Design of functionalised ligands and metal complexes for self-assembly at the liquid/solid interface: STM-visualisation of 2D nano-patterns

Abstract

The thesis is concerned with the design and synthesis of novel functionalised ligand systems and their transition metal complexes for the two-dimensional (2D) nanopatterning of surfaces. The resultant monolayers were visualised by scanning tunnelling microscopy (STM). The obtained compounds offer catalytically interesting properties and meet structural criteria for 2D self-assembly at the liquid/solid interface. The latter is a powerful method to create widely extended and highly ordered surface layers and was exploited in a wide range of organic compounds. In contrast, the number of defined metal complexes visualised by STM is still rare. Advantageous structural features are the flatness and shape persistence of the molecules, combined with long alkyl side groups that promote the immobilisation of the molecules by intermolecular van der Waals interactions. The long-term goal of this project is the creation of nano-decorated catalyst surfaces which exhibit a high density of active sites at variable and defined distances. Such systems might give access to important reactions that are based on the cooperation of two or more metal centres, for example Fischer-Tropsch synthesis of n-alkanes/n-alkenes or C-H activation of methane. As a fundamental advantage, the exposed plane surfaces allow in situ studies of reactions on transition metal complexes which are typically utilised as homogeneous systems or as immobilised catalysts on porous carrier materials. Surfaces which contain nano-patterned binding sites may further act as innovative sensors. Finally, the controlled and highly ordered deposition of metal complexes on solid surfaces may provide programmable matrices or building blocks for the bottom-up engineering of electronic and magnetic devices.