Indoles and Related Heterocycles

Indole and the related heterocycles have emerged as efficient building blocks for the creation of novel anion receptors. This chapter focuses on the employment of indoles, carbazoles, and indolocarbazoles in the creation of molecular clefts, macrocycles, oligomers, and sensors. The majority of these structures utilize the heterocyclic NH as a hydrogen bond donor in binding to anions of various sizes and geometries. These heterocycles are often connected by amides and ureas which also function as hydrogen bond donors in anion binding. Finally, molecular sensors based on indoles and carbazoles have been described, showing color or fluorescence changes upon anion binding or deprotonation of the heterocyclic NH by basic anions.