2,3:4,6‐Di‐O‐isopropylidene‐α‐l‐sorbofuranose and 2,3‐O‐isopropylidene‐α‐l‐sorbofuranose

In the title compounds, C₁₂H₂₀O₆, (I), and C₉H₁₆O₆, (II), the five‐membered furanose ring adopts a ⁴T₃ conformation and the five‐membered 1,3‐dioxolane ring adopts an E₃ conformation. The six‐membered 1,3‐dioxane ring in (I) adopts an almost ideal ^OC₃ conformation. The hydrogen‐bonding patterns for these compounds differ substantially: (I) features just one intramolecular O—H...O hydrogen bond [O...O = 2.933 (3) Å], whereas (II) exhibits, apart from the corresponding intramolecular O—H...O hydrogen bond [O...O = 2.7638 (13) Å], two intermolecular bonds of this type [O...O = 2.7708 (13) and 2.7730 (12) Å]. This study illustrates both the similarity between the conformations of furanose, 1,3‐dioxolane and 1,3‐dioxane rings in analogous isopropylidene‐substituted carbohydrate structures and the only negligible influence of the presence of a 1,3‐dioxane ring on the conformations of furanose and 1,3‐dioxolane rings. In addition, in comparison with reported analogs, replacement of the –CH₂OH group at the C1‐furanose position by another group can considerably affect the conformation of the 1,3‐dioxolane ring.     

Supramolecular structures of 5‐[3‐(4‐methyl­phenyl)‐ and 5‐[3‐(4‐chloro­phenyl)‐2‐propenyl­idene]‐2,2‐di­methyl‐1,3‐dioxane‐4,6‐dione

2,2‐Di­methyl‐5‐[3‐(4‐methyl­phenyl)‐2‐propenyl­idene]‐1,3‐di­ox­ane‐4,6‐dione, C₁₆H₁₆O₄, crystallizes in the triclinic space group , with two mol­ecules in the asymmetric unit. These mol­ecules and a centrosymmetrically related pair, linked together by weak C—H?O hydrogen bonds, form a tetramer. 5‐[3‐(4‐Chloro­phenyl)‐2‐propenyl­idene]‐2,2‐di­methyl‐1,3‐dioxane‐4,6‐dione, C₁₅H₁₃ClO₄, also crystallizes in the triclinic space group , with one mol­ecule in the asymmetric unit. Centrosymmetrically related mol­ecules are linked together by weak C—H?O hydrogen bonds to form dimers which are further linked by yet another pair of centrosymmetrically related C—H?O hydrogen bonds to form a tube which runs parallel to the a axis.     

2‐{[(3‐Fluorophenyl)amino]methylidene}‐3‐oxobutanenitrile and 5‐{[(3‐fluorophenyl)amino]methylidene}‐2,2‐dimethyl‐1,3‐dioxane‐4,6‐dione: X‐ray and DFT studies

In the crystal structures of the title compounds, C₁₁H₉FN₂O, (I), and C₁₃H₁₂FNO₄, (II), the molecules are joined pairwise via different hydrogen bonds and the constituent pairs are crosslinked by weak C—H...O hydrogen bonds. The basic structural motif in (I), which is partially disordered, comprises pairs of molecules arranged in an antiparallel fashion which enables C—H...N[triple‐bond]C interactions. The pairs of molecules are crosslinked by two weak C—H...O hydrogen bonds. The constituent pair in (II) is formed by intramolecular bifurcated C—H...O/O′ and combined inter‐ and intramolecular N—H...O hydrogen bonds. In both structures, F atoms form weak C—F...H—C interactions with the H atoms of the two neighbouring methyl groups, the H...F separations being 2.59/2.80 and 2.63/2.71 Å in (I) and (II), respectively. The bond orders in the molecules, estimated using the natural bond orbitals (NBO) formalism, correlate with the changes in bond lengths. Deviations from the ideal molecular geometry are explained by the concept of non‐equivalent hybrid orbitals. The existence of possible conformers of (I) and (II) is analysed by molecular calculations at the B3LYP/6–31+G** level of theory.     

