In the title salt, C7H11N2
−, the essentially planar cation (r.m.s. deviation = 0.006 Å) forms an N—H⋯Br hydrogen bond to one of the Br atoms of the almost linear anion [Br—Br—Br = 179.31 (2)°]. The crystal studied was found to be a racemic twin. The whole-molecule disorder of the cation and anion about a twofold rotation axis described earlier [Ng (2009). Acta Cryst. E65, o1276] is an artifact of halving one of the axes of the orthorhombic unit cell.
A preliminary X-ray study of the title molecular salt, [Ni(CH4N2S)6](NO3)2, has been reported twice previously, by Maďar [Acta Cryst. (1961), 14, 894] and Rodriguez, Cubero, Vega, Morente & Vazquez [Acta Cryst. (1961), 14, 1101], using film methods. We confirm the previous studies, but to modern standards of precision and with all H atoms located. The central Ni atom (site symmetry ) of the dication is octahedrally coordinated by six S-bound thiourea molecules. The crystal structure is stabilized by intra- and intermolecular N—H⋯S and N—H⋯O hydrogen bonds.
The crystal structure of the title compound, C9H10O4, was first reported by Swaminathan, Vimala & Lotter [Acta Cryst. (1976), B32, 1897–1900]. It has been re-examined, improving the precision of the derived geometric parameters. The asymmetric unit comprises a non-planar independent molecule, as the methoxy substituents force the carboxy group to be twisted away from the plane of the aromatic ring by 56.12 (9)°. Due to the antiplanar conformation adopted by the OH group, the molecular components do not form the conventional dimeric units, but are associated in the crystal in chains stabilized by linear O—H⋯O hydrogen bonds, involving the OH groups and the carbonyl O atoms, which form C(3) motifs.
The redetermined structure of title chalcone derivative, C23H16O2, corrects errors in the title, scheme and synthesis in the previous report of the same structure [Jasinski et al. (2011 ▶). Acta Cryst. E67, o795]. There are two independent molecules in the asymmetric unit with slight differences in bond lengths and angles. The dihedral angle between the benzene ring and the anthracene ring system is 73.30 (4)° in one molecule and 73.18 (4)° in the other. Both molecules feature an intramolecular O—H⋯O hydrogen bond, which generates an S(6) ring. In the crystal, molecules are arranged into sheets lying parallel to the ac plane and further stacked along the b axis by π–π interactions with centroid–centroid distances in the range 3.6421 (6)–3.7607 (6) Å. The crystal structure is further stabilized by C—H⋯π interactions. There are also C⋯O [3.2159 (15) Å] short contacts.
In the anion of the title molecular salt, C4H12N2
2−, the two acetate groups form torsion angles of 74.1 (1) and 7.1 (1)° with the central benzene ring, and the cation exhibits a chair conformation. In the crystal, N—H⋯O hydrogen bonds link the components into a two-dimensional supramolecular network lying parallel to the ab plane. A number of C—H⋯O interactions consolidate the packing.
In the title hydrated salt, C4H12N2
−·2H2O, the piperazinediium cation, lying about an inversion center, adopts a chair conformation. The benzene ring of the anion makes dihedral angles of 25.17 (8)° with the carboxylate group and angles of 8.50 (7), 20.07 (7) and 80.86 (8)° with the three carboxylic acid groups. In the crystal, the cations, anions and water molecules are connected by O—H⋯O and N—H⋯O hydrogen bonds into double layers parallel to (110).
The title compound, C30H25NOP2, is a bulky phosphazene derivative. Its previous crystal structure [Cameron et al. (1979 ▶). Acta Cryst. B35, 1373–1377] is confirmed and its H atoms have been located in the present study. The formal P=N double bond is about 0.05 Å shorter than the P—N single bond and the large P=N—P bond angle reflects the steric strain in the molecule. An intramolecular C—H⋯O interaction occurs. In the crystal, short C—H⋯O contacts connect the molecules into chains propagating in , which are cross-linked via C—H⋯π interactions, generating a three-dimensional network. Aromatic π–π stacking also occurs [shortest centroid–centroid separation = 3.6012 (11) Å].
