College of Materials Science & Engineering, Nanjing University of Science and Technology , Nanjing 210094, China.
School of Physics, Beihang University , Beijing 100191, China.
Langmuir. 2018 Jan 9;34(1):553-560. doi: 10.1021/acs.langmuir.7b03796. Epub 2017 Dec 28.
Construction of tunable and robust two-dimensional (2D) molecular arrays with desirable lattices and functionalities over a macroscopic scale relies on spontaneous and reversible noncovalent interactions between suitable molecules as building blocks. Halogen bonding, with active tunability of direction, strength, and length, is ideal for tailoring supramolecular structures. Herein, by combining low-temperature scanning tunneling microscopy and systematic first-principles calculations, we demonstrate novel halogen bonding involving single halogen atoms and phase engineering in 2D molecular self-assembly. On the Au(111) surface, we observed catalyzed dehalogenation of hexabromobenzene (HBB) molecules, during which negatively charged bromine adatoms (Br) were generated and participated in assembly via unique C-Br···Br interaction, drastically different from HBB assembly on a chemically inert graphene substrate. We successfully mapped out different phases of the assembled superstructure, including densely packed hexagonal, tetragonal, dimer chain, and expanded hexagonal lattices at room temperature, 60 °C, 90 °C, and 110 °C, respectively, and the critical role of Br in regulating lattice characteristics was highlighted. Our results show promise for manipulating the interplay between noncovalent interactions and catalytic reactions for future development of molecular nanoelectronics and 2D crystal engineering.
构建具有理想晶格和功能的可调谐和稳健的二维（2D）分子阵列，需要在宏观尺度上依靠合适分子作为构建块之间的自发和可逆非共价相互作用。卤键具有方向、强度和长度的主动可调性，是定制超分子结构的理想选择。在此，通过结合低温扫描隧道显微镜和系统的第一性原理计算，我们展示了涉及单个卤原子和二维分子自组装中的相工程的新型卤键。在 Au(111)表面，我们观察到六溴苯（HBB）分子的催化脱卤，在此过程中，带负电荷的溴原子（Br）被生成，并通过独特的 C-Br···Br 相互作用参与组装，这与在化学惰性的石墨烯衬底上的 HBB 组装截然不同。我们成功绘制出组装超结构的不同相，包括在室温、60°C、90°C 和 110°C 下分别密集堆积的六边形、四方、二聚链和扩展六边形晶格，突出了 Br 在调节晶格特征方面的关键作用。我们的结果为操纵非共价相互作用和催化反应之间的相互作用以促进未来分子纳米电子学和二维晶体工程的发展提供了希望。
