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首页> 外文期刊>Chemistry: A European journal >Self-Sorting of Cyclic Peptide Homodimers into a Heterodimeric Assembly Featuring an Efficient Photoinduced Intramolecular Electron-Transfer Process
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Self-Sorting of Cyclic Peptide Homodimers into a Heterodimeric Assembly Featuring an Efficient Photoinduced Intramolecular Electron-Transfer Process

机译：环肽均聚物的自分选成具有有效光诱导分子内电子转移过程的异二聚体组装。

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We describe the thermodynamic characterisation of the self-sorting process experienced by two homodimers assembled by hydrogen-bonding interactions through their cyclopeptide scaffolds and decorated with Zn–porphyrin and fullerene units into a heterodimeric assembly that contains one electron-donor (Zn–porphyrin) and one electronacceptor group (fullerene). The fluorescence of the Zn–porphyrin unit is strongly quenched upon heterodimer formation. This phenomenon is demonstrated to be the result of an efficient photoinduced electron-transfer (PET) process occurring between the Zn–porphyrin and the fullerene units of the heterodimeric system. The recombination lifetime of the charge-separated state of the heterodimer complex is in the order of 180 ns. In solution, both homo- and heterodimers are present as a mixture of three regioisomers: two staggered and one eclipsed. At the concentration used for this study, the high stability constant determined for the heterodimer suggests that the eclipsed conformer is the main component in solution. The application of the bound-state scenario allowed us to calculate that the heterodimer exists mainly as the eclipsed regioisomer (75–90 %). The attractive interaction that exists between the donor and acceptor chromophores in the heterodimeric assembly favours their arrangement in close contact. This is confirmed by the presence of charge-transfer bands centred at 720 nm in the absorption spectrum of the heterodimer. PET occurs in approximately 75% of the chromophores after excitation of both Zn–porphyrin and fullerene chromophores. Conversely, analogous systems, reported previously, decorated with extended tetrathiafulvalene and fullerene units showed a PET process in a significantly reduced extent (33%). We conclude that the strength (stability constant (K)×effective molarity (EM)) of the intramolecular interaction established between the two chromophores in the Zn–porphyrin/fullerene cyclopeptide- based heterodimers controls the regioisomeric distribution and regulates the high extent to which the PET process takes place in this system.
机译：我们描述了两个同型二聚体经历的自分选过程的热力学特征，该同型二聚体通过其环肽支架通过氢键相互作用组装并用Zn-卟啉和富勒烯单元修饰成一个包含一个电子供体（Zn-卟啉）的异二聚体组装体，一个电子受体基团（富勒烯）。异二聚体形成后，Zn-卟啉单元的荧光被强烈淬灭。事实证明，这种现象是锌-卟啉与异二聚体富勒烯单元之间发生有效的光致电子转移（PET）过程的结果。异二聚体复合物的电荷分离状态的重组寿命为约180ns。在溶液中，均二聚体和异源二聚体均以三种区域异构体的混合物形式存在：两种交错排列，一种黯然失色。在用于本研究的浓度下，对异二聚体测定的高稳定性常数表明，偏光的构象异构体是溶液中的主要成分。结合状态方案的应用使我们能够计算出异二聚体主要以黯淡的区域异构体（75–90％）的形式存在。在异二聚体组装体中，供体和受体生色团之间存在吸引作用，这有利于它们紧密接触。异二聚体的吸收光谱中以720 nm为中心的电荷转移带的存在证实了这一点。锌卟啉和富勒烯发色团激发后，PET约占发色团的75％。相反，以前报道的类似的系统，用扩展的四硫富瓦烯和富勒烯单元修饰，则表明PET工艺的程度大大降低（33％）。我们得出的结论是，基于锌卟啉/富勒烯环肽的异二聚体中两个生色团之间建立的分子内相互作用的强度（稳定性常数（K）×有效摩尔浓度（EM））控制区域异构体分布并调节了PET工艺在该系统中进行。

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