Portland State University. Department of Chemistry
Date of Award
Doctor of Philosophy (Ph.D.) in Chemistry
1 online resource (xiv, 128 pages)
Photochemistry focuses on various aspects of the interaction of light with molecules. This work entails new methodology for fundamental measurements of photochemistry along with novel applications of triplet-photosenstizers. Herein described are two separate methodologies developed for the determination of the quantum yield. A method for the singlet oxygen quantum yield was developed that utilizes the reaction between singlet oxygen and dimethyl sulfoxide (DMSO) to produce dimethyl sulfone. The rate of the reaction is measured by the pressure decrease that results from the consumption of oxygen from the headspace of a sealed system. It was found that the rate of pressure decrease was directly related to the singlet oxygen quantum yield. Additionally, an alternative method for the potassium ferrioxalate actinometer was developed. CO2 production was measured two different way; by the pressure increase in a sealed system and the volume change by trapping the CO2. Both methods were considerably less laborious and showed agreeable results as compared to the traditional spectroscopic methods.
A major focus of this the thesis comprises research with photosensitizers that have significant triplet yields. Incorporating heavy atoms into chromophores typically increases the triplet yield. A predictive model for the singlet oxygen quantum yield (a lower bound triplet yield approximation) was developed for fluorescein type dyes with heavy atoms of different identities and positions. Triplet-photosensitizers were also explored for use as an aerobic catalyst and for the conversion of light to preform pressure-volume work. A tellurium containing triplet-photosenstizer, known as a tellurorhodamine, was used for the oxidation of thiols to disulfides. Upon irradiation the tellurium dye creates singlet oxygen and reacts with it to form a telluroxide which can act as an oxidant. Near quantitative yields were obtained for aromatic thiols; thiophenol and 2-naphthalenethiol, while aliphatic thiols resulted in degradation to the tellurorhodamine.
A reversible reaction of singlet oxygen with 1,4-dimethylnapthalene was explored for the conversion of light to pressure-volume work. Singlet oxygen, generated by a triplet-photosenstizer, was used to react with 1,4-dimethylnaphthalene to produce its corresponding endoperoxide. Over time it was shown that oxygen is consumed from the headspace of a sealed system and can result in a pressure decrease. In dark conditions, near room temperature, the endoperoxide is metastable and releases oxygen to which results in a pressure increase.
Lutkus, Luke V., "Applications of Triplet-Photosensitizers and Development of Photochemical Methods" (2020). Dissertations and Theses. Paper 5417.
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