The research presented in the dissertation deals with the synthesis, characterization, photophysical, electrochemical, and pump probe studies of porphyrin-fullerene based donor-acceptor conjugates. The first chapter provides insights into the introduction of the thesis, which explains the events that occur in natural photosynthesis and the mimicking process of an artificial photosynthesis based on natural photosynthesis, works done in covalently and non-covalently linked donor acceptor systems, and the penetration of the literature related to the long-lived charge-separated states donor-acceptor conjugates. The second chapter details the physical methods employed to monitor the various photochemical processes in the donor-acceptor moiety. The third chapter focusses on designing and synthesizing a platinum porphyrin-fullerene dyad used for long-lived charged-separated state. The formation of a high-energy, long-lived radical ion pair by electron transfer from the triplet excited state is orchestrated in the dyad. The porphyrin ring is modified with three triphenylamine which act as secondary electron donors. The spin state of the electrons leading to the formation of long-lived charge-separated state is demonstrated by time-resolved optical and EPR spectroscopy. The fourth chapter studies metal ligand axial coordination. Two porphyrins were self-assembled via metal-ligand axial coordination of phenyl imidazole functionalized fulleropyrrolidine. A 1:2 complex formation with ImC60 was observed in the case of (TTP)Co, while for (TPA)4PCo only a 1:1 complex was possible. Spectroelectrochemistry revealed the formation of Co (III) porphyrin cation instead of Co (II) porphyrin radical cation during the oxidation of phenyl imidazole coordinated cobalt porphyrin. Using computational and electrochemical results, an energy level diagram was constructed to visualize the various photochemical events. Using femtosecond transient absorption spectroscopy, it was possible to observe the energy transfer and charge-separation process. The fifth chapter deals with the singlet oxygen generation of platinum and palladium porphyrins. In this chapter, a series of meso-substituted porphyrins are synthesized and metalated by platinum and pallidum porphyrins and characterized by several methods. The ability of both platinum and palladium porphyrins reveals higher electrochemical redox gaps as compared to their free base porphyrins. Both platinum and palladium porphyrins can generate singlet oxygen and probe by monitoring the photoluminescence of 1O2 at 1270 nm. The study highlights the importance of different meso-substituents in triplet porphyrin sensitizers that can estimate the singlet oxygen quantum yield, which is useful for photodynamic therapy, chemical synthesis, and other applications.
| Identifer | oai:union.ndltd.org:unt.edu/info:ark/67531/metadc2179300 |
| Date | 07 1900 |
| Creators | Subedi, Dili Raj |
| Contributors | D'Souza, Francis, Dzyuba, Sergei, Wang, Hong, Omary, Mohammad, Marshall, Paul |
| Publisher | University of North Texas |
| Source Sets | University of North Texas |
| Language | English |
| Detected Language | English |
| Type | Thesis or Dissertation |
| Format | Text |
| Rights | Public, Subedi, Dili Raj, Copyright, Copyright is held by the author, unless otherwise noted. All rights Reserved. |
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