Insights into the Planarization of Benzo-Thianthrene Rings: Relevance of Electronic and Steric Effects with Resulting Aromatic Properties

Covalent–organic frameworks (COFs) are useful architectures for two- (2D) and three-dimensional (3D) active materials. Recently, the characterization of the nonplanar benzo[5,6][1,4]dithiino[2,3-b]thianthrene-6,13-dicarbonitrile (bTEpCN), as a prototypical section of 2D COFs, enables further understanding of the properties on such extended networks. Upon adsorption on the Au(111) surface, planarization of bTEpCN is achieved. Here, we explore the factors driven by such an observation, driven by the increase in the destabilizing steric effect when going from the favored nonplanar to planar conformation. Interestingly, upon mono-oxidation, such a preference is reversed, favoring a planar conformation, revealing the key role of charge release from bTEpCN in reaching the planar conformation.