Solvation-Driven Charge Transfer and Localization in Metal Complexes
Solvation-Driven Charge Transfer and Localization in Metal Complexes
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金属配合物中溶剂驱动的电荷转移和局域化
DOI：
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发表时间：
2015
影响因子：
18.3
通讯作者：
A. Cannizzo
中科院分区：
文献类型：
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作者：
A. Rondi;Y. Rodriguez;T. Feurer;A. Cannizzo
在液体中的任何物理化学过程中，溶剂对溶质失去平衡的动态响应在速率和产物中起着至关重要的作用：溶剂分子对溶质的体积和电子密度的变化作出反应，以使溶液的自由能最小化，从而调节活化屏障并稳定（或破坏）中间状态。在极性溶剂的电荷转移（CT）过程中，溶剂的反应总是通过稳定局域电荷的能量来帮助电荷分离态的形成。因此，深入了解溶剂化机制和时间尺度对于正确描述任何致密相光化学过程以及设计基于CT激发态光敏剂的分子器件至关重要。近二十年来，随着超快时间分辨光谱的出现，描述极性溶剂化（溶剂和溶质分子都具有永久电偶极子，相互作用主要是偶极子-偶极子）相关情况的微观模型取得了巨大进展。无论每种模型的细节如何，它们都假设溶剂分子的静电场对溶质内部电子动力学的影响是微扰的，并且溶剂-溶质耦合主要是溶质与溶剂分子的恒定永久偶极子之间的静电相互作用。这一成熟的图像已被证明可以定量地合理化环境和电动力学的光谱效应（时间分辨斯托克斯位移、不均匀展宽等）。然而，最近的计算和实验研究，包括我们的研究，表明需要进一步改进。事实上，在过去的几年里，我们研究了几种表现出光激发CT态的分子配合物，我们发现目前对一组重要分子（如过渡金属配合物）中CT态的形成和稳定的描述是不准确的。特别是，我们证明了溶剂分子不仅是分子内电子密度再分布的旁观者，而且对其有显著的调节作用。我们的结果要求进一步发展量子力学计算方法来处理溶质和（至少）最接近的溶剂分子，包括局部静电效应的非摄动处理和直接溶剂-溶质相互作用，以描述溶剂响应过程中溶质激发态的动态变化。
Conspectus In any physicochemical process in liquids, the dynamical response of the solvent to the solutes out of equilibrium plays a crucial role in the rates and products: the solvent molecules react to the changes in volume and electron density of the solutes to minimize the free energy of the solution, thus modulating the activation barriers and stabilizing (or destabilizing) intermediate states. In charge transfer (CT) processes in polar solvents, the response of the solvent always assists the formation of charge separation states by stabilizing the energy of the localized charges. A deep understanding of the solvation mechanisms and time scales is therefore essential for a correct description of any photochemical process in dense phase and for designing molecular devices based on photosensitizers with CT excited states. In the last two decades, with the advent of ultrafast time-resolved spectroscopies, microscopic models describing the relevant case of polar solvation (where both the solvent and the solute molecules have a permanent electric dipole and the mutual interaction is mainly dipole–dipole) have dramatically progressed. Regardless of the details of each model, they all assume that the effect of the electrostatic fields of the solvent molecules on the internal electronic dynamics of the solute are perturbative and that the solvent–solute coupling is mainly an electrostatic interaction between the constant permanent dipoles of the solute and the solvent molecules. This well-established picture has proven to quantitatively rationalize spectroscopic effects of environmental and electric dynamics (time-resolved Stokes shifts, inhomogeneous broadening, etc.). However, recent computational and experimental studies, including ours, have shown that further improvement is required. Indeed, in the last years we investigated several molecular complexes exhibiting photoexcited CT states, and we found that the current description of the formation and stabilization of CT states in an important group of molecules such as transition metal complexes is inaccurate. In particular, we proved that the solvent molecules are not just spectators of intramolecular electron density redistribution but significantly modulate it. Our results solicit further development of quantum mechanics computational methods to treat the solute and (at least) the closest solvent molecules including the nonperturbative treatment of the effects of local electrostatics and direct solvent–solute interactions to describe the dynamical changes of the solute excited states during the solvent response.
影响因子：
15
作者：
Cannizzo, Andrea;Blanco-Rodriguez, Ana Maria;Chergui, Majed
通讯作者：
Chergui, Majed