Molecular Design and Synthesis of Novel Organic Dyes for Applications in Renewable Fuel Generation [electronic resource].

9781085724494

Ann Arbor : ProQuest Dissertations & Theses, 2019.

1 online resource (147 p.)

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Solar energy is an attractive source of energy because it is abundant and readily available. Systems that utilize solar energy to generate other useful energy, such as electricity and fuel, have made extensive progress in research and development thus far. Commercially-available technologies like Si-based solar cells, however, face limitations such as low efficiencies and stability issues. The dissertation presented herein is interested in the possibility of addressing some of those limitations by developing dye molecules for solar energy conversion systems, as well as by understanding the basic science behind the systems at a molecular level.The following chapters presented in this dissertation focuses on the design, synthesis, and application of light-harvesting dye molecules for the purpose of driving artificial photosynthesis. Specifically, Chapter 2 presents a short, convenient, and scalable protocol for the one-pot preparation of highly fluorescent 7,8-dihalo-2,3-diaminophenazines, which are attractive intermediates for the preparation of polyfunctional phenazines and extended polyheteroacenes, commonly used in a variety of applications ranging from industrial dyes to organic electronics. The synthetic route is based on the oxidative condensation of 4,5-dihalo-1,2-diaminobenzenes in aqueous conditions, and it was found that the undesired hydroxylation byproducts are completely suppressed by the addition of a stoichiometric amount of acetone during the oxidation step. Further derivatization is also discussed in this chapter. Importantly, most of these derivatives are strongly luminescent, with fluorescence quantum-yields of up to 80% in ethanol even under aerobic conditions, highlighting their potential as valuable fluorophores.In Chapter 3, the synthesis, characterization, and spectroscopy of electron-injection dynamics of free base trimesitylporphyrins with varying linker lengths grafted onto SnO2 are presented. Electron-injection dynamics of dye-sensitized photoelectrochemical cells depend on the length of the linker connecting the molecular photosensitizer to the metal oxide electron acceptor. A length range spanning 8.5-17.2 A is studied by employing phenylene, biphenylene, terphenylene, and benzanilide groups as the linker that bind the porphyrin to the carboxylate anchor group, and the electron-injection dynamics are measured using terahertz spectroscopy. A clear correlation between linker length and injection rates is observed which provides insights that will be exploited in the optimization of dye-sensitized photoelectrochemical cells.Chapter 4 presents a new class of panchromatic dyads comprised of phenazines coupled to tetrapyrroles with an anchoring group that can be grafted onto metal oxide surfaces. A proof-of-concept for this type of dye, which can be further tuned with structural modifications to improve performance, is demonstrated by molecular design and synthesis of phenazine-porphyrin dyads, as well as evaluation of their potential as photosensitizers. A significance of this study is that the rational design of the dyads is dependent on computationally predicted absorption profiles, which critically helped in determining the molecules for synthesis. The dyads are also integrated into dye-sensitized solar cells to characterize their performance in such systems.

Dissertations & Theses @ Yale University.

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English

January 17, 2020

Thesis (Ph.D.)--Yale University, 2019.

Yale University. Chemistry.