Syntheses and crystal structures of four 4-(4-meth­oxy­phen­yl)piperazin-1-ium salts: tri­fluoro­acetate, 2,3,4,5,6-penta­fluoro­benzoate, 4-iodo­benzoate, and a polymorph with 4-methyl­benzoate

Syntheses and X-ray crystal structures of four 4-(4-meth­oxy­phen­yl)piperazin-1-ium (MeOPP) salts, with 2,2,2-tri­fluoro­acetate, C(11)H(17)N(2)O(+)·C(2)F(3)O(2) (−) (I), 2,3,4,5,6-penta­fluoro­benzoate, C(11)H(17)N(2)O(+)·C(7)F(5)O(2) (−)·H(2)O (II), 4-iodo­benzoate C(11)H(17)N(2)O(+)·C(7)H(4)IO(2) (−)·H(2)O (III), and 4-methyl­benzoate, 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 qu­anti­ties of N-(4-meth­oxy­phen­yl)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-meth­oxy­benzene 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 inter­actions between cation and anion arene rings, and III exhibits I⋯I close contacts.