Synthesis and chain-breaking antioxidant activity of 6-amino-3-pyridinols and photochemistry of CdSe nanocrystals covered with functionalized cinnamates

摘要

Antioxidants are Nature's primary defense against lipid peroxidation, a process believed to be involved in a range of diseases such as atherosclerosis, cancer, Parkinson's and Alzheimer disease, and others. The best antioxidant Nature has is Vitamin E and it serves to trap free radicals, which are intermediates in lipid peroxidation. Over the last decade many attempts have been made to improve on Vitamin E, but these have failed. The first half of this thesis describes a different approach to this issue. A nitrogen atom was added to the aromatic ring of Vitamin E, after which the structure was further fine-tuned. This led to a new class of antioxidants, called 6-amino-3-pyridinols,that was 8 - 100 more potent than Vitamin E. Both in solution and as well as in human LDL ( bad cholesterol ), they greatly inhibited oxidation processes. Hence, they hold great promise for medicinal and industrial purposes. In the last decade, CdSe nanocrystals have evolved as a potential class of biomarkers. In order to direct the interaction of these species with a biological environment, organic surface ligands have been used. However, not much is understood about the direct interaction between the nanocrystal and the ligand. In the second part of this thesis, an investigation into this issue is presented. The nanocrystals were covered with functionalized cinnamate ligands, and the photochemistry of the resulting aggregates was studied. It was discovered that the ligand and the nanocrystal interact intimately upon irradiation with light. It was speculated that electron transfer was key in this. An interesting application of these findings was developed, in which irradiation with visible light led to the clean release of organic molecules from the nanocrystal. This release-by-visible-light system might have useful applications in drug delivery