Department of Chemistry and Biochemistry, University of California, Los Angeles , Los Angeles, California 90095-1569, United States.
Division of Frontier Materials Science, Graduate School of Engineering Science, Osaka University , Toyonaka, Osaka 560-8531, Japan.
Langmuir. 2016 Jun 7;32(22):5532-41. doi: 10.1021/acs.langmuir.6b00744. Epub 2016 May 26.
We have studied the self-assembly behavior of dehydro[24]annulene (D24A) derivatives 1, 2a-2d, and 3a-3c at the liquid/solid interface using scanning tunneling microscopy (STM). Both the relative placement and the nature of the four D24A substituents strongly influence the self-assembly pattern. Overall, the eight D24A derivatives examined in this study display seven types of 2D packing patterns. The D24A derivatives 1, 2a, and 3a have either two or four stearate groups and adopt face-on configurations of their macrocyclic cores with respect to the highly oriented pyrolytic graphite (HOPG) surface. Their 2D packing pattern is determined by the interchain spacings and number of stearate substituents. The D24A derivatives 2b-2d and 3b-3c bear hydrogen-bonding carbamate groups to further strengthen intermolecular interactions. Face-on patterns were also observed for most of these compounds, while an unstable edge-on self-assembly was observed in the case of 2b at room temperature. Stable edge-on self-assemblies of D24A derivatives were sought for this work as an important stepping stone to achieving the on-surface topochemical polymerization of these carbon-rich macrocycles into tubular π-conjugated nanowires. The overall factors determining the 2D packing patterns of D24As at the liquid/solid interface are discussed on the basis of theoretical simulations, providing useful guidelines for controlling the self-assembly pattern of future D24A macrocycles.
我们使用扫描隧道显微镜（STM）研究了脱氢[24]轮烯（D24A）衍生物 1、2a-2d 和 3a-3c 在液/固界面的自组装行为。四个 D24A 取代基的相对位置和性质强烈影响自组装模式。总的来说，在这项研究中检查的八个 D24A 衍生物显示出七种二维堆积模式。D24A 衍生物 1、2a 和 3a 要么具有两个要么具有四个硬脂酸基团，并采用其大环核相对于高度取向的热解石墨（HOPG）表面的面向上构象。它们的二维堆积模式由链间间距和硬脂酸取代基的数量决定。D24A 衍生物 2b-2d 和 3b-3c 带有氢键的氨基甲酸酯基团，以进一步增强分子间相互作用。这些化合物中的大多数也观察到面向上模式，而在室温下 2b 观察到不稳定的边缘自组装。作为实现这些富碳大环在表面上的拓扑聚合为管状π共轭纳米线的重要垫脚石，本工作寻求稳定的边缘自组装 D24A 衍生物。基于理论模拟，讨论了决定 D24A 在液/固界面上二维堆积模式的总体因素，为控制未来 D24A 大环的自组装模式提供了有用的指导。
