Core carbo‐mer of an extended tetrathiafulvalene: redox‐controlled reversible conversion to a carbo‐benzenic dication

Carbo -benzene is an aromatic molecule devised by inserting C 2 units within each C-C bond of the benzene molecule. By integrating the corresponding carbo -quinoid core as bridging unit in a p -extended tetrathiafulvalene (exTTF), it is shown that a carbo -benzene ring can be reversibly formed by electrochemical reduction or oxidation. The so-called carbo -exTTF molecule was thus experimentally prepared and studied by UV-visible absorption spectroscopy and cyclic voltammetry, as well as by X-ray crystallography and by scanning tunneling microscopy (STM) on a surface of highly oriented pyrolytic graphite (HOPG). The molecule and its oxidized and reduced forms were subjected to a computational study at the density functional theory (DFT) level, supporting carbo -aromaticity as a driving force for the formation of the dication, radical cation, and radical anion. By allowing co-planarity of the dithiolylidene rings and carbo -quinoidal core, carbo -exTTFs present a promising new class of redox-active systems.