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The crystal structure and a Hirshfeld surface analysis of the substituted anilinium salt 4-(dimethylazaniumyl)-2-hydroxyanilinium dichloride monohydrate, C8H14N2O+·2Cl−·H2O, at low temperature (90 K) are presented. The organic cation is essentially planar: the r.m.s. deviation of its non-hydrogen atoms (aside from the two methyl groups) is 0.0045 Å. The methyl carbons are 1.3125 (12) Å and 1.1278 (12) Å either side of the mean plane. The crystal packing involves extensive hydrogen bonding of types O—H...Cl, N—H...Cl, N—H...OW, and OW—HW...Cl (where W = water), which arrange into chains of R24(12) motifs that combine to form corrugated layers parallel to (10\overline{1}). Atom–atom contacts for the cation primarily involve hydrogen, leading to the most abundant coverage percentages being 51.3% (H...H), 23.0% (H...Cl), 12.9% (H...O), and 9.7% (C...H).

The syntheses and crystal structure studies of four organic salts of trihexyphenidyl, viz., trihexyphenidylium [1-(3-cyclohexyl-3-hydroxy-3-phenylpropyl)piperidin-1-ium] 4-nitrobenzoate, C20H32NO+·C7H4NO4− (I), trihexyphenidylium 4-hydroxybenzoate, C20H32NO+·C7H5O− (II), trihexyphenidylium 4-bromobenzoate, C20H32NO+·C7H4BrO2− (III), and trihexyphenidylium thiophene-2-carboxylate hemihydrate, 2C20H32NO+·2C5H3O2S−·H2O (IV), conducted at 90 K are described. Structures I, II, and III are solvent free with one cation–anion pair per asymmetric unit, while IV crystallizes as a hemihydrate, having two cation–anion pairs and one water of crystallization in its asymmetric unit. Structures I and III exhibit configurational disorder of the cation. Structure IV also exhibits disorder, but only of the thiophene-2-carboxylate anions. Structure II is a non-merohedric twin by a twofold rotation about [403]. The main supramolecular motifs in I, II, and III are similar R22(10) rings between cation–anion pairs, although their packing within the crystals is distinct. As a consequence of having two cation–anion pairs and a water molecule in its asymmetric unit, the packing in IV is by far the most complex of the four structures, its hydrogen-bonding patterns being quite different from I, II, or III. In all the crystals studied, N—H...O, O—H...O, and C—H...O interactions are observed, plus C—H...Br close contacts for III.

The synthesis and crystal structure of a monoclinic polymorph of 2-amino-5-chlorobenzophenone oxime, C13H11ClN2O, are presented. The molecular conformation results from twisting of the phenyl and 2-amino-5-chloro benzene rings attached to the oxime group, which subtend a dihedral angle of 80.53 (4)°. In the crystal, centrosymmetric dimers are formed as a result of pairs of strong O—H...N hydrogen bonds. A comparison is made to a previously known triclinic polymorph, including differences in atom–atom contacts obtained via a Hirshfeld-surface analysis.

The synthesis, crystal structure and spectroscopic analysis of (E)-1-(2,3-dihydrobenzo[b][1,4]dioxin-6-yl)-3-(4-chlorophenyl)prop-2-en-1-one (C17H13ClO3), a substituted chalcone, are described. The overall geometry of the molecule is largely planar (r.m.s. deviation = 0.1742 Å), but slightly kinked, leading to a dihedral angle between the planes of the benzene rings at either side of the molecule of 8.31 (9)°. In the crystal, only weak interactions determine the packing motifs. These include C—H...O and C—H...Cl hydrogen bonds and π–π overlap of aromatic rings.

The synthesis and crystal structure of C3HF3N2OS, systematic name 5-(trifluoromethyl)-1,3,4-thiadiazol-2(3H)-one (5-TMD-2-one), a compound containing the pharmacologically important heterocycle 1,3,4-thiadiazole, is presented. The asymmetric unit comprises six independent molecules (Z′ = 6), all of which are planar. The r.m.s. deviations from each mean plane range from 0.0063 to 0.0381 Å, not including the CF3 fluorine atoms. Within the crystal, two of the molecules form hydrogen-bonded dimers that in turn combine with inversion-related copies to form tetrameric constructs. Similar tetramers, but lacking inversion symmetry, are formed by the remaining four molecules. The tetramers are linked into tape-like motifs by S...O and O...O close contacts. The environments of each symmetry-independent molecule were compared via a Hirshfeld surface analysis. The most abundant atom–atom contacts are between fluorine atoms, while the strongest result from N—H...O hydrogen bonds.

The syntheses and crystal structures of four salts of amitriptynol (C20H25NO) with different carboxylic acids are described. The salts formed directly from solutions of amitriptyline (which first hydrolysed to amitriptynol) and the corresponding acid in acetonitrile to form amitriptynolium [systematic name: (3-{2-hydroxytricyclo[9.4.0.03,8]pentadeca-1(11),3,5,7,12,14-hexaen-2-yl}propyl)dimethylazanium] 4-methoxybenzoate monohydrate, C20H26NO+·C8H7O3−·H2O, (I), amitriptynolium 3,4-dimethoxybenzoate trihydrate, C20H26NO+·C9H9O4−·3H2O, (II), amitriptynolium 2-chlorobenzoate, C20H26NO+·C7H4ClO2−, (III), and amitriptynolium thiophene-2-carboxylate monohydrate, C20H26NO+·C5H3O2S−·H2O, (IV). Compound (III) crystallizes with two cations, two anions and six water molecules in the asymmetric unit. The different conformations of the amitriptynolium cations are determined by the torsion angles in the dimethylamino-propyl chains and the –CH2–CH2- bridge between the benzene rings in the tricyclic ring system, and are complicated by disorder of the bridging unit in II and III. The packing in all four salts is dominated by N—H...O and O—H...O hydrogen bonds. Hirshfeld surface analyses show that the amitriptynolium cations make similar inter-species contacts, despite the distinctly different packing in each salt.

The synthesis and crystal structure of the title compound, C12H16FNO3S, which is related to the herbicide flufenacet, are presented. The dihedral angle between the amide group and the fluorinated benzene ring is 87.30 (5)° and the N—C—C—S torsion angle defining the orientation of the methylsulfonyl substituent relative to the amide group is 106.91 (11)°. In the crystal, inversion-related molecules form dimers as a result of pairwise C—H...O hydrogen bonds, which appear to be reinforced by short O...π contacts [O...Cg = 3.0643 (11) Å]. A Hirshfeld surface analysis was used to quantify the various types of intermolecular contacts, which are dominated by H atoms.

