A Blueprint for Transforming Indigos to Photoresponsive Molecular Tools

Indigo, one of the most ancient and abundant dyes in human history, has recently emerged as a potential functional motif due to its intriguing photochemical properties. This review aims to provide insights into both the preparation of these molecules and their utilization in molecular systems. First, the synthesis of the indigo core as well as available methods to derivatize indigo are described to outline synthetic strategies to build the desired molecular structures. Then, the photochemical behavior of indigos is discussed, with particular focus on E-Z photoisomerization and photoinduced electron transfer. Connections between the molecular structures and their photochemical properties are highlighted and serve as guiding principles for designing indigos to be applied as photoresponsive tools.