Design Strategies for Boron Difluoride Formazanate Dyes with Near-Infrared Optical Properties
Abstract
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.