The crystal structures and Hirshfeld surface analyses of three salts of 1-(4-nitrophenyl)piperazine with 2-chlorobenzoic acid, 2-bromobenzoic acid and 2-iodobenzoic acid are reported. The chlorobenzoate salt, C10H14N3O2+·C7H4ClO2−, contains whole-ion-disordered cations and anions, which were modeled with two equivalent conformations with occupancies of 0.745 (10)/0.255 (10) and 0.563 (13)/0.437 (13), respectively. The bromobenzoate and iodobenzoate derivatives are isomorphous and crystallize as hemihydrates, viz. C10H14N3O2+·C7H4BrO2−·0.5H2O and C10H14N3O2+·C7H4IO2−·0.5H2O, respectively [the water molecule is disordered over two locations with occupancies of 0.276 (3)/0.223 (3) for the iodobenzoate derivative]. In the extended structures, all three salts feature an R44(12) loop of two anions and two cations linked by N—H...O hydrogen bonds.

Syntheses and X-ray crystal structures of four 4-(4-methoxyphenyl)piperazin-1-ium (MeOPP) salts, with 2,2,2-trifluoroacetate, C11H17N2O+·C2F3O2− (I), 2,3,4,5,6-pentafluorobenzoate, C11H17N2O+·C7F5O2−·H2O (II), 4-iodobenzoate C11H17N2O+·C7H4IO2−·H2O (III), and 4-methylbenzoate, C11H17N2O+·C8H7O2−·H2O (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.

The structures and Hirshfeld surface analysis of three salts of 1-(4-nitrophenyl)piperazine are discussed. In 4-(4-nitrophenyl)piperazin-1-ium salicylate (C10H14N3O2+·C7H5O3−), there are strong hydrogen bonds between cation and anion and the 4-nitrophenyl substituent occupies an equatorial position in the piperazinium ring. The cation and anion are linked together by supramolecular interactions [graph-set notation of hydrogen bonding C_{2}^{2}(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 interaction between a hydrogen atom on the piperazine ring and the phenyl ring within the salicyclate anion. In bis[4-(4-nitrophenyl)piperazin-1-ium] bis(4-fluorobenzoate) trihydrate (2C10H14N3O2+·2C7H4FO2−·3H2O), there are two cations, two anions, and three water molecules of solvation in the asymmetric unit, all linked by hydrogen bonds [graph-set notation of hydrogen bonding R22(20) between adjacent cations and R33(9) between a cation and its adjacent anion]. In the anion, the 4-nitrophenyl 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 interaction. Additionally, there is a C—H...π interaction between a hydrogen atom on the phenyl ring within a cation and the phenyl ring within an anion. In 4-(4-nitrophenyl)piperazin-1-ium 3,5-dinitrobenzoate (C10H14N3O2+·C7H4N2O6−), there is a strong N—H...O hydrogen bond linking the cation and anion and the 4-nitrophenyl 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 R22(8), R44(12) and R44(20) rings propogating in the a-axis direction. The nitrophenyl group is disordered with occupancies of 0.806 (10) and 0.194 (10).

The syntheses and crystal structures are presented for four organic salts of the 4-(4-nitrophenyl)piperazinium cation, namely, 4-(4-nitrophenyl)piperazinium hydrogen succinate, C10H14N3O2+·C4H5O4− (I), 4-(4-nitrophenyl)piperazinium 4-aminobenzoate monohydrate, C10H14N3O2+·C7H6NO2−·H2O (II), 4-(4-nitrophenyl)piperazinium 2-(4-chlorophenyl)acetate, C10H14N3O2+·C8H6ClO2− (III) and 4-(4-nitrophenyl)piperazinium 2,3,4,5,6-pentafluorobenzoate, C10H14N3O2+·C7F5O2− (IV). The salts form from mixtures of N-(4-nitrophenyl)piperazine and the corresponding acid [succinic acid (I), 4-aminobenzoic acid (II), 2-(4-chlorophenyl)acetic acid (III) and 2,3,4,5,6-pentafluorobenzoic acid (IV)] in mixed solvents of methanol and ethyl acetate. Salts I, III, and IV are anhydrous, whereas II is a monohydrate. In each structure, the overall conformation of the cation is determined by the disposition of the exocyclic N—C bond of the piperazine ring (either axial or equatorial) and twists about the N—C bond between the piperazine ring and its attached 4-nitrophenyl ring. The packing motifs in each structure are quite different, though all are dominated by strong N—H...O hydrogen bonds, which are augmented in I and II by O—H...O hydrogen bonds, and in III by a π–π stacking interaction between inversion-related 4-nitrophenyl groups.

The crystal structure of ethiprole {systematic name: 5-amino-1-[2,6-dichloro-4-(trifluoromethyl)phenyl]-4-ethanesulfinyl-1H-imidazole-3-carbonitrile}, C13H9Cl2F3N4OS, a phenylpyrazole-based insecticide, is presented. The pyrazole ring carries four substituents: an N-bound 2,6-dichloro-4-trifluoromethylphenyl ring and C-bound amine, ethanesulfinyl, and cyano groups. The sulfur atom of the ethanesulfinyl group is trigonal–pyramidal and stereogenic. The structure exhibits whole-molecule configurational disorder due to superposition of enantiomers. The crystal packing is dominated by strong N—H...O and N—H...N hydrogen bonds, which form R44(18) and R22(12) ring motifs. Since the ethiprole molecule is quite small, and structure solution and refinement were straightforward, the structure presents a convenient instructional example for modelling whole-body disorder of a non-rigid molecule. To this end, a step-by-step overview of the model-building and refinement process is also given. The structure could form the basis of a useful classroom, practical, or workshop-style example.

The synthesis and crystal structures of the molecular salts of 4-(4-nitrophenyl)piperazine with trifluoroacetate, namely, 4-(4-nitrophenyl)piperazin-1-ium trifluoroacetate, C10H14N3O2+·C2F3O2− (I), and with trichloroacetate, namely, 4-(4-nitrophenyl)piperazin-1-ium trichloroacetate, C10H14N3O2+·C2Cl3O2−, (II), are reported and compared. A partial positional disorder of the anions was found. In both structures, the piperazine rings adopt a chair conformation, whereas the positions of the nitrophenyl group on the piperazine ring differ from bisectional in (I) to equatorial in (II). In both structures, the supramolecular assemblies are mono-periodic on the basis of the chain-of-rings motifs supported by aromatic π–π interactions. Hirshfeld surface analysis was used to explore the intermolecular close contacts in both crystals. The most dominant contacts of the Hirshfeld surface of the cation–anion pairs of the asymmetric units are O...H/H...O, and those with a contribution of halogen atoms: F...H/H...F in (I) and Cl...H/H...Cl in (II), respectively.

