Crystal structure of (E)-4-hy-droxy-N'-(3-hy-droxy-benzyl-idene)benzohydrazide monohydrate.

In the title benzohydrazide hydrate, C14H12N2O3·H2O, the dihedral angle between the aromatic rings is 58.11 (6)° and the C=O and N-H groups adopt an anti orientation. The main twist in the mol-ecule occurs about the C(=O)-Car (ar = aromatic) bond, with an N-C(=O)-Car-Car torsion angle of -43.5 (2)°. In the crystal, the components are linked by N-H⋯O, O-H⋯N and O-H⋯O hydrogen bonds. These inter-actions generate [10-1] chains, with adjacent organic mol-ecules linked by inversion symmetry generating either pairs of N-H⋯O links [R 2 (2)(16) loops] or pairs of O-H⋯O links [R 2 (2)(20) loops]. Pairs of water mol-ecules are located in the R 2 (2)(20) loops and form their own O-H⋯O and O-H⋯N hydrogen bonds to adjacent organic mol-ecules in the chain. Finally, an inter-chain O-H⋯O hydrogen-bond link from the 4-hy-droxy group generates (010) sheets.

Contrasting the supramolecular structures in the isomeric pair 5-bromo-3-nitrosalicylaldehyde phenylhydrazone and 3-bromo-5-nitrosalicylaldehyde phenylhydrazone.

Isomeric 5-bromo-3-nitrosalicylaldehyde phenylhydrazone and 3-bromo-5-nitrosalicylaldehyde phenylhydrazone, C(13)H(10)BrN(3)O(3), both crystallize with two molecules in the asymmetric unit. In both isomers, an intramolecular O-H···N hydrogen bond links the hydroxy group and the imine N atom. In the 5-bromo-3-nitro isomer, there are two independent N-H···O hydrogen-bonded chains, each molecule in the asymmetric unit forming its own chain. These chains are then linked to form a three-dimensional framework by a combination of weak C-H···O, C-H···Br, C-H···π and π-π stacking interactions. In the 3-bromo-5-nitro isomer, N-H···O hydrogen bonds link the independent molecules alternately into a zigzag chain, which is reinforced by a weak C-H···O interaction. Individual chains are linked by a C-H···Br interaction and a three-dimensional framework is generated by π-π stacking interactions.

Two polymorphs of N-(2-methoxyphenyl)-4-oxo-4H-chromone-3-carboxamide.

The title compound, C17H13NO4, crystallizes in two polymorphic forms, each with two molecules in the asymmetric unit and in the monoclinic space group P21/c. All of the molecules have intramolecular hydrogen bonds involving the amide group. The amide N atoms act as donors to the carbonyl group of the pyrone and also to the methoxy group of the benzene ring. The carbonyl O atom of the amide group acts as an acceptor of the ß and ß' C atoms belonging to the aromatic rings. These intramolecular hydrogen bonds have a profound effect on the molecular conformation. In one polymorph, the molecules in the asymmetric unit are linked to form dimers by weak C-H∙∙∙O interactions. In the other, the molecules in the asymmetric unit are linked by a single weak C-H∙∙∙O hydrogen bond. Two of these units are linked to form centrosymmetric tetramers by a second weak C-H∙∙∙O interaction. Further interactions of this type link the molecules into chains, so forming a three-dimensional network. These interactions in both polymorphs are supplemented by π-π interactions between the chromone rings and between the chromone and methoxyphenyl rings.

4-Oxo-N-phenyl-4H-chromene-2-carboxamide and of a new polymorph of 7-methoxy-4-oxo-N-p-tolyl-4H-chromene-2-carboxamide and its hemihydrate.

4-Oxo-N-phenyl-4H-chromene-2-carboxamide, C16H11NO3, crystallizes in the space group P2(1)/n and its derivative 7-methoxy-4-oxo-N-p-tolyl-4H-chromene-2-carboxamide, C18H15NO4, forms two polymorphs which crystallize in the space groups P2(1)/c and P1. The structures have an anti-rotamer conformation about the C-N bond; however, the amide O atom can be either trans- or cis-related to the O atom of the pyran ring. The latter compound also crystallizes as a hemihydrate, C18H15NO4·0.5H2O, in the space group C2/c. This compound has a similar structure to that of the unsolvated compound.

Three 2-(methysulfanyl)nicotinamides.

The molecular conformations of three N-alkyl-2-(methylsulfanyl)nicotinamide derivatives, namely N-cyclohexyl-2-(methylsulfanyl)nicotinamide, C13H18N2OS, (I), N-isopropyl-2-(methylsulfanyl)nicotinamide, C10H14N2OS, (II), in which there are two molecules in the asymmetric unit which were chosen to form a hydrogen-bonded pair, and N-(2-hydroxyethyl)-2-(methylsulfanyl)nicotinamide dihydrate, C9H12N2O2S·2H2O, (III), are compared with those of four unsubstituted N-alkylnicotinamide compounds. The substituted compounds show a higher degree of torsion of the pyridine ring with respect to the amide group than do the unsubstituted compounds, with dihedral angles in the range 40-60° for the former and 20-35° for the latter. In (I) and (II), the supramolecular structure is defined by amide-N to carbonyl-O chains. In (III), the nicotinamide molecules are linked by hydrogen bonds to two water molecules resulting in two linked chains of rings which form the three-dimensional network.

