Observation of the Solvent Shell Reorganization around Photoexcited Atomic Solutes by Picosecond X-ray Absorption Spectroscopy

Pham, Van-Thai; Gawełda, Wojciech; Zaushitsyn, Yuri; Kaiser, M.; Grolimund, Daniel; Johnson, S. L.; Abela, R.; Bressler, Christian; Chergui, Majed

doi:10.1021/ja068466q

Cited by 62 publications

(62 citation statements)

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“…Several studies concerned the structural dynamics of photodissociated intermediates in the solution phase as in the case of NiTPP-L 2 and NiTMP (where TPP = nickel tetraphenylporphyrin, L = piperidine and TMP = tetramesitylporphyrin) [249,250]. Furthermore, TR-XAS was employed to monitor ultrafast spin crossover in iron complexes, unveiling also the structures of elusive high-spin states [160,[251][252][253], as well as to clarify the mechanism of solvent-shell rearrangements around atomic ionic solutes [254].…”

Section: (Py) 2 ] 2+mentioning

confidence: 99%

Synchrotron ultrafast techniques for photoactive transition metal complexes

Borfecchia

Garino

Salassa

et al. 2013

Phil. Trans. R. Soc. A.

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In the last decade, the use of time-resolved X-ray techniques has revealed the structure of lightgenerated transient species for a wide range of samples, from small organic molecules to proteins. Time resolutions of the order of 100 ps are typically reached, allowing one to monitor thermally equilibrated excited states and capture their structure as a function of time. This review aims at providing a general overview of the application of timeresolved X-ray solution scattering (TR-XSS) and time-resolved X-ray absorption spectroscopy (TR-XAS), the two techniques prevalently employed in the investigation of light-triggered structural changes of transition metal complexes. In particular, we herein describe the fundamental physical principles for static XSS and XAS and illustrate the theory of timeresolved XSS and XAS together with data acquisition and analysis strategies. Selected pioneering examples of photoactive transition metal complexes studied by TR-XSS and TR-XAS are discussed in depth.

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Section: (Py) 2 ] 2+mentioning

confidence: 99%

Synchrotron ultrafast techniques for photoactive transition metal complexes

Borfecchia

Garino

Salassa

et al. 2013

Phil. Trans. R. Soc. A.

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“…30À34 We previously presented 35 a preliminary picosecond XAS study of multiphoton-excited aqueous iodide, which showed significant changes in the XANES and EXAFS regions of the L 1,3 edges 50 ps after excitation, suggesting an extensive solvent rearrangement in the transition from iodide to iodine. However, these changes were not quantified by lack of a precise determination of the photolysis yield, which is a crucial parameter for the structural analysis.…”

Section: Introductionmentioning

confidence: 99%

Probing the Transition from Hydrophilic to Hydrophobic Solvation with Atomic Scale Resolution

et al. 2011

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Picosecond and femtosecond X-ray absorption spectroscopy is used to probe the changes of the solvent shell structure upon electron abstraction of aqueous iodide using an ultrashort laser pulse. The transient L1,3 edge EXAFS at 50 ps time delay points to the formation of an expanded water cavity around the iodine atom, in good agreement with classical and quantum mechanical/molecular mechanics (QM/MM) molecular dynamics (MD) simulations. These also show that while the hydrogen atoms pointed toward iodide, they predominantly point toward the bulk solvent in the case of iodine, suggesting a hydrophobic behavior. This is further confirmed by quantum chemical (QC) calculations of I–/I0(H2O) n=1–4 clusters. The L1 edge sub-picosecond spectra point to the existence of a transient species that is not present at 50 ps. The QC calculations and the QM/MM MD simulations identify this transient species as an I0(OH2) complex inside the cavity. The simulations show that upon electron abstraction most of the water molecules move away from iodine, while one comes closer to form the complex that lives for 3–4 ps. This time is governed by the reorganization of the main solvation shell, basically the time it takes for the water molecules to reform an H-bond network. Only then is the interaction with the solvation shell strong enough to pull the water molecule of the complex toward the bulk solvent. Overall, much of the behavior at early times is determined by the reorientational dynamics of water molecules and the formation of a complete network of hydrogen bonded molecules in the first solvation shell.

