Photoinduced charge separation in self-assembled cofacial pentamers of zinc-5,10,15,20-tetrakis(perylenediimide)porphyrin
Photoinduced charge separation in self-assembled cofacial pentamers of zinc-5,10,15,20-tetrakis(perylenediimide)porphyrin
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DOI：
10.1039/b617876f
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发表时间：
2007-01-01
影响因子：
3.3
通讯作者：
Wasielewski, Michael R.
中科院分区：
文献类型：
--
作者：
Ahrens, Michael J.;Kelley, Richard F.;Wasielewski, Michael R.
合成了一种由四个二萘嵌苯二甲酰亚胺（PDI）发色团包围的四苯基卟啉锌（ZnTPP）为电子给受体的双发色团分子（ZnTPP-PDI 4）。将该分子的性质与具有与单个PDI共价结合的ZnTPP的参比分子（ZnTPP-PDI）进行比较。在甲苯中，ZnTPP-PDI 4自组装成以柱状堆叠排列的五个分子的单分散聚集体（ZnTPP-PDI 4）（5）。该组装体的单分散性质与先前报道的具有1，7-双（3，5-二叔丁基苯氧基）基团的ZnTPP-PDI 4衍生物（ZnTPP-PPDI 4）形成鲜明对比。该组装体在溶液中的尺寸和结构通过使用高通量同步加速器X射线源的小角X射线散射（SAXS）来确定。ZnTPP-PDI参比分子不聚集。飞秒瞬态吸收光谱显示，ZnTPP-PDI和（ZnTPP-PDI 4）（5）两者的激光激发导致ZnTPP+的定量形成。PDI-。自由基离子对在几皮秒。（ZnTPP-PDI 4）（5）的瞬时吸收光谱表明PDI-。自由基与柱状叠层内的相邻PDI分子强烈相互作用。电荷复合在（ZnTPP-PDI 4）（5）（τ =4.8 ns）中比在ZnTPP-PDI（τ =3.0 ns）中更慢地发生，产生主要基态以及PDI的最低三重态的适度产率（3*PDI）。3* PDI的形成通过直接来自单重态自由基离子对的快速自旋-轨道诱导的系间穿越（SO-ISC）而发生，如通过其时间分辨电子顺磁共振谱所展示的电子自旋极化图案所证明的。
A bichromophoric electron donor - acceptor molecule composed of a zinc tetraphenylporphyrin ( ZnTPP) surrounded by four perylene-3,4: 9,10-bis( dicarboximide) (PDI) chromophores ( ZnTPP-PDI4) was synthesized. The properties of this molecule were compared to a reference molecule having ZnTPP covalently bound to a single PDI (ZnTPP-PDI). In toluene, ZnTPP-PDI4 self-assembles into monodisperse aggregates of five molecules arranged in a columnar stack, (ZnTPP-PDI4)(5). The monodisperse nature of this assembly contrasts sharply with previously reported ZnTPP-PDI4 derivatives having 1,7-bis(3,5-di-t-butylphenoxy) groups (ZnTPP-PPDI4). The size and structure of this assembly in solution was determined by small angle X-ray scattering (SAXS) using a high flux synchrotron X-ray source. The ZnTPP-PDI reference molecule does not aggregate. Femtosecond transient absorption spectroscopy shows that laser excitation of both ZnTPP-PDI and (ZnTPP-PDI4)(5) results in quantitative formation of ZnTPP+.-PDI-. radical ion pairs in a few picoseconds. The transient absorption spectra of ( ZnTPP-PDI4)(5) suggest that the PDI-. radicals interact strongly with adjacent PDI molecules within the columnar stack. Charge recombination occurs more slowly within ( ZnTPP-PDI4)(5) (tau=4.8 ns) than it does in ZnTPP-PDI (tau=3.0 ns) producing mostly ground state as well as a modest yield of the lowest triplet state of PDI (3*PDI). Formation of 3* PDI occurs by rapid spin - orbit induced intersystem crossing (SO-ISC) directly from the singlet radical ion pair as evidenced by the electron spin polarization pattern exhibited by its time-resolved electron paramagnetic resonance spectrum.