Charge transfer to solvent identified using dark channel fluorescence-yield L-edge spectroscopy

Aziz, Emad F.; Rittmann-Frank, Mercedes Hannelore; Lange, Kathrin M.; Bonhommeau, Sébastien; Chergui, Majed

doi:10.1038/nchem.768

Cited by 64 publications

(88 citation statements)

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“…Along these lines, Aziz et al. recently reported the so called "dark channel fluorescence yield" method (21,22). They found features in the total fluorescence yield (TFY) spectra when scanning the L-edges of 3d transition metal ions and complexes in solution at high concentration that dip below the fluorescence background of the solvent.…”

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confidence: 99%

“…They found features in the total fluorescence yield (TFY) spectra when scanning the L-edges of 3d transition metal ions and complexes in solution at high concentration that dip below the fluorescence background of the solvent. It was claimed that this could be used as a new tool to study charge transfer to solvent effects (21)(22)(23)(24). The dips where attributed, first, to ultrafast electron transfer from the metal d-orbitals to the solvent (21)(22)(23)(24) and, second, to a competition of solute and solvent fluorescence (25).…”

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Dissecting Local Atomic and Intermolecular Interactions of Transition-Metal Ions in Solution with Selective X-ray Spectroscopy

Wernet

Kunnus

Schreck

et al. 2012

J. Phys. Chem. Lett.

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Determining covalent and charge-transfer contributions to bonding in solution has remained an experimental challenge. Here the quenching of fluorescence-decay channels as expressed in dips in the L-edge x-ray spectra of solvated 3d transition-metal ions and complexes was reported as a probe. With a full set of experimental and theoretical ab initio L-edge x-ray spectra of aqueous Cr 3+ including resonant inelastic x-ray scattering we address covalency and charge-transfer for this prototypical transition-metal ion in solution. We dissect local atomic effects from intermolecular interactions and quantify x-ray optical effects. We find no evidence for the asserted ultrafast charge-transfer to the solvent and show that the dips are readily explained by xray optical effects and local atomic state dependence of the fluorescence yield. Instead we find, besides ionic interactions, a covalent contribution to the bonding in the aqueous complex of ligand to metal charge transfer character. 3 TOC Graphic:KEYWORDS Charge transfer to solvent, dark channel fluorescence yield, inverse partial fluorescence yield, total fluorescence yield, resonant inelastic x-ray scattering, transition metal ion, aqueous solution. 4The transfer of charge from a solvated ion or molecular complex to the surrounding solvent is an elementary step in numerous reactions in nature and in technological processes. Understanding charge transfer to solvent effects in molecular systems is thus of primary importance and x-ray spectroscopy with its specificity to elemental and chemical sites promises to add a new suite of powerful tools for their investigation (1). Specifically, time-resolved x-ray spectroscopy (2-11) appears to be the most direct way of probing charge transfer initiated by a pump pulse and probed as a function of time by scanning the delay of a short x-ray probe pulse. However, such effects can proceed on the few-femtosecond time scale and it is currently very challenging to achieve a corresponding time-resolution in pump-probe x-ray spectroscopy experiments.Therefore, it has been attempted to make use of the core-hole lifetime of a few femtoseconds to study ultrafast charge transfer processes for various systems such as for adsorbates on surfaces (12-18), ice (19) and aqueous solutions (20). Using resonant soft x-ray spectroscopy a coreelectron is excited into an unoccupied state of the system and the probability for it to transfer to the surroundings during the few-femtosecond core-hole lifetime will influence the core-hole decay channels. The Auger decay signal is thus the stronger, the higher the probability for its transfer to the surrounding medium during the core-hole lifetime is (15,17,18).As core-excited states can decay via Auger-electron ejection or fluorescence, the question arises whether such ultrafast electron-transfer processes are observable in the fluorescence decay channel as well. This relates to the more general questions as to whether and how bonding and charge-transfer processes can be revealed by with x-ray sp...

