Electron transfer fromoligothiophenes in the higher triplet excited states
Electron transfer fromoligothiophenes in the higher triplet excited states
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处于较高三重激发态的低聚噻吩的电子转移
DOI：
10.1021/jp106056e
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
TetsuroMajima
中科院分区：
文献类型：
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作者：
Mamoru Fujitsuka;Takeshi Nakatani;TetsuroMajima
本文研究了低聚噻吩（3T和4T）从高三重激发态（Tn）到分子间和分子内的电子转移过程。在分子间体系的情况下，双色双激光闪光光解，使用纳秒激光器施加到溶液中，包括二苯甲酮，低聚噻吩，卤代苯作为光敏剂，电子供体，和电子受体，分别。第一激光照射经由来自二苯甲酮的能量转移产生低聚噻吩的最低三重激发态（T1）。在第二激光照射时，低聚噻吩的自由基阳离子的吸收带出现，同时T1态的吸收带漂白，表明电子从低聚噻吩的T2态转移到电子受体。用Marcus理论解释了电子转移速率与自由能变化的关系。利用飞秒激光双色双激光闪光光解技术研究了噻吩齐聚物与受体分子的分子内电子转移。在产生Tn态的第二激光照射时，T1态的吸收带的动力学迹线显示漂白和恢复，其速率取决于低聚噻吩从T2态的电荷分离的驱动力。这一观察结果表明存在从T2态的电荷分离过程，并且电荷分离态的观察可能是困难的，这可能是由于低电荷分离产率和快速电荷复合。
In the present paper, we have investigated the inter- and intramolecular electron transfer processes from the higher triplet excited state (Tn) of oligothiophenes (3T and 4T). In the case of the intermolecular systems, two-color two-laser flash photolysis using nanosecond lasers was applied to the solution including benzophenone, oligothiophene, and halogenated benzene as a photosensitizer, an electron donor, and an electron acceptor, respectively. The first laser light irradiation generated the lowest triplet excited state (T1) of oligothiophene via energy transfer from benzophenone. Upon the second laser light irradiation, the absorption band of the radical cation of oligothiophene appeared with the simultaneous bleaching of the absorption band of the T1state, indicating the electron transfer from the T2state of the oligothiophene to the electron acceptor. The observed electron transfer rate dependent on the free energy change was explained on the basis of the Marcus theory. The intramolecular electron transfer in the dyad molecule of oligothiophene and acceptor was investigated using the two-color two-laser flash photolysis employing femtosecond laser. Upon the second laser light irradiation, which generates the Tnstate, the kinetic trace of the absorption band of T1state showed the bleaching and recovery, the rate of which depends on the driving force for the charge separation from the T2state of the oligothiophene. This observation suggests the existence of charge separation process from the T2state, and the observation of the charge-separated state was difficult probably due to the low charge separation yield and fast charge recombination.