Dynamics and mechanism of delocalized cationic state in organic photoconductive polymers

为了阐明分子组装中光诱导电荷分离产生电荷分离态的快速电荷转移反应的因素，我们研究了芳香族乙烯基聚合物体系在光激发后芳香族基团之间发生快速电荷转移反应的固相电子转移动力学。飞秒瞬时吸收光谱和二色性测量表明，在10~295K的温度范围内，阳离子在几个芳香族基团之间迅速发生离域过程。这种离域化导致阴离子和阳离子之间的离子间距离增加，导致吸引库仑相互作用减小，阳离子尺寸的增加降低了重组能。这些因素促进了电荷的快速移位反应，而传统的电子转移理论无法很好地解释这一现象。

To elucidate factors enabling the rapid charge shift reaction in the charge-separated state produced by photoinduced charge separation in molecular assemblies, we have studied the electron transfer dynamics in aromatic vinyl polymer systems in solid phase where rapid charge shift reaction takes place among aromatic groups after the photoexcitation. By femtosecond transient absorption spectroscopy and dichroism measurements in the temperature range of 10 to 295 K, it was revealed that the delocalization process of the cationic state occurred among several aromatic groups very rapidly. This delocalization leads to the increase in the inter-ionic distance between the anion and the cation resulting in the reduction of the attractive Coulombic interaction and the increase in the cationic size reduces the reorganization energy. These factors facilitate the rapid charge shift reaction which has not been well accounted for by the conventional electron transfer theories.