Disentangling Transient Charge Density and Metal–Ligand Covalency in Photoexcited Ferricyanide with Femtosecond Resonant Inelastic Soft X-ray Scattering

Jay, Raphael M.; Norell, Jesper; Eckert, Sebastian; Hantschmann, Markus; Beye, Martin; Kennedy, Brian; Quevedo, Wilson; Schlotter, W. F.; Dakovski, Georgi L.; Minitti, Michael P.; Hoffmann, Matthias C.; Mitra, A.; Moeller, Stefan; Nordlund, Dennis; Zhang, Wenkai; Liang, Huiyang W.; Kunnus, Kristjan; Kubiček, Katharina; Techert, Simone; Lundberg, Marcus; Wernet, Philippe; Gaffney, Kelly J.; Odelius, Michael; Föhlisch, Alexander

doi:10.1021/acs.jpclett.8b01429

Cited by 50 publications

(62 citation statements)

References 34 publications

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“…Oscillatory wavepacket motions have been clearly measured in time-resolved WAXS [19,27,32], however the effects of purely nuclear dynamics in ultrafast Kα/Kβ XES has not been observed [10][11][12][13][14]. This contrasts with other X-ray spectroscopic methods that directly involve valence orbitals, such as X-ray absorption [33][34][35][36][37][38] and resonant inelastic X-ray scattering [39][40][41], which are sensitive to both electronic and nuclear structure. The development of ultrafast XES requires understanding the impact of nuclear dynamics on Ka and Kb XES spectra.…”

Section: Introductionmentioning

confidence: 99%

Vibrational wavepacket dynamics in Fe carbene photosensitizer determined with femtosecond X-ray emission and scattering

et al. 2020

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The non-equilibrium dynamics of electrons and nuclei govern the function of photoactive materials. Disentangling these dynamics remains a critical goal for understanding photoactive materials. Here we investigate the photoinduced dynamics of the [Fe(bmip)2]2+ photosensitizer, where bmip = 2,6-bis(3-methyl-imidazole-1-ylidine)-pyridine, with simultaneous femtosecond-resolution Fe Kα and Kβ X-ray emission spectroscopy (XES) and X-ray solution scattering (XSS). This measurement shows temporal oscillations in the XES and XSS difference signals with the same 278 fs period oscillation. These oscillations originate from an Fe-ligand stretching vibrational wavepacket on a triplet metal-centered (3MC) excited state surface. This 3MC state is populated with a 110 fs time constant by 40% of the excited molecules while the rest relax to a 3MLCT excited state. The sensitivity of the Kα XES to molecular structure results from a 0.7% average Fe-ligand bond length shift between the 1 s and 2p core-ionized states surfaces.

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Section: Introductionmentioning

confidence: 99%

Vibrational wavepacket dynamics in Fe carbene photosensitizer determined with femtosecond X-ray emission and scattering

et al. 2020

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“…[6][7][8] While the excited-state potential energy landscape of Fe II complexes can now be routinely tailored, we still lack af undamental understanding of the valence electronic structure of charge-transfer states as the starting point of interfacial charge injection. They are commonly described by alocally oxidized/reduced metal site, [9][10][11] but the quantitative implications on charge and spin distributions are rather elusive.T his is in particular the case in the light of quantum chemical simulations suggesting that oxidizing the transition metal center,that is,reducing the 3d electron count, does not strongly influence its local electronic charge. [12,13] Reconciling these observations with the demonstrated interfacial charge injection from MLCT states of Fe-based dyes [14][15][16] is therefore not only important in terms of af undamental chemical understanding but also for the further development of lowcost and high-efficiency light-harvesting applications.…”

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confidence: 99%

Covalency‐Driven Preservation of Local Charge Densities in a Metal‐to‐Ligand Charge‐Transfer Excited Iron Photosensitizer

et al. 2019

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Covalency is found to even out charge separation after photo‐oxidation of the metal center in the metal‐to‐ligand charge‐transfer state of an iron photosensitizer. The σ‐donation ability of the ligands compensates for the loss of iron 3d electronic charge, thereby upholding the initial metal charge density and preserving the local noble‐gas configuration. These findings are enabled through element‐specific and orbital‐selective time‐resolved X‐ray absorption spectroscopy at the iron L‐edge. Thus, valence orbital populations around the central metal are directly accessible. In conjunction with density functional theory we conclude that the picture of a localized charge‐separation is inadequate. However, the unpaired spin density provides a suitable representation of the electron–hole pair associated with the electron‐transfer process.

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“…XAS and RIXS spectroscopy applied to metal–ligand complexes can provide an atom‐specific, chemical state selective, crystal field symmetry and orbital symmetry resolved description of the electronic structure . In References , it has been shown that this allows for scrutinizing traditional chemical concepts of metal–ligand bonding.…”

Section: Applicationsmentioning

confidence: 99%

Theoretical X‐ray spectroscopy of transition metal compounds

Bokarev

Kühn

2019

WIREs Comput Mol Sci

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X-ray spectroscopy is one of the most powerful tools to access structure and properties of matter in different states of aggregation as it allows to trace atomic and molecular energy levels in course of various physical and chemical processes. Xray spectroscopic techniques probe the local electronic structure of a particular atom in its environment, in contrast to ultraviolet/visible (UV/Vis) spectroscopy, where transitions generally occur between delocalized molecular orbitals. Complementary information is provided by using a combination of different absorption, emission, scattering as well as photo-and autoionization X-ray methods. However, interpretation of the complex experimental spectra and verification of experimental hypotheses is a nontrivial task and powerful first principles theoretical approaches that allow for a systematic investigation of a broad class of systems are needed. Focusing on transition metal compounds, L-edge spectra are of particular relevance as they probe the frontier d-orbitals involved in metal-ligand bonding. Here, neardegeneracy effects in combination with spin-orbit coupling lead to a complicated multiplet energy level structure, which poses a serious challenge to quantum chemical methods. Multiconfigurational self-consistent field (MCSCF) theory has been shown to be capable of providing a rather detailed understanding of experimental X-ray spectroscopy. However, it cannot be considered as a "blackbox" tool and its application requires not only a command of formal theoretical aspects, but also a broad knowledge of already existing applications. Both aspects are covered in this overview.

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Disentangling Transient Charge Density and Metal–Ligand Covalency in Photoexcited Ferricyanide with Femtosecond Resonant Inelastic Soft X-ray Scattering

Cited by 50 publications

References 34 publications

Vibrational wavepacket dynamics in Fe carbene photosensitizer determined with femtosecond X-ray emission and scattering

Vibrational wavepacket dynamics in Fe carbene photosensitizer determined with femtosecond X-ray emission and scattering

Covalency‐Driven Preservation of Local Charge Densities in a Metal‐to‐Ligand Charge‐Transfer Excited Iron Photosensitizer

Theoretical X‐ray spectroscopy of transition metal compounds

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