rac‐(Z)‐2‐(2‐Thienylmethylene)‐1‐azabicyclo[2.2.2]octan‐3‐ol

The asymmetric unit of the racemic form of the title compound, C₁₂H₁₅NOS, contains four crystallographically independent molecules. The olefinic bond connecting the 2‐thienyl and 1‐azabicyclo[2.2.2]octan‐3‐ol moieties has Z geometry. Strong hydrogen bonding occurs in a directed co‐operative O—H...O—H...O—H...O—H R₄⁴(8) pattern that influences the conformation of the molecules. Co‐operative C—H...π interactions between thienyl rings are also present. The average dihedral angle between adjacent thienyl rings is 87.09 (4)°.     

The diastereoisomers 2‐[(S/R)‐2‐chloro‐3‐quinolyl]‐2‐[(R)‐1‐(4‐methoxyphenyl)ethylamino]acetonitrile at 100 K

In the structures of the two enantiopure diastereoisomers of the title compound, C₂₀H₁₈ClN₃O, which crystallize in different space groups, the molecules are very similar as far as bond distances and angles are concerned, but more substantial differences are observed in some torsion angles. The crystal structures of both molecules can be described as zigzag layers along the c axis. The packing is stabilized by hydrogen‐bond interactions of N—H...O, C—H...Cl and C—H...π types for 2‐[(R)‐2‐chloro‐3‐quinolyl]‐2‐[(R)‐1‐(4‐methoxyphenyl)ethylamino]acetonitrile, and of N—H...N, C—H...O and C—H...π types for 2‐[(S)‐2‐chloro‐3‐quinolyl]‐2‐[(R)‐1‐(4‐methoxyphenyl)ethylamino]acetonitrile, resulting in the formation of two‐ and three‐dimensional networks.     

Two isomorphous azastilbene derivatives: 1‐(2‐chlorobenzyl)‐4‐[(E)‐2‐(4‐hydroxyphenyl)ethenyl]pyridinium chloride and 1‐(2‐bromobenzyl)‐4‐[(E)‐2‐(4‐hydroxyphenyl)ethenyl]pyridinium bromide

The crystal structures of the two title (E)‐stilbazolium halogenates, C₂₀H₁₇ClNO⁺·Cl⁻ and C₂₀H₁₇BrNO⁺·Br⁻, are isomorphous, with an isostructurality index of 0.985. The azastyryl fragments are almost planar, with dihedral angles between the benzene and pyridine rings of ca 4.5°. The rings of the benzyl groups are, in turn, almost perpendicular to the azastyryl planes, with dihedral angles larger than 80°. The cations and anions are connected by O—H...X⁻ (X = halogen) hydrogen bonds. The halide anions are `sandwiched' between the charged pyridinium rings of neighbouring molecules, and weak C—H...O hydrogen bonds and C—H...X and C—H...π interactions also contribute to the crystal structures.     

1‐(Thiophen‐3‐yl)ethanone

The structure of the title compound, C₆H₆OS, exhibits a flip‐type disorder of the thiophene ring [occupancy ratio = 0.848 (3):0.152 (3)], which is typical for many thiophene derivatives. The puckered thiophene ring is essentially coplanar with the plane formed by the non‐H atoms of the acetyl substituent, similar to its simple analogues, i.e. 3‐acetyl‐2‐carboxythiophene, 4‐acetyl‐3‐carboxythiophene and 3,5‐diacetyl‐2‐ethylamino‐4‐methylthiophene. In the crystal structure, molecules are connected by C—H...π hydrogen bonds, forming a sheet parallel to the (001) plane. Moreover, an inspection of the crystal lattice reveals that there are short S...O contacts connecting the molecules of adjacent sheets. Comparison of the title crystal structure with its simple 3‐methoxythiophene analogue shows a close similarity in the herringbone arrangement of molecules and in the presence of C—H...π interactions and S...O contacts.     

6‐(1‐Hydro­xy‐2,2‐di­phenyl­ethyl)‐4,4‐di­phenyl‐2‐cyclo­hexen‐1‐one

The crystal structure of the title compound, C₃₂H₂₈O₂, (I), confirms the erythro stereochemistry of the aldol adduct. In the crystal, (I) forms centrosymmetric O—H?O=C hydrogen‐bonded dimers which in turn are connected by C—H?O and C—H?π interactions.     