The structure of 2-chloro-1-(3-hydroxyphenyl)ethanone, C8H7ClO2, an α-haloketone is described. The molecule is planar (r.m.s. deviation = 0.0164 Å) and in the crystal, inversion-symmetric dimers are formed as a result of pairs of strong O—H...O and weak C—H...O hydrogen bonds. A brief comparison is made with structurally related compounds deposited in the CSD. In addition, the synthesis and some spectroscopic details are presented.

The structure of the title compound, C15H8N4Cl2F6OS, a phenylpyrazole-based insecticide related to ethiprole, fipronil, and derivatives thereof is presented. The pyrazole ring has four chemically diverse substituents, namely a nitrogen-bound 2,6-dichloro-4-trifluoromethylphenyl and carbon-bound cyano, ethylsulfanyl, and 2,2,2-trifluoroacetamide groups. The pyrazole and phenyl rings are perpendicular, subtending a dihedral angle of 89.80 (5)°. In the crystal, strong N—H...O hydrogen bonds link the molecules into chains that extend parallel to the a-axis.

Benzyl N′-[(E)-2-hydroxybenzylidene]hydrazinecarboxylate, C15H14N2O3 (I) and benzyl N′-[(E)-5-bromo-2-hydroxybenzylidene]hydrazinecarboxylate (II), C15H13BrN2O3, have been synthesized by the reaction of either 2-hydroxybenzaldehyde or 5-bromo-2-hydroxybenzaldehyde with benzyl carbazate, respectively. Both the compounds crystallize in the monoclinic crystal system with space groups Pn (Z′ = 1, I) and P21/c (Z′ = 2, II). Molecular conformations in each structure are similar, and both structures feature strong intramolecular O—H...N hydrogen bonds, which form S(6) ring motifs. There are also strong N—H...O and weak C—H...O hydrogen bonds in both structures, but their modes of packing within their respective crystals are markedly different. Some comparisons are made with the structures of a few related compounds.

The low (90 K) and room (298 K) temperature crystal structures of topiramate azidosulfate [systematic name 2,3:4,5-bis-O-(1-methylethylidene)-β-d-fructopyranose azidosulfate], C12H19N3O8S, an intermediate in the synthesis of the anti-convulsant drug topiramate, are described. Topiramate azidosulfate (I) finds use as a reference impurity standard for topiramate. A modified synthesis and some spectroscopic details are also presented.

Eleven (4-phenyl)piperazinium salts containing organic anions have been prepared and structurally characterized, namely, 4-phenylpiperazin-1-ium 4-fluorobenzoate monohydrate, C10H15N2+·C7H4FO2−·H2O, 1; 4-phenylpiperazin-1-ium 4-bromobenzoate monohydrate, C10H15N2+·C7H4BrO2−·H2O, 3; 4-phenylpiperazin-1-ium 4-iodobenzoate, C10H15N2+·C7H4IO2−, 4; 4-phenylpiperazin-1-ium 4-nitrobenzoate, C10H15N2+·C7H4NO4−, 5; 4-phenylpiperazin-1-ium 3,5-dinitrosalicylate, C10H15N2+·C7H3N2O7−, 6; 4-phenylpiperazin-1-ium 3,5-dinitrobenzoate, C10H15N2+·C7H3N2O6−, 7; 4-phenylpiperazin-1-ium picrate, C10H15N2+·C6H2N3O7−, 8; 4-phenylpiperazin-1-ium benzoate monohydrate, C10H15N2+·C7H5O2−·H2O, 9; 4-phenylpiperazin-1-ium p-toluenesulfonate, C10H15N2+·C7H7O3S−, 10; 4-phenylpiperazin-1-ium tartarate monohydrate, C10H15N2+·C4H5O6−·H2O, 11; and 4-phenylpiperazin-1-ium fumarate, C10H15N2+·C4H3O4−, 12. Compounds 1 and 3–12 are all 1:1 salts with the acid proton transferred to the phenylpiperaizine 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 phenylpiperazinium 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 interactions (6 and 8) and one structure (5) contains a –NO2...π interaction. 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.

Synthesis and crystal structures of 1-benzoyl-4-(4-nitrophenyl)piperazine, C17H17N3O3, (I) and 1-(4-bromobenzoyl)-4-phenylpiperazine, C17H17BrN2O, (II) are described. Compounds I and II crystallize in the orthorhombic and monoclinic crystal systems with space groups Pna21 (Z′ = 2, I) and P21 (Z′ = 1, II), respectively. The crystal of II was a two-component aggregate, treated as a `twin' for data-acquisition purposes. There are no conventional hydrogen bonds in either I or II, but there are weaker C—H...O contacts. Each molecule consists of a central piperazine ring in a chair conformation, with either benzoyl and nitrophenyl (I) or 4-bromobenzoyl and phenyl (II) groups attached to different nitrogen atoms of the piperazine. The various atom–atom contact coverages as quantified by Hirshfeld surface analysis fingerprint plots are given.

The structure of ebastinium hydrogen fumarate {systematic name: 1-[4-(4-tert-butylphenyl)-4-oxobutyl]-4-(diphenylmethoxy)piperidin-1-ium (E)-3-carboxy-1-hydroxyprop-2-en-1-olate}, C32H40NO2+·C4H3O4−, a 1:1 salt formed in the reaction between ebastine and fumaric acid is presented. All examined crystals were found to be twinned by pseudo-merohedry. The structure is extensively disordered, with over half (20 out of 35) its non-hydrogen atoms modelled as lying over two sets of sites. In the crystal, cation–anion pairs are linked by a strong N—H...O hydrogen bond [N...O = 2.697 (11) Å]. These units interact via weaker C—H...O and C—H...π contacts to form layers lying parallel to the bc plane. The hydrogen fumarate anions are linked by a very short O—H...O hydrogen bond [O...O = 2.5402 (17) Å], augmented by weak C—H...O contacts into pairs of R22(6) ring motifs to form chains that extend parallel to the b-axis direction. Comparisons to similar crystal structures are presented.

