Synthesis and Properties of Graphyne Model Compounds and an Electrochemical Study of Substituted Pentacenes

Abstract

The work described in this thesis focuses on two central topics: (1) the synthesis of carbon-rich macrocycles as model compounds of the carbon allotrope graphyne and the study of their electronic properties, and (2) the electrochemical investigation of the properties of substituted pentacene molecules. To this end, Chapter 1 first offers an introduction to conjugated organic materials, focusing on acetylene-rich macrocycles. Subsequently, the theoretical structures of graphyne are introduced, and their potential properties described. Previous synthetic efforts to prepare model compounds for graphyne are also discussed. Chapter 2 focuses on the synthesis of 12,12,12-graphyne. Described first are the syntheses of small molecules based on four molecular scaffolds: (1) aryl triazenes, (2) dibromoolefins, (3) tetraethynylethenes, and (4) vinyl triflates. These molecules are characterized using standard methods, including 1H and 13C NMR, IR, and mass spectrometries. These molecules are then used as building blocks toward the synthesis of expanded radialenes, which would serve as model compounds for 12,12,12-graphyne. Chapter 3 focuses on the use of small molecules prepared in Chapter 2 as building blocks toward a series of radiaannulene oligomers, which serve as model compounds for 6,6,12-graphyne. Several synthetic routes are explored in an effort to optimize preparation of the series of radiaannulenes. The products are characterized by 1H and 13C NMR, IR and mass spectrometries, as well as by X-ray crystallography. The electronic properties are investigated using UV-vis spectroscopy and cyclic voltammetry to provide insight into the potential properties of 6,6,12-graphyne. Chapter 4 focuses on the electrochemical properties of substituted pentacenes. A brief introduction to pentacene and functionalized pentacene is provided. The syntheses of several pentacene derivatives is outlined, and the synthesis of conjugated pentacene-thiophene molecules is described. The effect of the substituents on the HOMO and LUMO energy levels and band gaps of the pentacene molecules is described, based on results from cyclic voltammetry. The thesis concludes with a brief summary, an outlook for the synthesis graphyne model compounds, and a description of how radiaannulenes might serve as useful materials in the synthesis of other conjugated organic molecules