Tabletop Femtosecond M-edge XANES of FeTPPCl: Metalloporphyrin Photophysics from the Perspective of the Metal,Journal of the American Chemical Society

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Tabletop Femtosecond M-edge XANES of FeTPPCl: Metalloporphyrin Photophysics from the Perspective of the Metal
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2018-03-14 , DOI: 10.1021/jacs.8b01101
Elizabeth S. Ryland ₁ , Ming-Fu Lin ₁ , Max A. Verkamp ₁ , Kaili Zhang ₁ , Kristin Benke ₁ , Michaela Carlson ₁ , Josh Vura-Weis ₁

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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 M2,3-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. The LMCT state relaxes to a vibrationally hot ground state in 1.13 ps, without involvement of (d,d) intermediates. The tabletop extreme-ultraviolet probe, combined with semiempirical ligand field multiplet calculations, clearly distinguishes between metal-centered and ligand-centered excited states and resolves competing accounts of Fe(III) porphyrin relaxation. This work introduces tabletop M-edge XANES as a valuable tool for measuring femtosecond dynamics of molecular transition metal complexes in the condensed phase.

中文翻译：

FeTPPCl 的桌面飞秒 M 边 XANES：金属视角下的金属卟啉光物理学

铁卟啉是许多天然和人工催化剂的活性位点，它们的光致动力学被描述为松弛到振动热基态或通过金属中心态的级联反应。在这项工作中，我们使用飞秒 M2,3 边 X 射线吸收近边结构 (XANES) 光谱直接探测氯化铁 (III) 四苯基卟啉 (FeTPPCl) 的金属中心。400 nm 的光激发产生 (π,π*) 状态，该状态在 70 fs 内演变为铁 (II) 配体-金属电荷转移 (LMCT) 状态。LMCT 状态在 1.13 ps 内弛豫到振动热基态，不涉及（d，d）中间体。桌面极紫外探针，结合半经验配体场多重计算，清楚地区分以金属为中心和以配体为中心的激发态，并解决了 Fe(III) 卟啉弛豫的竞争性解释。这项工作介绍了桌面 M-edge XANES 作为测量凝聚相中分子过渡金属配合物的飞秒动力学的宝贵工具。

更新日期：2018-03-14

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