Stepwise Reduction of Azapentabenzocorannulene

Mono‐ and dianions of 2‐ tert ‐butyl‐3a 2 ‐azapentabenzo[ bc , ef , hi , kl , no ]corannulene ( 1 a ) were synthesized by chemical reduction with sodium and cesium metals, and crystallized as the corresponding salts in the presence of 18‐crown‐6 ether. X‐ray diffraction analysis of the sodium salt, [{Na + (18‐crown‐6)(THF) 2 } 3 {Na + (18‐crown‐6)(THF)}( 1 a 2− ) 2 ], revealed the presence of a naked dianion. In contrast, controlled reaction of 1 a with Cs allowed the isolation of singly and doubly reduced forms of 1 a , both forming π‐complexes with cesium ions in the solid state. In [{Cs + (18‐crown‐6)}( 1 a − )]⋅THF, asymmetric binding of the Cs + ion to the concave surface of 1 a − is observed, whereas in [{Cs + (18‐crown‐6)} 2 ( 1 a 2− )], two Cs + ions bind to both the concave and convex surfaces of the dianion. The present study provides the first successful isolation and characterization of the reduced products of heteroatom‐containing buckybowl molecules.