primary reaction involves the dissociation of a metal-oxygen bond. These results also indicate that excitation in the charge-transfer band is not a sufficient condition for the intramolecular electron transfer to be the dominant photochemistry reaction mechanism.photoreduction ͉ organometallic ͉ ultrafast spectroscopy ͉ time-resolved EXAFS ͉ photodissociation T he photochemistry of transition metal trisoxalato complexes (1) has been studied extensively (2, 3), not only because of their wide application in areas such as chemical actinometry (4), radical polymerization reaction initiation (5), degradation of organic pollutants (6) and as solar energy media (7), but also because they have served as textbook models for electron transfer (ET) (8, 9) and stereochemistry (10). For a long period, transition metal trisoxalato complexes were thought to undergo exclusively intramolecular ET from the oxalate group to the metal, ligand to metal, immediately after irradiation inside the charge-transfer band. This hypothesis was based on continuous wave, flash photolysis (11-14) and nanosecond laser spectroscopic experimental results (15) in both aqueous and nonaqueous (16, 17) solutions. However, the proposed intramolecular ET process was thought to occur in the picosecond range, which could not be time-resolved with the methods that were then used. Owing to the lack of direct experimental support, such as transient absorption spectra or the observation of transient structural changes, intermolecular and intramolecular ET remained speculative. Is excitation in the charge-transfer band a sufficient condition for intramolecular electron transfer? What is the photochemical behavior difference between chargetransfer (CT) and ligand-field (LF) bands and why? The development of ultrafast spectroscopy, especially ultrafast x-ray spectroscopy (18-22), allow us to reevaluate the photochemical mechanism of transition metal complexes. Previously, we performed static extended x-ray absorption fine structure (EXAFS) spectroscopic experiments that revealed the structures of only the initial and final product in the photolysis of CBr 4 without any attempt, as clearly stated, to measure the structure of any intermediate product (23). This was in contrast to a report (24) that suggested that time-resolved EXAFS studies were performed and CBr 4 photolysis intermediates in solution were not observed. In fact, the final Br 3 CCBr 3 product detected and measured (23) can only be formed by CBr 3 radical recombination. It is also to...

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confidence: 74%

mentioning

confidence: 99%

Photochemistry and electron-transfer mechanism of transition metal oxalato complexes excited in the charge transfer band

Chen

Zhang

Tomov

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

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“…In contrast to ultrafast diffraction that has been first demonstrated with versatile and accessible tabletop laser systems, the development of tabletop ultrafast x-ray absorption experiments has been limited, due to the very low x-ray fluxes reported in continuous spectra from bremsstrahlung emission [12,13]. The first demonstration of a few picosecond resolution has been reported on resonant absorption line vanishing during molecule photodissociation [14].…”

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Unraveling the Solid-Liquid-Vapor Phase Transition Dynamics at the Atomic Level with Ultrafast X-Ray Absorption Near-Edge Spectroscopy

et al. 2011

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X-ray absorption near-edge spectroscopy (XANES) is a powerful probe of electronic and atomic structures in various media, ranging from molecules to condensed matter. We show how ultrafast time resolution opens new possibilities to investigate highly nonequilibrium states of matter including phase transitions. Based on a tabletop laser-plasma ultrafast x-ray source, we have performed a time-resolved (∼3 ps) XANES experiment that reveals the evolution of an aluminum foil at the atomic level, when undergoing ultrafast laser heating and ablation. X-ray absorption spectra highlight an ultrafast transition from the crystalline solid to the disordered liquid followed by a progressive transition of the delocalized valence electronic structure (metal) down to localized atomic orbitals (nonmetal-vapor), as the average distance between atoms increases.

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“…Experiments with the highest time resolution ∼100 fs can be performed at X-ray free electron lasers (XFELs) [30] or slicing sources at synchrotrons [31]. Setups based on laboratory lasers with X-ray pulses generated in a laser-induced plasma are also under development [32,33]. XFELs provide high incident flux and are therefore broadly applicable while other sources can be used only in more specific cases.…”

Section: X-ray Absorption Spectroscopy -Xasmentioning

confidence: 99%

Time-resolved X-ray absorption spectroscopy for the study of molecular systems relevant for artificial photosynthesis

Smolentsev

Sundström

2015

Coordination Chemistry Reviews

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Electron transfer and dissociation mechanism of ferrioxalate: A time resolved optical and EXAFS study

Cited by 32 publications

References 34 publications

Photochemistry and electron-transfer mechanism of transition metal oxalato complexes excited in the charge transfer band

Photochemistry and electron-transfer mechanism of transition metal oxalato complexes excited in the charge transfer band

Unraveling the Solid-Liquid-Vapor Phase Transition Dynamics at the Atomic Level with Ultrafast X-Ray Absorption Near-Edge Spectroscopy

Time-resolved X-ray absorption spectroscopy for the study of molecular systems relevant for artificial photosynthesis

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