Content area
Abstract
Our ability to control the size and properties of large macromolecules has matured to allow synthetic chemists to design functional materials using concepts from Nature. The ability of a dendrimer to encapsulate reactive functionality in a chemically distinct microenvironment is reminiscent of how natural enzymes use a folded protein backbone to protect and tune the properties of a catalytic site. Branched polymer architectures are also capable of placing donor chromophores at suitable distances and orientations relative to acceptors to allow for energy concentration, mimicking the natural light harvesting strategy of photosynthesis. Heme proteins are some of the most common natural targets, due to their biological importance and wide variety of functions, ranging from catalytic oxidations to electron transport to oxygen binding. Many of these functions have been recreated using porphyrin containing dendrimers and star polymers. Continuing the effort towards mimicking these processes, this thesis describes the synthesis of various porphyrin containing polymer architectures to provide macromolecules capable of unique photochemical and catalytic functions. These investigations aim to answer fundamental questions about the design of artificial enzymes and also show promise for use in a variety of technological applications.
After an overview of porphyrin containing macromolecules (Chapter 1), the design of a new branched monomer for the synthesis of internally functionalized dendrimers is described in Chapter 2. The new monomer was utilized in the synthesis of complex light harvesting dendrimers containing two different types of donor chromophores that could efficiently concentrate absorbed energy at a porphyrin core. Chapter 3 describes our first attempt at utilizing a dendrimer backbone to aid in the catalytic turnover of a palladium porphyrin sensitized photoreaction, and this design was more successfully implemented using star polymer architectures described in Chapter 4. Light-harvesting porphyrin molecules are revisited in Chapter 5, this time utilizing donor chromophores capable of efficient two-photon absorption, leading to porphyrin derivatives capable of using 800 nm laser light to generate singlet oxygen. This goal is of interest for the next generation of photodynamic therapy agents. Finally, Chapter 6 briefly describes a novel synthesis of asymmetric porphyrins and designs for their use as either photodynamic therapy sensitizers or the targeted delivery of anticancer drugs.
