Hydrogen-Abstraction, Energy Transfer and Exciplex Formation in Photoactive Systems Based on Bile Acids
[EN] Bile acids are a family of amphiphilic steroids that play a pivotal role in physiological functions such as elimination of cholesterol or solubilization of lipids. Chemically, they share a steroidal skeleton with an unusual cis fusion between rings A and B, a short lateral chain ending in a car...
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| Format: | doctoral thesis |
| Publication Date: | 2016 |
| Country: | España |
| Institution: | Universitat Politècnica de València (UPV) |
| Repository: | RiuNet. Repositorio Institucional de la Universitat Politécnica de Valéncia |
| Language: | English |
| OAI Identifier: | oai:riunet.upv.es:10251/64084 |
| Online Access: | https://riunet.upv.es/handle/10251/64084 |
| Access Level: | Open access |
| Keyword: | Bile Acid Cyclobutane Pyrimidine Dimer Energy Transfer Exciplex Hydrogen Abstraction Laser Flash Photolysis Oxetane Through-Bond QUIMICA ORGANICA QUIMICA ANALITICA |
| Summary: | [EN] Bile acids are a family of amphiphilic steroids that play a pivotal role in physiological functions such as elimination of cholesterol or solubilization of lipids. Chemically, they share a steroidal skeleton with an unusual cis fusion between rings A and B, a short lateral chain ending in a carboxylic acid moiety and different number of hydroxyl groups on the alpha-face. Hence, bile acids offer a versatile architecture that can be used to investigate photophysical processes of interest such as hydrogen atom transfer, through-bond energy trasfer, through-bond exciplex formation and DNA photodamage-related reactions. First, unmodified bile acids have been used to evaluate hydrogen atom trasfer to benzophenone-like triplet carbonyls. Dehydrogenation of bile acids at positions C-3 and/or C-7 by a radical-mediated mechanism from the excited state of benzophenone has been demonstrated. Moreover, synthesized lithocholic acid derivatives including benzophenone or carbazole as donors and a naphthalene, biphenyl or thymine as acceptors have been employed to investigate through-bond energy transfer and exciplex formation processes. Thus, energy transfer from benzophenone to naphthalene or biphenyl and extended through-bond exciplex formation in benzophenone/naphthalene and benzophenone/biphenyl linked systems has been demostrated by laser flash photolysis. Finally, bile acid derivatives incorporating one benzophenone and two thymine units with different degrees of freedom have been prepared to investigate the photochemical formation of oxetanes or thymine dimers. Photosensitized formation of cyclobutane pyrimidine dimers through the generation of a delocalized triplet excited state has been demonstrated in intermolecular systems, while oxetane formation is observed when the degrees of freedom are reduced. |
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