3‐(4‐Chloro­benzoyl)‐7‐(N,N‐di­methyl­amino)‐1‐phenyl­indolizine and 3‐(2,4‐di­chloro­benzoyl)‐7‐(N,N‐di­methyl­amino)‐1‐phenyl­indolizine

In both of the title compounds, C₂₃H₁₉ClN₂O, (I), and C₂₃H₁₈Cl₂N₂O, (II), the molecular packing is influenced by weak intermolecular C—H⋯O and C—H⋯π interactions, but despite the chemical similarity of the compounds, the packing in (II) is entirely different from that observed in (I).     

3,5‐Dimethyl‐4‐[(E)‐(2‐nitrophenyl)diazenyl]‐1‐(2,3,4,5,6‐pentafluorophenyl)‐1H‐pyrazole

The title compound, C₁₇H₁₀F₅N₅O₂, is described and compared with its 4‐nitrophenyl isomer [Bustos, Sánchez, Schott, Alvarez‐Thon & Fuentealba (2007). Acta Cryst. E 63 , o1138–o1139]. The title molecule presents its nitro group split into two rotationally disordered components, which in conjunction with the rotation of the `unclamped' rings constitute the main molecular differences. Packing is directed by a head‐to‐tail type `I' C—F...F—C interaction, generating double‐chain strips running along [100]. These substructures are interlinked by a variety of weak F...F, O...F, F...π and O...π interactions.     

(η5‐Cyclopentadienyl)(3‐hydroxy‐3‐methylbut‐1‐ynyl‐κC1)(triphenylphosphine‐κP)nickel(II): novel O—H...π bonding in an organometallic molecule

In the title compound, [Ni(C₅H₅)(C₅H₇O)(C₁₈H₁₅P)], the molecule adopts the expected half‐sandwich structure with no unusual metal–ligand distances. No classical hydrogen bonds are found in the structure; instead, the OH group of the butynol unit is involved in an unusual O—H...π interaction with the C[triple‐bond]C group of an adjacent molecule. The crystal structure is further stabilized by C—H...O and C—H...π interactions, leading to an extensive network of spiral columns.     

Weak intermolecular interactions in isomorphous 5‐(2‐chloroethoxy)‐2,3‐dihydro‐1,4‐benzodioxine and 5‐(2‐bromoethoxy)‐2,3‐dihydro‐1,4‐benzodioxine: bonding or nonbonding interactions

The title compounds, C₁₀H₁₁ClO₃, (I), and C₁₀H₁₁BrO₃, (II), are isomorphous and effectively isostructural; all of the interatomic distances and angles are normal. The structures exhibit long intermolecular C—H...O and C—H...π contacts with attractive energies ranging from 1.17 to 2.30 kJ mol⁻¹. Weak C—H...O hydrogen bonds form C(3) and C(4) motifs, combining to form a two‐dimensional R₃⁴(12) net. No face‐to‐face stacking interactions are observed.     

`Segmented' crystals solved using synchrotron radiation: (2S,3R,4S,5R)‐4‐(10,10‐dimethyl‐3,3‐dioxo‐3λ6‐thia‐4‐azatricyclo[5.2.1.01,5]decan‐4‐ylcarbonyl)‐2,6‐diphenylperhydropyrrolo[3,4‐c]pyrrole‐1,3‐dione

The title compound, C₂₉H₃₁N₃O₅S, forms needle‐shaped `segmented' crystals, thereby inhibiting successful single‐crystal data collection using conventional laboratory facilities. One crystallite of dimensions 0.15 × 0.03 × 0.01 mm yielded sufficent single‐crystal diffraction data on the Australian Synchrotron PX1 beamline. The two independent molecules in the asymmetric unit are nearly superimposable and show only minor conformational deviations from closely related compounds. The molecules pack using one N—H...O hydrogen bond and several phenyl C—H...O(=S), phenyl C—H...O(=C) and methylene C—H...O(=C) hydrogen bonds and weak C—H...π interactions.     

