Synthesis of Functionalized Naphthalene Diimides and their Redox Properties

Abstract

In this article, we have discussed the recently developed synthetic routes to amplify the electron‐poor nature of the naphthalenediimides (NDIs) as well as the integration of electron‐rich donor groups towards ambipolar and strongly electron donating NDIs. Non‐conventional electron withdrawing groups (EWGs) have been applied, leading to highly electron deficient NDIs. Highly π‐acidic molecules with LUMO levels up to –5.0 eV have now been realized. Cationic EWGs have been integrated at the NDI‐core resulting in six‐electron acceptors called “electron‐sponge”. Electron donating groups like tetrathiafulvalene, dicyanomethides, amino‐groups, etc. have been substituted to realize ambipolar NDIs with high HOMO levels and “electron‐reservoir” properties. Diverse coupling reactions such as, Suzuki, Sonogashira, Stille, Buchwald–Hartwig, etc. have been performed to achieve attractive redox properties. Double cross‐coupling reactions have been successful with metallacyclopentadienes to establish highly extended NDIs. The new synthetic routes to NDIs have significantly extended the electrochemical window, improved their optical properties and have resulted in attractive panchromatic systems and driven new applications.