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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Solvent and spectral effects in the ultrafast charge recombination dynamics of excited donor-acceptor complexes
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Solvent and spectral effects in the ultrafast charge recombination dynamics of excited donor-acceptor complexes

机译：激发的供体-受体复合物超快电荷重组动力学中的溶剂和光谱效应

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摘要

The charge recombination dynamics of excited donor-acceptor complexes consisting of hexamethylbenzene (HMB), pentamethylbenzene (PMB), and isodurene (IDU) as electron donors and tetracyanoethylene (TCNE) as electron acceptor in various polar solvents has been investigated within the framework of the stochastic approach. The model accounts for the reorganization of intramolecular high-frequency vibrational modes as well as for the solvent reorganization. All electron-transfer energetic parameters have been determined from the resonance Raman data and from the analysis of the stationary charge transfer absorption band, while the electronic coupling has been obtained from the fit to the charge recombination dynamics in one solvent. It appears that nearly 100% of the initially excited donor-acceptor complexes recombine in a nonthermal (hot) stage when the nonequilibrium wave packet passes through a number of term crossings corresponding to transitions toward vibrational excited states of the electronic ground state. Once all parameters of the model have been obtained, the influence of the dynamic solvent properties (solvent effect) and of the carrier frequency of the excitation pulse (spectral effect) on the charge recombination dynamics have been explored. The main conclusions are (i) the model provides a globally satisfactory description for the IDU/TCNE complex although it noticeably overestimates the spectral effect, (ii) the solvent effect is quantitatively well described for the PMB/TCNE and HMB/TCNE complexes but the model fails to reproduce their spectral effects, and (iii) the positive spectral effect observed with the HMB/TCNE complex cannot be described within the framework of two-level models and the charge redistribution in the excited complexes should most probably be taken into account.
机译：已经研究了由六甲基苯（HMB），五甲基苯（PMB）和作为电子给体的异戊二烯（IDU）和作为电子受体的四氰基乙烯（TCNE）组成的激发供体-受体配合物在各种极性溶剂中的电荷重组动力学。随机方法。该模型考虑了分子内高频振动模式的重组以及溶剂的重组。根据共振拉曼数据和对固定电荷转移吸收带的分析，确定了所有电子转移能参数，而根据对一种溶剂中电荷复合动力学的拟合，获得了电子耦合。似乎当非平衡波包通过许多与电子向基态的振动激发态跃迁相对应的术语穿越时，将近100％的最初激发的供体-受体复合物在非热（热）阶段重组。一旦获得了模型的所有参数，就可以探索动态溶剂性质（溶剂效应）和激发脉冲的载频（频谱效应）对电荷复合动力学的影响。主要结论是：（i）尽管该模型明显高估了光谱效应，但该模型为IDU / TCNE复合物提供了一个全球令人满意的描述;（ii）PMB / TCNE和HMB / TCNE复合物的溶剂效应在定量上得到了很好的描述，但是该模型无法重现其光谱效应，并且（iii）在两级模型的框架内无法描述HMB / TCNE配合物观察到的正光谱效应，最有可能应考虑激发配合物中的电荷再分布。

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