Chiral crystals from an achiral molecule: 4,6‐di‐O‐benzyl‐1,3‐O‐benzylidene‐2‐O‐(4‐methoxybenzyl)‐myo‐5‐inosose

The title achiral compound, C₃₅H₃₄O₇, crystallizes in the chiral monoclinic space group P2₁. The molecules are densely packed to form a helical assembly along the crystallographic twofold screw axis via C—H...O and C—H...π interactions. Interestingly, the unit‐translated helical chains are loosely connected via a rather uncommon edge‐to‐edge Ph—H...H—Ph short contact (H...H = 2.33 Å).     

3‐Methyl‐7‐(2‐thienyl)pyrido[2,3‐d]pyrimidine‐2,4(1H,3H)‐dione: π‐stacked bilayers built from N—H...O,C—H...O and C—H...π hydrogen bonds

In the title compound, C₁₂H₉N₃O₂S, the thienyl substituent is disordered over two sets of sites with occupancies of 0.749 (3) and 0.251 (3). A combination of N—H...O, C—H...O and C—H...π hydrogen bonds links the molecules into bilayers and these bilayers are themselves linked into a continuous structure by π–π stacking interactions.     

Supramolecular structures of 2‐chloro‐5‐methyl­phenol and 4‐chloro‐3‐methyl­phenol (chlorocresol)

The crystal structures of the title compounds (both C₇H₇ClO) are characterized by two independent mol­ecules in each of the asymmetric units and feature O—H...O, C—H...π and π–π interactions. In addition, intermolecular C—H...Cl and intramolecular O—H...Cl interactions are present in 2‐chloro‐5‐methyl­phenol. For each crystal, the non‐covalent interactions emphasize the different spatial environments for the two independent mol­ecules.     

Helical supramolecular assembly of N2,N2′‐bis[3‐(morpholin‐4‐yl)propyl]‐N1,N1′‐(1,2‐phenylene)dioxalamide dimethyl sulfoxide monosolvate

In the title compound, C₂₄H₃₆N₆O₆·C₂H₆OS, the carbonyl groups are in an antiperiplanar conformation, with O=C—C=O torsion angles of 178.59 (15) and −172.08 (16)°. An intramolecular hydrogen‐bonding pattern is depicted by four N—H...O interactions, which form two adjacent S(5)S(5) motifs, and an N—H...N interaction, which forms an S(6) ring motif. Intermolecular N—H...O hydrogen bonding and C—H...O soft interactions allow the formation of a meso‐helix. The title compound is the first example of a helical 1,2‐phenylenedioxalamide. The oxalamide traps one molecule of dimethyl sulfoxide through N—H...O hydrogen bonding. C—H...O soft interactions give rise to the two‐dimensional structure.     

Hydrogen‐bonding patterns in enaminones: (2Z)‐1‐(4‐bromophenyl)‐2‐(pyrrolidin‐2‐ylidene)ethanone and its piperidin‐2‐ylidene and azepan‐2‐ylidene analogues

The title compounds, namely (2Z)‐1‐(4‐bromophenyl)‐2‐(pyrrolidin‐2‐ylidene)ethanone, C₁₂H₁₂BrNO, (I), (2Z)‐1‐(4‐bromophenyl)‐2‐(piperidin‐2‐ylidene)ethanone, C₁₃H₁₄BrNO, (II), and (2Z)‐2‐(azepan‐2‐ylidene)‐1‐(4‐bromophenyl)ethanone, C₁₄H₁₆BrNO, (III), are characterized by bifurcated intra‐ and intermolecular hydrogen bonding between the secondary amine and carbonyl groups. The former establishes a six‐membered hydrogen‐bonded ring, while the latter leads to the formation of centrosymmetric dimers. Weak C—H...Br interactions link the individual molecules into chains that run along the [011], [101] and [101] directions in (I)–(III), respectively. Additional weak Br...O, C—H...π and C—H...O interactions further stabilize the crystal structures.     

1‐(4‐Bromo­phenyl)‐3‐(4‐methyl­phenyl)­prop‐2‐en‐1‐one

In the mol­ecule of the title compound, C₁₆H₁₃BrO, the two benzene rings are rotated in opposite directions with respect to the central C—C=C—C part of the mol­ecule. The phenone O atom deviates from the least‐squares plane of the mol­ecule by 0.300 (3) Å. In the crystal structure, mol­ecules are paired through C—H⋯π interactions. The molecular pairs along [001] are hydrogen bonded through three translation‐related co‐operative hydrogen bonds in the `bay area', forming molecular chains, which are further hydrogen bonded through C—H⋯Br weak interactions, forming (010) molecular layers. In the third direction, there are only weak van der Waals interactions. The co‐operative hydrogen bonds in the `bay area' are discussed briefly.     

