The Synthesis and Functionalisation of Porphyrins and Related Systems

Abstract

There are many pathways one can take when designing a porphyrin, and the design itself has a huge impact on the potential properties and therefore function of that porphyrin. One of the main topics of work in this thesis is the functionalisation of the pre-formed deuteroporphyin IX skeleton. Due to its unsymmetrical nature, total synthesis of new derivatives would be far more complex, so the focus for this work was on the utilisation of the highly successful transition metal catalysed reactions. The synthesis of cationic derivatives which could be tested for photosensitising effects for antimicrobial PDT is explored. A short study into the photodegradation of Rhodamine B is discussed in Chapter 4. Here, cationic derivatives of tetramethylpyridylporphyrin were prepared and conjugated to graphene oxide. The resultant nanohybrids were tested for their ability to break down the dye in an attempt to find an efficient way to remove these waste-water contaminants. The method of quaternising the amines on the porphyrin periphery was used here again, and the resulting cationic charge enabled electrostatic interactions with the graphene oxide sheets in water. Finally, a study into the standard tetrapyrrole condensation chemistry will be discussed. Specifically, O-BODIPYs will be utilized as the parent compounds – via the preparation of an aldehyde functionality to act as the reaction partner with various pyrrole moieties. To-date, these compounds have not been reported in the direct construction of chromophores and tetrapyrroles. The aim of this project was to determine how feasible these molecules could be as building blocks for porphyrins and porphyrin derivatives. Initial investigations were carried out on symmetrical systems for ease of purification, however a long-term goal of this study is the development of asymmetric systems for the preparation of more complex systems.