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+·C8H4O42− (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 R44(18) and R1012(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 structures are reported for two molecular salts containing the 4-(4-nitrophenyl)piperazin-1-ium cation. Co-crystallization from methanol/ethyl acetate solution of N-(4-nitrophenyl)piperazine with benzoic acid gives the benzoate salt, which crystallizes as a monohydrate, C10H14N3O2·C7H5O2·H2O, (I), and similar co-crystallization with 3,5-dinitrosalicylic acid yields the 2-carboxy-4,6-dinitrophenolate salt, C10H14N3O2·C7H3N2O7, (II). In the structure of (I), a combination of O—H...O, N—H...O and C—H...O hydrogen bonds links the components into sheets, while in the structure of (II), the supramolecular assembly, generated by hydrogen bonds of the same types as in (I), is three dimensional. Comparisons are made with the structures of some related compounds.

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.

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-1 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.

As part of our ongoing investigation on the chemical and biological properties of piperazinium salts, we synthesized three novel compounds: 1-ethylpiperazinium 3,5-dinitrobenzoate (I), 1-methylpiperazinium 3,5-dinitrobenzoate (II) and 1-methylpiperazinium 4-iodobenzoate (III). The crystal structures of these compounds are built up of organic layers formed by the strong connection between the molecules by hydrogen bonds of type N—H...O. These layers are linked through N—H...O hydrogen bonds and C—H...O interactions or C—I...N halogen bonding, leading to the formation of a three-dimensional network.

The title compound, C29H25N3O3S, crystallizes in the monoclinic space group P21/n. The molecule contains a central four-ring system in which all of the rings are almost coplanar. Both the 4-methoxyphenyl ring and the prop-2-ynyloxy substituent are disordered over two equivalent conformations with occupancy ratios of 0.903 (2):0.097 (2) and 0.776 (5):0.224 (5), respectively. In the crystal, π–π interactions [centroid–centroid distance = 3.7327 (11) Å] between the dihydropyrazole ring and the 4-methoxyphenyl ring link the molecules into centrosymmetric dimers. In addition, there are weak C—H...S, C—H...N and C—H...O interactions, which link the molecules into a complex three-dimensional array.

The structure of the title compound, C18H13NO4, shows that the whole molecule is almost planar but with a dihedral angle between the two phenyl rings of 19.22 (5)°. The molecules are linked by C—H...O interactions, forming sheets in the (21\overline{1}) plane.

In the title compound, C28H22FN3OS, four rings are almost coplanar, with the fluorophenyl ring substantially twisted. In the extended structure, aromatic π–π stacking interactions between the pyrazole ring and the tolyl ring link the molecules into centrosymmetric dimers.

The title compound, C10H13NO2, crystallizes with two molecules (A and B) in the asymmetric unit. For A, the dihedral angle between the plane of the phenyl ring and the i-propyl substituent is 65.4 (3)° while for B this angle is 67.8 (3)°. In the crystal, the molecules are linked by N—H...O and N—H...N hydrogen bonds to generate double chains propagating in the [100] direction.

In the title compound, C18H16N2O2, the phenyl and pyrazole rings subtend a dihedral angle of 22.68 (8)°. The packing of the title compound features aromatic π–π stacking and weak C—H...π interactions.

Crystal structures are reported for three amides containing N-benzo[d]thiazole substituents. In N-(benzo[d]thiazol-6-yl)-3-bromobenzamide, C14H9BrN2OS, where the two ring systems are nearly parallel to one another [dihedral angle = 5.8 (2)°], the molecules are linked by N—H...O and C—H...N hydrogen bonds to form ribbons of R33(19) rings, which are linked into sheets by short Br...Br interactions [3.5812 (6) Å]. N-(6-Methoxybenzo[d]thiazol-2-yl)-2-nitrobenzamide, C15H11N3O4S, crystallizes with Z′ = 2 in space group Pna21: the dihedral angles between the ring systems [46.43 (15) and 66.35 (13)°] are significantly different in the independent molecules and a combination of two N—H...N and five C—H...O hydrogen bonds links the molecules into a three-dimensional network. The molecules of 5-cyclopropyl-N-(6-methoxybenzo[d]thiazol-2-yl)isoxazole-3-carboxamide, C15H13N3O3S, exhibit two forms of disorder, in the methoxy group and in the cyclopropylisoxazole unit; symmetry-related pairs of molecules are linked into dimers by pairwise N—H...N hydrogen bonds. Comparisons are made with the structures of some related compounds.

The crystal structures of three benzimidazole esters containing aryl or heterocyclic substituents at position 2 are reported, and all three exhibit disorder of molecular entities. In ethyl 1-methyl-2-[4-(prop-2-ynoxy)phenyl]-1H-benzimidazole-5-carboxylate, C20H18N2O3, (I), the prop-2-yn-1-oxyphenyl unit is disordered over two sets of atomic sites having effectively equal occupancies, 0.506 (5) and 0.494 (5). The propyl substituent in ethyl 1-propyl-2-(pyren-1-yl)-1H-benzimidazole-5-carboxylate, C29H24N2O2, (II), is disordered over two sets of atomic sites having occupancies 0.601 (8) and 0.399 (8), and the ester unit in ethyl 1-methyl-2-(5-chloro-3-methyl-1-phenyl-1H-pyrazol-4-yl)-1H-benzimidazole-5-carboxylate, C21H19ClN4O2 (III), is disordered over two sets of atomic sites having occupancies 0.645 (7) and 0.355 (7). In each of the C—H...π(arene) hydrogen bonds in (I), the donor and acceptor form parts of different disorder components, so that no continuous aggregation is possible. The molecules of (II) are linked by a single C—H...O hydrogen bond into C(10) chains, which are linked into sheets by a π–π stacking interaction, whereas those of (III) are just linked into C(13) chains, again by a single C—H...O hydrogen bond. Comparisons are made with the structures of some related compounds.

