Doctor of Philosophy
Joe B. Gilroy
This thesis describes the synthesis and characterization of boron difluoride complexes of formazanate ligands. The resulting compounds have rich redox-active properties and optical properties in the far-red to near-infrared (NIR) spectral regions of the electromagnetic spectrum. This thesis contextualizes the growing interest in NIR-capable compounds and attempts to demonstrate the utility and accessibility of BF2 formazanate dyes as candidates for this class of materials. Furthermore, Chapters 2‒4 summarizes the effects of structural variation to the properties of the final formazanate-based dyes. Different substituents are incorporated into the formazanate framework to enhance or disrupt π-conjugation. New synthetic routes are described which can give access to larger π-conjugated systems or to new ligand frameworks. Chapter 2 describes the effects of the substitution of benzothiazole to the heteroatom-rich formazan backbone. The frontier molecular orbitals are examined to rationalize the changes in optoelectronic properties. Chapter 3 describes a new synthetic route that gives access to strong electron-donating groups like arylamines. This work builds upon a previously reported breakthrough candidate and expands the library of amine-substituted boron difluoride formazanates. The NIR properties of these dyes are explored experimentally and computationally. Chapter 4 summarizes the results of combining the popular dye, BODIPY, with BF2 formazanates. The photophysics of these first-of-their-kind dye-dye conjugates are studied. Unusual and unexpected optical and electrochemical properties are rationalized using time-dependent density functional theorem. Chapter 5 summarizes the synthetic efforts invested into a bis-formazan macrocycle. This new target is analogous to the porphyrinoids family of dyes and could promise to be a privileged ligand. Lastly, Chapter 6 combines the key conclusions of Chapters 2‒5 and applies it to new avenues towards near-infrared optical properties. Several new series of dyes are proposed along with their applications as small organic materials.
Summary for Lay Audience
Dyes are broadly defined as molecules that impart color or change the color of materials like fabrics, paints and even food. The colours we see comprise the visible region of the wide spectra of light. In contrast, other regions, like ultraviolet, infrared and microwave, are invisible to our eyes. This thesis explores different classes of dyes that interact with far-red and infrared light in interesting ways. These dyes are increasingly important for a variety of research areas and applications like cell-imaging, cancer therapy, solar cells, and display technologies. Chapter 1 digs deep into how changing the structure of these dyes impacts their properties and describes the strategies to make them even more versatile: Different elements are added to the dye's structure to either boost or alter its interaction with light. Structural twists that disrupt conjugation are employed to achieve unexpected phenomena. Lastly, the structure-to-property relationships of champion dyes in this field are explored to give context to the following experimental chapters.
Chapters 2‒5 build on existing knowledge by introducing new methods to create boron difluoride complexes of formazanates. This is achieved by combining these dyes with other popular ones like BODIPY, offering surprising and unusual characteristics, for example. The redox behaviors of these dyes are also extensively studied since the properties that govern their interaction electrons are closely tied to the ways they interact with light. Additionally, the studies in this work use computational chemistry to rationalize the optical and electronic behaviors of BF2 formazanates. This enables a more thorough understanding of why certain structural changes lead to observed properties, offering a roadmap for strategic molecular design in the future. This work concludes in Chapter 6 by exploiting these findings and proposing new types of structures that aim to go beyond the properties that have been explored thus far in BF2 formazanate dyes.
Buguis, Francis L., "Design Strategies for Boron Difluoride Formazanate Dyes with Near-Infrared Optical Properties" (2023). Electronic Thesis and Dissertation Repository. 9798.
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