The crystal structures of salts of N-(4-fluoro-phen-yl)piperazine with four aromatic carb-oxy-lic acids and with picric acid.

The structures are reported for five salts formed by reactions between N-(4-fluoro-phen-yl)piperazine and aromatic acids. In 4-(4-fluoro-phen-yl)piperazin-1-ium 2-fluoro-benzoate monohydrate, C10H14FN2 +·C7H4FO2 -·H2O, (I), the components are linked by a combination of N-H⋯O and O-H⋯O hydrogen bonds to form a chain of alternating R 4 6(12) and R 6 6(16) rings. The ionic components of 4-(4-fluoro-phen-yl)piperazin-1-ium 2-bromo-benzoate 0.353-hydrate, C10H14FN2 +·C7H4BrO2 -·0.353H2O, (II), are linked by N-H⋯O hydrogen bonds to form a centrosymmetric four-ion aggregate containing an R 4 4(12) motif, and these aggregates are linked into a mol-ecular ladder by a single C-H⋯π(arene) hydrogen bond. 4-(4-Fluoro-phen-yl)piperazin-1-ium 2-iodo-benzoate, C10H14FN2 +·C7H4IO2 -, (III), crystallizes with Z' = 2 in space group P : the four independent ions are linked by N-H⋯O hydrogen bonds to form a non-centrosymmetric aggregate again containing an R 4 4(12) motif, and aggregates of this type are linked into a ribbon by a combination of C-H⋯O and C-H⋯π(arene) hydrogen bonds. The anion in 4-(4-fluoro-phen-yl)piperazin-1-ium 2,4,6-tri-nitro-phenolate, C10H14FN2 +·C6H2N3O7 -, (IV), shows clear evidence of extensive electronic delocalization from the phenolate O atom into the adjacent ring. The ions are linked by a combination of two-centre N-H⋯O and three-centre N-H⋯(O)2 hydrogen bonds to form centrosymmetric four-ion aggregates containing three types of ring. The ions in 4-(4-fluoro-phen-yl)piperazin-1-ium 3,5-di-nitro-benzoate, C10H14FN2 +·C7H3N2O6 -, (V), are again linked by N-H⋯O hydrogen bonds to form centrosymmetric R 4 4(12) aggregates, which are themselves linked by a C-H⋯π(arene) hydrogen bond to form sheets, the stacking of which leads to the formation of narrow channels, containing disordered and/or mobile solvent entities. Comparisons are made with some related structures.