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“…As there are a limited number of experimental methods for studying the hydration of short-lived radicals lacking a strong chromophore, new techniques capable of yielding direct structural information with atomic resolution are required. Time-resolved x-ray scattering 1 and x-ray absorption spectroscopy [2][3][4][5][6][7] ͑XAS͒ are such techniques. In this Communication, we report the study of the hydration of a simple open-shell system, the Br 0 atom, using transient XAS.…”

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confidence: 99%

“…Recently, Pham et al 7 reported XAS measurements of I 0 atoms following biphotonic electron detachment from aqueous iodide. They observe a prominent change of the spectra at the L 1 and L 3 absorption edges, but their interpretation is complicated by the reaction of I 0 with excess I − to form a substantial amount of I 2 − and I 3 − within the ϳ80 ps duration of the x-ray pulse.…”

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Transient x-ray absorption spectroscopy of hydrated halogen atom

Elles

Shkrob

Crowell

et al. 2008

The Journal of Chemical Physics

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Time-resolved x-ray absorption spectroscopy has been used to observe the transient species generated by one-photon detachment of an electron from aqueous bromide. The K-edge spectrum of the short-lived Br 0 atom exhibits a resonant 1s-4p transition that is absent for the Br − precursor. The strong 1s-4p resonance suggests that there is very little charge transfer from the solvent to the open-shell atom, whereas weak oscillations above the absorption edge indicate that the solvent shell around a neutral Br 0 atom is defined primarily by hydrophobic interactions. These conclusions are in agreement with Monte Carlo and quantum chemical simulations of the solvent structure. © 2008 American Institute of Physics. ͓DOI: 10.1063/1.2827456͔Reactions of small inorganic radicals in aqueous solution are important for aerosol, marine, photo-and radiation chemistry. The reactivity of such radicals depends on their interaction with polar water molecules. As there are a limited number of experimental methods for studying the hydration of short-lived radicals lacking a strong chromophore, new techniques capable of yielding direct structural information with atomic resolution are required. Time-resolved x-ray scattering 1 and x-ray absorption spectroscopy 2-7 ͑XAS͒ are such techniques. In this Communication, we report the study of the hydration of a simple open-shell system, the Br 0 atom, using transient XAS.Details about the hydration of halogen atoms are not well known.2,3 The hydration of halogen atoms ͑X 0 ͒ is very different from the hydration of negatively charged halide anions ͑X − ͒. Whereas the anion forms strong hydrogen bonds with several water molecules in the first solvent shell ͓Fig. 1͑a͔͒, hydrophobic effects dominate the solvation of neutral halogen atoms ͓Fig. 1͑b͔͒. The bromine atom resides in a solvent cavity and interacts with the solvent to give a charge transfer ͑CT͒ absorption band at 4.6 eV. 8 The CT absorption promotes an electron from the water molecule͑s͒ onto the halogen atom ͓Fig. 1͑c͔͒. In the case of Cl 0 , electron spin resonance measurements 9 suggest that the Cl 0 atom and one of the water molecules form a two center, three electron ͑ 2 * 1 ͒ bond in the ground state. Similar bonding may also occur for Br 0 and I 0 in water. 10 The much stronger halogenhalogen bonding between a halogen atom and its anion is also a two center, three electron bond ͓Fig. 1͑d͔͒.Recently, Pham et al. 7 reported XAS measurements of I 0 atoms following biphotonic electron detachment from aqueous iodide. They observe a prominent change of the spectra at the L 1 and L 3 absorption edges, but their interpretation is complicated by the reaction of I 0 with excess I − to form a substantial amount of I 2 − and I 3 − within the ϳ80 ps duration of the x-ray pulse. Rapid formation of molecular anions in their experiment is a consequence of the high concentration of I − ͑500 mol/ m 3 ͒, which is necessary to overcome inefficient two-photon absorption. In contrast, efficient onephoton electron detachment from Br − at 200 nm ͑Re...

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Observation of the Solvent Shell Reorganization around Photoexcited Atomic Solutes by Picosecond X-ray Absorption Spectroscopy

Cited by 62 publications

References 14 publications

Synchrotron ultrafast techniques for photoactive transition metal complexes

Synchrotron ultrafast techniques for photoactive transition metal complexes

Probing the Transition from Hydrophilic to Hydrophobic Solvation with Atomic Scale Resolution

Transient x-ray absorption spectroscopy of hydrated halogen atom

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