Cycloaddition reactions between 3-(5-aryloxy-3-methyl-1-phenyl-1H-pyrazol-4-yl)-1-(thiophen-2-yl)prop-2-en-1-ones and thiosemicarbazide leads to the formation of reduced 3,4′-bipyrazole-2-carbothioamides. Further cycloaddition of these intermediates with either diethyl acetylenedicarboxylate or 4-bromophenacyl bromide leads to reduced 3,4′-bipyrazoles carrying oxothiazole or thiazole substituents, respectively. The structures of two representative intermediates and two representative products established unambiguously the regiochemistry of the cycloaddition reactions. The molecules of 3′-methyl-5′-(2-methylphenoxy)-1′-phenyl-5-(thiophen-2-yl)-3,4-dihydro-1′H,2H-3,4′-bipyrazole-2-carbothioamide, C25H23N5OS2 (Ia), are linked by N—H...N hydrogen bonds to form simple C(8) chains. The analogous compound 5′-(2,4-dichlorophenoxy)-3′-methyl-1′-phenyl-5-(thiophen-2-yl)-3,4-dihydro-1′H,2H-3,4′-bipyrazole-2-carbothioamide hemihydrate crystallizes as a hemihydrate, C24H19Cl2N5OS2·0.5H2O (Ib), and the independent components are linked into a chain of spiro-fused R44(20) rings by a combination of O—H...N and N—H...O hydrogen bonds. In the structure of ethyl (Z)-2-{2-[3′-methyl-1′-phenyl-5-(thiophen-2-yl)-5′-(2-methylphenoxy)-3,4-dihydro-1′H,2H-3,4′-bipyrazole-2-yl]-4-oxo-4,5-dihydrothiazol-5-ylidene}acetate, C31H27N5O4S2 (II), inversion-related pairs of molecules are linked by paired C—H...π(arene) hydrogen bonds to form cyclic centrosymmetric dimers, but there are no direction-specific intermolecular interactions in 4-(4-bromophenyl)-2-[5′-(2,4-dichlorophenoxy)-3′-methyl-1′-phenyl-5-(thiophen-2-yl)-3,4-dihydro-1′H,2H-3,4′-bipyrazole-2-yl]-4-thiazole, C32H22BrCl2N5OS2 (III). Comparisons are made with the structures of some related compounds.

Fifteen 4-(2-methoxyphenyl)piperazin-1-ium salts containing organic anions have been prepared and structurally characterized. In the isostructural 4-chlorobenzoate and 4-bromobenzoate salts, C11H17N2O+·C7H4ClO2− (I) and C11H17N2O+·C7H4BrO2− (II), and the 4-iodobenzoate salt C11H17N2O+·C7H4IO2− (III), the ions are linked by N—H...O hydrogen bonds, forming centrosymmetric R44(12) four-ion aggregates; a similar aggregate is formed in the 2-chlorobenzoate salt (V), isomeric with (I). In the 2-fluorobenzoate salt C11H17N2O+·C7H4FO2− (IV), and the isomorphous pair of salts, the 2-bromobenzoate (VI), isomeric with (II) and 2-iodobenzoate (VII), isomeric with (III), N—H...O and C—H...π(arene) interactions link the components into three-dimensional arrays. Four-ion R44(12) aggregates are also found in the 2-methylbenzoate, 4-aminobenzoate and 4-nitrobenzoate 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.

Two new substituted propanedioate esters have been synthesized using a three-component solvent-free thermal reaction between diethyl propanedioate (diethyl malonate), 5-chloro-3-methyl-1-phenyl-1H-pyrazole-4-carbaldehyde and an aryl azide, forming two new C—C bonds in a single step. The products diethyl (RS)-2-[(4-bromophenyl)(5-methyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)methyl]propanedioate, C24H25BrN2O5 (I), and diethyl (RS)-2-[(4-chlorophenyl)(5-methyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)methyl]propanedioate, C24H25ClN2O5 (II), are isomorphous, with Z′ = 2 in space group P21/n. The two independent molecules in compound (I) are both fully ordered, while each of the independent molecules in compound (II) is disordered, but in different ways. In one molecule of (II), the N-phenyl ring is disordered over two sets of atomic sites having occupancies 0.635 (10) and 0.365 (10), and in the other molecule the ester function is disordered over two sets of atomic sites having occupancies 0.690 (5) and 0.310 (5). In both structures, the two independent molecules adopt different conformations and, in each structure, the molecules are linked into complex sheets by a combination of N—H...O, C—H...O and C—H...π(arene) hydrogen bonds. Comparisons are made with some related structures.

In the title salt {systematic name: 4-[6-chloro-2,9-diazatricyclo[9.4.0.03,8]pentadeca-1(15),3(8),4,6,9,11,13-heptaen-10-yl]-1-methylpiperazin-1-ium 3,5-dinitrobenzoate–3,5-dinitrobenzic acid (1/1)}, C18H20ClN4+·C7H3N2O6−·C7H4N2O6, there is a very short, asymmetric, O—H...O hydrogen bond [O...O = 2.453 (3) Å] within the anion. The oxygen atoms of one of the nitro groups of the anion are disordered over two sets of sites having occupancies of 0.56 (3) and 0.44 (3). The fused tricyclic portion of the cation adopts a butterfly conformation, with a dihedral angle of 45.59 (6)° between the planes of the two aryl rings. In the crystal, a combination of O—H...O, N—H...O and C—H...O hydrogen bonds links the component species into a three-dimensional framework. Comparisons are made with the structures of some related compounds.

The structures are reported for five salts formed by reactions between N-(4-fluorophenyl)piperazine and aromatic acids. In 4-(4-fluorophenyl)piperazin-1-ium 2-fluorobenzoate monohydrate, C10H14FN2+·C7H4FO2−·H2O, (I), the components are linked by a combination of N—H...O and O—H...O hydrogen bonds to form a chain of alternating R46(12) and R66(16) rings. The ionic components of 4-(4-fluorophenyl)piperazin-1-ium 2-bromobenzoate 0.353-hydrate, C10H14FN2+·C7H4BrO2−·0.353H2O, (II), are linked by N—H...O hydrogen bonds to form a centrosymmetric four-ion aggregate containing an R44(12) motif, and these aggregates are linked into a molecular ladder by a single C—H...π(arene) hydrogen bond. 4-(4-Fluorophenyl)piperazin-1-ium 2-iodobenzoate, C10H14FN2+·C7H4IO2−, (III), crystallizes with Z′ = 2 in space group P\overline{1}: the four independent ions are linked by N—H...O hydrogen bonds to form a non-centrosymmetric aggregate again containing an R44(12) motif, and aggregates of this type are linked into a ribbon by a combination of C—H...O and C—H...π(arene) hydrogen bonds. The anion in 4-(4-fluorophenyl)piperazin-1-ium 2,4,6-trinitrophenolate, C10H14FN2+·C6H2N3O7−, (IV), shows clear evidence of extensive electronic delocalization from the phenolate O atom into the adjacent ring. The ions are linked by a combination of two-centre N—H...O and three-centre N—H...(O)2 hydrogen bonds to form centrosymmetric four-ion aggregates containing three types of ring. The ions in 4-(4-fluorophenyl)piperazin-1-ium 3,5-dinitrobenzoate, C10H14FN2+·C7H3N2O6−, (V), are again linked by N—H...O hydrogen bonds to form centrosymmetric R44(12) aggregates, which are themselves linked by a C—H...π(arene) hydrogen bond to form sheets, the stacking of which leads to the formation of narrow channels, containing disordered and/or mobile solvent entities. Comparisons are made with some related structures.

