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

自组装电子给体-受体连接系统由于易于保持电子给体和受体之间的短距离而在人工光合系统中起着非常重要的作用。利用共价链供受体系统进行人工光合作用的研究有很多。本文建立了自组装的卟啉锌和富勒[C60]体系，构建了含有它们的超分子，实现了光致电子转移反应的高效率和长寿命的电荷分离状态，如光合反应中心。在这些超分子体系中，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。利用近红外区瞬态光谱测定了电荷分离态的寿命。在C_<60>上引入吡啶和咪唑基团，通过锌卟啉之间的配位键构建了超分子体系。以咪唑为例，我们获得了较高的超分子形成平衡常数和较高的电荷分离效率。在低温条件下获得较高的轴向配位平衡常数。这意味着在较低的温度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。在这些体系中，C_<60>有一个环来捕获axel，其中有卟啉作为阻止物。通过时间分辨荧光和瞬态吸收测量，我们发现这些轮烷具有高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；在小轮烷中，变化分离从激发态单线态开始，而在大轮烷中，变化分离从激发态三重态开始。

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.