4‐Ethoxycarbonyl‐3‐hydroxy‐3‐phenylcyclohexanone

The title compound, ethyl 2‐hydroxy‐4‐oxo‐2‐phenyl­cyclo­hexane­carboxyl­ate, C₁₅H₁₈O₄, was obtained by a Michael–Aldol condensation and has the cyclo­hexanone in a chair conformation. The attached hydroxy, ethoxy­carbonyl and phenyl groups are disposed in β‐axial, β‐equatorial and α‐­equatorial configurations, respectively. An intermolecular hydrogen bond, with an O?O distance of 2.874 (2) Å, links the OH group and the ring carbonyl. Weak intermolecular C—H?O=C (ester and ketone), O—H?O=C (ketone) and C—H?OH hydrogen bonds exist.     

Two‐component molecular crystals composed of chloronitrobenzoic acids and 4‐aminopyridine

The crystal structures of the four isomeric organic salts 4‐amino­pyridinium 2‐chloro‐4‐nitro­benzoate, (I), 4‐amino­pyridinium 2‐chloro‐5‐nitro­benzoate, (II), 4‐amino­pyridinium 5‐chloro‐2‐nitro­benzoate, (III), and 4‐amino­pyridinium 4‐chloro‐2‐nitro­benzoate, (IV), all C₅H₇N₂⁺·C₇H₃ClNO₄^?, are presented. Compound (I) has one intramolecular hydrogen bond, one intermolecular C—H?O hydrogen bond and π–π‐stacking interactions. Compound (II) has N—H?O, C—H?O and C—H?Cl hydrogen bonds, and Cl?O—C electrostatic interactions. Compound (III) has N—H?O and C—H?O hydrogen bonds. Compound (IV) has a π–π‐stacking interaction, but no C—H?O hydrogen bonds.     

Cocrystallization of adamantane‐1,3‐dicarboxylic acid and 4,4′‐bipyridine

The cocrystallization of adamantane‐1,3‐dicarboxylic acid (adc) and 4,4′‐bipyridine (4,4′‐bpy) yields a unique 1:1 cocrystal, C₁₂H₁₆O₄·C₁₀H₈N₂, in the C2/c space group, with half of each molecule in the asymmetric unit. The mid‐point of the central C—C bond of the 4,4′‐bpy molecule rests on a center of inversion, while the adc molecule straddles a twofold rotation axis that passes through two of the adamantyl C atoms. The constituents of this cocrystal are joined by hydrogen bonds, the stronger of which are O—H...N hydrogen bonds [O...N = 2.6801 (17) Å] and the weaker of which are C—H...O hydrogen bonds [C...O = 3.367 (2) Å]. Alternate adc and 4,4′‐bpy molecules engage in these hydrogen bonds to form zigzag chains. In turn, these chains are linked through π–π interactions along the c axis to generate two‐dimensional layers. These layers are neatly packed into a stable crystalline three‐dimensional form via weak C—H...O hydrogen bonds [C...O = 3.2744 (19) Å] and van der Waals attractions.     

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, C₁₃H₁₀BrN₃O₃, 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.     

Methyl 4‐[(1‐acetyl‐3‐tert‐butyl‐1H‐pyrazol‐5‐yl)amino]‐3‐nitrobenzoate

In the molecule of the title compound, C₁₇H₂₀N₄O₅, there are two intramolecular N—H...O hydrogen bonds having amidic and nitro‐group O atoms as the acceptors and together forming a three‐centre N—H...(O)₂ system. These interactions appear to play an important role in controlling the relative orientation of the pyrazole and aryl rings. The bond distances provide evidence for some polarization of the electronic structure. Molecules are linked into simple chains by a single C—H...O hydrogen bond.     

2‐Iodo‐N‐(3‐nitrobenzyl)aniline and 3‐iodo‐N‐(3‐nitrobenzyl)aniline exhibit entirely different patterns of supramolecular aggregation

In 2‐iodo‐N‐(3‐nitro­benzyl)­aniline, C₁₃H₁₁IN₂O₂, the mol­ecules are linked into a three‐dimensional structure by a combination of C—H?O hydrogen bonds, iodo–nitro interactions and aromatic π–π‐stacking interactions, but N—H?O and C—H?π(arene) hydrogen bonds are absent. In the isomeric 3‐iodo‐N‐(3‐nitro­benzyl)­aniline, a two‐dimensional array is generated by a combination of N—H?O, C—H?O and C—H?π(arene) hydrogen bonds, but iodo–nitro interactions and aromatic π–π‐stacking interactions are both absent.     

