Crystal structures of six 4-(4-nitrophenyl)piperazin-1-ium salts

Six piperazinium salts, namely 4-(4-nitrophenyl)piperazin-1-ium 4-bromobenzoate dihydrate, C10H14N3O2+·C7H4BrO2−·2H2O, (I), 4-(4-nitrophenyl)piperazin-1-ium 4-iodobenzoate dihydrate, C10H14N3O2+·C7H4IO2−·2H2O, (II), 4-(4-nitrophenyl)piperazin-1-ium 4-hydroxybenzoate monohydrate, C10H14N3O2+·C7H5O3−·H2O, (III), 4-(4-nitrophenyl)piperazin-1-ium 4-methylbenzoate monohydrate, C10H14N3O2+·C8H7O2−·H2O, (IV), 4-(4-nitrophenyl)piperazin-1-ium 4-methoxybenzoate hemihydrate, 2C10H14N3O2+·2C8H7O3−·H2O, (V), and 4-(4-nitrophenyl)piperazin-1-ium 4-ethoxybenzoate, 2C10H14N3O2+·2C9H9O3−, (VI), have been synthesized and their crystal structures solved by single-crystal X-ray diffraction, revealing that all of them crystallize in the triclinic space group P-1 except for (V), which crystallizes in the monoclinic space group P21/c and has a disordered nitro group. Compounds (I) and (II) are isostructural. The crystal packing of (I)–(V) is constructed from organic chains formed by a combination of hydrogen bonds of type N—H...O and/or O—H...O and other weak interactions of type C—H...O and/or C—H...π, forming sheets, whereas (VI) shows a cationic and anionic-based layer structure.