Crystal-structure studies of 4-phenyl-piperazin-1-ium 4-eth-oxy-benzoate monohydrate, 4-phenyl-piperazin-1-ium 4-meth-oxy-benzoate monohydrate, 4-phenyl-piperazin-1-ium 4-methyl-benzoate monohydrate and 4-phenyl-piperazin-1-ium tri-fluoro-acetate 0.12-hydrate.

In this study, four new piperazinium salts, namely, 4-phenyl-piperazin-1-ium 4-eth-oxy-benzoate monohydrate, C9H9O3·C10H15N2·H2O (I); 4-phenyl-piperazin-1-ium 4-meth-oxy-benzoate monohydrate, C10H15N2·C8H7O3·H2O (II); 4-phenyl-piperazin-1-ium 4-methyl-benzoate monohydrate, C10H15N2·C8H7O2·H2O (III); and 4-phenyl-piperazin-1-ium tri-fluoro-acetate 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 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 inter-actions 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 inter-actions, forming sheets which in turn inter-act to maintain the crystal structure by linking through the oxygen atoms of water mol-ecules and van der Waals inter-actions, giving the whole structure.

Crystal structures of six 4-(4-nitro-phenyl)-piperazin-1-ium salts.

Six piperazinium salts, namely 4-(4-nitro-phenyl)-piperazin-1-ium 4-bromo-ben-zo-ate dihydrate, C10H14N3O2 +·C7H4BrO2 -·2H2O, (I), 4-(4-nitro-phenyl)-pi-per-a-zin-1-ium 4-iodo-benzoate dihydrate, C10H14N3O2 +·C7H4IO2 -·2H2O, (II), 4-(4-nitro-phenyl)-piperazin-1-ium 4-hy-droxy-benzoate monohydrate, C10H14N3O2 +·C7H5O3 -·H2O, (III), 4-(4-nitro-phenyl)-piperazin-1-ium 4-methyl-benzoate monohydrate, C10H14N3O2 +·C8H7O2 -·H2O, (IV), 4-(4-nitro-phenyl)-piperazin-1-ium 4-meth-oxy-benzoate hemihydrate, 2C10H14N3O2 +·2C8H7O3 -·H2O, (V), and 4-(4-nitro-phenyl)-piperazin-1-ium 4-eth-oxy-benzoate, 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 inter-actions of type C-H⋯O and/or C-H⋯π, forming sheets, whereas (VI) shows a cationic and anionic-based layer structure.

Formation of 1-(thia-zol-2-yl)-4,5-di-hydropyrazoles from simple precursors: synthesis, spectroscopic characterization and the structures of an inter-mediate and two products.

Two new 1-(thia-zol-2-yl)-4,5-di-hydropyrazoles have been synthesized from simple precursors, and characterized both spectroscopically and structurally. In addition, two inter-mediates in the reaction pathway have been isolated and characterized, one of them structurally. The mol-ecules of the inter-mediate (E)-1-(4-meth-oxy-phen-yl)-3-[4-(prop-2-yn-yloxy)phen-yl]prop-2-en-1-one, C19H16O3 (I), are linked by a combination of C-H⋯O and C-H⋯π(arene) hydrogen bonds to form ribbons. The products (RS)-5-(4-meth-oxy-phen-yl)-1-(4-phenythiazol-2-yl)-3-[4-(prop-2-yn--yloxy)phen-yl]-4,5-di-hydro-1H-pyrazole, C28H23N3O2S (II), and (RS)-5-(4-meth-oxy-phen-yl)-1-[4-(4-methyl-phen-yl)thia-zol-2-yl]-3-[4-(prop-2-yn-yloxy)phen-yl]-4,5-di-hydro-1H-pyrazole, C29H25N3O2S (III), are closely related - differing only by presence or absence of a methyl group at the aryl-thia-zolyl substituent - and crystallize in an isomorphous setting. Both mol-ecules contain an effectively planar di-hydro-pyrazole ring, and possess an overall T-shaped structure, which is a characteristic of triaryl-substituted 4,5-di-hydro-1-(thia-zol-2-yl)pyrazole compounds. The crystal packing is characterized by inter-molecular C-H⋯S and C-H⋯π (ar-yl/alkyne) inter-actions. A combination of two C-H⋯π(arene) hydrogen bonds links the product mol-ecules into sheets.

Different patterns of supra-molecular aggregation in three amides containing N-(benzo[d]thia-zol-yl) substituents.

Crystal structures are reported for three amides containing N-benzo[d]thia-zole substituents. In N-(benzo[d]thia-zol-6-yl)-3-bromo-benzamide, C14H9BrN2OS, where the two ring systems are nearly parallel to one another [dihedral angle = 5.8 (2)°], the mol-ecules are linked by N-H⋯O and C-H⋯N hydrogen bonds to form ribbons of R 3 3(19) rings, which are linked into sheets by short Br⋯Br inter-actions [3.5812 (6) Å]. N-(6-Meth-oxy-benzo[d]thia-zol-2-yl)-2-nitro-benzamide, 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 mol-ecules and a combination of two N-H⋯N and five C-H⋯O hydrogen bonds links the mol-ecules into a three-dimensional network. The mol-ecules of 5-cyclo-propyl-N-(6-meth-oxy-ben-zo[d]thia-zol-2-yl)-isoxazole-3-carboxamide, C15H13N3O3S, exhibit two forms of disorder, in the meth-oxy group and in the cyclo-propyl-isoxazole unit; symmetry-related pairs of mol-ecules are linked into dimers by pairwise N-H⋯N hydrogen bonds. Comparisons are made with the structures of some related compounds.

The crystal structure of 1-(2-iodo-benzo-yl)-4-(pyrimidin-2-yl)piperazine: a three-dimensional hydrogen-bonded framework, augmented by π-π stacking inter-actions and I⋯N halogen bonds.

In 1-(2-iodo-benzo-yl)-4-(pyrimidin-2-yl)piperazine, C15H15IN4O, the central piperazine ring adopts an almost perfect chair conformation with the pyrimidine substituent in an equatorial site. The planar amide unit makes a dihedral angle of 80.44 (7)° with the phenyl ring. A combination of C-H⋯O and C-H⋯π(arene) hydrogen bonds links the mol-ecules into a complex three-dimensional network structure, augmented by a π-π stacking inter-action and an I⋯N halogen bond, all involving different pairs of inversion-related mol-ecules. Comparisons are made with the structures of a number of related compounds.

Three closely related 1-[(1,3-benzodioxol-5-yl)methyl]-4-(halobenzo-yl)piperazines: similar mol-ecular structures but different inter-molecular inter-actions.

In each of the compounds 1-[(1,3-benzodioxol-5-yl)methyl]-4-(3-fluoro-benzo-yl)piperazine, C19H19FN2O3 (I), 1-[(1,3-benzodioxol-5-yl)methyl]-4-(2,6-di-fluoro-benzo-yl)piperazine, C19H18F2N2O3 (II), and 1-[(1,3-benzodioxol-5-yl)methyl]-4-(2,4-di-chloro-benzo-yl)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 supra-molecular inter-actions in (I)-(III) differ: in (I), a combination of C-H⋯O and C-H⋯π(arene) hydrogen bonds links the mol-ecules 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 mol-ecules.