Syntheses and crystal structures of three salts of 1-(4-nitro-phenyl)-piperazine.

The crystal structures and Hirshfeld surface analyses of three salts of 1-(4-nitro-phenyl)-piperazine with 2-chloro-benzoic acid, 2-bromo-benzoic acid and 2-iodo-benzoic acid are reported. The chloro-benzoate salt, C 10 H 14 N 3 O 2 + ·C 7 H 4 ClO 2 - , contains whole-ion-disordered cations and anions, which were modeled with two equivalent conformations with occupancies of 0.745 (10)/0.255 (10) and 0.563 (13)/0.437 (13), respectively. The bromo-benzoate and iodo-benzoate derivatives are isomorphous and crystallize as hemihydrates, viz . C 10 H 14 N 3 O 2 + ·C 7 H 4 BrO 2 - ·0.5H 2 O and C 10 H 14 N 3 O 2 + ·C 7 H 4 IO 2 - ·0.5H 2 O, respectively [the water mol-ecule is disordered over two locations with occupancies of 0.276 (3)/0.223 (3) for the iodo-benzoate derivative]. In the extended structures, all three salts feature an R 4 4 (12) loop of two anions and two cations linked by N-H⋯O hydrogen bonds.