C—H⃛O and C—H⃛π interactions in 1‐acetyl‐4‐(p‐chloro­benzyl­idene­amino)‐3‐ethyl‐4,5‐di­hydro‐1H‐1,2,4‐triazol‐5‐one

The title compound, C₁₃H₁₃ClN₄O₂, contains both a phenyl and a triazole ring, both of which are approximately coplanar with the entire mol­ecule. The triazole ring has substituents at the 1‐, 2‐ and 4‐positions. Intramolecular C—H⃛O and C—H⃛N interactions, together with intermolecular C—H⃛O and C—H⃛π interactions, help to stabilize the structure.     

A new polymorph of 1‐ferrocenyl‐3‐(3‐nitroanilino)propan‐1‐one

Recrystallization of the title compound, [Fe(C₅H₅)(C₁₄H₁₃N₂O₃)], from a mixture of n‐hexane and dichloromethane gave the new polymorph, denoted (I), which crystallizes in the same space group (P) as the previously reported structure, denoted (II). The Fe—C distances in (I) range from 2.015 (3) to 2.048 (2) Å and the average value of the C—C bond lengths in the two cyclopentadienyl (Cp) rings is 1.403 (13) Å. As indicated by the smallest C—Cg1—Cg2—C torsion angle of 1.4° (Cg1 and Cg2 are the centroids of the two Cp rings), the orientation of the Cp rings in (I) is more eclipsed than in the case of (II), for which the value was 15.3°. Despite the pronounced conformational similarity between (I) and (II), the formation of self‐complementary N—H...O hydrogen‐bonded dimers represents the only structural motif common to the two polymorphs. In the extended structure, molecules of (I) utilize C—H...O hydrogen bonds and, unlike (II), an extensive set of intermolecular C—H...π interactions. Fingerprint plots based on Hirshfeld surfaces are used to compare the packing of the two polymorphs.     

2‐Ethyl‐6‐methylpyridin‐3‐ol and its salt bis(2‐ethyl‐3‐hydroxy‐6‐methylpyridinium) succinate

The title compounds, C₈H₁₁NO, (I), and 2C₈H₁₂NO⁺·C₄H₄O₄²⁻, (II), both crystallize in the monoclinic space group P2₁/c. In the crystal structure of (I), intermolecular O—H...N hydrogen bonds combine the molecules into polymeric chains extending along the c axis. The chains are linked by C—H...π interactions between the methylene H atoms and the pyridine rings into polymeric layers parallel to the ac plane. In the crystal structure of (II), the succinate anion lies on an inversion centre. Its carboxylate groups interact with the 2‐ethyl‐3‐hydroxy‐6‐methylpyridinium cations via intermolecular N—H...O hydrogen bonds with the pyridine ring H atoms and O—H...O hydrogen bonds with the hydroxy H atoms to form polymeric chains, which extend along the [01] direction and comprise R₄⁴(18) hydrogen‐bonded ring motifs. These chains are linked to form a three‐dimensional network through nonclassical C—H...O hydrogen bonds between the pyridine ring H atoms and the hydroxy‐group O atoms of neighbouring cations. π–π interactions between the pyridine rings and C—H...π interactions between the methylene H atoms of the succinate anion and the pyridine rings are also present in this network.     

Supramolecular structure of racemic 5‐hydroxy‐4‐(4‐methoxyphenyl)‐10‐oxa‐4‐azatricyclo[5.2.1.02,6]dec‐8‐en‐3‐one

The structure of the title compound, C₁₅H₁₅NO₄, comprises a racemic mixture of chiral molecules containing five stereogenic centres. The cyclohexane ring tends towards a boat conformation and the two tetrahydrofuran rings adopt envelope conformations. Molecules are linked into sheets parallel to (100) by a combination of O—H...O, C—H...O and C—H...π hydrogen bonds, leading to a two‐dimensional supramolecular structure.