Syntheses and crystal structures of four 4-(4-meth-oxy-phen-yl)piperazin-1-ium salts: tri-fluoro-acetate, 2,3,4,5,6-penta-fluoro-benzoate, 4-iodo-benzoate, and a polymorph with 4-methyl-benzoate.

Syntheses and X-ray crystal structures of four 4-(4-meth-oxy-phen-yl)piperazin-1-ium (MeOPP) salts, with 2,2,2-tri-fluoro-acetate, C 11 H 17 N 2 O + ·C 2 F 3 O 2 - ( I ), 2,3,4,5,6-penta-fluoro-benzoate, C 11 H 17 N 2 O + ·C 7 F 5 O 2 - ·H 2 O ( II ), 4-iodo-benzoate C 11 H 17 N 2 O + ·C 7 H 4 IO 2 - ·H 2 O ( III ), and 4-methyl-benzoate, C 11 H 17 N 2 O + ·C 8 H 7 O 2 - ·H 2 O ( IV ) anions are presented. The salts form directly from equimolar qu-anti-ties of N -(4-meth-oxy-phen-yl)piperazine and the corresponding organic acid in methanol and crystallize from 1:1 methanol/ethyl acetate. Salt I is anhydrous whereas II , III , and IV are all monohydrates. In all cases, the MeOPP cation conformation is determined by the torsion about the N-C bond between the piperazinium and 4-meth-oxy-benzene rings. Crystal packing in each structure is largely dictated by N-H⋯O and (in II , III , and IV ) O-H⋯O hydrogen bonds, although each also features weak C-H⋯O-type hydrogen bonds. Salt II also has π-π-stacking inter-actions between cation and anion arene rings, and III exhibits I⋯I close contacts.