The work carried out during the project consisted in the development of synthetic routes towards redox-active π-conjugated macrocycles capable of transporting both electrons and ions (with an initial focus on the development of synthetic routes to cyanated macrocycles) and in the investigation of their properties. Such mixed ionic-electronic conductors are important for various state-of-the-art applications, for example organic battery electrodes, electrochemical transistors, electrochromic devices, and light-emitting electrochemical cells. Before this project, macrocycles were considerably underexplored regarding these applications.
While the synthesis of cyanated macrocycles was found to be challenging via the proposed synthetic routes, the synthesis of π-conjugated macrocycles with other electron-withdrawing groups was highly successful. In line with the objectives of the project, π-conjugated macrocycles with different aromatic units were synthesised and their properties were investigated. The investigation of the properties has advanced our fundamental understanding of such compounds. The subsequent work on applications has exceeded the expectations by far. The cyclic shape of the molecules was found to be highly beneficial for application as organic battery electrode materials. Even the simplest compound paracyclophanetetraene, a macrocycle without substituents synthesised as a reference compound for the substituted macrocycles, performed surprisingly well when tested as anode material in sodium-ion batteries. These results were recently published (Angew. Chem., Int. Ed. 2020, 59, 12958-12964).
