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首页> 外文期刊>Chemistry: A European journal >Regioisomeric control induced by DABCO coordination to rotatable self-assembled bis-and tetraporphyrin α,γ-Cyclic octapeptide dimers
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Regioisomeric control induced by DABCO coordination to rotatable self-assembled bis-and tetraporphyrin α,γ-Cyclic octapeptide dimers

机译：DABCO配位作用诱导的可旋转自组装双和四卟啉α，γ-环八肽二聚体的区域异构控制

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摘要

The design and synthesis of two α,γ-cyclic octapeptides decorated with one and two Zn-porphyrin units in their periphery is described. In nonpolar organic solvents the α,γ-cyclic octapeptides quantitatively self-assemble into Zn-bis-or -tetraporphyrin architectures that could act as molecular tweezers. The self-assembly process, however, is not regioselective and affords a mixture of different regioisomers that are involved in chemical exchange processes. The regioisomers with the Zn-porphyrin units positioned in register with respect to each other are proposed to be the less abundant species in the solution mixture. It has been demonstrated that the coordination of 1,4-diazabicyclo[2.2.2]octane (DABCO) to the supramolecular bis-or tetraporphyrin tweezers is an effective way to achieve regioisomeric control of the self-assembled mixture of dimers. Thus, DABCO functions as an external molecular trigger and, when used under strict stoichiometric control with respect to the Zn-porphyrin units, provokes the exclusive formation of self-assembled dimers with a cofacial arrangement of Zn-porphyrin units through the formation of sandwich-type complexes. The use of excess DABCO fragments the sandwich complexes and affords open dimers of high stoichiometry with DABCO molecules axially monocoordinated to the Zn-porphyrin units, probably as a regioisomeric mixture. In the case of Zn-tetraporphyrin tweezers, the ditopic coordination of DABCO at the two binding sites shows a moderate positive cooperativity factor, αP=5. These assemblies have potential applications as light-induced energy and electron-transfer switches regulated by DABCO coordination; such applications would require the introduction of additional chromophores in the cyclic peptide scaffold.
机译：描述和设计了两个α，γ-环八肽修饰并在其外围装饰有一个和两个Zn-卟啉单元的合成方法。在非极性有机溶剂中，α，γ-环八肽定量自组装成Zn-双-或-四卟啉结构，可以用作分子镊子。然而，自组装过程不是区域选择性的，并且提供了涉及化学交换过程的不同区域异构体的混合物。 Zn-卟啉单元相对于彼此定位的区域异构体被认为是溶液混合物中含量较低的物质。已经证明1，4-二氮杂双环[2.2.2]辛烷（DABCO）与超分子双-或四卟啉镊子的配位是实现区域异构控制自组装二聚体混合物的有效方法。因此，DABCO起到了外部分子触发的作用，当在严格的化学计量控制下使用锌卟啉单元时，会通过形成夹心结构形成锌卟啉单元的界面排列，从而独家形成自组装二聚体。类型复合体。使用过量的DABCO会使三明治复合物断裂，并提供具有高化学计量比的开放二聚体，其中DABCO分子轴向单配于Zn-卟啉单元，可能是区域异构体混合物。在锌-四卟啉镊子的情况下，DABCO在两个结合位点的对位配位显示中等的正协同因子，αP= 5。这些组件具有潜在的应用，如受DABCO协调调节的光感应能量和电子传输开关。这样的应用将需要在环肽支架中引入其他生色团。

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