Fifteen 4-(2-meth-oxy-phen-yl)piperazin-1-ium salts containing organic anions: supra-molecular assembly in zero, one, two and three dimensions

Syntheses, crystal structures and Hirshfeld surface analysis of three salts of 1-(4-nitro-phenyl)-piperazine

The structures and Hirshfeld surface analysis of three salts of 1-(4-nitro-phenyl)-piperazine are discussed. In 4-(4-nitro-phen-yl)piperazin-1-ium salicylate (C₁₀H₁₄N₃O₂ ⁺·C₇H₅O₃ ^-), there are strong hydrogen bonds between cation and anion and the 4-nitro-phenyl substituent occupies an equatorial position in the piperazinium ring. The cation and anion are linked together by supra-molecular inter-actions [graph-set notation of hydrogen bonding (6) propagating in the a-axis direction]. Additionally, there is π-π stacking involving the salicylate anion and the piperazinium cation in adjacent asymmetric units as well as a C-H⋯π inter-action between a hydrogen atom on the piperazine ring and the phenyl ring within the salicyclate anion. In bis-[4-(4-nitro-phen-yl)piperazin-1-ium] bis-(4-fluoro-benzoate) trihydrate (2C₁₀H₁₄N₃O₂ ⁺·2C₇H₄FO₂ ^-·3H₂O), there are two cations, two anions, and three water mol-ecules of solvation in the asymmetric unit, all linked by hydrogen bonds [graph-set notation of hydrogen bonding R ² ₂(20) between adjacent cations and R ³ ₃(9) between a cation and its adjacent anion]. In the anion, the 4-nitro-phenyl ring occupies an axial substitution position in the piperazinium ring, which is relatively rare. Within the asymmetric unit, the phenyl groups in the cations show an offset π-π inter-action. Additionally, there is a C-H⋯π inter-action between a hydrogen atom on the phenyl ring within a cation and the phenyl ring within an anion. In 4-(4-nitro-phen-yl)piperazin-1-ium 3,5-di-nitro-benzoate (C₁₀H₁₄N₃O₂ ⁺·C₇H₄N₂O₆ ^-), there is a strong N-H⋯O hydrogen bond linking the cation and anion and the 4-nitro-phenyl ring occupies an axial substitution position in the piperazinium ring, as seen in the previous structure. In the crystal, the cation and the anion form a complex three-dimensional hydrogen-bonded array involving R ² ₂(8), R ⁴ ₄(12) and R ⁴ ₄(20) rings propogating in the a-axis direction. The nitro-phenyl group is disordered with occupancies of 0.806 (10) and 0.194 (10).

The structures of eleven (4-phen-yl)piperazinium salts containing organic anions

Eleven (4-phen-yl)piperazinium salts containing organic anions have been prepared and structurally characterized, namely, 4-phenyl-piperazin-1-ium 4-fluoro-benzoate monohydrate, C₁₀H₁₅N₂ ⁺·C₇H₄FO₂ ^-·H₂O, 1; 4-phenyl-piperazin-1-ium 4-bromo-benzoate monohydrate, C₁₀H₁₅N₂ ⁺·C₇H₄BrO₂ ^-·H₂O, 3; 4-phenyl-piperazin-1-ium 4-iodo-benzoate, C₁₀H₁₅N₂ ⁺·C₇H₄IO₂ ^-, 4; 4-phenyl-piperazin-1-ium 4-nitro-benzoate, C₁₀H₁₅N₂ ⁺·C₇H₄NO₄ ^-, 5; 4-phenyl-piperazin-1-ium 3,5-di-nitro-salicylate, C₁₀H₁₅N₂ ⁺·C₇H₃N₂O₇ ^-, 6; 4-phenyl-piperazin-1-ium 3,5-di-nitro-benzoate, C₁₀H₁₅N₂ ⁺·C₇H₃N₂O₆ ^-, 7; 4-phenyl-piperazin-1-ium picrate, C₁₀H₁₅N₂ ⁺·C₆H₂N₃O₇ ^-, 8; 4-phenyl-piperazin-1-ium benzoate monohydrate, C₁₀H₁₅N₂ ⁺·C₇H₅O₂ ^-·H₂O, 9; 4-phenyl-piperazin-1-ium p-toluene-sulfonate, C₁₀H₁₅N₂ ⁺·C₇H₇O₃S^-, 10; 4-phenyl-piperazin-1-ium tartarate monohydrate, C₁₀H₁₅N₂ ⁺·C₄H₅O₆ ^-·H₂O, 11; and 4-phenyl-piperazin-1-ium fumarate, C₁₀H₁₅N₂ ⁺·C₄H₃O₄ ^-, 12. Compounds 1 and 3-12 are all 1:1 salts with the acid proton transferred to the phenyl-piperaizine basic N atom (the secondary amine) with the exception of 3 where there is disorder in the proton position with it being 68% attached to the base and 32% attached to the acid. Of the structures with similar stoichiometries only 3 and 9 are isomorphous. The 4-phenyl substituent in all cases occupies an equatorial position except for 12 where it is in an axial position. The crystal chosen for structure 7 was refined as a non-merohedral twin. There is disorder in 5, 6, 10 and 11. For both 5 and 6, a nitro group is disordered and was modeled with two equivalent orientations with occupancies of 0.62 (3)/0.38 (3) and 0.690 (11)/0.310 (11), respectively. For 6, 10 and 11, this disorder is associated with the phenyl ring of the phenyl-piperazinium cation with occupancies of 0.687 (10)/0.313 (10), 0.51 (7)/0.49 (7) and 0.611 (13)/389 (13), respectively. For all salts, the packing is dominated by the N-H⋯O hydrogen bonds formed by the cation and anion. In addition, several structures contain C-H⋯π (1, 3, 4, 8, 9, 10, and 12) and aromatic π-π stacking inter-actions (6 and 8) and one structure (5) contains a -NO₂⋯π inter-action. For all structures, the Hirshfeld surface fingerprint plots show the expected prominent spikes as a result of the N-H⋯O and O-H⋯O hydrogen bonds.

