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Femtosecond XANES study of the light-induced spin crossover dynamics in an iron(II) complex

Bressler, Ch ; Milne, C. ; Elnahhas, A. ; Van Der Veen, R. M. ; Gawelda, W. ; Johnson, S. ; Beaud, P. ; Grolimund, D. ; Kaiser, M. and Borca, C. N. , et al. (2009) In Science 323(5913). p.489-492
Abstract


X-ray absorption spectroscopy is a powerful probe of molecular structure, but it has previously been too slow to track the earliest dynamics after photoexcitation. We investigated the ultrafast formation of the lowest quintet state of aqueous iron(II) tris(bipyridine) upon excitation of the singlet metal-to-ligand-charge-transfer (
1
MLCT) state by femtosecond optical pump/x-ray probe techniques based on x-ray absorption near-edge structure (XANES). By recording the intensity of a characteristic XANES feature as a function of laser pump/x-ray probe time delay, we find that the quintet state is populated in about 150 femtoseconds.... (More)


X-ray absorption spectroscopy is a powerful probe of molecular structure, but it has previously been too slow to track the earliest dynamics after photoexcitation. We investigated the ultrafast formation of the lowest quintet state of aqueous iron(II) tris(bipyridine) upon excitation of the singlet metal-to-ligand-charge-transfer (
1
MLCT) state by femtosecond optical pump/x-ray probe techniques based on x-ray absorption near-edge structure (XANES). By recording the intensity of a characteristic XANES feature as a function of laser pump/x-ray probe time delay, we find that the quintet state is populated in about 150 femtoseconds. The quintet state is further evidenced by its full XANES spectrum recorded at a 300-femtosecond time delay. These results resolve a long-standing issue about the population mechanism of quintet states in iron(II)-based complexes, which we identify as a simple
1
MLCT→
3
MLCT→
5
T cascade from the initially excited state. The time scale of the
3
MLCT→
5
T relaxation corresponds to the period of the iron-nitrogen stretch vibration.

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publishing date
type
Contribution to journal
publication status
published
subject
in
Science
volume
323
issue
5913
pages
4 pages
publisher
American Association for the Advancement of Science (AAAS)
external identifiers
  • scopus:58849154526
ISSN
0036-8075
DOI
10.1126/science.1165733
language
English
LU publication?
no
id
24630d25-a618-4406-81da-4f565e24278c
date added to LUP
2019-06-30 10:00:57
date last changed
2022-03-25 21:14:15
@article{24630d25-a618-4406-81da-4f565e24278c,
  abstract     = {{<p><br>
                            X-ray absorption spectroscopy is a powerful probe of molecular structure, but it has previously been too slow to track the earliest dynamics after photoexcitation. We investigated the ultrafast formation of the lowest quintet state of aqueous iron(II) tris(bipyridine) upon excitation of the singlet metal-to-ligand-charge-transfer (<br>
                            <sup>1</sup><br>
                            MLCT) state by femtosecond optical pump/x-ray probe techniques based on x-ray absorption near-edge structure (XANES). By recording the intensity of a characteristic XANES feature as a function of laser pump/x-ray probe time delay, we find that the quintet state is populated in about 150 femtoseconds. The quintet state is further evidenced by its full XANES spectrum recorded at a 300-femtosecond time delay. These results resolve a long-standing issue about the population mechanism of quintet states in iron(II)-based complexes, which we identify as a simple <br>
                            <sup>1</sup><br>
                            MLCT→<br>
                            <sup>3</sup><br>
                            MLCT→<br>
                            <sup>5</sup><br>
                            T cascade from the initially excited state. The time scale of the <br>
                            <sup>3</sup><br>
                            MLCT→ <br>
                            <sup>5</sup><br>
                            T relaxation corresponds to the period of the iron-nitrogen stretch vibration.<br>
                        </p>}},
  author       = {{Bressler, Ch and Milne, C. and Elnahhas, A. and Van Der Veen, R. M. and Gawelda, W. and Johnson, S. and Beaud, P. and Grolimund, D. and Kaiser, M. and Borca, C. N. and Ingold, G. and Abela, R. and Chergui, M. and Pham, Van-Thai}},
  issn         = {{0036-8075}},
  language     = {{eng}},
  month        = {{01}},
  number       = {{5913}},
  pages        = {{489--492}},
  publisher    = {{American Association for the Advancement of Science (AAAS)}},
  series       = {{Science}},
  title        = {{Femtosecond XANES study of the light-induced spin crossover dynamics in an iron(II) complex}},
  url          = {{http://dx.doi.org/10.1126/science.1165733}},
  doi          = {{10.1126/science.1165733}},
  volume       = {{323}},
  year         = {{2009}},
}