Hydrogen‐bonded sheet structures in methyl 4‐(4‐chloroanilino)‐3‐nitrobenzoate and methyl 1‐benzyl‐2‐(4‐chlorophenyl)‐1H‐benzimidazole‐5‐carboxylate

In methyl 4‐(4‐chloroanilino)‐3‐nitrobenzoate, C₁₄H₁₁ClN₂O₄, (I), there is an intramolecular N—H...O hydrogen bond and the intramolecular distances provide evidence for electronic polarization of the o‐quinonoid type. The molecules are linked into sheets built from N—H...O, C—H...O and C—H...π(arene) hydrogen bonds, together with an aromatic π–π stacking interaction. The molecules of methyl 1‐benzyl‐2‐(4‐chlorophenyl)‐1H‐benzimidazole‐5‐carboxylate, C₂₂H₁₇ClN₂O₂, (II), are also linked into sheets, this time by a combination of C—H...π(arene) hydrogen bonds and aromatic π–π stacking interactions.     

2,3‐Dihydro‐1,3‐benzothiazol‐2‐iminium hydrogen oxydiacetate: a combined structural and theoretical study

In the title compound, C₇H₇N₂S⁺·C₄H₅O₅⁻, the ions are connected by N—H...O hydrogen bonds. The hydrogen oxydiacetate residues are linked together by O—H...O hydrogen bonds disordered about centres of inversion into hydrogen‐bonded ribbon layers crosslinked by weak C—H...O and stacking interactions. The cation exists mainly in the 2,3‐dihydro‐1,3‐benzothiazol‐2‐iminium form, with a small participation of the 2‐aminobenzothiazolium form, based on the structural data and quantum mechanical calculations. This study provides structural insights relevant to the biochemical activity of benzothiazole molecules.     

Ethyl N‐(2‐benzyl­amino‐6‐benzyl­oxy‐5‐nitro­sopyrimidin‐4‐yl)­glycinate: sheets built from a three‐centre N—H⋯(N,O), and two‐centre C—H⋯O and C—H⋯π(arene) hydrogen bonds

In the title compound, C₂₂H₂₃N₅O₄, the mol­ecules are linked into chains by a three‐centre N—H?(N,O) hydrogen bond, reinforced by a two‐centre C—H?O hydrogen bond, and the chains are further linked into sheets by a combination of C—H?O and C—H?π(arene) hydrogen bonds.     

Cocrystals of 1,4‐diethynylbenzene with 1,3‐diacetylbenzene and benzene‐1,4‐dicarbaldehyde exhibiting strong nonconventional alkyne–carbonyl C—H…O hydrogen bonds between the components

Weak interactions between organic molecules are important in solid‐state structures where the sum of the weaker interactions support the overall three‐dimensional crystal structure. The sp‐C—H…N hydrogen‐bonding interaction is strong enough to promote the deliberate cocrystallization of a series of diynes with a series of dipyridines. It is also possible that a similar series of cocrystals could be formed between molecules containing a terminal alkyne and molecules which contain carbonyl O atoms as the potential hydrogen‐bond acceptor. I now report the crystal structure of two cocrystals that support this hypothesis. The 1:1 cocrystal of 1,4‐diethynylbenzene with 1,3‐diacetylbenzene, C₁₀H₆·C₁₀H₁₀O₂, (1), and the 1:1 cocrystal of 1,4‐diethynylbenzene with benzene‐1,4‐dicarbaldehyde, C₁₀H₆·C₈H₆O₂, (2), are presented. In both cocrystals, a strong nonconventional ethynyl–carbonyl sp‐C—H…O hydrogen bond is observed between the components. In cocrystal (1), the C—H…O hydrogen‐bond angle is 171.8 (16)° and the H…O and C…O hydrogen‐bond distances are 2.200 (19) and 3.139 (2) Å, respectively. In cocrystal (2), the C—H…O hydrogen‐bond angle is 172.5 (16)° and the H…O and C…O hydrogen‐bond distances are 2.25 (2) and 3.203 (2) Å, respectively.     

