Femtosecond X-ray Spectroscopy Directly Quantifies Transient Excited-State Mixed Valency

Liekhus-Schmaltz, Chelsea; Fox, Zachary W.; Andersen, Amity; Kjaer, Kasper S.; Alonso-Mori, Roberto; Biasin, Elisa; Carlstad, Julia; Chollet, Matthieu; Gaynor, James D.; Glownia, James M.; Hong, Kiryong; Kroll, Thomas; Lee, Jae Hyuk; Poulter, Benjamin I.; Reinhard, Marco; Sokaras, Dimosthenis; Zhang, Yu; Doumy, Gilles; March, Anne Marie; Southworth, Stephen H.; Mukamel, Shaul; Cordones, Amy A.; Schoenlein, Robert W.; Govind, Niranjan; Khalil, Munira

doi:10.1021/acs.jpclett.1c03613

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Femtosecond X-ray Spectroscopy Directly Quantifies Transient Excited-State Mixed Valency

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Abstract

Quantifying charge delocalization associated with short-lived photoexcited states of molecular complexes in solution remains experimentally challenging, requiring local element specific femtosecond experimental probes of time-evolving electron transfer. In this study, we quantify the evolving valence hole charge distribution in the photoexcited charge transfer state of a prototypical mixed valence bimetallic iron–ruthenium complex, [(CN) 5 Fe II CNRu III (NH 3 ) 5 ]-, in water by combining femtosecond X-ray spectroscopy measurements with time-dependent density functional theory calculations of the excited-state dynamics. We estimate the valence hole charge that accumulated at the Fe atom to be 0.6 ± 0.2, resulting from excited-state metal-to-metal charge transfer, on an ~ 60 fs time scale. Our combined experimental and computational approach provides a spectroscopic ruler for quantifying excited-state valency in solvated complexes.

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Liekhus-Schmaltz, Chelsea, Fox, Zachary W., Andersen, Amity, Kjaer, Kasper S., Alonso-Mori, Roberto, Biasin, Elisa, Carlstad, Julia, Chollet, Matthieu, Gaynor, James D., Glownia, James M., Hong, Kiryong, Kroll, Thomas, Lee, Jae Hyuk, Poulter, Benjamin I., Reinhard, Marco, Sokaras, Dimosthenis, Zhang, Yu, Doumy, Gilles, March, Anne Marie, Southworth, Stephen H., Mukamel, Shaul, Cordones, Amy A., Schoenlein, Robert W., Govind, Niranjan, Khalil, Munira. 2022-01-05. Femtosecond X-ray Spectroscopy Directly Quantifies Transient Excited-State Mixed Valency. https://doi.org/10.1021/acs.jpclett.1c03613

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