AbstractThe title compound, C18H27N6O4+.Cl-, is the product of addition of two molecules of DABCO (1,4-diazabicyclo2.2.2octane) to one molecule of 1-chloro-2,4-dinitrobenzene. One of the DABCO molecules undergoes ring opening in the reaction, to give a piperazine ring, one N atom of which is connected to a 2,4-dinitrophenyl group, while the other is connected to an intact DABCO moiety via an ethylene linkage. The displaced chloride serves as counter-ion to balance the positive charge on the DABCO quaternary ammonium centre. The crystal structure determination confirms the structure deduced from NMR spectroscopy. Molecular dimensions are unexceptional.