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 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¿¿, forming sheets, whereas (VI) shows a cationic and anionic-based layer structure.
NM is grateful to the University of Mysore for research facilities. HSY thanks the UGC for a BSR Faculty fellowship for three years. SGG gratefully acknowledges financial support from the Spanish Ministerio de Ciencia e Innovacio´n (PID2020–113558RB-C41) and Gobierno del Principado de Asturias (AYUD/2021/50997).