The structure of the title compound (common name: amodiaquinium dichloride dihydrate), C20H24ClN3O2
+·2Cl−·2H2O, was previously determined from powder diffraction data [Llinàs et al. (2006 ▶). Acta Cryst. E62, o4196-o4199]. It has now been refined from diffractometer data to a significantly higher precision. The dihedral angle between the quinoline and benzene rings is 54.57 (6)°. The central amino N atom interacts more strongly with the quinoline ring than with the benzene ring, as indicated by the shorter C—N bond length [1.341 (2) Å compared to 1.431 (2) Å]. In the crystal, molecules are packed into a three-dimensional network/supramolecular structure through hydrogen bonds between the amodiaquinium cations, chloride anions and water molecules.
The asymmetric unit of the title compound, C8H8O2, contains two crystallographically independent molecules, which form dimers linked by O⋯H—O hydrogen bonds. The benzene rings in the dimers are inclined at a dihedral angle of 7.30 (8)° and both methyl groups display rotational disorder. This redetermination results in a crystal structure with significantly higher precision than the original determination [Ellas & García-Blanco (1963 ▶). Acta Cryst. 16, 434], in which the authors reported only the unit-cell parameters and space group, without any detailed information on the atomic arrangement. In the crystal, dimers are connected by weak C—H⋯O interactions, forming R
2(10) and R
4(18) rings along  and an infinite zigzag chain of dimers along the  direction also occurs.
The title compound, C13H9NO4, crystallizes in a zwitterionic form with the pyridine N atom protonated and the carboxyl OH group deprotonated. The benzene and pyridinium rings are inclined with a dihedral angle of 31.42 (14)° between them. A previous report of this stucture claims, we believe incorrectly, that neither of the carboxylate groups is deprotonated [Zhang et al. (2010 ▶). Acta Cryst. E66, o2928–o2928]. In the crystal, intermolecular O—H⋯O, N—H⋯O and weak C—H⋯O hydrogen-bonding interactions link adjacent molecules into a three-dimensional supramolecular network.
In the title hydrated molecular salt, C6H16N2
−·2H2O, the complete 1,4-dimethylpiperazine-1,4-diium dication is generated by crystallographic inversion symmetry and both C—N bonds are in equatorial orientations. In the crystal, the components are linked by O—H⋯F and N—H⋯O hydrogen bonds but there are no direct links between cations and anions.
In the crystal structure of the title compound, (C10H15ClN2)[ZnCl4]·H2O, the Zn atom is coordinated by four Cl atoms in a tetrahedral geometry. The water molecules and the 1-(4-chlorophenyl)piperazine-1,4-diium cations interact with the [ZnCl4]2− anions through O—H⋯Cl, N—H⋯Cl, N—H⋯O and C—H⋯Cl hydrogen bonds (five simple and one bifurcated). Intermolecular π–π stacking interactions are present between adjacent aromatic rings of 1-(4-chlorophenyl)piperazine-1,4-diium cations (the centroid–centroid distance is 3.453 Å).
The redetermined, low temperature (150 K), structure of tetra-n-butylammonium bromide, (C4H9)4N+·Br−, has been found to be merohedrally twinned via twin law −1 0 0, 0 − 1 0, 1 0 1. The structure was previously determined, with low precision, no inclusion of H atoms and only the bromide ion refined with anisotropic displacement parameters, by Wang et al. (1995 ▶). Mol. Cryst. Liq. Cryst. Sci. Tech. A, 264, 115–129. The redetermined structure has considerably improved precision in all geometrical parameters, has all non-H atoms refined anisotropically, H atoms included, and is isomorphous with the iodide analogue. The structure is otherwise routine, with the shortest cation to anion contacts being between the bromide anion and the CH atoms close to the ammonium nitrogen centre at a distance of ca. 2.98–3.11 Å. Each anion makes eight such contacts to four different anions. The n-butyl chains are fully extended, adopting an all-anti conformation with approximate S
4 point symmetry.
