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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Excited-State Dynamics of Hybrid Multichromophoric Systems: Toward an Excitation Wavelength Control of the Charge Separation Pathways
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Excited-State Dynamics of Hybrid Multichromophoric Systems: Toward an Excitation Wavelength Control of the Charge Separation Pathways

机译：混合多发色体系的激发态动力学：电荷分离途径的激发波长控制。

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摘要

The photophysical properties of two hybrid multichromophoric systems consisting of an oligophenylethynyl (OPE) scaffold decorated by 10 red or blue naphthalene diimides (NDIs) have been investigated using femtosecond spectroscopy. Ultrafast charge separation was observed with both red and blue systems. However, the nature of the charge-separated state and its lifetime were found to differ substantially. For the red system, electron transfer occurs from the OPE scaffold to an NDI unit, independently of whether the OPE or an NDI is initially excited. However, charge separation upon OPE excitation is about 10 times faster, and takes place with a 100 fs time constant. The average lifetime of the ensuing charge-separated state amounts to about 650 ps. Charge separation in the blue system depends on which of the OPE scaffold or an NDI is excited. In the first case, an electron is transferred from the OPE to an NDI and the hole subsequently shifts to another NDI unit, whereas in the second case symmetry-breaking charge separation between two NDI units occurs. Although the charges are located on two NDIs in both cases, different recombination dynamics are observed. This is explained by the location of the ionic NDI moieties that depends on the charge separation pathway, hence on the excitation wavelength. The very different dynamics observed with red and blue systems can be accounted for by the oxidation potentials of the respective NDIs that are higher and lower than that of the OPE scaffold. Because of this, the relative energies of the two charge-separated states (hole on the OPE or an NDI) are inverted.
机译：使用飞秒光谱研究了由10个红色或蓝色萘二酰亚胺（NDI）装饰的由寡苯基乙炔基（OPE）支架组成的两个杂化多发色体系的光物理性质。在红色和蓝色系统中均观察到超快电荷分离。然而，发现电荷分离状态的性质及其寿命存在很大差异。对于红色系统，电子是从OPE支架转移到NDI单元的，而与OPE或NDI最初是否被激发无关。但是，OPE激发时的电荷分离大约快10倍，并且以100 fs的时间常数进行。随后的电荷分离状态的平均寿命约为650 ps。蓝色系统中的电荷分离取决于被激活的OPE支架或NDI。在第一种情况下，电子从OPE转移到NDI，空穴随后转移到另一个NDI单元，而在第二种情况下，两个NDI单元之​​间发生对称破坏电荷分离。尽管在两种情况下电荷都位于两个NDI上，但观察到了不同的重组动力学。这由离子NDI部分的位置解释，该位置取决于电荷分离途径，因此取决于激发波长。用红色和蓝色系统观察到的非常不同的动力学可以由相应的NDI的氧化电势高于和低于OPE支架的氧化电势来解释。因此，两个电荷分离状态（OPE或NDI上的空穴）的相对能量被反转。

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