Syntheses and crystal structures of 4-(4-methoxyphenyl)piperazin-1-ium 4-methylbenzoate monohydrate and bis[4-(4-methoxyphenyl)piperazin-1-ium] benzene-1,2-dicarboxylate

Co-crystallization of N-(4-methoxyphenyl)piperazine with 4-methylbenzoic acid and with benzene-1,2-dicarboxylic acid yields the salts 4-(4-methoxyphenyl)piperazin-1-ium 4-methylbenzoate monohydrate, C11H17N2O+·C8H7O2 −·H2O (I), and bis[4-(4-methoxyphenyl)piperazin-1-ium] benzene-1,2-dicarboxylate, 2C11H17N2O+·C8H4O4 2− (II). These salts both crystallize with Z′ = 2, in space groups P\overline{1} and Pna21, respectively. In compound (I), a combination of four O—H...O, four N—H...O, one C—H...O and one C—H...π(arene) hydrogen bonds link the six independent components into complex sheets, within which the two piperazine rings, the two anions, and the two water molecules are related by an approximate, non-crystallographic translation along the b-axis direction. In compound (II), sheets containing R 4 4(18) and R 10 12(38) rings are formed by the combined action of eight independent N—H...O hydrogen bonds. Comparisons are made with the structures of some related compounds.

Crystal structure of 4-(2-methoxyphenyl)piperazin-1-ium 3,5-dintrosalicylate

The different intra and inter­molecular hydrogen-bonding inter­actions in the crystal structure of the title salt are discussed.

The title salt [systematic name: 4-(2-methoxyphenyl)piperazin-1-ium 2-carboxy-4,6-dinitrophenolate], C₁₁H₁₇N₂O⁺·C₇H₃N₂O₇⁻, exhibits secondary nitro­gen atoms (N—H) in the 2-meth­oxy­phenyl­piperazine (2MeOPP) cation, which is protonated with a phenolic hydrogen atom of 3,5-di­nitro­salicylic acid (DNSA). One of the oxygen atoms of the nitro group in the 3,5-di­nitro­salicylate anion is disordered over two orientations with occupancy factors of 0.65 (7) and 0.35 (7) . The 2-meth­­oxy­phenyl­piperazinium cation and 3,5-di­nitro­salicylate anion are linked in the asymmetric unit by a bifurcated N—H⋯O hydrogen bond, which formed is between the H atom in the protonated piperazinium unit of the cation and the carb­oxy­lic acid group in the anion. The piperazine ring adopts a chair conformation. The crystal structure features N—H⋯O and C—H⋯O hydrogen bonds inter­actions, which lead to the formation of a sandwich-like arrangement. Hirshfeld surface analysis was used to determine the relative contributions of various inter­molecular inter­actions, indicating that that H⋯O/O⋯H (38. 3%) and H⋯H (31. 8%) contacts are the major contributors.