The structure of the title compound, C7H9NO2S, was previously determined from powder diffraction data [Tremayne, Seaton & Glidewell (2002). Acta Cryst. B58, 823–834]. It has now been refined to a significantly higher precision. The amino N-atom is bent with a C—C—S—N torsion angle of −65.8 (2)deg;. In the crystal, molecules are packed into a three-dimensional framework/supramolecular structure through hydrogen bonds between the two H atoms of the sulfonamide group and sulfonyl O atoms of neighbouring molecules.
The title compound, C18H21N3O3, is a potential bidentate Schiff base ligand. The whole molecule is disordered with a refined site-occupancy ratio of 0.567 (4):0.433 (4) and not just one ethyl group as reported previously [Sarojini et al. (2007 ▶). Acta Cryst. E63, o4782–o4782]. Using the whole molecule disorder, R values are much smaller than those published. An intramolecular O—H⋯N hydrogen bond generates a six-membered ring, producing an S(6) ring motif. The dihedral angle between the mean plane of the two benzene rings (major component) is 9.0 (5)°. The crystal structure shows short C⋯C [3.189 (15)–3.298 (12) Å] and C⋯O [2.983 (5)–3.149 (13) Å] contacts. Intermolecular C—H⋯O interactions link neighbouring molecules into dimers with R
2(18) motifs. In the crystal structure, these dimers are linked together by intermolecular C—H⋯O interactions into one-dimensional extended chains along the b axis. The crystal structure is further stabilized by intermolecular π–π stacking interactions [centroid–centroid distances = 3.458 (8)–3.691 (6) Å].
In the title salt, C23H27F3N2OS+·2C4H3O4
−, a non-merohedral twin [ratio of the twin components = 0.402 (1):0.598 (1)], the –CF3 group is disordered over two sets of sites with occupancy factors in the ratio 0.873 (2):0.127 (2). The dihedral angle between the two outer aromatic rings of the 9H-thioxanthene unit, whose thiopyran ring has a screw-boat conformation, is 33.01 (9)°. The diprotonated piperazine ring adopts a chair conformation. In the crystal, intermolecular O—H⋯O, N—H⋯O and C—H⋯O hydrogen bonds between neighboring molecules form zigzag chains along the a axis and contribute to the stabilization of the packing.
In the title compound, C23H27F3N2OS+·2Cl−, the piperazinediium ring adopts a chair conformation. The dihedral angle between the two outer aromatic rings of the 9H-thioxanthene unit is 40.35 (18)°. The F atoms in the trifluoromethyl group are disordered over two sets of sites with occupancies of 0.803 (6) and 0.197 (6). In the crystal, molecules are connected by N—H⋯Cl, O—H⋯Cl C—H⋯O and C—H⋯Cl hydrogen bonds, forming chains propagating along . There are also C—H⋯π interactions present in the crystal structure.
The organic cation of the title salt, C17H12N4O2+·2Cl−·H2O, is nearly planar, the dihedral angle between two pyridine rings being 2.53 (16)° and that between the pyridinum and furan rings being 4.17 (19)°. Molecules are linked via N—H⋯O, N—H⋯Cl and O—H⋯Cl hydrogen bonds, forming a three-dimensional framework and π–π stacking interactions help to stabilize the crystal structure [the imidazole–pyridine and imidazole–benzene centroid–centroid distances are 3.501 (3) and 3.674 (3) Å; respectively].
The crystal structure of the title compound, C7H14NO2
+·Cl−, was reported previously [Chacko, Srinivasan & Zand (1975 ▶). J. Cryst. Mol. Struct.
