Emerging Trends in Phenothiazine Embedded Macrocycles

Phenothiazine is a very useful heterocyclic compound with applications in drugs, dyes, and electronic industries. Because of the presence of electron‐rich sulfur and nitrogen atoms in its core, phenothiazines are strong electron donors and form charge‐transfer salts with many acceptors. Phenothiazines are involved in fast and reversible electron transfer reactions and have been used as photoactive materials in organic light‐emitting devices and solar cells. Phenothiazine possesses several active positions on its core where different functional groups have been introduced, and several useful phenothiazine derivatives have been synthesized for various applications. In recent times, attention has been directed toward synthesis of phenothiazine unit(s) as a part of a macrocyclic framework because of their interesting photophysical and redox properties and their potential applications in different fields. Thus, various phenothiazine‐embedded macrocyclesa such as calix[n]phenothiazines, phenothiazine‐based imine‐bridged macrocycles, phenothiazine‐based cyclophanes, phenothiazine‐based crown ethers, cyclic phenothiaizine arrays, phenothiazine‐embedded porphyrinoids, and so on have been synthesized in recent years and exploited their structure and physicochemical properties. In this review, synthesis, structure, and properties of various types of phenothiazine‐embedded macrocycles has been described with a hope of stimulating further research on phenothiazine containing macrocycles and their use for a wide range of potential applications.