Photoinduced hydrogen evolution with highly functional photocatalyst

合成了多种紫精连接的紫精，在同一分子中提供了光敏剂和电子载体，合成了不同亚甲基数目的紫精，并将其用于光诱导分子内电子转移，荧光衰变曲线由两个一阶衰变和两个寿命组成。紫精连接的卟啉的长荧光寿命与未连接紫精的卟啉的荧光寿命几乎相同。可以合理地假设，具有长寿命的组分的荧光衰减是自发的，因此与紫精和卟啉环之间的距离无关。相反，较短的寿命强烈地依赖于亚甲基链的长度，并且随着链长的增加而增加。因此，短寿命组分的荧光衰减可能是由于连接的紫精直接猝灭了卟啉的光激发单线态。分子内电子转移速率常数强烈地依赖于亚甲基链长，并且随着亚甲基链长的增加而减小。在分子内电子转移过程中，电子沿着亚甲基链从光激发的卟啉转移到紫精。紫精偶联的卟啉在可见光照射下完成了光诱导放氢反应。

Various viologen linked porphyrins have been synthesized, which provide photosensitizer and electron carrier in the same molecule.Porphyrin containing viologen with different numbers of methylene groups were synthesized and used for photoinduced intramolecular electron transfer.The fluorescence decay profiles consist of the sum of two first order decays with two lifetimes. The long fluorescence lifetimes of the viologen linked porphyrins are almost the same as the lifetime of the porphyrin without viologen. It is reasonable to assume that the fluorescence decay of the component with a long lifetime is spontaneous and is therefore independent of the distance between the viologen and the porphyrin ring. In contrast, the shorter lifetime strongly depends on the length of the methylene chain and the value increases with longer chain lengths. Therefore the fluorescence decay of the component with the short lifetime may arise from the direct quenching of the photoexcited singlet state of the porphyrin by the linked viologen.The intramolecular electron transfer rate constant strongly depends on the methylene chain length and it decreases with increasing methylene chain length. In the intramolecular electron transfer process, the electron transfers from the photoexcited porphyrin to the viologen along the methylene chain. Photoinduced hydrogen evolution was accomplished with the viologen-linked porphyrin by the irradiation of visible light.