Syntheses and crystal structures of four 4-(4-nitro-phen-yl)piperazinium salts with hydrogen succinate, 4-amino-benzoate, 2-(4-chloro-phen-yl)acetate and 2,3,4,5,6-penta-fluoro-benzoate anions.

The syntheses and crystal structures are presented for four organic salts of the 4-(4-nitro-phen-yl)piperazinium cation, namely, 4-(4-nitro-phen-yl)piperazinium hydrogen succinate, C 10 H 14 N 3 O 2 + ·C 4 H 5 O 4 - ( I ), 4-(4-nitro-phen-yl)piperazinium 4-amino-benzoate monohydrate, C 10 H 14 N 3 O 2 + ·C 7 H 6 NO 2 - ·H 2 O ( II ), 4-(4-nitro-phen-yl)piperazinium 2-(4-chloro-phen-yl)acetate, C 10 H 14 N 3 O 2 + ·C 8 H 6 ClO 2 - ( III ) and 4-(4-nitro-phen-yl)piperazinium 2,3,4,5,6-penta-fluoro-benzoate, C 10 H 14 N 3 O 2 + ·C 7 F 5 O 2 - ( IV ). The salts form from mixtures of N -(4-nitro-phen-yl)piperazine and the corresponding acid [succinic acid ( I ), 4-amino-benzoic acid ( II ), 2-(4-chloro-phen-yl)acetic acid ( III ) and 2,3,4,5,6-penta-fluoro-benzoic acid ( IV )] in mixed solvents of methanol and ethyl acetate. Salts I , III , and IV are anhydrous, whereas II is a monohydrate. In each structure, the overall conformation of the cation is determined by the disposition of the exocyclic N-C bond of the piperazine ring (either axial or equatorial) and twists about the N-C bond between the piperazine ring and its attached 4-nitro-phenyl ring. The packing motifs in each structure are quite different, though all are dominated by strong N-H⋯O hydrogen bonds, which are augmented in I and II by O-H⋯O hydrogen bonds, and in III by a π-π stacking inter-action between inversion-related 4-nitro-phenyl groups.