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Updated: Feb 28, 2026

Ultrafast Time-resolved Near-IR Stimulated Raman Measurements of Functional π-conjugate Systems
Published on: February 10, 2020
Investigating the kinetics of spin-crossover transitions using Raman spectroscopy
Gérald Kämmerer1, Lea Kämmerer1, Stephan Sleziona1
1Faculty of Physics and Center for Nanointegration Duisburg-Essen (CENIDE), University Duisburg-Essen, Lotharstraße 1, 47057 Duisburg, Germany. gerald.kaemmerer@uni-due.de.
None:
The room-temperature spin-crossover iron(II) complex Fe(1-bpp-COOC2H5)2(BF4)2CH3CN exhibits reversible switching between the low-spin and high-spin states. The observation of coexisting spin domains within polycrystalline samples of Fe(1-bpp-COOC2H5)2(BF4)2CH3CN allows for real-time video recording of domain boundary propagation under an optical microscope. Quantitative analysis of this motion provides valuable information regarding the phenomenological transition involved in the spin-state switching process. To elucidate the intricate dynamics of this spin transition, a synergistic approach combining temperature-dependent Raman spectroscopy with ab initio computational methods is employed. Within this investigation, a comprehensive classification of Raman vibrational modes has been achieved, categorizing them based on their spin-state dependence and vibrational characteristics, symmetries, including stretching, bending, and tilting motions. Notably, low-frequency Raman modes associated with the iron center and its nitrogen ligand environment provide crucial insights into the local coordination and its role in the spin-crossover mechanism. This work reveals distinct spin-state-induced structural changes, including bond stretching and softening, which manifest as unique spectroscopic fingerprints for each spin state.
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