Syntheses and crystal structures of four 4-(4-nitro-phenyl)piperazinium salts with hydrogen succinate, 4-aminobenzoate, 2-(4-chlorophenyl)acetate and 2,3,4,5,6-pentafluorobenzoate anions.

The syntheses and crystal structures are presented for four organic salts of the 4-(4-nitrophenyl)piperazinium cation, namely, 4-(4-nitrophenyl)piperazinium hydrogen succinate, C₁₀H₁₄N₃O₂⁺·C₄H₅O₄^- (I), 4-(4-nitrophenyl)piperazinium 4-aminobenzoate monohydrate, C₁₀H₁₄N₃O₂⁺·C₇H₆NO₂^-·H₂O (II), 4-(4-nitrophenyl)piperazinium 2-(4-chlorophenyl)acetate, C₁₀H₁₄N₃O₂⁺·C₈H₆ClO₂^- (III) and 4-(4-nitrophenyl)piperazinium 2,3,4,5,6-pentafluorobenzoate, C₁₀H₁₄N₃O₂⁺·C₇F₅O₂^- (IV). The salts form from mixtures of N-(4-nitrophenyl)piperazine and the corresponding acid [succinic acid (I), 4-aminobenzoic acid (II), 2-(4-chlorophenyl)acetic acid (III) and 2,3,4,5,6-pentafluorobenzoic 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-nitrophenyl 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 interaction between inversion-related 4-nitrophenyl groups. [ABSTRACT FROM AUTHOR]