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首页> 外文期刊>The journal of physical chemistry, B. Condensed matter, materials, surfaces, interfaces & biophysical >Singlet-State Electron Transfer between a Porphyrin and Ubiquinone: A Transient Resonance Raman and Quantum Chemical Study
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Singlet-State Electron Transfer between a Porphyrin and Ubiquinone: A Transient Resonance Raman and Quantum Chemical Study

机译：卟啉与泛醌之间的单态电子转移：瞬态共振拉曼和量子化学研究

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摘要

Radical ion pairs resulting from bimolecular electron transfer between excited singlet porphyrin donors and quinone acceptors have such short lifetimes that they are rarely observed. Here we report the results of a spectroscopic investigation of the photodynamics of a noncovalent complex of a free base meso-tetrakis (4-sulfonatophenyl)porphine (P) and 2,3-dimethoxy-5-methyl-l,4-benzoquinone (ubiquinone, UQ↓(0)). P and UQ↓(0) form a weak ground-state complex (K↓(a) ≈ 1.0 ×10↑(3) M↑(-1)), which decays via a CT intermediate after photoexcitation of a local porphyrin π－π↑(*) excited state. Transient resonance Raman spectroscopy (TRRS) was employed to identify and characterize singlet-correlated electron-transfer intermediates in this process. The transient porphyrin cation modes are well-characterized and conform to previous assignments. While some of the modes expected of the ubiquinone radical anion are obscured by the porphyrin vibrations, the predominantly C=C and C＝O modes are clearly discernible in the transient RR spectra. Ab initio calculations were used to help assign the observed modes of the UQ↓(0) and calculate “self-exchange” reorganizational energy (≈0.60 eV) for the UQ↓(0)/UQ↓(0)↑(·-) radical anion pair. These results are discussed in the context of modem theories of electron transfer.
机译：由激发的单重态卟啉供体和醌受体之间的双分子电子转移产生的自由基离子对具有如此短的寿命，因此很少被观察到。在这里，我们报告的光谱研究的游离碱的内消旋四（4-磺基苯基）卟啉（P）和2,3-二甲氧基-5-甲基-1,4-苯醌（泛醌）的非共价配合物的光动力学研究的结果，UQ↓（0））。 P和UQ↓（0）形成弱的基态复合物（K↓（a）≈1.0×10↑（3）M↑（-1）），在局部激发卟啉π－后，通过CT中间物衰减π↑（*）激发态。在此过程中，采用瞬态共振拉曼光谱（TRRS）来鉴定和表征单峰相关的电子转移中间体。瞬态卟啉阳离子模式具有很好的特征，并符合以前的要求。尽管卟啉的振动掩盖了泛醌自由基阴离子的某些预期模态，但在瞬态RR谱中主要可以分辨出C = C和C = O模态。从头算就可以帮助分配观察到的UQ↓（0）模式，并为UQ↓（0）/ UQ↓（0）↑（·-）计算“自交换”重组能（≈0.60eV）自由基阴离子对。这些结果是在电子转移的现代理论的背景下讨论的。

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