Crystal-structure studies of 4-phenylpiperazin-1-ium 4-ethoxybenzoate monohydrate, 4-phenylpiperazin-1-ium 4-methoxybenzoate monohydrate, 4-phenylpiperazin-1-ium 4-methylbenzoate monohydrate and 4-phenylpiperazin-1-ium trifluoroacetate 0.12-hydrate

In this study, four new piperazinium salts, namely, 4-phenylpiperazin-1-ium 4-ethoxybenzoate monohydrate, C9H9O3·C10H15N2·H2O (I); 4-phenylpiperazin-1-ium 4-methoxybenzoate monohydrate, C10H15N2·C8H7O3·H2O (II); 4-phenylpiperazin-1-ium 4-methylbenzoate monohydrate, C10H15N2·C8H7O2·H2O (III); and 4-phenylpiperazin-1-ium trifluoroacetate 0.12 hydrate, C10H15N2·C2F3O2·0.12H2O (IV), have been synthesized. The single-crystal structures of these compounds reveal that all of them crystallize in the triclinic P\overline{1} space group and the crystal packing of (I)–(III) is built up of ribbons formed by a combination of hydrogen bonds of type N—H...O, O—H...O and other weak interactions of type C—H...O and C—H...π, leading to a three-dimensional network. In the crystal of (IV), the cations and the anions are connected by C—H...O, N—H...O and C—H...F hydrogen bonds and by C—H...π interactions, forming sheets which in turn interact to maintain the crystal structure by linking through the oxygen atoms of water molecules and van der Waals interactions, giving the whole structure.

Crystal structures of six 4-(4-nitrophenyl)piperazin-1-ium salts

Six piperazinium salts are reported, five of them are hydrated and two crystallized as 2:2 salts. They exhibit asymmetric units of a common 4-nitro­phenyl­piperazine cation and different p-substituent benzoate anions. Their crystal structures mainly pack as chains stabilized by strong N—H⋯O and O—H⋯O hydrogen bonds and other weak inter­actions such as C—H⋯O and C—H⋯π.

Six piperazinium salts, namely 4-(4-nitro­phenyl)­piperazin-1-ium 4-bromo­ben­zo­ate dihydrate, C₁₀H₁₄N₃O₂⁺·C₇H₄BrO₂⁻·2H₂O, (I), 4-(4-nitro­phenyl)­pi­per­a­zin-1-ium 4-iodo­benzoate dihydrate, C₁₀H₁₄N₃O₂⁺·C₇H₄IO₂⁻·2H₂O, (II), 4-(4-nitro­phenyl)­piperazin-1-ium 4-hy­droxy­benzoate monohydrate, C₁₀H₁₄N₃O₂⁺·C₇H₅O₃⁻·H₂O, (III), 4-(4-nitro­phenyl)­piperazin-1-ium 4-methyl­benzoate monohydrate, C₁₀H₁₄N₃O₂⁺·C₈H₇O₂⁻·H₂O, (IV), 4-(4-nitro­phenyl)­piperazin-1-ium 4-meth­oxy­benzoate hemihydrate, 2C₁₀H₁₄N₃O₂⁺·2C₈H₇O₃⁻·H₂O, (V), and 4-(4-nitro­phenyl)­piperazin-1-ium 4-eth­oxy­benzoate, 2C₁₀H₁₄N₃O₂⁺·2C₉H₉O₃⁻, (VI), have been synthesized and their crystal structures solved by single-crystal X-ray diffraction, revealing that all of them crystallize in the triclinic space group P except for (V), which crystallizes in the monoclinic space group P2₁/c and has a disordered nitro group. Compounds (I) and (II) are isostructural. The crystal packing of (I)–(V) is constructed from organic chains formed by a combination of hydrogen bonds of type N—H⋯O and/or O—H⋯O and other weak inter­actions of type C—H⋯O and/or C—H⋯π, forming sheets, whereas (VI) shows a cationic and anionic-based layer structure.

Crystal structure studies of 4-ethyl-piperazin-1-ium 3,5-di-nitro-benzoate, 4-methyl-piperazin-1-ium 3,5-di-nitro-benzoate and 4-methyl-piperazin-1-ium 4-iodo-benzoate

As part of our ongoing investigation on the chemical and biological properties of piperazinium salts, we synthesized three novel compounds: 1-ethyl-piperazinium 3,5-di-nitro-benzoate (I), 1-methyl-piperazinium 3,5-di-nitro-benzoate (II) and 1-methyl-piperazinium 4-iodo-benzoate (III). The crystal structures of these compounds are built up of organic layers formed by the strong connection between the mol-ecules by hydrogen bonds of type N-H⋯O. These layers are linked through N-H⋯O hydrogen bonds and C-H⋯O inter-actions or C-I⋯N halogen bonding, leading to the formation of a three-dimensional network.

