Natural and Synthetic Oligopyrroles as Chromophores and Electron Reservoirs in Metal Complexes
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PublisherThe University of Arizona.
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EmbargoRelease after 07/09/2023
AbstractOligopyrroles are prevalent throughout nature in a variety of roles, from light-gathering pigments vital to photosynthesis to active sites in enzymes performing complex biochemical modifications. The versatility of oligopyrroles is due largely to their ability to harbor unpaired electrons, which allows them to stabilize multiple redox states independent of their metal cations. Oligopyrroles are “non-innocent” ligands which can undergo reduction and oxidation independent of the metal center. Their structure often forms stable, planar complexes with many metals, and their extended π-conjugation produces lower-energy absorbances in the near-IR – a property of organic materials which is increasingly important for many emerging technologies, including bioimaging and photovoltaic materials. Because of the proven utility of many natural oligopyrroles, many synthetic oligopyrroles and their metal complexes have also been synthesized. The first chapter of this thesis introduces photoacoustic imaging, an emerging bio-imaging technique, and presents the progress we have made towards the synthesis of a sensor molecule which would allow photoacoustic imaging of metals in-vivo. The starting material, methyl pheophorbide-a, is a chlorin pigment which can be extracted from Spirulina maxima, an algae that is widely available as a health supplement. We have established several pathways for modifying methyl pheophorbide-a and have successfully isolated two novel chelating molecules. The second chapter focuses on complexes with the synthetic tripyrrole hexaethyl tripyrrin-1,14-dione. Previous work in our group outlined the chemistry of complexes of tripyrrindione with Pd(II), Cu(II), and Zn(II). In all these past complexes, an aqua ligand occupies the fourth coordination site in a square planar geometry. We recently discovered that primary amines can occupy this position in Pd(II) complexes of tripyrrindione. We also discovered a unique interaction between nitriles and Pd(II) tripyrrindione which may be emerging evidence of the catalytic potential of tripyrrindione complexes.
Degree ProgramGraduate College