Simulating Ru L3-Edge X-ray Absorption Spectroscopy with Time-Dependent Density Functional Theory: Model Complexes and Electron Localization in Mixed-Valence Metal Dimers

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• 作者：Benjamin E. Van Kuiken ; Marat Valiev ; Stephanie L. Daifuku ; Caitlin Bannan ; Matthew L. Strader ; Hana Cho ; Nils Huse ; Robert W. Schoenlein ; Niranjan Govind ; Munira Khalil
• 刊名：The Journal of Physical Chemistry A
• 出版年：2013
• 出版时间：May 30, 2013
• 年：2013
• 卷：117
• 期：21
• 页码：4444-4454
• 全文大小：478K
• 年卷期：v.117,no.21(May 30, 2013)
• ISSN：1520-5215

文摘

Ruthenium L₃-edge X-ray absorption (XA) spectroscopy probes unoccupied 4d orbitals of the metal atom and is increasingly being used to investigate the local electronic structure in ground and excited electronic states of Ru complexes. The simultaneous development of computational tools for simulating Ru L₃-edge spectra is crucial for interpreting the spectral features at a molecular level. This study demonstrates that time-dependent density functional theory (TDDFT) is a viable and predictive tool for simulating ruthenium L₃-edge XA spectroscopy. We systematically investigate the effects of exchange correlation functional and implicit and explicit solvent interactions on a series of Ru^II and Ru^III complexes in their ground and electronic excited states. The TDDFT simulations reproduce all of the experimentally observed features in Ru L₃-edge XA spectra within the experimental resolution (0.4 eV). Our simulations identify ligand-specific charge transfer features in complicated Ru L₃-edge spectra of [Ru(CN)₆]^4- and Ru^II polypyridyl complexes illustrating the advantage of using TDDFT in complex systems. We conclude that the B3LYP functional most accurately predicts the transition energies of charge transfer features in these systems. We use our TDDFT approach to simulate experimental Ru L₃-edge XA spectra of transition metal mixed-valence dimers of the form [(NC)₅M^II-CN-Ru^III(NH₃)₅]^{鈭?/sup> (where M = Fe or Ru) dissolved in water. Our study determines the spectral signatures of electron delocalization in Ru L₃-edge XA spectra. We find that the inclusion of explicit solvent molecules is necessary for reproducing the spectral features and the experimentally determined valencies in these mixed-valence complexes. This study validates the use of TDDFT for simulating Ru 2p excitations using popular quantum chemistry codes and providing a powerful interpretive tool for equilibrium and ultrafast Ru L₃-edge XA spectroscopy.}