Crystal structures of six 4-(4-nitro-phenyl)-piperazin-1-ium salts.

Six piperazinium salts, namely 4-(4-nitro-phenyl)-piperazin-1-ium 4-bromo-ben-zo-ate dihydrate, CHNO ·CHBrO ·2HO, (I), 4-(4-nitro-phenyl)-pi-per-a-zin-1-ium 4-iodo-benzoate dihydrate, CHNO ·CHIO ·2HO, (II), 4-(4-nitro-phenyl)-piperazin-1-ium 4-hy-droxy-benzoate monohydrate, CHNO ·CHO ·HO, (III), 4-(4-nitro-phenyl)-piperazin-1-ium 4-methyl-benzoate monohydrate, CHNO ·CHO ·HO, (IV), 4-(4-nitro-phenyl)-piperazin-1-ium 4-meth-oxy-benzoate hemihydrate, 2CHNO ·2CHO ·HO, (V), and 4-(4-nitro-phenyl)-piperazin-1-ium 4-eth-oxy-benzoate, 2CHNO ·2CHO , (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 except for (V), which crystallizes in the monoclinic space group 2/ 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 inter-actions of type C-H⋯O and/or C-H⋯π, forming sheets, whereas (VI) shows a cationic and anionic-based layer structure.