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+center dot C7H4BrO2- center dot 2H(2)O, (I), 4-(4-nitrophenyl)piperazin-1-ium 4-iodobenzoate dihydrate, C10H14N3O2+center dot C7H4IO2-center dot 2H(2)O, (II), 4-(4-nitrophenyl)piperazin-1-ium 4-hydroxybenzoate monohydrate, C10H14N3O2+center dot-C7H5O3-center dot H2O, (III), 4-(4-nitrophenyl)piperazin-1-ium 4-methylbenzoate monohydrate, C10H14N3O2+center dot C8H7O2-center dot H2O, (IV), 4-(4-nitrophenyl)piperazin-1-ium 4-methoxybenzoate hemihydrate, 2C(10)H(14)N(3)O(2)(+)center dot 2C(8)H(7)O(3)(-)center dot H2O, (V), and 4-(4nitrophenyl)piperazin-1-ium 4-ethoxybenzoate, 2C(10)H(14)N(3)O(2)(+)center dot 2C(9)H(9)O(3)(-), (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 P1 except for (V), which crystallizes in the monoclinic space group P2(1)/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 center dot center dot center dot O and/or O-H center dot center dot center dot O and other weak interactions of type C-H center dot center dot center dot O and/or C-H center dot center dot center dot pi, forming sheets, whereas (VI) shows a cationic and anionic-based layer structure.