In Search of Highly Emissive Fully Organic Compounds for Application in Molecular Electronics

Abstract

The contents of this thesis can be summarised with two separate undertakings, with an overall goal to design, synthesise, and study novel organic materials. The first undertaking (Chapter Two) required detailed synthetic methodological studies to develop novel pathways towards PAH-type molecules (from all carbon to nitrogen doped, to boron doped nanographenes). The second undertaking (Chapters Three and Four) focuses on designing and synthesising small donor-acceptor systems for application in the OLED devices. Chapter Two focuses extensively on developing novel synthetic methodologies towards novel PAH-type molecules, with specific focus on all carbon, nitrogen-doped, and boron and nitrogen doped PAH synthesis. Unprecedented electronic and conductive properties of these compounds are predicted, with these compounds potentially useful as single molecule junctions and semiconductors. Chapter Three summarises the design, synthesis, and photophysical studies of five novel A-π-D-π-A systems, with a PTZ donor centre and varying acceptor appendages. An acetylene linker was incorporated into all structures to ensure planarity, full conjugation extension, and HOMO/LUMO orbital separation. All compounds synthesised possess ICT emissive character and were green to orange emitters. Chapter Four gives a detailed account of the design, synthesis, and photophysical studies of highly twisted D-π-A-π-D and D-A-D compounds with a central azaborine accepting core and varying donor appendages. This chapter contains a detailed discussion on C-N bond forming reactions, specifically a series of Buchwald-Hartwig amination reactions. The strength of the donor as well as the acceptor, and a moderate twisted structure is more important than a direct focus on the dihedral angle alone. In all compounds, azaborine was a very efficient electron acceptor, but combined with a strong donor, resulted in very efficient TADF candidate. Overall, this thesis describes a myriad of synthetic and photophysical studies towards novel organic molecules for application in organic electronics. The synthetic targets ranged from planar all carbon PAH molecules to small twisted organic architectures. Where possible, photophysical properties of the synthesised targets were elucidated to gain further understanding in their potential applications in the organic electronics industry.