Vibronic Dynamics Localize Charge in Photoexcited CoFe Prussian Blue Analogue Nanoparticles
Gerrit N Christenson1, Edoardo Buttarazzi2,3, Alessio Petrone2,3,4
1Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States.
The Journal of Physical Chemistry Letters
|March 2, 2026
Summary
Prussian Blue analogues are photoswitchable materials. This study reveals how light-induced charge transfer dynamics in CsCoFe nanoparticles are influenced by molecular vibrations, impacting spin states.
Area of Science:
- Materials Science
- Photochemistry
- Spectroscopy
Background:
- Prussian Blue analogues (PBAs) are key photoswitchable materials.
- Understanding photoexcited states and spin dynamics in PBAs is crucial for photomagnetism.
- Molecular vibronic dynamics' role in spin-related photochemistry needs further elucidation.
Purpose of the Study:
- Investigate the ultrafast dynamics of CsCoFe Prussian Blue analogue nanoparticles.
- Elucidate the influence of vibronic dynamics on photoexcited states and charge distribution.
- Connect molecular-level behavior to macroscopic properties like photomagnetism.
Main Methods:
- Transient infrared absorption spectroscopy utilizing tunable excitation pulses (350–700 nm).
- Probing the photoexcited CN stretch vibration.
- First-principles density functional theory (DFT) analysis.
Main Results:
- All excited states converge to a metal-to-metal charge-transfer (MCT) manifold within 300 fs.
- The MCT state efficiently populates a metal-to-ligand charge-transfer (MLCT) state within 500 fs.
- Charge localization occurs on bridging CN ligands.
Conclusions:
- Electronic, spin, and structural dynamics are coupled in CsCoFe nanoparticles.
- These coupled degrees of freedom collectively govern charge distribution after photoexcitation.
- Provides molecular-level insights into the photochemistry of PBAs.
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