Oligosilane chain-length dependence of electron transfer of zinc porphyrin-oligosilane-fullerene molecules
Oligosilane chain-length dependence of electron transfer of zinc porphyrin-oligosilane-fullerene molecules
复制标题
DOI：
10.1021/jp066749z
复制
发表时间：
2007-04-26
影响因子：
2.9
通讯作者：
Ito, Osamu
中科院分区：
文献类型：
--
作者：
Sasaki, Mikio;Shibano, Yuki;Ito, Osamu
合成了一系列新型的柔性低聚硅烷链ZnP-[Si-n]-C-60（n =1-5）桥联的锌卟啉-富勒烯分子，用稳态和时间分辨光谱方法研究了这些分子的物理性质。光谱观测结果可以很好地解释，假设共存的扩展构象和折叠构象，即，所观察到的发射是从扩展构象，而折叠构象形成非常短的寿命nonfluorescent激发态电荷转移（CT）复合物。时间分辨的瞬态吸收光谱表明产生的分子内自由基离子对，具有亚微秒的寿命。随着桥连低聚硅烷的硅原子的数目，自由基-离子对的寿命不规律地变化，表明自由基-阳离子部分与自由基-阴离子部分的分子内碰撞控制电荷重组速率。基于低聚硅烷链长对荧光寿命的依赖性，通过电荷分离速率的桥长依赖性评估硅链的电子转移的衰减因子为0.16埃（-1）。这是我们所知的一维Si-Si链的衰减因子的第一次评估。
A new series of zinc porphyrin- fullerenes bridged by flexible oligosilane chains ZnP-[Si-n]-C-60 (n =1-5) was synthesized, and the photophysical properties of these molecules were investigated using steady-state and time- resolved spectroscopic methods. The spectral observations can be well explained by assuming the coexistence of extended conformers and folded conformers, that is, the observed emissions are from the extended conformers while the folded conformers form very short lifetime nonfluorescent excited-state charge transfer (CT) complexes. Time-resolved transient absorption spectra suggest the generation of intramolecular radical- ion pairs that have sub-microsecond lifetimes. With the number of silicon atoms of the bridged oligosilane, the lifetimes of the radical- ion pairs do not vary regularly, indicating that intramolecular collision of the radical- cation moiety with the radical-anion moiety controls the charge-recombination rate. The attenuation factor of the electron transfer of the silicon chain was evaluated by the bridge-length dependence of charge-separation rate to be 0.16 angstrom(-1) on the basis of the oligosilane chain-length dependence of fluorescence lifetimes. This is the first evaluation of the attenuation factor for the one-dimensional Si-Si chain to the best of our knowledge.