Substituted 4-alkoxy-7-Cl-quinolines exhibiting π-π stacking.

The molecules of 4-allyloxy-7-chloroquinoline, C(12)H(10)ClNO, (I), 7-chloro-4-methoxyquinoline, C(10)H(8)ClNO, (II), and 7-chloro-4-ethoxyquinoline, C(11)H(10)ClNO, (III), are all planar. In all three structures, π-π interactions between the quinoline ring systems are generated by unit-cell translations along the a axes, irrespective of space group. These structures are the first reported for 4-alkoxyquinolines.

Five N'-benzylidene-N-methylpyrazine-2-carbohydrazides.

The compounds N'-benzylidene-N-methylpyrazine-2-carbohydrazide, C13H12N4O, (IIa), N'-(2-methoxybenzylidene)-N-methylpyrazine-2-carbohydrazide, C14H14N4O2, (IIb), N'-(4-cyanobenzylidene)-N-methylpyrazine-2-carbohydrazide dihydrate, C14H11N5O·2H2O, (IIc), N-methyl-N'-(2-nitrobenzylidene)pyrazine-2-carbohydrazide, C13H11N5O3, (IId), and N-methyl-N'-(4-nitrobenzylidene)pyrazine-2-carbohydrazide, C13H11N5O3, (IIe), have dihedral angles between the pyrazine rings and the benzene rings in the range 55-78°. These methylated pyrazine-2-carbohydrazides have supramolecular structures which are formed by weak C-H···O/N hydrogen bonds, with the exception of (IIc) which is hydrated. There are π-π stacking interactions in all five compounds. Three of these structures are compared with their nonmethylated counterparts, which have dihedral angles between the pyrazine rings and the benzene rings in the range 0-6°.

Comparison of the structure of (E)-2-(2-benzylidenehydrazinylidene)quinoxaline with those of its chloro- and bromobenzylidene analogues.

(E)-2-(2-Benzylidenehydrazinylidene)quinoxaline, C15H12N4, crystallized with two molecules in the asymmetric unit. The structures of six halogen derivatives of this compound were also investigated: (E)-2-[2-(2-chlorobenzylidene)hydrazinylidene]quinoxaline, C15H11ClN4; (E)-2-[2-(3-chlorobenzylidene)hydrazinylidene]quinoxaline, C15H11ClN4; (E)-2-[2-(4-chlorobenzylidene)hydrazinylidene]quinoxaline, C15H11ClN4; (E)-2-[2-(2-bromobenzylidene)hydrazinylidene]quinoxaline, C15H11BrN4; (E)-2-[2-(3-bromobenzylidene)hydrazinylidene]quinoxaline, C15H11BrN4; (E)-2-[2-(4-bromobenzylidene)hydrazinylidene]quinoxaline, C15H11BrN4. The 3-Cl and 3-Br compounds are isomorphous, as are the 4-Cl and 4-Br compounds. In all of these compounds, it was found that the supramolecular structures are governed by similar predominant patterns, viz. strong intermolecular N-H...N(pyrazine) hydrogen bonds supplemented by weak C-H∙∙∙N(pyrazine) hydrogen-bond interactions in the 2- and 3-halo compounds and by C-H∙∙∙Cl/Br interactions in the 4-halo compounds. In all compounds, there are π-π stacking interactions.

A low-temperature polymorph of m-quinquephenyl.

A low-temperature polymorph of 1,1':3',1'':3'',1''':3''',1''''-quinquephenyl (m-quinquephenyl), C(30)H(22), crystallizes in the space group P2(1)/c with two molecules in the asymmetric unit. The crystal is a three-component nonmerohedral twin. A previously reported room-temperature polymorph [Rabideau, Sygula, Dhar & Fronczek (1993). Chem. Commun. pp. 1795-1797] also crystallizes with two molecules in the asymmetric unit in the space group P-1. The unit-cell volume for the low-temperature polymorph is 4120.5 (4) Å(3), almost twice that of the room-temperature polymorph which is 2102.3 (6) Å(3). The molecules in both structures adopt a U-shaped conformation with similar geometric parameters. The structural packing is similar in both compounds, with the molecules lying in layers which stack perpendicular to the longest unit-cell axis. The molecules pack alternately in the layers and in the stacked columns. In both polymorphs, the only interactions between the molecules which can stabilize the packing are very weak C-H...π interactions.

1,3-Bis(propan-2-yl)naphthalene.

In the title compound, C(16)H(20), one of the isopropyl groups shows almost equal displacements [1.252 (1) and -1.270 (1) Å] of its methyl-C atoms from the mean plane of the naphthalene ring system, while the other shows asymmetric displacements [1.586 (2) and -0.315 (1) Å]. In the crystal, the mol-ecules are linked into sheets lying in the ab plane by three C-H⋯π contacts, two involving donors belonging to the isopropyl groups and the third a donor atom from the naphthalene ring system. The different orientations of the isopropyl groups might be attributed to the fact that the C-H⋯π inter-action involving one of them is enhanced by the C-H⋯π inter-action involving the aromatic ring.

