Modulating Paratropicity in Heteroarene-Fused Expanded Pentalenes.

Pentalenes are formally eight-π-electron antiaromatic, but π-expanded pentalenes can display varying levels of paratropicity depending on the choice of annelated (hetero)arenes and the geometry of π-expansion (i.e., linear vs bent topologies) around the [4 n ] core. Here, we explain the effects of annelation on the paratropicity of π-expanded pentalenes by relating the electronic structure of pentalenes to a pair of conjoined pentafulvenes.