1-{2-[4-(4-Nitrophenyl) piperazin-1-yl]-ethyl}-4-aza-1-azoniabicyclo[2.2.2]-octane iodide

The title compound, C18H28N5O2+center dot I-, was observed as a main product in an intended 1: 1 reaction between 4-iodonitrobenzene and 1,4-diazabicyclo[2.2.2] octane (DABCO). In the reaction, DABCO undergoes a ring opening to yield a quaternary salt of DABCO and 1-ethyl-4-(4-nitrophenyl)piperazine with an iodide anion. The crystal structure determination was carried out as no crystal structure had been previously reported in the investigations describing the corresponding reaction with 4-chloronitrobenze. Indeed, the crystal structure of the title compound confirms the molecular composition proposed earlier for the analogous chloride salt. The cation conformation is similar to the previously reported dinitro analogue 1-{2-[4-(2,4-dinitrophenyl) piperazin-1-yl]ethyl}-4-aza-1-azoniabicyclo[ 2.2.2] octane chloride [Clegg et al. (2004). Acta Cryst. E60, o291-o293]. The crystal packing is dominated by cation center dot center dot center dot I- interactions in addition to weak intermolecular C-H center dot center dot center dot O2N and C-H center dot center dot center dot N interactions between the cations.