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Elucidation of the photoaquation reaction mechanism in ferrous hexacyanide using synchrotron x-rays with sub-pulse-duration sensitivity

March, Anne Marie ; Doumy, Gilles ; Andersen, Amity ; Al Haddad, Andre ; Kumagai, Yoshiaki ; Tu, Ming Feng ; Bang, Joohee ; Bostedt, Christoph ; Uhlig, Jens LU and Nascimento, Daniel R. , et al. (2019) In Journal of Chemical Physics 151(14).
Abstract

Ligand substitution reactions are common in solvated transition metal complexes, and harnessing them through initiation with light promises interesting practical applications, driving interest in new means of probing their mechanisms. Using a combination of time-resolved x-ray absorption spectroscopy and hybrid quantum mechanics/molecular mechanics (QM/MM) molecular dynamics simulations and x-ray absorption near-edge spectroscopy calculations, we elucidate the mechanism of photoaquation in the model system iron(ii) hexacyanide, where UV excitation results in the exchange of a CN- ligand with a water molecule from the solvent. We take advantage of the high flux and stability of synchrotron x-rays to capture high precision... (More)

Ligand substitution reactions are common in solvated transition metal complexes, and harnessing them through initiation with light promises interesting practical applications, driving interest in new means of probing their mechanisms. Using a combination of time-resolved x-ray absorption spectroscopy and hybrid quantum mechanics/molecular mechanics (QM/MM) molecular dynamics simulations and x-ray absorption near-edge spectroscopy calculations, we elucidate the mechanism of photoaquation in the model system iron(ii) hexacyanide, where UV excitation results in the exchange of a CN- ligand with a water molecule from the solvent. We take advantage of the high flux and stability of synchrotron x-rays to capture high precision x-ray absorption spectra that allow us to overcome the usual limitation of the relatively long x-ray pulses and extract the spectrum of the short-lived intermediate pentacoordinated species. Additionally, we determine its lifetime to be 19 (±5) ps. The QM/MM simulations support our experimental findings and explain the ∼20 ps time scale for aquation as involving interconversion between the square pyramidal (SP) and trigonal bipyramidal pentacoordinated geometries, with aquation being only active in the SP configuration.

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organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Journal of Chemical Physics
volume
151
issue
14
article number
144306
publisher
American Institute of Physics (AIP)
external identifiers
  • pmid:31615248
  • scopus:85073205776
ISSN
0021-9606
DOI
10.1063/1.5117318
language
English
LU publication?
yes
id
55610248-4bd4-4638-9f68-522d014f537c
date added to LUP
2019-10-21 12:48:02
date last changed
2020-10-27 01:49:49
@article{55610248-4bd4-4638-9f68-522d014f537c,
  abstract     = {<p>Ligand substitution reactions are common in solvated transition metal complexes, and harnessing them through initiation with light promises interesting practical applications, driving interest in new means of probing their mechanisms. Using a combination of time-resolved x-ray absorption spectroscopy and hybrid quantum mechanics/molecular mechanics (QM/MM) molecular dynamics simulations and x-ray absorption near-edge spectroscopy calculations, we elucidate the mechanism of photoaquation in the model system iron(ii) hexacyanide, where UV excitation results in the exchange of a CN<sup>-</sup> ligand with a water molecule from the solvent. We take advantage of the high flux and stability of synchrotron x-rays to capture high precision x-ray absorption spectra that allow us to overcome the usual limitation of the relatively long x-ray pulses and extract the spectrum of the short-lived intermediate pentacoordinated species. Additionally, we determine its lifetime to be 19 (±5) ps. The QM/MM simulations support our experimental findings and explain the ∼20 ps time scale for aquation as involving interconversion between the square pyramidal (SP) and trigonal bipyramidal pentacoordinated geometries, with aquation being only active in the SP configuration.</p>},
  author       = {March, Anne Marie and Doumy, Gilles and Andersen, Amity and Al Haddad, Andre and Kumagai, Yoshiaki and Tu, Ming Feng and Bang, Joohee and Bostedt, Christoph and Uhlig, Jens and Nascimento, Daniel R. and Assefa, Tadesse A. and Németh, Zoltán and Vankó, György and Gawelda, Wojciech and Govind, Niranjan and Young, Linda},
  issn         = {0021-9606},
  language     = {eng},
  number       = {14},
  publisher    = {American Institute of Physics (AIP)},
  series       = {Journal of Chemical Physics},
  title        = {Elucidation of the photoaquation reaction mechanism in ferrous hexacyanide using synchrotron x-rays with sub-pulse-duration sensitivity},
  url          = {http://dx.doi.org/10.1063/1.5117318},
  doi          = {10.1063/1.5117318},
  volume       = {151},
  year         = {2019},
}