The Synthesis and Single-Molecule Conductance of Conjugated Molecular Wires

Abstract

The past decades have seen the fast development of electronic devices in the industrial sector. There is increasingly rapid growth in the demand for alternative electronic building blocks to compliment, and possibly replace, the conventional silicon-based products. Electronic devices based on organic molecules, especially those based on single molecules, receive intense studies both theoretically and experimentally.
In this presented work, a new family of oligo(aryleneethenylene)s (OAE)s with molecular lengths (N…N distance) of ca. 2-6 nm were designed to investigate the length dependence of conductance at the single molecule level. X-ray molecular structures of OAEs with a molecular length up to 5.3 nm were successfully analysed and presented.
Secondly, four groups of pyridyl terminated oligo(phenyleneethylene) (OPE) derivatives were studied for the quantum interference effects. A dramatic destructive quantum interference effect was observed which decreased the single molecule conductance by several orders of magnitude. Unsymmetrical molecules with only one anchor group were noticed to form π-π stacking between two molecules.
Thirdly, amino terminated OPEs bearing various substituents on the central phenyl rings were explored to present the robustness of the central OPE backbone towards various functionalising substituents.
Fourthly, diaryloligoynes with different anchor groups were synthesised and the single-molecule conductances were studied. The stability of the tetrayne compounds is discussed and X-ray crystal structures of the stable tetraynes are presented.
Finally, pyridyl terminated OAE derivatives bearing an anthraquinone core were synthesised to investigate the charge transport through the central anthraquinone core, with special purpose of investigating quantum interference effects and the switching process of the central anthraquinone core.