Tropylium

Other names: cyclo­hepta­tri­enyl cation, cyclo­hepta­trienyl­ium

[C₇H₇]⁺

9/50 common

The tropylium cation is the conjugate acid of the simple hydrocarbon cycloheptatriene. The loss of a hydride equivalent from C₇H₈ leaves tropylium, with 6 electrons in a conjugated π system to satisfy the Hückel criterion for aromatic ring stabilization. In this sense, tropylium may be understood as part of a family of 6π aromatic hydrocarbons, along with benzene and cyclopentadienide, and it likewise capable of "sandwich-type" ligand binding in various coordination complexes such as troticene.