Two new N-{[4-(3-aryl-4-sydnonylideneamino)-5-sulfanylidene-1H-1,2,4-triazol-3-yl]methyl}benzamides have been prepared by acid-promoted condensation reactions between 3-aryl-4-formylsydnones and N-[(4-amino-5-sulfanylidene-1H-1,2,4-triazol-3-yl)methyl]benzamide, and both have been crystallized as ethanol monosolvates. N-{[4-(3-Phenyl-4-sydnonylideneamino)-5-sulfanylidene-1H-1,2,4-triazol-3-yl]methyl}benzamide ethanol monosolvate, C19H15N7O3S·C2H6O (I), and N-({4-[3-(4-methylphenyl)-4-sydnonylideneamino]-5-sulfanylidene-1H-1,2,4-triazol-3-yl}methyl)benzamide ethanol monosolvate, C20H17N7O3S·C2H6O (II), differ only in the presence of a methyl group for (II) instead of a hydrogen atom for (I), and in both of them the ethanol component is disordered over two sets of atomic sites having occupancies of 0.836 (6) and 0.164 (6) in (I), and 0.906 (6) and 0.094 (6) in (II). Combinations of O—H...O and N—H...O hydrogen bonds link the molecules into cyclic, centrosymmetric four-molecule aggregates. Comparisons are made with the structures of some related compounds.

Three salts containing the 4-(4-fluorophenyl)piperazin-1-ium cation have been prepared and structurally characterized. In 4-(4-fluorophenyl)piperazin-1-ium 2-hydroxy-3,5-dinitrobenzoate, C10H14FN2+·C7H3N2O7−, (I), the anion contains an intramolecular O—H...O hydrogen bond, and it has a structure similar to that of the picrate ion. The cations and anions are linked into [001] chains of rings by a combination of two three-centre N—H...(O)2 hydrogen bonds. The anion in 4-(4-fluorophenyl)piperazin-1-ium hydrogen oxalate, C10H14FN2+·C2HO4−, (II), is planar, and the cations and anions are linked into (100) sheets by multiple hydrogen bonds including two-centre N—H...O, three-centre N—H...(O)2, O—H...O, C—H...O and C—H...π(arene) types. In 4-(4-fluorophenyl)piperazin-1-ium hydrogen (2R,3R)-tartrate monohydrate, C10H14FN2+·C4H5O6−·H2O, (III), the anion exhibits an approximate non-crystallographic twofold rotation symmetry with antiperiplanar carboxyl groups. A combination of eight hydrogen bonds, encompassing two- and three-centre N—H...O systems, O—H...O and C—H...π(arene) types, link the independent components into a three-dimensional framework. Comparisons are made with some related structures.

Five examples each of 3-(5-aryloxy-3-methyl-1-phenyl-1H-pyrazol-4-yl)-1-[4-(prop-2-yn-1-yloxy)phenyl]prop-2-en-1-ones and the corresponding 1-(4-azidophenyl)-3-(5-aryloxy-3-methyl-1-phenyl-1H-pyrazol-4-yl)prop-2-en-1-ones have been synthesized in a highly efficient manner, starting from a common source precursor, and structures have been determined for three examples of each type. In each of 3-[5-(2-chlorophenoxy)-3-methyl-1-phenyl-1H-pyrazol-4-yl]-1-[4-(prop-2-yn-1-yloxy)phenyl]prop-2-en-1-one, C28H21ClN2O3, (Ib), the isomeric 3-[5-(2-chlorophenoxy)-3-methyl-1-phenyl-1H-pyrazol-4-yl]-1-[4-(prop-2-yn-1-yloxy)phenyl]prop-2-en-1-one, (Ic), and 3-[3-methyl-5-(naphthalen-2-yloxy)-1-phenyl-1H-pyrazol-4-yl]-1-[4-(prop-2-ynyloxy)phenyl]prop-2-en-1-one, C32H24N2O3, (Ie), the molecules are linked into chains of rings, formed by two independent C—H...O hydrogen bonds in (Ib) and by a combination of C—H...O and C—H...π(arene) hydrogen bonds in each of (Ic) and (Ie). There are no direction-specific intermolecular interactions in the structure of 1-(4-azidophenyl)-3-[3-methyl-5-(2-methylphenoxy)-1-phenyl-1H-pyrazol-4-yl]prop-2-en-1-one, C26H21N5O2, (IIa). In 1-(4-azidophenyl)-3-[5-(2,4-dichlorophenoxy)-3-methyl-1-phenyl-1H-pyrazol-4-yl]prop-2-en-1-one, C25H17Cl2N5O2, (IId), the dichlorophenyl group is disordered over two sets of atomic sites having occupancies 0.55 (4) and 0.45 (4), and the molecules are linked by a single C—H...O hydrogen bond to form cyclic, centrosymmetric R22(20) dimers. Similar dimers are formed in 1-(4-azidophenyl)-3-[3-methyl-5-(naphthalen-2-yloxy)-1-phenyl-1H-pyrazol-4-yl]prop-2-en-1-one, C29H21N5O2, (IIe), but here the dimers are linked into a chain of rings by two independent C—H..π(arene) hydrogen bonds. Comparisons are made between the molecular conformations within both series of compounds.

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.

