Lee Hyun, Lee Dongwhan
Department of Chemistry, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 08826, Korea.
Commun Chem. 2022 Dec 28;5(1):180. doi: 10.1038/s42004-022-00802-4.
A face-to-face stacking of aromatic rings is an effective non-covalent strategy to build functional architectures, as elegantly exemplified with protein folding and polynucleotide assembly. However, weak, non-directional, and context-sensitive van der Waals forces pose a significant challenge if one wishes to construct well-organized π-stacks outside the confines of the biological matrix. To meet this design challenge, we have devised a rigid polycyclic template to create a non-collapsible void between two parallel oriented π-faces. In solution, these shape-persistent aromatic clips self-dimerize to form quadruple π-stacks, the thermodynamic stability of which is enhanced by self-complementary N-H···N hydrogen bonds, and finely regulated by the regioisomerism of the π-canopy unit. With assistance from sufficient electrostatic polarization of the π-surface and bifurcated hydrogen bonds, a small polyheterocyclic guest can effectively compete against the self-dimerization of the host to afford a triple π-stack inclusion complex. A combination of solution spectroscopic, X-ray crystallographic, and computational studies aided a detailed understanding of this cooperative vs competitive process to afford layered aromatics with extraordinary structural regularity and fidelity.
芳香环的面对面堆积是构建功能结构的一种有效非共价策略，蛋白质折叠和多核苷酸组装就是很好的例证。然而，如果想在生物基质范围之外构建有序的π-堆积，弱的、非定向的且依赖环境的范德华力会带来重大挑战。为应对这一设计挑战，我们设计了一种刚性多环模板，以在两个平行取向的π-面之间创建一个不可塌陷的空隙。在溶液中，这些形状持久的芳香夹子会自二聚形成四重π-堆积，其热力学稳定性通过自互补的N-H···N氢键得到增强，并由π-冠单元的区域异构精细调节。在π-表面充分的静电极化和分叉氢键的辅助下，一个小的多杂环客体可以有效地与主体的自二聚作用竞争，从而形成一个三重π-堆积包合物。溶液光谱、X射线晶体学和计算研究相结合，有助于详细理解这种协同与竞争过程，从而得到具有非凡结构规整性和保真度的层状芳烃。
