Crystal structures of the recreational drug N-(4-methoxyphenyl)piperazine (MeOPP) and three of its salts

Abstract

Crystal structures are reported for N-(4-methoxyphenyl)piperazine (MeOPP), (I), and for its 3,5-dinitrobenzoate, 2,4,6-trinitrophenolate (picrate) and 4-aminobenzoate salts, (II)–(IV), the last of which crystallizes as a monohydrate. In MeOPP, C11H16N2O, (I), the 4-methoxyphenyl group is nearly planar and it occupies an equatorial site on the piperazine ring: the molecules are linked into simple C(10) chains by N—H...O hydrogen bonds. In each of the salts, i.e., C11H17N2O+·C7H3N2O6 −, (II), C11H17N2O+·C6H2N3O7 −, (III), and C11H17N2O+·C7H6NO2 −·H2O, (IV), the effectively planar 4-methoxyphenyl substituent again occupies an equatorial site on the piperazine ring. In (II), two of the nitro groups are disordered over two sets of atomic sites and the bond distances in the anion indicate considerable delocalization of the negative charge over the C atoms of the ring. The ions in (II) are linked by two N—H...O hydrogen bonds to form a cyclic, centrosymmetric four-ion aggregate; those in (III) are linked by a combination of N—H...O and C—H...π(arene) hydrogen bonds to form sheets; and the components of (IV) are linked by N—H...O, O—H...O and C—H...π(arene) hydrogen bonds to form a three-dimensional framework structure. Comparisons are made with the structures of some related compounds.

Hydrogen-Bonded Chain of Rings Motif in N-(4-Methoxyphenyl)piperazin-1-ium Salts with Benzoate Anions: Supramolecular Assemblies and Their Energy Frameworks

“…), we also estimated the binding energy of the graph-set ring motifs, 𝑅 6 4 ( 12) and 𝑅 6 6 ( 16), which play a dominant role in supramolecular architecture of many salts with the N-(4-methoxyphenyl)piperazin-1-ium cation. The same principal chain-of-rings motifs have been found in the five structures of salts of the mentioned cations with 4-amino-, 4-chloro-, 4-fluoro-, 4-bromo-and unsubstituted benzoate monohydrate [21,22]. Each motif consists of six molecules: two cations, two anions and two water molecules related by the inversion centre, but the combination of hydrogen bonds differs (Figure 3).…”

“…In view of the facts mentioned above and in continuation of our research work [21][22][23], in the present report, the synthesis and structural characterization of some novel heterocyclic compounds containing the phenylpiperazine moiety have been carried out.…”

“…The results show that the effect of the different substituent (ethoxy, methoxy, hydroxyl groups, respectively) in the anion molecule is negligible compared to the total binding energy of such pairs. 4-methoxyphenyl)piperazine (MeOPP) differs both from its corresponding ionic moiety in the crystal studied and from the neutral one determined in the solid state (IHILOD refcode; [21]). Figure 7 shows the superposition of two neutral MeOPP molecules, and the main differences are observed in the mutual orientation of rings and the position of the H atom at the N2 atom.…”

“…Energies of neutral molecular pairs are nearly eight times lower than for corresponding ionic pairs: −61.10 (I), −61.37 (II) and −61.62 (III), respectively. Interestingly, the molecular conformation of N-(4-methoxyphenyl)piperazine (MeOPP) differs both from its corresponding ionic moiety in the crystal studied and from the neutral one determined in the solid state (IHILOD refcode; [21]). Figure 7 shows the superposition of two neutral MeOPP molecules, and the main differences are observed in the mutual orientation of rings and the position of the H atom at the N2 atom.…”