Chalcones of type 4-XC6H4C(O)CH=CHC6H4(OCH2CCH)-4, where X = Cl, Br or MeO, have been converted to the corresponding 4,5-dihydropyrazole-1-carbothioamides using a cyclocondensation reaction with thiosemicarbazide. The chalcones 1-(4-chlorophenyl)-3-[4-(prop-2-ynyloxy)phenyl]prop-2-en-1-one, C18H13ClO2, (I), and 1-(4-bromophenyl)-3-[4-(prop-2-ynyloxy)phenyl]prop-2-en-1-one, C18H13BrO2, (II), are isomorphous, and their molecules are linked into sheets by two independent C—H...π(arene) interactions, both involving the same aryl ring with one C—H donor approaching each face. In each of the products (RS)-3-(4-chlorophenyl)-5-[4-(prop-2-ynyloxy)phenyl]-4,5-dihydropyrazole-1-carbothioamide, C19H16ClN3OS, (IV), (RS)-3-(4-bromophenyl)-5-[4-(prop-2-ynyloxy)phenyl]-4,5-dihydropyrazole-1-carbothioamide, C19H16BrN3OS, (V), and (RS)-3-(4-methoxyphenyl)-5-[4-(prop-2-ynyloxy)phenyl]-4,5-dihydropyrazole-1-carbothioamide, C20H19N3O2S, (VI), the reduced pyrazole ring adopts an envelope conformation with the C atom bearing the 4-prop-2-ynyloxy)phenyl substituent, which occupies the axial site, displaced from the plane of the four ring atoms. Compounds (IV) and (V) are isomorphous and their molecules are linked into chains of edge-fused rings by a combination of N—H...S and C—H...S hydrogen bonds. The molecules of (VI) are linked into sheets by a combination of N—H...S, N—H...N and C—H...π(arene) hydrogen bonds. Comparisons are made with the structures of some related compounds.

Two new chalcones containing both pyrazole and thiophene substituents have been prepared and structurally characterized. 3-(3-Methyl-5-phenoxy-1-phenyl-1H-pyrazol-4-yl)-1-(thiophen-2-yl)prop-2-en-1-one, C23H18N2O2S (I), and 3-[3-methyl-5-(2-methylphenoxy)-1-phenyl-1H-pyrazol-4-yl]-1-(thiophen-2-yl)prop-2-en-1-one, C24H20N2O2S (II), are isomorphous as well as isostructural, and in each the thiophene substituent is disordered over two sets of atomic sites having occupancies 0.844 (3) and 0.156 (3) in (I), and 0.883 (2) and 0.117 (2) in (II). In each structure, the molecules are linked into sheets by a combination of C—H...N and C—H...O hydrogen bonds. Comparisons are made with some related compounds.

Three title compounds, namely, 2-(4-chlorobenzyl)-5-[(1H-indol-3-yl)methyl]-6-phenylimidazo[2,1-b][1,3,4]thiadiazole, C26H19ClN4S, (I), 2-(4-chlorobenzyl)-6-(4-fluorophenyl)-5-[(1H-indol-3-yl)methyl]imidazo[2,1-b][1,3,4]thiadiazole, C26H18ClFN4S, (II), and 6-(4-bromophenyl)-2-(4-chlorobenzyl)-5-[(1H-indol-3-yl)methyl]imidazo[2,1-b][1,3,4]thiadiazole, C26H18BrClN4S, (III), have been prepared using a reductive condensation of indole with the corresponding 6-aryl-2-(4-chlorobenzyl)imidazo[2,1-b][1,3,4]thiadiazole-5-carbaldehydes (aryl = phenyl, 4-fluorophenyl or 4-bromophenyl), and their crystal structures have been determined. The asymmetric unit of compound (I) consists of two independent molecules and one of the molecules exhibits disorder of the 4-chlorobenzyl substituent with occupancies 0.6289 (17) and 0.3711 (17). Each type of molecule forms a C(8) chain motif built from N—H...N hydrogen bonds, which for the fully ordered molecule is reinforced by C—H...π interactions. In compound (II), the chlorobenzyl unit is again disordered, with occupancies 0.822 (6) and 0.178 (6), and the molecules form C(8) chains similar to those in (I), reinforced by C—H...π interactions involving only the major disorder component. The chlorobenzyl unit in compound (III) is also disordered with occupancies of 0.839 (5) and 0.161 (5). The molecules are linked by a combination of one N—H...N hydrogen bond and four C—H...π interactions, forming a three-dimensional framework.

The crystal structures of three salts, namely N-(4-methoxyphenyl)piperazin-1-ium ethoxybenzoate monohydrate (I), N-(4-methoxyphenyl)piperazin-1-ium methoxybenzoate monohydrate (II) and N-(4-methoxyphenyl)piperazin-1-ium hydroxybenzoate monohydrate (III), have been determined and compared. In each of them, the ionic components and the water molecules are linked by a combination of N—H···O and O—H···O hydrogen bonds to form infinite chains of edge-fused centrosymmetric rings running parallel to the [100] direction. The C—H···O, C—H···π(arene) interactions and O—H···O in (III) are responsible for the further propagation of the aforementioned chains into di-periodic layers or tri-periodic networks. From an energetic point of view, all structures are primarily di-periodic; the very strong ionic interactions determine the periodicity. For comparison purposes, quantum chemical calculations were performed to show the difference between the ionic and neutral components. The energy of the hydrogen-bonded ring motifs was also estimated.

Twelve 4-(4-methoxyphenyl)piperazin-1-ium salts containing organic anions have been prepared and structurally characterized. The monohydrated benzoate, 4-fluorobenzoate, 4-chlorobenzoate and 4-bromobenzoate salts, C11H17N2O+·C7H5O2−·H2O (I), C11H17N2O+·C7H4FO2−·H2O (II), C11H17N2O+·C7H4ClO2−·H2O (III), and C11H17N2O+·C7H4BrO2−·H2O (IV), respectively, are isomorphous and all exhibit disorder in the 4-methoxyphenyl unit: the components are linked by N—H...O and O—H...O hydrogen bond to form chains of rings. The unsolvated 2-hydroxybenzoate, pyridine-3-carboxylate and 2-hydroxy-3,5-dinitrobenzoate salts, C11H17N2O+·C7H5O3− (V), C11H17N2O+·C6H4NO2− (VI) and C11H17N2O+·C7H3N2O7− (VII), respectively, are all fully ordered: the components of (V) are linked by multiple N—H...O hydrogen bonds to form a chain of rings; those of (VI) are linked into a three-dimensional framework by a combination of N—H...O, C—H...O and C—H...N hydrogen bonds and those of (VII), where the anion has a structure reminiscent of the picrate anion, are linked into a three-dimensional array by N—H...O and C—H...O hydrogen bonds. The hydrogensuccinate and hydrogenfumarate salts, C11H17N2O+·C4H5O4− (VIII) and C11H17N2O+·C4H3O3− (IX), respectively, are isomorphous, and both exhibit disorder in the anionic component: N—H...O and O—H...O hydrogen bonds link the ions into sheets, which are further linked by C—H...π(arene) interactions. The anion of the hydrogenmaleate salt, C11H17N2O+·C4H3O3− (X), contains a very short and nearly symmetrical O...H...O hydrogen bond, and N—H...O hydrogen bonds link the anions into chains of rings. The ions in the trichloroacetate salt, C11H17N2O+·C2Cl3O2− (XI), are linked into simple chains by N—H...O hydrogen bonds. In the hydrated chloranilate salt, 2C11H17N2O+·C6Cl2O42−·2H2O (XII), which crystallizes as a non-merohedral twin, the anion lies across a centre of inversion in space group P21/n, and a combination of N—H...O and O—H...O hydrogen bonds generates complex sheets. Comparisons are made with the structures of some related compounds.

