The structures of eleven (4-phen-yl)piperazinium salts containing organic anions

Eleven (4-phen-yl)piperazinium salts containing organic anions have been prepared and structurally characterized, namely, 4-phenyl-piperazin-1-ium 4-fluoro-benzoate monohydrate, C₁₀H₁₅N₂ ⁺·C₇H₄FO₂ ^-·H₂O, 1; 4-phenyl-piperazin-1-ium 4-bromo-benzoate monohydrate, C₁₀H₁₅N₂ ⁺·C₇H₄BrO₂ ^-·H₂O, 3; 4-phenyl-piperazin-1-ium 4-iodo-benzoate, C₁₀H₁₅N₂ ⁺·C₇H₄IO₂ ^-, 4; 4-phenyl-piperazin-1-ium 4-nitro-benzoate, C₁₀H₁₅N₂ ⁺·C₇H₄NO₄ ^-, 5; 4-phenyl-piperazin-1-ium 3,5-di-nitro-salicylate, C₁₀H₁₅N₂ ⁺·C₇H₃N₂O₇ ^-, 6; 4-phenyl-piperazin-1-ium 3,5-di-nitro-benzoate, C₁₀H₁₅N₂ ⁺·C₇H₃N₂O₆ ^-, 7; 4-phenyl-piperazin-1-ium picrate, C₁₀H₁₅N₂ ⁺·C₆H₂N₃O₇ ^-, 8; 4-phenyl-piperazin-1-ium benzoate monohydrate, C₁₀H₁₅N₂ ⁺·C₇H₅O₂ ^-·H₂O, 9; 4-phenyl-piperazin-1-ium p-toluene-sulfonate, C₁₀H₁₅N₂ ⁺·C₇H₇O₃S^-, 10; 4-phenyl-piperazin-1-ium tartarate monohydrate, C₁₀H₁₅N₂ ⁺·C₄H₅O₆ ^-·H₂O, 11; and 4-phenyl-piperazin-1-ium fumarate, C₁₀H₁₅N₂ ⁺·C₄H₃O₄ ^-, 12. Compounds 1 and 3-12 are all 1:1 salts with the acid proton transferred to the phenyl-piperaizine basic N atom (the secondary amine) with the exception of 3 where there is disorder in the proton position with it being 68% attached to the base and 32% attached to the acid. Of the structures with similar stoichiometries only 3 and 9 are isomorphous. The 4-phenyl substituent in all cases occupies an equatorial position except for 12 where it is in an axial position. The crystal chosen for structure 7 was refined as a non-merohedral twin. There is disorder in 5, 6, 10 and 11. For both 5 and 6, a nitro group is disordered and was modeled with two equivalent orientations with occupancies of 0.62 (3)/0.38 (3) and 0.690 (11)/0.310 (11), respectively. For 6, 10 and 11, this disorder is associated with the phenyl ring of the phenyl-piperazinium cation with occupancies of 0.687 (10)/0.313 (10), 0.51 (7)/0.49 (7) and 0.611 (13)/389 (13), respectively. For all salts, the packing is dominated by the N-H⋯O hydrogen bonds formed by the cation and anion. In addition, several structures contain C-H⋯π (1, 3, 4, 8, 9, 10, and 12) and aromatic π-π stacking inter-actions (6 and 8) and one structure (5) contains a -NO₂⋯π inter-action. For all structures, the Hirshfeld surface fingerprint plots show the expected prominent spikes as a result of the N-H⋯O and O-H⋯O hydrogen bonds.