Self-Assembly Processes of Organic Molecules on Surfaces: Analysis of Intermolecular Halogen Bonds by High Resolution Low Temperature Atomic Force Microscopy

表面有机分子的自组装过程：高分辨率低温原子力显微镜分析分子间卤素键

• 批准号: 448547917
• 负责人: Dr. Daniel Ebeling
• 金额: --
• 依托单位: Universidad Autónoma de Madrid
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/448547917?language=en
• 关键词: Self; Assembly; Processes; Organic; Molecules

On-surface self-assembly of molecules represents a very promising strategy for building nano structures with controllable properties. Many growth processes in nature serve as a role model for this, since complex functional units are often put together “molecule by molecule”. Unfortunately, the molecular recognition mechanisms that control the structural growth are not yet well understood, which hampers the design of new materials with new properties. In the last few years, the possibilities for characterizing single adsorbed molecules on surface have been significantly improved. By using CO-functionalized AFM tips, the chemical structure of single molecules can be directly visualized, which represents a new toolset for studying molecular recognition processes. In this project, this so-called bond-imaging-method will be employed for analyzing intermolecular halogen bonds. Halogens that are covalently bound to an organic molecule have a electrophilic region at the outer end of their bonding axis, the σ-hole. This anisotropic charge distribution within the halogen leads to a remarkable directionality of halogen bonds, whose strength can be tuned by the choice of halogen or molecular rest. Due to these unique properties halogen bonds are ideally suited for applications in the fields of crystal engineering, supramolecular chemistry, drug design, etc. Halogen bonds on surfaces can be tuned by another control knob: the surface material. In this project, we will systematically study the influence of different surface materials on the σ-hole of different halogens. Therefore, the bond-imaging technique will be applied to determine binding selectivities, bond lengths, bond angles, and adsorption conformations of various model compounds on both relatively inert and relatively reactive substrates. In another step, we will study the binding types that occur on different substrate materials and how their binding geometries can be actively controlled by the choice of substrate. The experimental results will be complemented by DFT computations. These will allow gaining knowledge about the charge transfer between the substrate and the molecule, the charge distribution inside the molecules and the different parts of binding energy (e.g. molecule-molecule vs. molecule-substrate). The project should help to obtain a better understanding about the nature of the halogen bond to be able to control self-assembly processes in the future and use these for the design of new molecular structures with unique properties.

分子的表面自组装代表了构建具有可控特性的纳米结构的非常有前途的策略。自然界中的许多生长过程都是这种情况的榜样，因为复杂的功能单元通常是“一个分子一个分子”地组合在一起。不幸的是，控制结构生长的分子识别机制尚未得到很好的理解，这阻碍了具有新性能的新材料的设计。在过去的几年中，表征表面上单个吸附分子的可能性已得到显着提高。通过使用CO功能化的AFM针尖，可以直接可视化单分子的化学结构，这代表了研究分子识别过程的新工具集。在该项目中，这种所谓的键成像方法将用于分析分子间卤素键。与有机分子共价结合的卤素在其键合轴外端有一个亲电子区域，即 σ 孔。卤素内的这种各向异性电荷分布导致卤素键具有显着的方向性，其强度可以通过选择卤素或分子其余来调节。由于这些独特的特性，卤素键非常适合晶体工程、超分子化学、药物设计等领域的应用。表面上的卤素键可以通过另一个控制旋钮进行调整：表面材料。在本项目中，我们将系统研究不同表面材料对不同卤素的σ空穴的影响。因此，键成像技术将用于确定各种模型化合物在相对惰性和相对反应性基质上的结合选择性、键长、键角和吸附构象。在另一个步骤中，我们将研究不同基质材料上发生的结合类型，以及如何通过选择基质来主动控制它们的结合几何形状。实验结果将通过 DFT 计算得到补充。这些将允许获得有关基质和分子之间的电荷转移、分子内部的电荷分布以及结合能的不同部分（例如分子-分子与分子-基质）的知识。该项目应有助于更好地了解卤素键的性质，以便能够控制未来的自组装过程，并将其用于设计具有独特性能的新分子结构。