Photoactive materials enabled by and for emerging synthetic technologies

Abstract

In recent years there has been a significant increase in the development and commercialisation of new synthetic tools and technologies, which offer significant advantages compared to traditional round-bottomed flask chemistry. This work explores the use of some of these emerging technologies with the goal of developing new photocatalytic processes, which would not otherwise be easily feasible with batch techniques. Specifically, we have used continuous flow chemistry, mechanochemistry, and 3D printing in four distinct research projects. This thesis is split into five chapters in total. Chapter 1 aims to act as a global introduction to the different synthetic technologies that were used and compare their utility and drawbacks against traditional batch synthetic methodologies. The remaining chapters 2-5 each represent a separate research project that utilises these new technologies. Each chapter contains its own introduction to the topic of research along with conclusions and proposed future work. Specifically, in Chapter 2, a rapid, high yielding, and work-up free synthesis of an unusual organic luminophore is developed. Its twisted, propeller-like geometry gives rise to much sought aggregation induced emission properties. Moreover, we were able to use this material as a reusable heterogeneous photosensitiser to produce singlet oxygen under continuous flow conditions. In Chapter 3, we report the unprecedented ring contraction of 1,2,6-thiadiazines to 1,2,5- thiadiazole 1-oxides. The transformation is fast, work-up free, offers quantitative yields, and is mediated by auto-photosensitised singlet oxygen. We exploited continuous flow processes to further improve the reaction scope and efficiency. Then, in Chapter 4 we describe the batch and mechanochemical syntheses of optically active dihydroxamic acids ligands, and their subsequent use for the synthesis of metalloorganic assemblies. Finally, Chapter 5 demonstrates how mechanochemical and 3D printing technologies were used to access a series of N-aryl amides from O-protected hydroxamic acids. The broad scope of this work aims to demonstrate the usefulness of alternative reactor designs in chemical synthesis and encourage their implementation by others.