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

Abstract

A negatively curved aza‐nanographene (NG) containing two octagons was synthesized via a regioselective and stepwise cyclodehydrogenation procedure, where 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, enabling the exploration of 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, offering record‐high binding constants (Ka = 9.5 × 103 M–1 with C60, Ka = 3.7 × 104 M–1 with C70) among reported negatively curved polycyclic aromatic compounds. The tight association of aza‐NG with C60 was further elucidated by X‐ray diffraction analysis of their co‐crystal, showing the formation of 1:1 complex with substantial concave‐convex interactions.