On-Surface Synthesis of Functionalized Honeycombene Macrocycles and Related Two-Dimensional Polymer Structures

表面合成是一种很有前途的界面改性和功能化以及制备新功能材料的方法。虽然在过去的五年中，这种方法在一维和二维聚合物的合成中得到了一些关注，但大有机分子的表面合成仍处于起步阶段。同样，在表面上形成共价键的合适反应也很少。在我们隔壁实验室的联合初步研究的鼓舞下，我们将把Hilt集团在有机合成方面的专业知识与Gottfried集团的表面科学能力相结合。具体而言，我们将使用过渡金属催化的方法，灵活的合成（聚）官能化的oligophenylene前体结合超高真空（UHV）为基础的方法，用于合成，分析和表征复杂的大环和聚合物框架的金属或金属氧化物表面。将使用扫描隧道显微镜（STM）、光电子能谱（XPS/UPS）和其他方法进行产品分析，以进行完整的结构和成分分析。（a）表面合成大的共轭大环（蜂窝烯），这种大环通过自组装在金属和金属氧化物的单晶表面上形成长程有序结构。(b)在蜂窝结构单元的外围的官能化将用于进一步的共价/配位连接，作为一种新颖的方法来定义良好的2D聚合物。(c)蜂窝烯的向内官能化将使得能够在中心腔或二次组装过程中进行后续分子识别，例如，催化活性金属纳米颗粒的尺寸控制。(d)我们将尝试利用前所未有的金属纳米颗粒表面合成来产生毫克级的各种蜂窝烯。(e)我们打算确定新的键形成反应对多官能化的蜂窝烯和相关结构，扩大目前非常有限的阿森纳合适的表面反应。特别是，催化吸附原子将探索通过金属催化的[2+2]-环加成反应产生新的大环结构，如分子十二元。(f)最后，表面介导的反应的反应机理将使用表面光谱和显微技术的组合进行研究，建立一个系统的发展和优化这些反应的基础。

On-surface synthesis is a promising approach for the modification and functionalization of interfaces and for generating new functional materials. While this approach has found some attention for the synthesis of one- and two-dimensional polymers during the past five years, the on-surface synthesis of large organic molecules is still its infancy. Likewise, suitable reactions for covalent bond formation on surfaces are scarce. Encouraged by our joint preliminary studies in our next-door laboratories, we will combine the expertise in organic synthesis from the Hilt group with the surface science competence in the Gottfried group. Specifically, we will use transition-metal catalyzed methods for the flexible synthesis of (poly)functionalized oligophenylene precursors in combination with ultrahigh-vacuum (UHV) based methods for the synthesis, analysis and characterization of complex macrocycles and polymeric frameworks on metal or metal oxide surfaces. Product analysis will be performed with scanning tunneling microscopy (STM), photoelectron spectroscopy (XPS/UPS) and other methods for full structural and compositional analysis. The following aims will be pursued: (a) On-surface synthesis of large conjugated macrocycles (honeycombenes), which undergo self-assembly to form long-range ordered structures on single-crystal surfaces of metals and metal oxides. (b) Functionalization at the periphery of the honeycombene building blocks will be used for further covalent/coordination linkage as a novel approach to well-defined 2D polymers. (c) The inward-functionalization of the honeycombenes will enable follow-up molecular recognition in the central cavity or secondary assembly processes, e.g., the size control of catalytically active metal nanoparticles. (d) We will attempt to generate various honeycombenes on a milligram scale utilizing unprecedented on-surface synthesis on metal nanoparticles. (e) We intend to identify novel bond formation reactions towards poly-functionalized honeycombenes and related structures, expanding the presently very limited arsenal of suitable on-surface reactions. In particular, catalysis by absorbed adatoms will be explored to generate novel macrocyclic structures, such as molecular dodecagrams, via metal-catalyzed [2+2]-cycloaddition reactions. (f) Finally, the reaction mechanisms of the surface-mediated reactions will be investigated using a combination of surface spectroscopic and microscopic techniques, to establish a basis for a systematic development and optimization of these reactions.