Publications by authors named "Kristopher Benke"

Iron porphyrins are the active sites of many natural and artificial catalysts, and their photoinduced dynamics have been described as either relaxation into a vibrationally hot ground state or as a cascade through metal-centered states. In this work, we directly probe the metal center of iron(III) tetraphenyl porphyrin chloride (FeTPPCl) using femtosecond M-edge X-ray absorption near-edge structure (XANES) spectroscopy. Photoexcitation at 400 nm produces a (π,π*) state that evolves in 70 fs to an iron(II) ligand-to-metal charge transfer (LMCT) state.

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We show that the electronic structure of molecular first-row transition-metal complexes can be reliably measured using tabletop high-harmonic XANES at the metal M2,3 edge. Extreme ultraviolet photons in the 50-70 eV energy range probe 3p → 3d transitions, with the same selection rules as soft X-ray L2,3-edge absorption (2p → 3d excitation). Absorption spectra of model complexes are sensitive to the electronic structure of the metal center, and ligand field multiplet simulations match the shapes and peak-to-peak spacings of the experimental spectra.

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