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, CHNO·CFO (), 2,3,4,5,6-penta-fluoro-benzoate, CHNO·CFO ·HO (), 4-iodo-benzoate CHNO·CHIO ·HO (), and 4-methyl-benzoate, CHNO·CHO ·HO () anions are presented. The salts form directly from equimolar qu-anti-ties of -(4-meth-oxy-phen-yl)piperazine and the corresponding organic acid in methanol and crystallize from 1:1 methanol/ethyl acetate. Salt is anhydrous whereas , , and 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 , , and ) O-H⋯O hydrogen bonds, although each also features weak C-H⋯O-type hydrogen bonds. Salt also has π-π-stacking inter-actions between cation and anion arene rings, and exhibits I⋯I close contacts.