Fifteen 4-(2-meth­­oxy­phen­yl)piperazin-1-ium salts containing organic anions: supra­molecular assembly in zero, one, two and three dimensions

Fifteen 4-(2-meth­oxy­phen­yl)piperazin-1-ium salts containing organic anions have been prepared and structurally characterized. In the isostructural 4-chloro­benzoate and 4-bromo­benzoate salts, C11H17N2O+·C7H4ClO2− (I) and C11H17N2O+·C7H4BrO2− (II), and the 4-iodo­benzoate salt C11H17N2O+·C7H4IO2− (III), the ions are linked by N—H⋯O hydrogen bonds, forming centrosymmetric R44(12) four-ion aggregates; a similar aggregate is formed in the 2-chloro­benzoate salt (V), isomeric with (I). In the 2-fluoro­benzoate salt C11H17N2O+·C7H4FO2− (IV), and the isomorphous pair of salts, the 2-bromo­benzoate (VI), isomeric with (II) and 2-iodo­benzoate (VII), isomeric with (III), N—H⋯O and C—H⋯π(arene) interactions link the components into three-dimensional arrays. Four-ion R44(12) aggregates are also found in the 2-methyl­benzoate, 4-amino­benzoate and 4-nitro­benzoate salts, C11H17N2O+·C8H7O2− (VIII), C11H17N2O+·C7H6NO2− (IX) and C11H17N2O+·C7H4NO4− (X), but those in (IX) are linked into complex sheets by an additional N—H⋯O hydrogen bond. In the 3,5-dinitrobenzoate salt, C11H17N2O+·C7H3N2O6−·2H2O (XI), N—H⋯O and O—H⋯O hydrogen bonds link the components into a complex ribbon structure. In the picrate salt, C11H17N2O+·C6H2N3O7− (XII), the four-ion aggregates are linked into chains of rings by C—H⋯O hydrogen bonds. In the hydrogen maleate salt, C11H17N2O+·C4H3O4− (XIII), two- and three-centre hydrogen bonds link the ions into a ribbon structure while both anions contain very short but asymmetric O—H⋯O hydrogen bonds, having O⋯O distances of 2.4447 (16) and 2.4707 (17) Å. O—H⋯O Hydrogen bonds link the anions in the hydrogen fumarate salt (XIV), isomeric with (XIII), into chains that are linked into sheets via N—H⋯O hydrogen bonds. In the hydrogen (2R,3R)-tartrate salt, C11H17N2O+·C4H5O6−·1.698H2O (XV), the anions are linked into sheets by O—H⋯O hydrogen bonds. Comparisons are made with the structures of some related compounds