Department of Chemistry, University of Washington, Seattle, Washington 98195, USA.
J Phys Chem A. 2013 May 30;117(21):4444-54. doi: 10.1021/jp401020j. Epub 2013 May 17.
Ruthenium L3-edge X-ray absorption (XA) spectroscopy probes unoccupied 4d orbitals of the metal atom and is increasingly being used to investigate the local electronic structure in ground and excited electronic states of Ru complexes. The simultaneous development of computational tools for simulating Ru L3-edge spectra is crucial for interpreting the spectral features at a molecular level. This study demonstrates that time-dependent density functional theory (TDDFT) is a viable and predictive tool for simulating ruthenium L3-edge XA spectroscopy. We systematically investigate the effects of exchange correlation functional and implicit and explicit solvent interactions on a series of Ru(II) and Ru(III) complexes in their ground and electronic excited states. The TDDFT simulations reproduce all of the experimentally observed features in Ru L3-edge XA spectra within the experimental resolution (0.4 eV). Our simulations identify ligand-specific charge transfer features in complicated Ru L3-edge spectra of Ru(CN)6 and Ru(II) polypyridyl complexes illustrating the advantage of using TDDFT in complex systems. We conclude that the B3LYP functional most accurately predicts the transition energies of charge transfer features in these systems. We use our TDDFT approach to simulate experimental Ru L3-edge XA spectra of transition metal mixed-valence dimers of the form (NC)5M(II)-CN-Ru(III)(NH3)5 (where M = Fe or Ru) dissolved in water. Our study determines the spectral signatures of electron delocalization in Ru L3-edge XA spectra. We find that the inclusion of explicit solvent molecules is necessary for reproducing the spectral features and the experimentally determined valencies in these mixed-valence complexes. This study validates the use of TDDFT for simulating Ru 2p excitations using popular quantum chemistry codes and providing a powerful interpretive tool for equilibrium and ultrafast Ru L3-edge XA spectroscopy.
钌 L3 边 X 射线吸收（XA）光谱探测金属原子的未占据 4d 轨道，并且越来越多地用于研究 Ru 配合物的基态和激发电子态中的局部电子结构。用于模拟 Ru L3 边光谱的计算工具的同时发展对于在分子水平上解释光谱特征至关重要。本研究表明，含时密度泛函理论（TDDFT）是模拟钌 L3 边 XA 光谱的可行且可预测的工具。我们系统地研究了交换相关函数以及隐式和显式溶剂相互作用对一系列 Ru(II)和 Ru(III)配合物在基态和电子激发态中的影响。TDDFT 模拟再现了 Ru L3 边 XA 光谱中所有实验观察到的特征，分辨率为 0.4 eV。我们的模拟确定了 Ru(CN)6和 Ru(II)多吡啶配合物复杂的 Ru L3 边光谱中的配体特异性电荷转移特征，说明了在复杂体系中使用 TDDFT 的优势。我们得出结论，B3LYP 函数最准确地预测了这些体系中电荷转移特征的跃迁能。我们使用我们的 TDDFT 方法模拟了形式为(NC)5M(II)-CN-Ru(III)(NH3)5（其中 M = Fe 或 Ru）的过渡金属混合价二聚体在水中的 Ru L3 边 XA 实验光谱。我们的研究确定了 Ru L3 边 XA 光谱中电子离域的光谱特征。我们发现，对于再现这些混合价配合物的光谱特征和实验确定的价态，必须包含显式溶剂分子。这项研究验证了使用流行的量子化学代码模拟 Ru 2p 激发的 TDDFT 的使用，并为平衡和超快 Ru L3 边 XA 光谱学提供了强大的解释工具。