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Dissecting Local Atomic and Intermolecular Interactions of Transition-Metal Ions in Solution with Selective X-ray Spectroscopy

Wernet

Kunnus

Schreck

et al. 2012

J. Phys. Chem. Lett.

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“…4 and 7-11. For three-dimensional complexes, the electronic structure [12][13][14][15][16][17] and charge transfer [18][19][20][21][22][23][24] have been investigated using many spectroscopic [25][26][27][28][29][30][31] and theoretical [32][33][34][35][36][37][38][39][40] methods.…”

Section: Introductionmentioning

confidence: 99%

Electronic structure of Fe- vs. Ru-based dye molecules

Johnson

Cook

Zegkinoglou

et al. 2013

The Journal of Chemical Physics

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In order to explore whether Ru can be replaced by inexpensive Fe in dye molecules for solar cells, the differences in the electronic structure of Fe-and Ru-based dyes are investigated by X-ray absorption spectroscopy and first-principles calculations. Molecules with the metal in a sixfold, octahedral N cage, such as tris(bipyridines) and tris(phenanthrolines), exhibit a systematic downward shift of the N 1s-to-π * transition when Ru is replaced by Fe. This shift is explained by an extra transfer of negative charge from the metal to the N ligands in the case of Fe, which reduces the binding energy of the N 1s core level. The C 1s-to-π * transitions show the opposite trend, with an increase in the transition energy when replacing Ru by Fe. Molecules with the metal in a fourfold, planar N cage (porphyrins) exhibit a more complex behavior due to a subtle competition between the crystal field, axial ligands, and the 2+ vs. 3+ oxidation states.

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Section: Introductionmentioning

confidence: 99%

“…Furthermore, the type and number of neighbors have strong effects on CT states [13]. CT processes from core-excited metal ions to solvent molecules may quench radiative relaxation processes as observed in fluorescence-yield spectra [14].For elements from the first rows of the periodic table, electronic Auger decay is the main relaxation channel of core-hole states. Core-hole lifetime ranging usually in the femtosecond and sub-femtosecond timescales may serve as an internal reference clock.…”

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Ultrafast Charge Transfer Processes Accompanying KLL Auger Decay in Aqueous KCl Solution

et al. 2017

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X-ray photoelectron spectroscopy (XPS) and KLL Auger spectra of aqueous KCl solution were measured for the K + and Cledges. While the XPS spectra of potassium and chloride have similar structures, both exhibiting only weak satellite structures near the main line, the Auger spectra of these isoelectronic ions differ dramatically. A very strong satellite peak was found in the K + KLL Auger spectrum at the low kinetic energy side of the 1 D state. Using equivalent core models and ab initio calculations this spectral structure was assigned to electron transfer processes from solvent water molecules to the solvated K + cation. Contrary to the potassium case, no extra peak was found in the KLL Auger spectrum of solvated Cl -indicating on a strong dependence of the underlying processes on ionic charge. The observed charge transfer processes are suggested to play an important role in charge redistribution following single and multiple core-hole creation in atomic and molecular systems placed into an environment.Charge transfer (CT) processes and related phenomena are topics of wide relevance in chemistry, physics and biology. They are responsible for numerous important transformations in living organisms and are involved in fundamental steps describing, e.g., the photosynthesis [1] and respiration [2] mechanisms. The creation of a charge (or hole) in a DNA chain, by oxidation or photoionization processes, is quickly followed by its migration along portions of the molecular backbone leading to possible bonds breaking and irreversible damages [3]. Naturally, the use of such very fast elemental processes for technological purposes has attracted an extraordinary large amount of scientists whose research programs -both theoretical and experimental -focus on energy conversion based for instance on photovoltaic or optoelectronic devices [see e.g. ref. [4]].CT may accompany core-hole creation in atoms and molecules which have neighbors, and the corresponding spectral signatures are manifested in XPS spectra as lowenergy CT satellites. Particularly strong CT screening satellites were found in XPS spectra of weak chemisorption systems [5,6], in crystals [7,8], in weakly bound atomic [9] and microsolvated [10][11][12] clusters. As shown in the latter studies, the energy positions and intensities of CT satellites are sensitive to cluster geometries. Furthermore, the type and number of neighbors have strong effects on CT states [13]. CT processes from core-excited metal ions to solvent molecules may quench radiative relaxation processes as observed in fluorescence-yield spectra [14].For elements from the first rows of the periodic table, electronic Auger decay is the main relaxation channel of core-hole states. Core-hole lifetime ranging usually in the femtosecond and sub-femtosecond timescales may serve as an internal reference clock. Using this reference and the relative intensities of spectral peaks, the core-hole clock method allows one to determine timescales of various processes competing to Auger decay, in particular ...

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Charge transfer to solvent identified using dark channel fluorescence-yield L-edge spectroscopy

Cited by 64 publications

References 30 publications

Dissecting Local Atomic and Intermolecular Interactions of Transition-Metal Ions in Solution with Selective X-ray Spectroscopy

Dissecting Local Atomic and Intermolecular Interactions of Transition-Metal Ions in Solution with Selective X-ray Spectroscopy

Electronic structure of Fe- vs. Ru-based dye molecules

Ultrafast Charge Transfer Processes Accompanying KLL Auger Decay in Aqueous KCl Solution

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