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- Karlsson, Erik, 1982-
(författare)
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Catalysts for Oxygen Production and Utilization : Closing the Oxygen Cycle: From Biomimetic Oxidation to Artificial Photosynthesis
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis describes the development and study of catalysts for redox reactions, which either utilize oxygen or hydrogen peroxide for the purpose of selectively oxidizing organic substrates, or produce oxygen as the necessary byproduct in the production of hydrogen by artificial photosynthesis.The first chapter gives a general introduction about the use of environmentally friendly oxidants in the field of organic synthesis, and about the field of artificial photosynthesis. The second chapter describes a computational study of the mechanism of palladium-catalyzed oxidative carbohydroxylation of allene-substituted conjugated dienes. The proposed mechanism, which was supported by DFT calculations, involves an unusual water attack on a (π-allyl)palladium complex. The third chapter describes a computational study of the oxidation of unfunctionalized hydrocarbons, ethers and alcohols with hydrogen peroxide, catalyzed by methyltrioxorhenium (MTO). The mechanism was found to proceed via rate-limiting hydride abstraction followed by hydroxide transfer in a single concerted, but highly asynchronous, step as shown by intrinsic reaction coordinate (IRC) scans. The fourth chapter describes the use of a new hybrid (hydroquinone-Schiff base)cobalt catalyst as electron transfer mediator (ETM) in the palladium-catalyzed aerobic carbocyclization of enallenes. Covalently linking the two ETMs gave a fivefold rate increase compared to the use of separate components. The fifth chapter describes an improved synthetic route to the (hydroquinone-Schiff base)cobalt catalysts. Preparation of the key intermediate 5-(2,5-hydroxyphenyl)salicylaldehyde was improved by optimization of the key Suzuki coupling and change of protecting groups from methyl ethers to easily cleaved THP groups. The catalysts could thus be prepared in good overall yield from inexpensive starting materials.Finally, the sixth chapter describes the preparation and study of two catalysts for water oxidation, both based on ligands containing imidazole groups, analogous to the histidine residues present in the oxygen evolving complex (OEC) and in many other metalloenzymes. The first, ruthenium-based, catalyst was found to catalyze highly efficient water oxidation induced by visible light. The second catalyst is, to the best of our knowledge, the first homogeneous manganese complex to catalyze light-driven water oxidation.
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| 2. |
- Lantz, Linda, 1985-
(författare)
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Synthesis of donor–acceptor–donor thiophene based ligands that can be utilized for optical assignment of pathological targets
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Thiophene based ligands represent a class of molecular reporters proven superior in discerning pathological targets involved in neurodegenerative diseases, as well as bacterial infection. By fluorometric detection that depends on the milieu surrounding the ligand these biological processes can be studied with fluorescence spectroscopy and hyper-spectral confocal microscopy. The binding of a thiophene-based ligand to a biological target can entail specific fluorescent read-out through the conformation-sensitive ligand. Thus, the photo-physical properties of these molecules and the optical connection of binding make them valuable tools in the study of pathological events. As optical detection of pathological phenomena can be realized through several fluorescence parameters, including changes in fluorescent intensity, wavelength shifts, energy transfer, or emission lifetime, molecular studies of pathological targets in several biological systems have been realized by employing thiophene-based ligands. For instance, utilization of conjugated polydisperse and monodisperse thiophene-based molecules has in several studies demonstrated detection of disease associated protein aggregates in vitro, ex vivo and in vivo. My doctoral studies have included the synthesis and characterization of thiophene based donor-acceptor-donor (D–A–D) molecules and evaluation of how changes in side-chain positions, molecular length and number of negatively charged carboxylates impact interaction with biological targets. This thesis describes the utilization of the D–A–D molecules as fluorescent ligands for protein aggregates associated with Alzheimer’s disease and optical assignment of specific bacteria. The design and synthesis of these novel D–A–D thiophene-based fluorophores, with alterations in back bone, distribution of side chains and negatively charged groups, have generated novel insights regarding the ligands chemical structure on ligand performance, by the assessment of binding mode of the respective ligand to distinct pathological entities. Furthermore, the D–A–D molecules hold alternative photo-physical properties compared to thiophene-based ligand and these optical properties of the ligands have been employed to provide new insights in questions regarding protein aggregate polymorphism in Alzheimer’s disease. Overall, by organic synthesis we have fine-tuned the properties of thiophene-based D-A-D molecules and evaluated how modifications affect interactions with distinct biological, pathological targets and we foresee that D–A–D thiophene-based ligands will expand the toolbox for studying pathological targets in neurodegenerative diseases, as well as bacterial infection.
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