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, CHO·CHN·HO (); 4-phenyl-piperazin-1-ium 4-meth-oxy-benzoate monohydrate, CHN·CHO·HO (); 4-phenyl-piperazin-1-ium 4-methyl-benzoate monohydrate, CHN·CHO·HO (); and 4-phenyl-piperazin-1-ium tri-fluoro-acetate 0.12 hydrate, CHN·CFO·0.12HO (), have been synthesized.

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, CHNO ·CHBrO ·2HO, (I), 4-(4-nitro-phenyl)-pi-per-a-zin-1-ium 4-iodo-benzoate dihydrate, CHNO ·CHIO ·2HO, (II), 4-(4-nitro-phenyl)-piperazin-1-ium 4-hy-droxy-benzoate monohydrate, CHNO ·CHO ·HO, (III), 4-(4-nitro-phenyl)-piperazin-1-ium 4-methyl-benzoate monohydrate, CHNO ·CHO ·HO, (IV), 4-(4-nitro-phenyl)-piperazin-1-ium 4-meth-oxy-benzoate hemihydrate, 2CHNO ·2CHO ·HO, (V), and 4-(4-nitro-phenyl)-piperazin-1-ium 4-eth-oxy-benzoate, 2CHNO ·2CHO , (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 except for (V), which crystallizes in the monoclinic space group 2/ 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 ()-1-(4-meth-oxy-phen-yl)-3-[4-(prop-2-yn-yloxy)phen-yl]prop-2-en-1-one, CHO (I), are linked by a combination of C-H⋯O and C-H⋯π(arene) hydrogen bonds to form ribbons.

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, CHFNO (I), 1-[(1,3-benzodioxol-5-yl)methyl]-4-(2,6-di-fluoro-benzo-yl)piperazine, CHFNO (II), and 1-[(1,3-benzodioxol-5-yl)methyl]-4-(2,4-di-chloro-benzo-yl)piperazine, CHClNO (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.

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, CHINO, 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.