Sequence-Defined Macrocycles for Understanding and Controlling the Build-up of Hierarchical Order in Self-Assembled 2D Arrays
Sequence-Defined Macrocycles for Understanding and Controlling the Build-up of Hierarchical Order in Self-Assembled 2D Arrays
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DOI：
10.1021/jacs.9b06410
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发表时间：
2019-11-06
影响因子：
15
通讯作者：
Flood, Amar H.
中科院分区：
文献类型：
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作者：
Dobscha, James R.;Castillo, Henry D.;Flood, Amar H.
安芬森的教条，即序列决定结构是理解蛋白质的活动和组装的基础。这个想法已被应用到所有方式的低聚物，但没有环状低聚物，又名大环的行为。我们这样做，在这里提供的第一个证据表明，顺序控制非生物大环的层次组装，在这种情况下，在石墨表面。为了设计具有一个（AAA）、两个（AAB）或三个（ABC）不同咔唑单元的大环，我们需要颠覆一锅法大环化的合成偏好。我们开发了一种新的逐步合成与序列定义的目标，在11，17和22个步骤，分别为25，10和5%的产率。一级序列（1）的线性建立也使热Huisgen环加成反应能够首次使用几何控制进行区域选择性。所得大环是平面的（2度结构），并在表面形成H键合的二聚体（3度）。扫描隧道显微镜（STM）显示的主要序列编码成套件的三碳大环影响下一个层次的超分子有序（4度）和二维结晶多晶型（5度）在溶液石墨界面。AAB大环的STM成像揭示了一个新的间隙相的形成，这是不可访问的仅使用C-3-对称大环。另外两个序列控制的大环（AAD，ABE）的STM成像使我们能够确定驱动这种新的多晶型形成的因素。这种序列如何控制大环的分级模式的演示提高了逐步合成相对于一锅大环化的重要性，以提供新的方法来更好地理解和控制分级组装。
Anfinsen's dogma that sequence dictates structure is fundamental to understanding the activity and assembly of proteins. This idea has been applied to all manner of oligomers but not to the behavior of cyclic oligomers, aka macrocycles. We do this here by providing the first proofs that sequence controls the hierarchical assembly of nonbiological macrocycles, in this case, at graphite surfaces. To design macrocycles with one (AAA); two (AAB), or three (ABC) different carbazole units, we needed to subvert the synthetic preferences for one-pot macrocyclizations. We developed a new stepwise synthesis with sequence-defined targets made in 11, 17, and 22 steps with 25, 10, and 5% yields, respectively. The linear build up of primary sequence (1) also enabled a thermal Huisgen cycloaddition to proceed regioselectively for the first time using geometric control. The resulting macrocycles are planar (2 degrees structure) and form H-bonded dimers (3 degrees) at surfaces. Primary sequences encoded into the suite of tricarb macrocycles were shown by scanning-tunneling microscopy (STM) to impact the next levels of supramolecular ordering (4 degrees) and 2D crystalline polymorphs (5 degrees) at solution graphite interfaces. STM imaging of an AAB macrocycle revealed the formation of a new gap phase that was inaccessible using only C-3-symmetric macrocycles. STM imaging of two additional sequence-controlled macrocycles (AAD, ABE) allowed us to identify the factors driving the formation of this new polymorph. This demonstration of how sequence controls the hierarchical patterning of macrocycles raises the importance of stepwise syntheses relative to one-pot macrocyclizations to offer new approaches for greater understanding and control of hierarchical assembly.