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Probing the transition from hydrophilic to hydrophobic solvation with atomic scale resolution

Pham, Van-Thai LU ; Penfold, Thomas J. ; Van Der Veen, Renske M. ; Lima, Frederico ; El Nahhas, Amal LU ; Johnson, Steve L. ; Beaud, Paul ; Abela, Rafael ; Bressler, Christian and Tavernelli, Ivano , et al. (2011) In Journal of the American Chemical Society 133(32). p.12740-12748
Abstract


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 L
1,3
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... (More)


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 L
1,3
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
-
/I
0
(H
2
O)
n=1-4
clusters. The L
1
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 I
0
(OH
2
) 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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publishing date
type
Contribution to journal
publication status
published
subject
in
Journal of the American Chemical Society
volume
133
issue
32
pages
9 pages
publisher
The American Chemical Society (ACS)
external identifiers
  • scopus:80051597345
  • pmid:21740023
ISSN
0002-7863
DOI
10.1021/ja203882y
language
English
LU publication?
no
id
999d7ea9-1be8-487e-8076-717ce2b720aa
date added to LUP
2019-06-30 09:51:03
date last changed
2021-03-24 06:01:04
@article{999d7ea9-1be8-487e-8076-717ce2b720aa,
  abstract     = {<p><br>
                            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 L <br>
                            <sub>1,3</sub><br>
                             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 <br>
                            <sup>-</sup><br>
                            /I <br>
                            <sup>0</sup><br>
                            (H <br>
                            <sub>2</sub><br>
                            O) <br>
                            <sub>n=1-4</sub><br>
                             clusters. The L <br>
                            <sub>1</sub><br>
                             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 I <br>
                            <sup>0</sup><br>
                            (OH <br>
                            <sub>2</sub><br>
                            ) 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.</p>},
  author       = {Pham, Van-Thai and Penfold, Thomas J. and Van Der Veen, Renske M. and Lima, Frederico and El Nahhas, Amal and Johnson, Steve L. and Beaud, Paul and Abela, Rafael and Bressler, Christian and Tavernelli, Ivano and Milne, Christopher J. and Chergui, Majed},
  issn         = {0002-7863},
  language     = {eng},
  month        = {08},
  number       = {32},
  pages        = {12740--12748},
  publisher    = {The American Chemical Society (ACS)},
  series       = {Journal of the American Chemical Society},
  title        = {Probing the transition from hydrophilic to hydrophobic solvation with atomic scale resolution},
  url          = {http://dx.doi.org/10.1021/ja203882y},
  doi          = {10.1021/ja203882y},
  volume       = {133},
  year         = {2011},
}