Department of Chemistry and Bioengineering, Tampere University of Technology, P.O. Box 541, 33101 Tampere, Finland.
Inorg Chem. 2013 Sep 3;52(17):9761-73. doi: 10.1021/ic400474b. Epub 2013 Aug 13.
Three new perylene diimide (PDI)-based ligands have been synthesized by the covalent attachment of dipyrido[a,c]phenazine moiety to one of the bay-positions of PDI, while the second position has been substituted with either a 4-tert-butylphenoxy or a pyrrolidinyl group to obtain two types of chromophores, Ph-PDI and Py-PDI, respectively, with distinct properties. In the case of Py-PDI, the resultant 1,7- and 1,6-regioisomers have been successfully separated by column chromatography and characterized by (1)H NMR spectroscopy. The ligands have been employed to prepare donor-acceptor-based ensembles incorporating the covalently linked PDI and Ru(II) polypyridine complex as the acting chromophores. A comprehensive study of the excited-state photodynamics of the ensembles has been performed by means of electrochemical and steady state and time-resolved spectroscopic methods. Although, in all the three ensembles, the photoexcitation of either chromophore resulted in a long-lived triplet excited state of PDI ((3)PDI) as the final excited state, the photochemical reactions leading to the triplet states were found to be essentially different for the two types of the ensembles. In the case of the Ph-PDI-based ensemble, the excitation of either chromophore leads to the electron transfer from the Ru(II) complex to Ph-PDI, whereas for the Py-PDI-based ensembles, the electron transfer is observed in the opposite direction and only when the Ru(II) complex is excited. The difference in the behavior was rationalized based on electrochemical study of the compounds, which has shown that the Ph-PDI chromophore is a better electron acceptor and the Py-PDI chromophores are relatively better electron donors. This study shows a chemical approach to control the photoreactions in PDI-based dichromophoric ensembles including the possibility to switch the direction of the photoinduced electron transfer.
三种新型苝二酰亚胺（PDI）基配体通过将二吡啶[a,c]吩嗪部分共价连接到 PDI 的一个苯并位置来合成，而第二个位置则用 4-叔丁基苯氧基或吡咯烷基取代，以获得两种类型的生色团，分别为 Ph-PDI 和 Py-PDI，它们具有不同的性质。在 Py-PDI 的情况下，通过柱层析成功分离出得到的 1,7-和 1,6-区域异构体，并通过（1）H NMR 光谱进行了表征。该配体已被用于制备供体-受体基集合体，其中包含共价连接的 PDI 和作为作用生色团的 Ru(II) 多吡啶配合物。通过电化学和稳态和时间分辨光谱方法对集合体的激发态光动力学进行了全面研究。尽管在所有三种集合体中，任一生色团的光激发都导致 PDI 的长寿命三重态激发态（3PDI）作为最终激发态，但导致三重态的光化学反应对于两种类型的集合体而言基本上是不同的。在 Ph-PDI 基集合体的情况下，任一生色团的激发都会导致电子从 Ru(II) 配合物转移到 Ph-PDI，而在 Py-PDI 基集合体的情况下，仅当 Ru(II) 配合物被激发时才观察到电子转移到相反的方向。基于化合物的电化学研究对这种行为差异进行了合理化解释，该研究表明 Ph-PDI 生色团是更好的电子受体，而 Py-PDI 生色团则是相对较好的电子供体。这项研究展示了一种控制基于 PDI 的双生色团集合体中光反应的化学方法，包括可能切换光诱导电子转移的方向。
