Syntheses and crystal structures of three salts of 1-(4-nitro­phenyl)­piperazine

The crystal structures and Hirshfeld surface analyses of three salts of 1-(4-nitro­phenyl)­piperazine with 2-chloro­benzoic acid, 2-bromo­benzoic acid and 2-iodo­benzoic acid are reported. The chloro­benzoate 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 bromo­benzoate and iodo­benzoate 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 mol­ecule is disordered over two locations with occupancies of 0.276 (3)/0.223 (3) for the iodo­benzoate 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.