Deep-Saddle-Shaped Nanographene Induced by Four Heptagons: Efficient Synthesis and Properties
Boris Borrisov, Giovanni M. Beneventi, Yubin Fu, Zhen‐Lin Qiu, Hartmut Komber, Qingsong Deng, Phillip M. Greißel, Alejandro Cadranel, Dirk M. Guldi, Ji Ma, Xinliang Feng
Abstract
The construction of multiple heptagonal rings in nanographene is the key step for obtaining exotic carbon nanostructures with a negative curvature and intriguing properties. Herein, a novel saddle-shaped nanographene ( 1 ) with four embedded heptagons is synthesized via a highly efficient one-shot Scholl reaction from a predesigned oligophenylene precursor. Notably, a quadruple [6]helicene intermediate was also obtained and isolated by controlling the Scholl reaction conditions. Interestingly, the single crystal structures of 1 display a saddle geometry induced by the four embedded heptagons, resulting in a deep curvature with a width of 16.5 Å and a depth of 8.0 Å. Theoretical calculations at the molecular level suggest a weak antiaromatic character of the heptagons in 1 . Remarkably, compound 1 exhibits dual fluorescence from S 1 and S 2 . The deep-saddle-shaped geometry in 1 defines host–guest interactions with fullerenes, which were explored in titration experiments and by theoretical methods. The resulting 1@C 60 are stable and are subject to an electron transfer from photoexcited 1 to C 60 . Our current study underscores the influence of heptagon rings on the photophysical, self-assembly, and electron-donating properties of NGs.