Abstract
Fifteen 4-(2-meth-oxy-phen-yl)piperazin-1-ium salts containing organic anions have been prepared and structurally characterized. In the isostructural 4-chloro-benzoate and 4-bromo-benzoate salts, C11H17N2O+·C7H4ClO2 - (I) and C11H17N2O+·C7H4BrO2 - (II), and the 4-iodo-benzoate salt C11H17N2O+·C7H4IO2 - (III), the ions are linked by N-H⋯O hydrogen bonds, forming centrosymmetric R 4 4(12) four-ion aggregates; a similar aggregate is formed in the 2-chloro-benzoate salt (V), isomeric with (I). In the 2-fluoro-benzoate salt C11H17N2O+·C7H4FO2 - (IV), and the isomorphous pair of salts, the 2-bromo-benzoate (VI), isomeric with (II) and 2-iodo-benzoate (VII), isomeric with (III), N-H⋯O and C-H⋯π(arene) interactions link the components into three-dimensional arrays. Four-ion R 4 4(12) aggregates are also found in the 2-methyl-benzoate, 4-amino-benzoate and 4-nitro-benzoate salts, C11H17N2O+·C8H7O2 - (VIII), C11H17N2O+·C7H6NO2 - (IX) and C11H17N2O+·C7H4NO4 - (X), but those in (IX) are linked into complex sheets by an additional N-H⋯O hydrogen bond. In the 3,5-dinitrobenzoate salt, C11H17N2O+·C7H3N2O6 -·2H2O (XI), N-H⋯O and O-H⋯O hydrogen bonds link the components into a complex ribbon structure. In the picrate salt, C11H17N2O+·C6H2N3O7 - (XII), the four-ion aggregates are linked into chains of rings by C-H⋯O hydrogen bonds. In the hydrogen maleate salt, C11H17N2O+·C4H3O4 - (XIII), two- and three-centre hydrogen bonds link the ions into a ribbon structure while both anions contain very short but asymmetric O-H⋯O hydrogen bonds, having O⋯O distances of 2.4447 (16) and 2.4707 (17) Å. O-H⋯O Hydrogen bonds link the anions in the hydrogen fumarate salt (XIV), isomeric with (XIII), into chains that are linked into sheets via N-H⋯O hydrogen bonds. In the hydrogen (2R,3R)-tartrate salt, C11H17N2O+·C4H5O6 -·1.698H2O (XV), the anions are linked into sheets by O-H⋯O hydrogen bonds. Comparisons are made with the structures of some related compounds.
Highlights
In the isostructural 4chlorobenzoate and 4-bromobenzoate salts, C11H17N2O+ÁC7H4ClO2À (I) and C11H17N2O+ÁC7H4BrO2À (II), and the 4-iodobenzoate salt C11H17N2O+ÁC7H4IO2À (III), the ions are linked by N—HÁ Á ÁO hydrogen bonds, forming centrosymmetric R44(12) four-ion aggregates; a similar aggregate is formed in the 2-chlorobenzoate salt (V), isomeric with (I)
O—HÁ Á ÁO Hydrogen bonds link the anions in the hydrogen fumarate salt (XIV), isomeric with (XIII), into chains that are linked into sheets via N—HÁ Á ÁO hydrogen bonds
As a continuation of this study, we have investigated a number of salts of the isomeric N-(2-methoxyphenyl)piperazine (2-MeOPP), which has been used as a building block in the synthesis of both 5-HT1A receptor ligands (Orjales et al, 1995) and dopamine D2 and D3 ligands (Hackling et al, 2003) and as a building block for the synthesis of derivatives exhibiting antidepressant-like activity (Waszkielewicz et al, 2015)
Summary
We have recently reported the molecular and supramolecular structures of the recreational drug N-(4-methoxyphenyl)piperazine (4-MeOPP) (Kiran Kumar et al, 2020) and those of a range of salts formed by 4-MeOPP with organic acids (Kiran Kumar, Yathirajan, Foro et al, 2019; Kiran Kumar et al 2020), as well as those of a number of N-aroyl derivatives (Kiran Kumar, Yathirajan, Sagar et al, 2019). We have redetermined this structure and found, that one of the nitro groups is disordered over three sets of atomic sites having occupancies 0.850 (5), 0.080 (4) and. The 1:1 salt (XIV) derived from fumaric acid, which is isomeric with maleic acid, crystallizes with two independent hydrogen fumarate anions, each lying across a centre of inversion: one of the anions is fully ordered but the other is disordered over two sets of atomic sites having occupancies 0.572 (9) and 0.428 (9) (Fig. 14). In none of the salts reported does the cation exhibit any internal symmetry: all are conformationally chiral but, with the exception of compounds (VI) and (VII), the space groups indicate that equal numbers of both conformational enantiomers are present. The two independent ions in compound (XIII) both contain a very short O—HÁ Á ÁO hydrogen bond (Table 1): while these are both nearly linear, the two O—H distances in each are significantly different, as established both by refinement of the atomic coordinates for the H atom, and from the final difference maps
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