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X-ray Transient Absorption Spectroscopy: Characterizing the Excited-State Structural Dynamics of Transition Metal Complexes.

机译：X射线瞬态吸收光谱：表征过渡金属配合物的激发态结构动力学。

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摘要

With the development of 3rd generation synchrotron sources and more advanced laser systems, ultrafast pump-probe experiments implementing an X-ray probe are now feasible, opening the door to new methods for excited-state structural characterization. X-ray transient absorption (XTA) spectroscopy measures the structure around a unique atomic center in a system in any medium while simultaneously measuring the electronic structure of that unique atom. When combined with time-resolved optical spectroscopy, such as optical transient absorption (TA), the excited-state dynamics of any system can be fully characterized, potentially guiding the design of more effective solar energy harvesting devices. In this thesis, the excited-state structural and electronic dynamics of two transition metal complexes are analyzed. The correlation between their atomic rearrangements and the functions of these chemical systems is deciphered, answering long-standing fundamental questions regarding their dynamics and reaction mechanisms.;The first portion of this work focuses on myoglobin and iron protoporphyrin IX and the dissociation/recombination dynamics of carbon monoxide to their iron centers. The properties of these systems differ due to the presence of the protein macrostructure, which is present for myoglobin and absent for porphyrin. The ligand recombination dynamics are measured by a combined optical TA and XTA approach and the heme reorganization associated with the formation of the "domed" structure upon ligand loss are measured. The effect of the protein globin on these structural reorganizations is discussed.;The second portion of this work focuses on the relationship between ground-state structure and excited-state dynamics of copper(I) bisphenanthrolines. Changing the substituents at the 2,9 positions of the phenanthroline ligand causes massive alterations in the ground state structure, optical absorption, and excited-state dynamics. The photophysical properties of two such complexes, the tetrahedral [Cu(I)(dtbp)2]+ (with tBu substituents), and the heavily flattened [Cu(I)(dpp)2]+ (with phenyl substituents), are probed using TA, XTA, and TD-DFT methods. The relationship of these different groups on the Jahn-Teller states are discussed, as well as their effects on the flattening, intersystem crossing, and phosphorescence rates. Carboxylated forms of [Cu(I)(dpp)2]+ are attached to TiO2; ultrafast electron injection into the TiO 2 is observed, and conclusions are drawn regarding the electron injection mechanism.
机译：随着第三代同步加速器源和更先进的激光系统的发展，实现X射线探针的超快泵浦探针实验现在变得可行，这为激发态结构表征的新方法打开了大门。 X射线瞬态吸收（XTA）光谱仪可在任何介质中测量系统中唯一原子中心周围的结构，同时测量该唯一原子的电子结构。当与时间分辨光谱（例如光学瞬态吸收（TA））结合使用时，可以充分表征任何系统的激发态动力学特性，从而有可能指导更有效的太阳能收集设备的设计。本文分析了两种过渡金属配合物的激发态结构和电子动力学。解释了它们的原子重排与这些化学系统的功能之间的相关性，回答了有关其动力学和反应机理的长期存在的基本问题。这项工作的第一部分着重于肌红蛋白和原卟啉IX以及解离/重组动力学。一氧化碳进入其铁中心。这些系统的特性因蛋白质宏观结构的存在而有所不同，蛋白质宏观结构存在于肌红蛋白中，而卟啉则不存在。通过光学TA和XTA的组合方法测量配体的重组动力学，并测量与配体损失时形成“圆顶”结构有关的血红素重组。讨论了蛋白质珠蛋白对这些结构重组的影响。第二部分研究的重点是铜（I）双菲咯啉的基态结构与激发态动力学之间的关系。改变菲咯啉配体的2,9位上的取代基会导致基态结构，光吸收和激发态动力学发生巨大变化。探究了两个这样的配合物的光物理性质，即四面体[Cu（I）（dtbp）2] +（具有tBu取代基）和高度扁平化的[Cu（I）（dpp）2] +（具有苯基取代基）使用TA，XTA和TD-DFT方法。讨论了这些不同基团在Jahn-Teller态上的关系，以及它们对展平，系统间交叉和磷光速率的影响。 [Cu（I）（dpp）2] +的羧基化形式连接到TiO2上；观察到将超快电子注入到TiO 2中，并得出关于电子注入机理的结论。

著录项

  • 作者

    Mara, Michael W.;

  • 作者单位

    Northwestern University.;

  • 授予单位 Northwestern University.;
  • 学科 Chemistry Physical.
  • 学位 Ph.D.
  • 年度 2014
  • 页码 245 p.
  • 总页数 245
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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