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Other names: cyclo­hepta­tri­enyl cation, cyclo­hepta­trienyl­ium


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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.