Control of the photoinduced charge separation in the self-organized porphyrin-fullerene supramolecule systems

自组织卟啉-富勒烯超分子体系中光致电荷分离的控制

基本信息

批准号：
14350449
负责人：
ITO Osamu
金额：
$ 9.34万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2003
项目状态：
已结题

项目摘要

Self-Assembled electron donor-acceptor linked systems play a very important role in the artificial photosynthetic system because of the easy way to keep the short distance between the electron donor and acceptor. The various researches for the artificial photosynthesis with covalently linked donor-acceptor systems exist. In this work we established the self-assembled zinc porphyrin and fullerence[C60]system to build up the supramolecules containing them and to achieve the photoinduced electron transfer reactions with high efficiency and the long-lived charge separated state like a photosynthetic reaction center. In these supramolecular systems, efficient charge separation was confirmed by the time-resolved fluorescence measurements and by the fs-ps transient absorption methods. The lifetimes of charge-separated states were determined by the ns transient spectra in near IR region.The pyridine and imodazole moieties were introduced on C_<60> to construct the supramolecular systems via coordination bonds between zinc porphyrin. In the case of imodazole, we obtained the higher equilibrium constant in the formation of the supramolecule and the high efficiency of the charge separation. The higher equilibrium constant for axial coordination was obtained at low temperature. This means that the more efficient charge separation occurred at the low temperature.On the other hand, we found that the supramolecular systems in rotaxanes containing C_<60> and porphyrin. In these systems, C_<60> has a ring to catch the axel, which has porphyrin as a stopper. By the time-resolved fluorescence and transient absorption measurements, we found the efficient intra-rotaxane charge separation and long-lived charge separated state in these rotaxane. Interestingly, we found the size dependency of the charge separation type ; the change separation starts from the excited singlet state in the small rotaxane, however, it starts from the excited triplet state in the large one.

自组装电子供体-受体连接系统由于可以轻松保持电子供体和受体之间的距离较短，因此在人工光合作用系统中发挥着非常重要的作用。存在利用共价连接的供体-受体系统进行人工光合作用的各种研究。在这项工作中，我们建立了自组装锌卟啉和富勒烯[C60]体系来构建含有它们的超分子，并实现高效率的光诱导电子转移反应和像光合反应中心一样长寿命的电荷分离状态。在这些超分子系统中，通过时间分辨荧光测量和 fs-ps 瞬态吸收方法证实了有效的电荷分离。通过近红外区的纳秒瞬态光谱测定电荷分离态的寿命。在C_<60>上引入吡啶和咪唑部分，通过锌卟啉之间的配位键构建超分子体系。在咪唑的情况下，我们在超分子的形成中获得了更高的平衡常数和高效率的电荷分离。在低温下获得了较高的轴向配位平衡常数。这意味着在低温下发生更有效的电荷分离。另一方面，我们发现轮烷中的超分子体系含有C_<60>和卟啉。在这些系统中，C_<60>有一个环来捕获轴，轴上有卟啉作为塞子。通过时间分辨荧光和瞬态吸收测量，我们发现这些轮烷中有效的轮烷内电荷分离和长寿命的电荷分离状态。有趣的是，我们发现了电荷分离类型的尺寸依赖性；小轮烷中的变化分离是从激发单重态开始的，而大轮烷中是从激发三重态开始的。