A Dipleiadiene‐Embedded Aromatic Saddle Consisting of 86 Carbon Atoms

This study presents a new type of negatively curved nanographene (C86H32) that contains an unprecedented pattern of heptagons. A tert‐butylated derivative of C86H32 was successfully synthesized using tetrabenzodipleiadiene as a key building block. This synthesis involved a ring expansion reaction as a key step to form the seven‐membered rings in the framework of tetrabenzodipleiadiene. The single‐crystal structure reveals a saddle‐shaped molecule with a highly bent naphthalene moiety at the center of the polycyclic backbone. As found from the DFT calculations, this aromatic saddle is flexible at room temperature and has a saddle‐shaped geometry as the dominant conformation. The DFT calculations along with experimental results show that the attachment of t‐butyl groups to the central tetrabenzodipleiadiene moiety of nanographene C86H32 can stabilize the saddle conformation and make this nanographene less flexible. Class of 86: A type of negatively curved nanographene with an unprecedented pattern of heptagons in a polycyclic framework of 86 sp2 carbon atoms was successfully synthesized with ring expansion as a key step. The saddle‐shaped π‐backbone was revealed by X‐ray crystallography, and its stereochemical dynamics were studied by DFT calculations. (Picture: substituents in crystal structure removed for clarity.)