Construction of Two Stable Co(II)-Based Hydrogen-Bonded Organic Frameworks as a Luminescent Probe for Recognition of Fe3+ and Cr2O72- in H2O

A pair of cobalt(II)-based hydrogen-bonded organic frameworks (HOFs), [Co(pca)2(bmimb)]n (1) and [Co2(pca)4(bimb)2] (2), where Hpca = p-chlorobenzoic acid, bmimb = 1,3-bis((2-methylimidazol-1-yl)methyl)benzene, and bimb = 1,4-bis(imidazol-1-ylmethyl)benzene were hydrothermally synthesized and characterized through infrared spectroscopy (IR), elemental and thermal analysis (EA), power X-ray diffraction (PXRD), and single-crystal X-ray diffraction (SCXRD) analyses. X-ray diffraction structural analysis revealed that 1 has a one-dimensional (1D) infinite chain network through the deprotonated pca- monodentate chelation and with a μ2-bmimb bridge Co(II) atom, and 2 is a binuclear Co(II) complex construction with a pair of symmetry-related pca- and bimb ligands. For both 1 and 2, each cobalt atom has four coordinated twisted tetrahedral configurations with a N2O2 donor set. Then, 1 and 2 are further extended into three-dimensional (3D) or two-dimensional (2D) hydrogen-bonded organic frameworks through C-H···Cl interactions. Topologically, HOFs 1 and 2 can be simplified as a 4-connected qtz topology with a Schläfli symbol {64·82} and a 4-connected sql topology with a Schläfli symbol {44·62}, respectively. The fluorescent sensing application of 1 was investigated; 1 exhibits high sensitivity recognition for Fe3+ (Ksv: 10970 M-1 and detection limit: 19 μM) and Cr2O72- (Ksv: 12960 M-1 and detection limit: 20 μM). This work provides a feasible detection platform of HOFs for highly sensitive discrimination of Fe3+ and Cr2O72- in aqueous media.

Six 1-halobenzoyl-4-(2-meth-oxy-phen-yl)piperazines having Z' values of one, two or four; disorder, pseudosymmetry, twinning and supra-molecular assembly in one, two or three dimensions

Six 1-halobenzoyl-4-(2-meth-oxy-phen-yl)piperazines have been prepared using carbodi-imide-mediated coupling reactions between halo-benzoic acids and N-(2-meth-oxy-phen-yl)piperazine. The mol-ecules of 1-(4-fluoro-benzo-yl)-4-(2-meth-oxy-phen-yl)piperazine, C18H19FN2O2 (I), are linked into a chain of rings by a combination of C-H⋯O and C-H⋯π(arene) hydrogen bonds. 1-(4-Chloro-benzo-yl)-4-(2-meth-oxy-phen-yl)piperazine, C18H19ClN2O2 (II), crystallizes in the space group Pca21 with Z' = 4 and it exhibits both pseudosymmetry and inversion twinning: a combination of six C-H⋯O and two C-H⋯π(arene) hydrogen bonds generate a three-dimensional assembly. In 1-(4-bromo-benzo-yl)-4-(2-meth-oxy-phen-yl)piperazine, C18H19BrN2O2 (III), which also crystallizes in space group Pca21 but with Z' = 2, the bromo-benzoyl unit in one of the mol-ecules is disordered. Pseudosymmetry and inversion twinning are again present, and a combination of three C-H⋯O and one C-H⋯π(arene) hydrogen bonds generate a two-dimensional assembly. A single C-H⋯O hydrogen bond links the mol-ecules of 1-(4-iodo-benzo-yl)-4-(2-meth-oxy-phen-yl)piperazine, C18H19IN2O2 (IV), into simple chains but in the isomeric 3-iodo-benzoyl analogue (V), which crystallizes in space group P212121 with Z' = 2, a two-dimensional assembly is generated by a combination of four C-H⋯O and two C-H⋯π(arene) hydrogen bonds; pseudosymmetry and inversion twinning are again present. A single C-H⋯O hydrogen bond links the mol-ecules of 1-(2-fluoro-benzo-yl)-4-(2-meth-oxy-phen-yl)piperazine, C18H19FN2O2 (VI), into simple chains. Comparisons are made with the structures of some related compounds.

1-(3,5-Dinitrobenzoyl)-4-(2-methoxyphenyl)piperazine

The mol­ecules of the title compound are linked into sheets by two π–π stacking inter­actions.

In the title compound, C₁₈H₁₈N₄O₆, the piperazine ring adopts a chair conformation, the amidic N atom is planar (sum of angles = 360°) and the non-amidic N atom is pyramidal (343°). There are no hydrogen bonds of any kind in the crystal, but the mol­ecules are linked by two independent π(nitro­benzene)⋯π(meth­oxy­benzene) stacking inter­actions to form π-stacked sheets with inter-centroid separations of 3.8444 (12) and 3.9197 (12) Å.