Light-induced spin crossover probed by ultrafast optical and X-ray spectroscopies

Wojciech Gawelda, Andrea Cannizzo, Van Thai Pham, Amal El Nahhas, Christopher J. Milne, Renske Van Der Veen, Christian Bressler, Majed Chergui

Research output: Contribution to journalArticlepeer-review


The photoinduced energy and structural relaxation of aqueous iron(II)-tris-bipyridine ([FeII(bpy)3]2+), upon excitation into its singlet metal-to-ligand charge transfer (1MLCT) band, and the population of its short-lived (≤0.6 ns) high-spin excited state have been characterized by combined ultrafast optical and X-ray spectroscopies. Polychromatic femtosecond fluorescence up-conversion reveals a very short lived 1MLCT emission band, which decays in ≤20 fs by intersystem crossing to a 3MLCT, whose very weak emission is also observed. Transient absorption studies show that the latter decays in <150 fs, while the population of the lowest excited high spin quintet state 5T 2 occurs in ∼1 ps. Subsequently it decays in ∼665 ps to the ground state. Therefore, we determined the structure of the high-spin excited state by picosecond X-ray absorption spectroscopy at the K edge of Fe. The structural analysis of both the transient difference and excited state X-ray spectra delivered an Fe-N bond elongation of 0.2 Å in the quintet state compared to the singlet ground state.

Original languageEnglish (US)
Pages (from-to)179-183
Number of pages5
Issue number4
StatePublished - 2007
Externally publishedYes


  • Fluorescence
  • Iron (II) complexes
  • Optical absorption
  • Spin crossover
  • Ultrafast
  • X-ray absorption

ASJC Scopus subject areas

  • General Chemistry


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