Terrylene: Synthesis, Modifications, and Multifaceted Applications

As a higher homologue of rylene with six fused benzene rings, terrylene exhibits distinct optoelectronic properties compared to its lower analogues, naphthalene, and perylene. In 1948, E. Clar reported the synthesis of terrylene for the first time, marking the beginning of higher rylene chemistry. Numerous synthetic routes have led to the establishment of a diverse array of terrylene-based chromophores in the literature so far. The extensive π-conjugated surface of terrylene derivatives promotes strong intermolecular π-π stacking interactions. Synthesis challenges and poor solubilities hindered the progress of core terrylene molecules and their analogues, such as aza-terrylenes and benzo-fused terrylenes, in multiple application domains. However, the field gained significant momentum with Müllen and coworkers' pioneering report of terrylene tetracarboxydiimide (TDI) in 1997. Following the initial report, the chemistry of TDI and its derivatives has been explored in multiple domains due to their high solubility, optimal bandgap, and unique optoelectronic and redox properties. Due to the presence of a large π-surface, terrylene derivatives often exert strong intermolecular π-π stacking interactions. Facilitating these unique properties, TDI and its derivatives were explored in bulk heterojunction organic solar cells, organic field-effect transistors, photochromic switching, single-molecule photophysics, bioimaging, and supramolecular chemistry. In this review article, we focus on the synthesis of various terrylenes, TDIs, and their derivatives, as well as their applications in multiple domains.