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

自组装电子给体-受体连接系统由于其能使电子给体和受体之间保持较短的距离而在人工光合系统中起着非常重要的作用。人工光合作用与共价连接的供体-受体系统的各种研究存在。本工作建立了锌卟啉和富勒烯[C60]的自组装体系，构建了含锌卟啉和富勒烯[C60]的超分子，实现了高效的光诱导电子转移反应，并获得了类似光合反应中心的长寿命电荷分离态。在这些超分子体系中，有效的电荷分离证实了时间分辨荧光测量和fs-ps瞬态吸收方法。通过近红外区的ns瞬态光谱确定了电荷分离态的寿命，并通过锌卟啉之间的配位键将吡啶和咪唑引入到C_2上<60>，构建了超分子体系。在咪唑的情况下，我们得到了较高的平衡常数在形成的超分子和高效率的电荷分离。在低温下得到较高的轴向配位平衡常数。另一方面，我们发现含C_2和卟啉的轮烷超分子体系中，C_2和卟啉的存在有利于电荷的分离<60>。在这些体系中，C_<60>有一个环来捕获阿克塞尔，卟啉作为终止物。通过时间分辨荧光光谱和瞬态吸收光谱的测量，我们发现这些轮烷中存在有效的轮烷内电荷分离和长寿命的电荷分离态。有趣的是，我们发现了电荷分离类型的尺寸依赖性;变化分离在小轮烷中从激发单重态开始，然而，它在大轮烷中从激发三重态开始。

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.