Insights into the Induced Ultrafast Electron Delocalization in Fe(CO)₅ Using Dark Channel Fluorescence Yield X‐Ray Absorption

Abstract

Well-coordinated: L(2,3) -edge X-ray absorption measurements of Fe(CO)(5), carried out for the first time in solution, are discussed. Using the dark channel fluorescence yield technique, ultrafast delocalization processes on the femtosecond time-scale yield new insights into the electronic structure.

Probing the Electronic Structure of Substituted Ferrocenes with High‐Resolution XANES Spectroscopy

“…So far, the lifetime broadening of conventional K‐edge XAS experiments limits their applicability for probing the LUMO states. On the other hand, in L‐edge XAS3 a more intense 2p→nd transition can be used,4 but because of the use of low‐energy radiation, in situ studies of catalytic reactions are not possible with this technique. Therefore, a hard X‐ray technique with a better resolution of the final d‐states than in conventional XAS is required to probe the electronic structure of catalysts in situ.…”

Dissecting Local Atomic and Intermolecular Interactions of Transition-Metal Ions in Solution with Selective X-ray Spectroscopy

“…In the context of "dark channel fluorescence yield" Aziz et al interpreted this orbital mixing as supportive for the assertion of ultrafast electron transfer from the metal d-orbitals to the solvent as deduced from the metal-ion L-edge spectra (21). This electron transfer would occur during the core-hole lifetime of core-excited state in the metal-ion: As the electron excited upon x-ray absorption would have transferred to the solvent, the corresponding fluorescence decay channel would be quenched leaving a dip in the metal-ion L-edge spectrum (21)(22)(23)(24). It was claimed that the transfer would be the more efficient and correspondingly the dip would be the deeper, the stronger the orbital overlap between the metal d-orbitals and the solvent orbitals would be.…”

“…They found features in the total fluorescence yield (TFY) spectra when scanning the L-edges of 3d transition metal ions and complexes in solution at high concentration that dip below the fluorescence background of the solvent. It was claimed that this could be used as a new tool to study charge transfer to solvent effects (21)(22)(23)(24). The dips where attributed, first, to ultrafast electron transfer from the metal d-orbitals to the solvent (21)(22)(23)(24) and, second, to a competition of solute and solvent fluorescence (25).…”

“…It was claimed that this could be used as a new tool to study charge transfer to solvent effects (21)(22)(23)(24). The dips where attributed, first, to ultrafast electron transfer from the metal d-orbitals to the solvent (21)(22)(23)(24) and, second, to a competition of solute and solvent fluorescence (25). Earlier, Näslund et al proposed strong orbital mixing between the 3d orbitals of Fe ions solvated in water based on an analysis of the O K-edge absorption spectrum of aqueous solutions (26) without making a connection to any charge transfer.…”

Ligand discrimination of myoglobin in solution: an iron L-edge X-ray absorption study of the active centre

“…Such reduction of the L 3 intensity in TFY-XA spectra at the L-edge of 3-d transition metals in aqueous solution has recently been correlated with ultrafast charge-transfer processes to the solvent. [23][24][25] Orbital mixing leads to electron delocalization between the valence d-orbitals of the transition metal and the valence bands of the solvent molecules, quenching some of the metal X-ray fluorescence bands. 26 It was argued that electron delocalization which contributes to the non-radiative process is faster than L 3 core-hole life time (2 fs) 14 and slower than the L 2 one (0.7 fs), 14 affecting accordingly mainly the L 3 -edge.…”