5, 353–357] from Weissenberg photographic data with R = 0.113. It has now been redetermined, providing a significant increase in the precision of the derived geometric parameters, viz. mean σ(C—C) = 0.003 Å in the present work compared with 0.021 Å for the previous work. The complete cation is generated by crystallographic mirrror symmetry, with three C atoms, two O atoms and the N atom lying on the reflecting plane; the chloride anion also has m site symmetry. The crystal structure is established by a two-dimensional network of O—H⋯Cl and N—H⋯Cl hydrogen bonds, generating C
2(4) and C
2(7) chains, and R
4(8) and R
In the redetermined [for the previous study, see Søtofte (1976 ▶). Acta Chem. Scand. Ser. A, 30, 309–311] crystal structure of the title compound, C2H10N2
2+·2Br−, the H atoms have been located and the hydrogen-bonding scheme is described. The ethane-1,2-diammonium cation lies over a crystallographic inversion centre and straddles a crystallographic mirror plane with the C and N atoms in special positions. In the crystal, the cations and anions are linked by N—H⋯Br and N—H⋯(Br,Br) hydrogen bonds, which generate various ring and chain motifs including an R
In the title compound, (C12H20N2)[ZnCl4]·H2O, the two piperazine N atoms are protonated and the [ZnCl4]2− anions adopt a slightly distorted tetrahedral configuration. In the crystal, O—H⋯Cl hydrogen bonds link the tetrachloridozincate anions and the water molecules into corrugated inorganic chains parallel to . The crystal structure is stabilized by N—H⋯Cl, N—H⋯O and O—H⋯Cl hydrogen bonds, with the N—H hydrogen bond originating from one of the two N atoms being trifurcated.
The previous structure determination [Gillier-Pandraud et al. (1972 ▶). C. R. Acad. Sci. Ser. C, 275, 1495] of the title compound, C8H10O, did not report atomic coordinates. There are two molecules in the asymmetric unit, A and B, which both show approximate non-crystallographic C
s symmetry. The intracyclic C—C—C angles cover the range 118.74 (12)–121.76 (13)°. In the crystal, molecules are linked by O—H⋯O hydrogen bonds, generating  C
2(4) chains such that molecules A and B alternate. There is no aromatic π–π stacking in the crystal as the shortest centroid–centroid distance is greater than 4.74 Å.
In the title salt, C10H10N2
−, the complete 4,4′-bipyridine-1,1′-diium dication is generated by a center of symmetry. In the crystal, N—H⋯N hydrogen bonds are observed between the cations and anions.
The structure of the title compound, C19H28O2, has been redermined at 295 (2) K, with much improved precision. The structure and molecular packing of the title compound was first reported by Coiro et al. [Acta Cryst. (1973). B29, 1404–1409] by means of potential-energy calculations. The cell parameters in this study differ considerably in space group C2. It is a derivative of testosterone and consists of a cyclopentanone ring (A) fused to to successive cyclohexane (B and C) and cyclohexanone (D) rings. The three cyclohexanone rings are in slightly distorted boat configurations and the cyclopentanone ring is a distorted half-chair. The crystal packing is stabilized by weak intermolecular C—H⋯O interactions involving O atoms from each of the cyclohexanone and cyclopentanone rings and H atoms from each of their respective rings.
The crystal structure of the title compound [systematic name: 3,5,7-triaza-1-azoniatricyclo[188.8.131.52,7]decane (E)-3-carboxyprop-2-enoate], C6H13N4
−, had been determined previously by Bowes et al. [Acta Cryst. (2003), B59, 100–117]. Their structure contained an approximately 3:1 ratio of fumarate and succinate monoanions disordered over the same position. The succinate anion component forms a similar structural role to the fumarate anion and came about due to an impurity in the starting material, fumaric acid. In this work, the crystal structure of the pure salt is presented, which is identical, apart from the lack of disorder of the anions, to the previous structure. In the crystal, the ions assemble in the solid state, forming chains via N+—H⋯O− and O—H⋯O− hydrogen bonds, which are linked into a three-dimensional network by C—H⋯O interactions.