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Chiral control of spin-crossover dynamics in Fe(II) complexes

Oppermann, Malte
Chergui, Majed
Published in Nature chemistry. 2022, vol. 14, no. 7, p. 739-745
Abstract Iron-based spin-crossover complexes hold tremendous promise as multifunctional switches in molecular devices. However, real-world technological applications require the excited high-spin state to be kinetically stable-a feature that has been achieved only at cryogenic temperatures. Here we demonstrate high-spin-state trapping by controlling the chiral configuration of the prototypical iron(II)tris(4,4′-dimethyl-2,2′-bipyridine) in solution, associated for stereocontrol with the enantiopure Δ-or Λ-enantiomer of tris(3,4,5,6-tetrachlorobenzene-1,2-diolato-κ2O1,O2)phosphorus(V) (P(O2C6Cl4)3- or TRISPHAT) anions. We characterize the high-spin-state relaxation using broadband ultrafast circular dichroism spectroscopy in the deep ultraviolet in combination with transient absorption and anisotropy measurements. We find that the high-spin-state decay is accompanied by ultrafast changes of its optical activity, reflecting the coupling to a symmetry-breaking torsional twisting mode, contrary to the commonly assumed picture. The diastereoselective ion pairing suppresses the vibrational population of the identified reaction coordinate, thereby achieving a fourfold increase of the high-spin-state lifetime. More generally, our results motivate the synthetic control of the torsional modes of iron(II) complexes as a complementary route to manipulate their spin-crossover dynamics.
Keywords Circular dichroismExcited statesOrganometallic chemistryPhotochemistryOptical spectroscopy
PMID: 35618767
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Other version: https://www.nature.com/articles/s41557-022-00933-0
Dataset: https://doi.org/10.5281/zenodo.6255933
Research group Groupe Lacour
(ISO format)
OPPERMANN, Malte et al. Chiral control of spin-crossover dynamics in Fe(II) complexes. In: Nature chemistry, 2022, vol. 14, n° 7, p. 739-745. doi: 10.1038/s41557-022-00933-0 https://archive-ouverte.unige.ch/unige:161907

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Deposited on : 2022-07-05

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