A nitrogen-doped bowl-shaped molecule containing a central heptagonal ring

Abstract

The incorporation of heptagonal rings in a polycyclic aromatic system can cause the molecule to be negatively curved to form a saddle-shaped structure. Thus, a molecular bowl with a central heptagonal ring that can be regarded as a fragment of a fullerene violating the isolated pentagon rule is quite rare. Here the synthesis of a nitrogen-doped heptagon-centered bowl-shaped compound is presented. The bowl-shaped conformation, which is confirmed by crystallographic analysis, is induced by the four peripheral pentagonal rings. The presence of fused pentagon and heptagon alters the molecular electronic structure and properties. The onset of the absorption spectrum is up to 800 nm with no fluorescence detectable. The aromaticity of adjacent hexagonal rings of the central heptagonal ring is weakened with one even being antiaromatic. The relatively low oxidation potential of the molecular bowl makes it possible to be chemically oxidized to generate a cationic radical.