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, C₁₁H₁₇N₂O+πC₂F₃O₂^- (I), 2,3,4,5,6-pentafluorobenzoate, C₁₁H₁₇N₂O+πC₇F₅O₂^-πH₂O (II), 4-iodobenzoate C₁₁H₁₇N₂O+πC₇H₄IO₂^-πH₂O (III), and 4-methylbenzoate, C₁₁H₁₇N₂O⁺π- C⁸H₇O₂^-πH₂O (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 IVare 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--Hπ π πO and (in II, III, and IV) O--Hπ π πO hydrogen bonds, although each also features weak C--Hπ π πO-type hydrogen bonds. Salt II also has π-π-stacking interactions between cation and anion arene rings, and III exhibits Iπ π πI close contacts. [ABSTRACT FROM AUTHOR]