Negatively Curved Octagon‐Incorporated Aza‐nanographene and its Assembly with Fullerenes

A negatively curved aza‐nanographene (NG) containing two octagons was synthesized by a regioselective and stepwise cyclodehydrogenation procedure, in which a double aza[7]helicene was simultaneously formed as an intermediate. Their saddle‐shaped structures with negative curvature were unambiguously confirmed by X‐ray crystallography, thereby enabling the exploration of the structure–property relationship by photophysical, electrochemical and conformational studies. Moreover, the assembly of the octagon‐embedded aza‐NG with fullerenes was probed by fluorescence spectral titration, with record‐high binding constants ( K a =9.5×10 3 M −1 with C 60 , K a =3.7×10 4 M −1 with C 70 ) found among reported negatively curved polycyclic aromatic compounds. The tight association of aza‐NG with C 60 was further elucidated by X‐ray diffraction analysis of their co‐crystal, which showed the formation of a 1 : 1 complex with substantial concave‐convex interactions.