Development of Supramolecular Photocatalytic Systems

通过使用合适的发色团和氧化还原组分，即锌卟啉（或锌氯）和富勒烯，通过共价键连接，实现了比天然光合反应中心更长的电荷分离（CS）状态寿命。与天然光合反应中心相比，使用一个简单的供体-受体二元体9-甲基亚基-10-甲基吖啶鎓离子也获得了一个非常长的电子转移态。然而，由于合成难度大，构建包含多个光合反应中心的人工光合模型系统仍然是一个巨大的挑战。我们已经开发出了由光捕获多卟啉单元和电荷分离单元组成的多个光合反应中心，它们通过π-π相互作用和配位等非共价键结合，获得了长寿命的CS态。首先，利用卟啉树状大分子和卟啉肽低聚物构建了多卟啉体系。然后，它们通过非共价键与带有电子受体的反应中心单元结合。例如，π扩展紫素衍生物可以与自由碱卟啉树状大分子形成超分子配合物。在卟啉单元之间发生了有效的能量迁移，然后是有效的电子转移。CS态的寿命随着卟啉树状大分子生成的增加而延长。这表明卟啉单元间的空穴迁移延长了CS寿命。在298 K的PhCN中，含有16个卟啉单元的游离基卟啉树状大分子的超分子配合物的CS寿命最长为1.3 ms。含吡啶配位体（C_<60>py）或咪唑配位体（C_<60>py）的富勒吡咯烷也与卟啉锌树状大分子和卟啉锌肽低聚物形成超分子配合物。超分子配合物的CS态通过激光闪光光解测量作为瞬态吸收光谱进行检测。含16个卟啉单元的锌-肽十六聚体的超分子配合物在298 K时在苯腈（PhCN）中C_<60>py， CS寿命最长为1.7 ms。这种卟啉和富勒烯分子的组织已被应用于构建高效的光能转换系统，如光伏器件。少

Longer lifetimes of the charge-separated (CS) state than that of the natural photosynthetic reaction center have been achieved by using suitable chromophores and redox components, namely zinc porphyrins (or zinc chlorins) and fullerenes, which are linked with covalent bonds. A remarkably long lived electron-transfer state as compared with the natural photosynthetic reaction center has also been attained by using a simple donor-acceptor dyad, 9-mesityl-10-methylacridinium ion. However, construction of artificial photosynthetic model systems containing multiple photosynthetic reaction centers has remained as a great challenge because of the synthetic difficulty. We have developed multiple photosynthetic reaction centers composed of light-harvesting multi-porphyrin units and charge-separation units, which have been combined by non-covalent bonds such as π-π-interaction and coordination to attain long-lived CS states. First, multi-porphyrin systems were developed using porphyrin dendrimers … More and porphyrin-peptide oligomers. Then, they are combined with the reaction center units with electron acceptors by non-covalent bonds. For example, a π-extended viologen derivative can form a supramolecular complex with free base porphyrin dendrimers. The energy migration occurs efficiently among the porphyrin units, followed by efficient electron transfer. The lifetime of CS state becomes longer with increasing generation of porphyrin dendrimer. This indicates that the CS lifetime is elongated by the hole migration among porphyrin units. The longest CS lifetime was determined as 1.3 ms for the supramolecular complex of a free base porphyrin dendrimer, which contains 16 porphyrin units, with a π-extended viologen derivative in PhCN at 298 K. Fulleropyrrolidine bearing a pyridine coordinating ligand (C_<60>py) or imidazole ligand (C_<60>Im) also forms supramolecular complexes with zinc porphyrin dendrimers and zinc porphyrin-peptide oligomers. The CS states of the supramolecular complexes were detected as the transient absorption spectra by laser flash photolysis measurements. The longest CS lifetime was attained as 1.7 ms for the supramolecular complex of a zinc porphyrin-peptide hexadecamer, which contains 16 porphyrin units, with C_<60>py in benzonitrile (PhCN) at 298 K. The organization of such porphyrin and fullerene molecules has been applied to construct efficient light energy conversion systems such as photovoltaic devices. Less