2,4,5-Tris(biphenyl-2-yl)-1-bromo-benzene.

In the title compound, C(42)H(29)Br, the dihedral angles between the central benzene ring and the three attached benzene rings are very similar, lying in the range 52.65 (6)-57.20 (7)°. Of the dihedral angles between the rings of the o-biphenyl substituents, two are similar [46.34 (7) and 47.35 (7)°], while the other differs significantly [64.17 (7)°]. In the crystal, mol-ecules are linked into centrosymmetric dimers by two weak C-H⋯π inter-actions.

A second monoclinic polymorph of N-(diethyl-amino-thio-carbon-yl)-N'-phenyl-benzamidine.

The asymmetric unit of the title compound, C(18)H(21)N(3)S, contains five mol-ecules. The equivalent bond distances in the five mol-ecules are in excellent agreement, the r.m.s. fit being within 0.007 Å. The five mol-ecules are linked into a chain consisting of alternating pseudo-enanti-omers by N-H⋯S hydrogen bonds supplemented by weak C-H⋯π inter-actions. The action of a glide plane links the asymmetric unit into an extended chain. A polymorph of the title compound with one mol-ecule in the asymmetric unit was reported by Braun et al. [Cryst. Res. Technol. (1988), 23, 35-39].

1,3-Diphenyl-propan-2-one (2,4-dinitro-phen-yl)hydrazone.

In the title compound, C(21)H(18)N(4)O(4), there is an intra-molecular N-H⋯O hydrogen bond between the amino H atom and an O atom of the 2-nitro group of the adjacent benzene ring. The central benzene ring forms dihedral angles of 79.98 (7) and 82.88 (7)° with the two phenyl rings. In the crystal structure, mol-ecules are linked into a three-dimensional network by weak C-H⋯N, C-H⋯O and C-H⋯π inter-actions.

N'-Benzoyl-N,N-diethyl-thio-urea: a monoclinic polymorph.

In the crystal of the title compound, C(12)H(16)N(2)OS, inversion dimers linked by pairs of N-H⋯S hydrogen bonds occur, generating R(2) (2)(8) loops. The mol-ecules are also linked by weak C-H⋯O hydrogen bonds. The structure is isostructural with that of N'-benzoyl-N,N-diethyl-seleno-urea [Bruce et al. (2007 ▶). New J. Chem.31, 1647-1653].

3,3'-Bithio-phene.

The title compound, C(8)H(6)S(2), is disordered [occupancy ratio = 0.839 (2):0.161 (2)] and sits across a centre of symmetry. In the crystal, the mol-ecules are linked by a weak C-H⋯π inter-action.

4-(1-Naphth-yl)benzonitrile.

The title compound, C(17)H(11)N, crystallizes with two mol-ecules in the asymmetric unit which are linked by a weak C-H⋯N hydrogen bond. The dihedral angles between the benzene ring and the naphthalene ring system in the two mol-ecules are 60.28 (3) and 60.79 (3)°. In the crystal, mol-ecules are linked into a three-dimensional network by weak C-H⋯π inter-actions.

4,4'-(1,8-Naphthalene-1,8-di-yl)dibenzonitrile.

In the title mol-ecule, C(24)H(14)N(2), the exterior C-C-C angle of the naphthalene ring system involving the two phenyl-substituted C atoms is 126.06 (11)° and the dihedral angles between the mean plane of the naphthalene ring system and those of the benzene rings are 66.63 (5) and 67.89 (5)°. In the crystal, mol-ecules are linked into a ladders by four weak C-H⋯π inter-actions.

The synthesis, crystal structure and Hirshfeld analysis of 4-(3,4-di-methyl-anilino)-N-(3,4-di-methyl-phen-yl)quinoline-3-carboxamide.

The structure of the title quinoline carboxamide derivative, C26H25N3O, is described. The quinoline moiety is not planar as a result of a slight puckering of the pyridine ring. The secondary amine has a slightly pyramidal geometry, certainly not planar. Both intra- and inter-molecular hydrogen bonds are present. Hirshfeld surface analysis and lattice energies were used to investigate the inter-molecular inter-actions.

4-(1-Naphth-yl)benzoic acid.

In the title mol-ecule, C(17)H(12)O(2), the dihedral angle between the mean plane of the benzene ring and that of the naphthalene ring system is 49.09 (6)°. In the crystal structure, mol-ecules are linked to form centrosymmetric dimers via inter-molecular O-H⋯O hydrogen bonds. The hydr-oxy H atom is disordered over two sites with refined occupancies of 0.62 (3) and 0.38 (3).

(E)-1-Phenyl-butan-2-one (2,4-dinitro-phen-yl)hydrazone.

In the title compound, C(16)H(16)N(4)O(4), the dihedral angle between the aromatic rings is 79.04 (8)° and an intra-molecular N-H⋯O hydrogen bond occurs. In the crystal, weak C-H.·O and C-H..π inter-actions link the mol-ecules, forming sheets.