Synthesis, Structures and Properties of Trioxa[9]circulene and Diepoxycyclononatrinaphthalene

This article presents trioxa[9]circulene (3) as a novel member of hetero[n]circulenes. Its synthesis began with the synthesis of dimethoxydioxa[8]helicene (5) and used dimethoxydiepoxycyclononatrinaphthalene (4) as a key intermediate, despite the condensation reaction predominantly yielding a 1,4‐addition byproduct. The structures and properties of 3–5 were extensively investigated using experimental and computational methods. Analysis of the crystal structures reveal elongation of the internal C‐C bonds in the nine‐membered ring of 3 compared to 4 and 5. Computational calculations demonstrate the remarkable flexibility of trioxa[9]circulene's saddle‐shaped polycyclic framework, while the other two compounds are rigid with large racemization barriers. Optically pure forms of 4 and 5 exhibit absorption and luminescence dissymmetry factors on the order of 10−2, with smaller values observed for compound 4. In the crystal structures, molecules of 3 stack to form columns with remarkable π‐π overlap, and the π‐π interactions of 4 exhibit short intermolecular C‐to‐C contacts. Consequently, the solution‐processed film of 4 functioned as a p‐type organic semiconductor in field effect transistors.