Exploring environmentally sensitive fluorescent dyes and their applications

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Warner, Caroline Chow
Major Professor
VanVeller, Brett
Winter, Arthur
Jenks, William
Stanley, Levi
Venditti, Vincenzo
Committee Member
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This dissertation consists of five chapters which discuss the development of benzothiadiazole derivatives in an effort to further understand the relationship between the structure and photophysical properties as well as expand their applications in biological settings. Chapter 2 was published in Organic Letters in 2019 and discusses the investigation into the components of the benzothiadiazole moiety and the effects of removing the nitrogen atoms from the 5-membered ring. We designed and synthesized two benzothiadiazole derivatives and their benzofuran counterparts and compared the photophysical properties of the two, finding that the nitrogen atoms do not play a significant role in the environmental sensitivity of the dyes but do affect the quantum yield of fluorescence. Chapter 3 is modified from a paper published in Organic & Biomolecular Chemistry in 2020 which discusses the application of a benzothiadiazole derivative as a lipid droplet stain. Due to the environmental sensitivity of the dye, it was found that it successfully labelled lipid droplets with much higher accuracy than the more commonly used Nile Red stain. Chapter 4 of this dissertation is modified from a paper published in Chemistry Select in 2020 which discusses the application of the benzothiadiazole core as a photocleavable protecting group (PPG). In contrast to other known PPGs which cleave upon a certain wavelength of light, our PPG was designed to cleave upon a certain wavelength of light and only in non-polar environments in an effort to create a photocleavable protecting group that is able to turn its reactivity on and off. While full cleavage of the leaving group was not observed, we were successful in demonstrating the PPG was reactive in only non-polar environments. Chapter 5 of this dissertation provides general conclusions and possible projects that will be investigated in the future. Please note that the work discussed in this dissertation does not reflect the entirety of my graduate studies while at Iowa State, but instead is a compilation of the work focused on the fluorophore benzo(heteroatom)diazole. During the past five years here, in addition to the work on the benzo(heteroatom)diazole dyes discussed here, I have worked collaboratively on several other topics. These projects include the synthesis of thioamides in peptide backbones, the synthesis and photophysical characterization of Tafamadis and Luciferin derivatives, and the synthesis and photocleavage studies of a functional benzothiadiazole photocleavable protecting group.
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