Role of the special pair in the charge-separating event in photosynthesis
Role of the special pair in the charge-separating event in photosynthesis
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DOI：
10.1002/chem.200400624
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发表时间：
2004-12-17
影响因子：
4.3
通讯作者：
Okada, T
中科院分区：
文献类型：
--
作者：
Ozeki, H;Nomoto, A;Okada, T
我们合成了一个特殊的对/电子受体系统组成的互补滑动共面二聚体的咪唑取代的锌卟啉，轴承作为电子受体的均苯四甲酸二酰亚胺。在二聚体的情况下，在差示脉冲伏安法测量中，第一和第二氧化电位被分成总共四个峰。此外，通过改变溶剂极性获得的二聚体的第一氧化电位的位移值几乎是那些观察到的单体的一半。这些结果表明，自由基阳离子是离域的整个π系统的二聚体。时间分辨瞬态吸收测量结果表明，相对于相应的单体，二聚体加速电荷分离速率，但减速的电荷复合速率。相对于单体系统，滑动的共面二聚体的重组能较小，表明了光合作用中有效电荷分离的特殊对排列的意义。
We synthesized special-pair/ electron -acceptor systems consisting of a complementary slipped cofacial dimer of imidazolyl-substituted zinc porphyrin, bearing pyromellitdiimide as the electron acceptor. In the case of the dimer, the first and second oxidation potentials were split into a total of four peaks in the differential pulse voltammetry measurement. Furthermore, the shift values of the first oxidation potentials obtained by changing the solvent polarity for the dimer were almost half of those observed for the monomer. These results indicate that the radical cation is delocalized over the whole pi system of the dimer. Time-resolved transient absorption measurements revealed that, relative to the corresponding monomer, the dimer accelerated the charge separation rate, but decelerated the charge recombination rate. The smaller reorganization energy of the slipped coafacial dimer relative to that of the monomeric system demonstrates the significance of the special-pair arrangement for efficient charge seperation in photosynthesis.