Tuning Electron-Transfer Driving Force in Photosynthetic Special Pair Models

Visible-light excitation of a family of bimetallic ruthenium polypyridines with the formula [RuII(tpy)(bpy)(μ-CN)RuII(py)4L]n+ (RuRuLn+), where L = Cl-, NCS-, DMAP and ACN, was used to prepare photoinduced mixed-valence (PI-MV) MLCT states as models of the photosynthetic reaction center. Ultrafast t...

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Published in:Chemistry : a European journal 2024-11, p.e202402700
Main Authors: Ramírez-Wierzbicki, Ivana, Merlinsky, Luciano Sanchez, Pieslinger, German E, Domínguez, Sofía, Slep, Leonardo D, Baraldo, Luis M, Cadranel, Alejandro
Format: Article
Language:English
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Summary:Visible-light excitation of a family of bimetallic ruthenium polypyridines with the formula [RuII(tpy)(bpy)(μ-CN)RuII(py)4L]n+ (RuRuLn+), where L = Cl-, NCS-, DMAP and ACN, was used to prepare photoinduced mixed-valence (PI-MV) MLCT states as models of the photosynthetic reaction center. Ultrafast transient absorption spectroscopy allowed to monitor photoinduced IVCT bands between 6000 and 11000 cm-1. Mulliken spin densities resulting from DFT and (TD)DFT computations revealed the modulation of the charge density distribution depending on the ligand substitution pattern. Results are consistent with PI-MV systems ranging from non-degenerate Class II to degenerate Class III, with electronic couplings between 1000 and 3500 cm-1. These findings guide the control electron localization-delocalization in charge-transfer/charge-separated excited states, like those involved in the photosynthetic reaction center.
ISSN:0947-6539
1521-3765
1521-3765
DOI:10.1002/chem.202402700