Resolving structures of transition metal complex reaction intermediates with femtosecond EXAFS

Britz, Alexander; Abraham, Baxter; Biasin, Elisa; Driel, Tim Brandt van; Gallo, Alessandro; Garcia‐Esparza, Angel T.; Glownia, James M.; Loukianov, Anton; Nelson, S.; Reinhard, Marco; Sokaras, Dimosthenis; Alonso-Mori, Roberto

doi:10.1039/c9cp03483h

Cited by 24 publications

(21 citation statements)

References 47 publications

(57 reference statements)

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“…A commonly studied reaction coordinate-the ultrafast elongation of the metal-ligand bond-has been interpreted to be the key structural signature of SCO 23,[28][29][30] . In BPY and other SCO systems 28,[30][31][32][33][34][35] , it has been proposed that this nuclear motion is dynamically coupled to various structural distortions of the ligand. The potential nuclear motions leading to an expanded HS molecule were first discussed in an earlier timeresolved X-ray diffraction (TR-XRD) experiment 36 and a number of theoretical studies 7,11,13,37 .…”

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confidence: 99%

Direct observation of nuclear reorganization driven by ultrafast spin transitions

et al. 2020

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One of the most basic molecular photophysical processes is that of spin transitions and intersystem crossing between excited states surfaces. The change in spin states affects the spatial distribution of electron density through the spin orbit coupling interaction. The subsequent nuclear reorganization reports on the full extent of the spin induced change in electron distribution, which can be treated similarly to intramolecular charge transfer with effective reaction coordinates depicting the spin transition. Here, single-crystal [Fe II (bpy) 3 ](PF 6 ) 2 , a prototypical system for spin crossover (SCO) dynamics, is studied using ultrafast electron diffraction in the single-photon excitation regime. The photoinduced SCO dynamics are resolved, revealing two distinct processes with a (450 ± 20)-fs fast component and a (2.4 ± 0.4)-ps slow component. Using principal component analysis, we uncover the key structural modes, ultrafast Fe-N bond elongations coupled with ligand motions, that define the effective reaction coordinate to fully capture the relevant molecular reorganization.

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confidence: 99%

Direct observation of nuclear reorganization driven by ultrafast spin transitions

et al. 2020

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“…Although excitation and deactivation take place at a single FeII center, the photoinduced dynamics in Fe3 differ from the ones observed in mononuclear Fe II complexes. As known from extensive phenomenology, mononuclear Fe II complexes with a rigid FCS, such as [Fe II (bpy) 3 ] 2+(bpy= 2,2′-bipyridine)[32][33][34] or [Fe II (terpy) 2 ] 2+ (terpy= 2,2′:6′,2″-terpyridine)35,36 exhibit subpicosecond vibrational coherence, the IVR and VC take place in a few picoseconds and the HS state lives for some ns. For mononuclear Fe II complexes with a flexible FCS such as…”

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Revealing Hot and Long-Lived Metastable Spin States in the Photoinduced Switching of Solvated Metallogrid Complexes with Femtosecond Optical and X-ray Spectroscopies

Naumova

Kalinko

Wong

et al. 2020

J. Phys. Chem. Lett.

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An atomistic understanding of the photoinduced spin-state switching (PSS) within polynuclear systems of d 4 -d 7 transition metal ion complexes is required for their rational integration into light-driven reactions of chemical and biological interests. However, in contrast to mononuclear systems, the multidimensional dynamics of the PSS in solvated molecular arrayshave not yet been elucidated, due to the expected complications associated to the connectivity between the metal centers and the strong interactions with the surroundings. In this work, the PSS in a solvated triiron(II) metallogrid complex is characterized using transient optical absorption and X-ray emission spectroscopies on the femtosecond timescale. The complementary measurements reveal the photoinduced creation of energy-rich (hot) and longlived quintet states, whose dynamics differ critically from their mononuclear congeners. This finding opens major prospects for developing novel schemes in solution-phase spin chemistry that are driven by the dynamic PSS process in compact oligometallic arrays. TOC GRAPHICSKEYWORDS molecular squares, photophysics, time-resolved X-ray techniques, light-induced processes, ultrafast phenomena, spin-state switching.

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“…This will be important for identifying how the photophysics and photochemistry varies for isoelectronic 3d, 4d, and 5d complexes. The increase in repetition rate will enable ultrafast X-ray spectroscopy based on weaker signals, including valence-to-core K-edge XES [133][134][135] and extended X-ray absorption ne structure (EXAFS) 136 measurements that directly characterize the inner coordination sphere geometry of the absorbing atom.…”

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confidence: 99%

Capturing photochemical and photophysical transformations in iron complexes with ultrafast X-ray spectroscopy and scattering

Gaffney

2021

Chem. Sci.

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Resolving structures of transition metal complex reaction intermediates with femtosecond EXAFS

Abstract: Femtosecond EXAFS is implemented at an XFEL and can be used to observe short-lived intermediate states of photoexcited transition metal complexes in solution.

Cited by 24 publications

References 47 publications

Direct observation of nuclear reorganization driven by ultrafast spin transitions

Direct observation of nuclear reorganization driven by ultrafast spin transitions

Revealing Hot and Long-Lived Metastable Spin States in the Photoinduced Switching of Solvated Metallogrid Complexes with Femtosecond Optical and X-ray Spectroscopies

Capturing photochemical and photophysical transformations in iron complexes with ultrafast X-ray spectroscopy and scattering

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