Six new 1-aroyl-4-(4-methoxyphenyl)piperazines have been prepared, using coupling reactions between benzoic acids and N-(4-methoxyphenyl)piperazine. There are no significant hydrogen bonds in the structure of 1-benzoyl-4-(4-methoxyphenyl)piperazine, C18H20N2O2, (I). The molecules of 1-(2-fluorobenzoyl)-4-(4-methoxyphenyl)piperazine, C18H19FN2O2, (II), are linked by two C—H...O hydrogen bonds to form chains of rings, which are linked into sheets by an aromatic π–π stacking interaction. 1-(2-Chlorobenzoyl)-4-(4-methoxyphenyl)piperazine, C18H19ClN2O2, (III), 1-(2-bromobenzoyl)-4-(4-methoxyphenyl)piperazine, C18H19BrN2O2, (IV), and 1-(2-iodobenzoyl)-4-(4-methoxyphenyl)piperazine, C18H19IN2O2, (V), are isomorphous, but in (III) the aroyl ring is disordered over two sets of atomic sites having occupancies of 0.942 (2) and 0.058 (2). In each of (III)–(V), a combination of two C—H...π(arene) hydrogen bonds links the molecules into sheets. A single O—H...O hydrogen bond links the molecules of 1-(2-hydroxybenzoyl)-4-(4-methoxyphenyl)piperazine, C18H20N2O3, (VI), into simple chains. Comparisons are made with the structures of some related compounds.

In the title compound, C61H15ClN2O3, the heterocyclic ring adopts an envelope conformation, folded across the N...N line, with the 2,5-dimethoxyphenyl unit occupying a quasi-axial site. There are two N—H...O hydrogen bonds in the structure: one hydrogen bond links molecules related by a 41 screw axis to form a C(6) chain, and the other links inversion-related pairs of molecules to form an R22(8) ring. The ring motif links all of the chains into a continuous three-dimensional framework structure. Comparisons are made with the structures of some related compounds.

The syntheses and structures of five molecular salts of protonated 4,4,7,7-tetramethyl-3a,5,6,7a-tetrahydrobenzothiazol-2-ylamine (C11H19N2S+) with different deprotonated carboxylic acids (4-methylbenzoic acid, 4-bromobenzoic acid, 3,5-dinitrobenzoic acid, fumaric acid and succinic acid) are reported, namely 2-amino-4,4,7,7-tetramethyl-4,5,6,7-tetrahydro-1,3-benzothiazol-3-ium 4-methylbenzoate, C11H19N2S+·C8H7O2−, (I), 2-amino-4,4,7,7-tetramethyl-4,5,6,7-tetrahydro-1,3-benzothiazol-3-ium 4-bromobenzoate, C11H19N2S+·C7H4BrO2−, (II), 2-amino-4,4,7,7-tetramethyl-4,5,6,7-tetrahydro-1,3-benzothiazol-3-ium 3,5-dinitrobenzoate, C11H19N2S+·C7H3N2O6−, (III), bis(2-amino-4,4,7,7-tetramethyl-4,5,6,7-tetrahydro-1,3-benzothiazol-3-ium) fumarate, 2C11H19N2S+·C4H2O42−,(IV), and the 1:1 co-crystal of bis(2-amino-4,4,7,7-tetramethyl-4,5,6,7-tetrahydro-1,3-benzothiazol-3-ium) succinate and 2-amino-4,4,7,7-tetramethyl-4,5,6,7-tetrahydro-1,3-benzothiazol-3-ium hydrogen succinate 4,4,7,7-tetramethyl-3a,5,6,7a-tetrahydrobenzothiazol-2-ylamine, 1.5C11H19N2S+·0.5C4H4O42−·0.5C4H5O4−. 0.5C11H18N2S, (V). In every case, the cation protonation occurs at the N atom of the thiazole ring and the six-membered ring adopts a half-chair conformation (in some cases, the deviating methylene groups are disordered over two sets of sites). The C—N bond lengths of the nominal –NH+=C—NH2 fragment of the cation are indistinguishable, indicating a significant contribution of the –NH—C=N+H2 resonance form to the structure. The packing for (I)–(V) features a robust local R22(8) loop motif in which the cation forms two near-linear N—H...O hydrogen bonds from the N+—H group and syn H atom of the amine group to the carboxylate group of an adjacent anion [(V) shows disorder of one of these bonds over N—H...O and N...H—O contributors but the same R22(8) loop results for both disorder components]. The anti H atom of the –NH2 group also forms an N—H...O hydrogen bond, which results in [001] chains in (I) and (II), isolated centrosymmetric tetramers in (III) and [100] chains in (IV) and (V). Hirshfeld fingerprint plots and contact percentages for the different types of contacts of the cations are discussed.

In each of the compounds 1-[(1,3-benzodioxol-5-yl)methyl]-4-(3-fluorobenzoyl)piperazine, C19H19FN2O3 (I), 1-[(1,3-benzodioxol-5-yl)methyl]-4-(2,6-difluorobenzoyl)piperazine, C19H18F2N2O3 (II), and 1-[(1,3-benzodioxol-5-yl)methyl]-4-(2,4-dichlorobenzoyl)piperazine, C19H19Cl2N2O3 (III), the piperazine rings adopt a chair conformation with the (1,3-benzodioxol-5-yl)methyl substituent occupying an equatorial site: the five-membered rings are all slightly folded across the O...O line leading to envelope conformations. The dihedral angle between the planar amidic fragment and the haloaryl ring is 62.97 (5)° in (I) but 77.72 (12)° and 75.50 (5)° in (II) and (III), respectively. Despite their similarity in constitution and conformation, the supramolecular interactions in (I)–(III) differ: in (I), a combination of C—H...O and C—H...π(arene) hydrogen bonds links the molecules into a three-dimensional framework structure, but there are no hydrogen bonds of any sort in either (II) or (III), although the structure of (III) contains a short Cl...Cl contact between inversion-related pairs of molecules.