Chapter 16: Photochemistry in Supercritical Fluids

In this chapter, the generation and subsequent decay of singlet oxygen in a range of supercritical fluids is reviewed. Factors including the solvent radial distribution function and local density augmentation around the solute, which are a function of proximity to the critical point, are considered. Specific solvent effects, such as electronic-to-vibrational energy transfer and spin–orbit coupling, are also examined. In addition, the application of supercritical fluids as solvents for singlet oxygen-mediated oxidations, which is an attractive proposition based on the long singlet-oxygen lifetimes in these systems and low fluid viscosity, are discussed. These include batch and continuous-flow approaches, and also biphasic systems to facilitate photosensitizer separation and recycling.