A new color in green chemistry: Photochromic molecular switches as components of multifunctional catalytic systems

Abstract In this chapter, an overview on the applications of photochromic molecular switches in catalytic transformations is given. The structure of these molecules can be reversibly controlled by light as an external stimulus, thereby not requiring any additional material that might turn to be a waste at the end of the process. The light-induced changes in molecular structure or shape can be associated with changes in function such as catalytic activity, solubility, aggregation, or selective binding. The diversity of their applications is gradually expanding and departs from the original goal of activity control (ON/OFF, high/low) in homogeneous systems towards controlling selectivity, including stereoselectivity, controlling phase transfer, facilitating catalyst recycling and reuse, and the development of heterogeneous and supported systems. These latter examples are well in line with the principles and aims of green chemistry.