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修饰和功能化方法，也是制备新型功能材料的有效途径。虽然在过去的五年里，这种方法在一维和二维聚合物的合成方面引起了一些关注，但大分子有机分子的表面合成仍然处于起步阶段。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励下，我们将把希尔特集团在有机合成方面的专业知识与戈特弗里德集团的表面科学能力结合起来。具体地说，我们将使用过渡金属催化的方法灵活地合成(多)官能化低聚苯前体，并结合基于超高真空(UHV)的方法来合成、分析和表征金属或金属氧化物表面的复杂大环和聚合物骨架。产品分析将使用扫描隧道显微镜(STM)、光电子能谱(XPS/UPS)和其他方法进行全面的结构和成分分析。将追求以下目标：(A)表面合成大的共轭大环(蜂窝)，它们经过自组装，在金属和金属氧化物的单晶表面形成长程有序结构。(B)蜂窝结构块外围的官能化将被用于进一步的共价/配位连接，作为一种新的方法来获得定义明确的2D聚合物。(C)蜂窝状分子的向内官能化将能够在中心腔或二次组装过程中实现后续的分子识别，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规模的各种蜂窝。(E)我们打算确定针对多官能化蜂窝烯和相关结构的新的成键反应，扩大目前非常有限的适合表面反应的武器库。特别是，通过金属催化的[2+2]-环加成反应，吸附原子的催化作用将被探索以产生新的大环结构，例如分子十二烷基图。(F)最后，将结合表面光谱和显微技术研究表面介导反应的反应机理，为系统地开发和优化这些反应奠定基础。

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.