On-surface synthesis of covalently bonded molecular structures on insulators

近年来，在表面上自底向上制造定制的有机分子纳米结构的领域已经转向共价键合结构--除了其他原因外，因为它们更稳定，允许强烈的电子耦合。一个最突出的例子是自下而上合成原子精密的石墨烯纳米带。在迄今使用的表面化学反应中，金属衬底在启动反应中发挥了关键作用，研究绝缘体需要新的策略来形成有机分子之间的键。然而，对于在光电子和纳米电子中的应用，需要绝缘表面。该项目的目的是能够在超高真空条件下在绝缘衬底上自下而上地制造定制的有机分子纳米结构。为此，我们将仔细研究两条路线，即钯催化的交叉偶联和光诱导自由基的形成，然后在自由基之间进行化学合成。研究结构和可能的中间体的选择方法将是扫描探针技术，包括它们的光谱操作模式。实验研究将得到我们合作伙伴最先进的理论分析的支持，包括密度泛函理论计算、图像模拟和具有电子跃迁的非绝热分子动力学。我们相信，如果该项目得到资助，将在表面反应中提供全新的路线，从而为绝缘体的自下而上合成创造一个平台。

The field of bottom-up fabrication of tailored organic molecular nanostructures on surfaces has shifted towards covalently bonded structures in recent years - among other reasons, because they are more stable and allow for a strong electronic coupling. A most prominent example is the bottom-up synthesis of atomically precise graphene nanoribbons. As in the on-surface chemical reactions employed so far the metal substrate played a key role in initiating the reaction, working on insulators requires new strategies for bond formation between organic molecules. However for applications in opto- and nano-electronics insulating surfaces are required. The aim of this project is to enable bottom-up fabrication of tailored organic molecular nanostructures also on insulating substrates under ultra-high-vacuum conditions. To this end, we will scrutinize two routes, namely Pd-catalyzed cross-coupling and light-induced radical formation followed by a chemical synthesis between radicals. The methods of choice to investigate the structures and possible intermediates will be scanning probe techniques including their spectroscopic modes of operation. The experimental studies will be supported by state-of-the-art theoretical analysis from our collaboration partner including density functional theory calculations, image simulations and non-adiabatic molecular dynamics with electronic transitions. We are convinced that this project - if funded - will provide completely novel routes in on-surface reactions and thereby create a platform for bottom-up synthesis on insulators.