Synthesis of new functional molecules for molecular electronics

Abstract

Molecular electronics is an interdisciplinary field where chemists, physicists and biologists come together to investigate electronic phenomena at the molecular level. From the chemists point of view the design and synthesis of new model compounds which have a controllable function is very much in the foreground. In this work we focus on the synthetic aspect towards such new compounds especially on the incorporation of ferrocene into macrocycles which can act as molecular wires. The fascinating property of ferrocene is its switchable redox-state which has a direct influence on the molecular energy levels and thus the electronic properties including conductivity. Chapter 1 provides an introduction to the field of molecular electronics. First, the integration techniques of single molecules into electric circuits are described. The structure-property relationships of molecules are then discussed and illustrated with a few examples. Then, the work which has been done with ferrocene and macrocycles is described followed by a collection of synthetic strategies which are useful to assemble complex structures such as ferrocene-macrocycles. Chapter 1 is then completed with a description of the individual projects. Chapter 2 describes the synthesis of halogen end-capped oligo-phenylene-ethynylenes to study the interactions at the solid/liquid interface and in crystal structures. In addition the possibility of contacting halogen-end groups with gold electrodes is discussed. Chapter 3 describes the synthesis of a molecular switch where a ferrocene was incorporated into an oligo-phenylene-vinylene structure. Electrochemical-, spectroelectrochemical- and break junction-experiments are discussed. Chapter 4 describes the synthesis of two macrocycles which incorporate a ferrocene unit. The focus lies on the synthetic strategy to develop a route which allows control of the shape of the macrocycle at a very late stage of the synthetic sequence by introducing different linker molecules. Chapter 5 describes the synthesis towards a macrocycle comprising two ferrocene units. Chapter 6 summarizes the work and provides an outlook. Chapter 7 provides the experimental details including the characterization of all compounds described throughout the thesis.