Functional optimization by control of the electronic and structural properties of organic molecules on surfaces studied by scanning tunnelling microscopy

有机场效应晶体管(OFET)、太阳能电池和分子开关等分子器件的电学和光学性质，在很大程度上取决于其与其直接相邻分子间的相互作用以及表面辅助有机薄膜系统中分子-衬底的相互作用。复杂功能分子体系中不同类型的相互作用的优化需要详细的理论理解和合理的分子结构设计。研究分级体系的系统方法从固体基质上的单分子开始，包括具有可控范德华键的2D分子自组装，以及配位键，最后是共价键，后者允许在环境条件下产生稳定的体系。在这里，我们将集中于通过控制选定的分子体系的电子和结构性质来进行功能优化。在单分子水平上，我们将利用LT-STM/STS研究金属配位大环等单分子的功能。在此背景下，将研究菲衍生物对轻化学元素(H)的钉扎能力和新的金属配位键形成能力。关于单体体系的复杂图案的形成，我们将通过系统地控制分子间(例如van der Waals)相互作用和竞争的分子-底物相互作用来研究紧密堆积的层，特别是关于它们的取向有序-无序行为，这是我们最近在WWU的STM实验室发现的。最后，基于六重多齿分子形成层的共价2D分子网络将被研究，鉴于它们在产生热电和光响应系统方面的潜力。作为这些实验研究的补充，还将进行系统的理论研究，以详细了解分子-底物和分子间相互作用的影响以及所研究体系的电子和光学性质，作为优化和开发新的功能分子自组装控制方案的基础。

The electronic and optical properties of molecular devices such as Organic Field Effect Transistors (OFETs), Solar Cells and molecular switches critically depend on the intermolecular interaction with their direct neighbors as well as the molecule-substrate interaction occurring in surface assisted thin organic film systems. The optimization of the different types of interplay occurring in complex functional molecular systems requires detailed theoretical understanding and rational design of the molecular structure. A systematic approach of the investigation of hierarchical systems starts from single molecules on solid substrates, and will include 2D molecular self-assemblies with controllable van der Waals- and coordination bonding, and finally covalent bonding, the latter allowing to generate stable systems under ambient conditions. Here, we will focus on the functional optimization by control of the electronic and structural properties of selected molecular systems. On the single molecule level we will study the functionality of single molecules such as metal coordinated macrocycles by LT-STM/STS. In this context phenantrene derivatives will be investigated with respect to their pinning capabilities for light chemical elements (H) and new metal coordination bond formation capabilities. With respect to complex pattern formation of monomeric systems we will investigate close packed layers in particular with respect to their orientation order-disorder behavior as discovered recently in our STM lab at WWU by controlling systematically the interplay of the intermolecular (e.g. van der Waals) interaction and the competing molecule-substrate interaction. Finally, covalent 2D-molecular network forming layers based on six-fold multidentate molecules will be investigated in view of their potential for the generation of thermoelectric and photo-responsive systems. Complementary to these experimental studies, systematic theoretical investigations will be performed to understand in detail the influence of molecule-substrate and intermolecular interactions as well as the electronic and optical properties of the studied systems as a basis for optimization and developing new control schemes for functional molecular self-assemblies.