`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.     

(2R*,4S*)‐2‐(Pyridin‐3‐yl)‐2,3,4,5‐tetrahydro‐1H‐1‐benzazepin‐4‐ol: a three‐dimensional framework built from O—H...N,C—H...O and C—H...π(arene) hydrogen bonds

The title compound, C₁₅H₁₆N₂O, crystallizes in the space group P2₁2₁2₁ with Z′ = 1. The seven‐membered ring adopts a chair‐type conformation with the hydroxy and pyridyl substituents in equatorial sites. Molecules are linked into a three‐dimensional framework structure by a combination of O—H...N, C—H...O and C—H...π(arene) hydrogen bonds, but N—H...O and N—H...π(arene) interactions are absent from the structure. Comparisons are made with some related compounds.     

N,N′‐Diethyl‐4‐nitrobenzene‐1,3‐diamine, 2,6‐bis(ethylamino)‐3‐nitrobenzonitrile and bis(4‐ethylamino‐3‐nitrophenyl) sulfone

N,N′‐Diethyl‐4‐nitrobenzene‐1,3‐diamine, C₁₀H₁₅N₃O₂, (I), crystallizes with two independent molecules in the asymmetric unit, both of which are nearly planar. The molecules differ in the conformation of the ethylamine group trans to the nitro group. Both molecules contain intramolecular N—H...O hydrogen bonds between the adjacent amine and nitro groups and are linked into one‐dimensional chains by intermolecular N—H...O hydrogen bonds. The chains are organized in layers parallel to (101) with separations of ca 3.4 Å between adjacent sheets. The packing is quite different from what was observed in isomeric 1,3‐bis(ethylamino)‐2‐nitrobenzene. 2,6‐Bis(ethylamino)‐3‐nitrobenzonitrile, C₁₁H₁₄N₄O₂, (II), differs from (I) only in the presence of the nitrile functionality between the two ethylamine groups. Compound (II) crystallizes with one unique molecule in the asymmetric unit. In contrast with (I), one of the ethylamine groups, which is disordered over two sites with occupancies of 0.75 and 0.25, is positioned so that the methyl group is directed out of the plane of the ring by approximately 85°. This ethylamine group forms an intramolecular N—H...O hydrogen bond with the adjacent nitro group. The packing in (II) is very different from that in (I). Molecules of (II) are linked by both intermolecular amine–nitro N—H...O and amine–nitrile N—H...N hydrogen bonds into a two‐dimensional network in the (10) plane. Alternating molecules are approximately orthogonal to one another, indicating that π–π interactions are not a significant factor in the packing. Bis(4‐ethylamino‐3‐nitrophenyl) sulfone, C₁₆H₁₈N₄O₆S, (III), contains the same ortho nitro/ethylamine pairing as in (I), with the position para to the nitro group occupied by the sulfone instead of a second ethylamine group. Each 4‐ethylamino‐3‐nitrobenzene moiety is nearly planar and contains the typical intramolecular N—H...O hydrogen bond. Due to the tetrahedral geometry about the S atom, the molecules of (III) adopt an overall V shape. There are no intermolecular amine–nitro hydrogen bonds. Rather, each amine H atom has a long (H...O ca 2.8 Å) interaction with one of the sulfone O atoms. Molecules of (III) are thus linked by amine–sulfone N—H...O hydrogen bonds into zigzag double chains running along [001]. Taken together, these structures demonstrate that small changes in the functionalization of ethylamine–nitroarenes cause significant differences in the intermolecular interactions and packing.     

4‐Amino‐3‐methyl‐6‐phenyl‐1,2,4‐triazin‐5(4H)‐one (metamitron) and 4‐amino‐6‐methyl‐3‐phenyl‐1,2,4‐triazin‐5(4H)‐one (isometamitron)

The title structures, both C₁₀H₁₀N₄O, are substitutional isomers. The N—N bond lengths are longer and the C=N bond lengths are shorter by ca 0.025 Å than the respective average values in the C=N—N=C group of asymmetric triazines; the assessed respective bond orders are 1.3 and 1.7. There are N—H⋯O and N—H⋯N hydrogen bonds in both structures, with 4‐­amino‐3‐methyl‐6‐phenyl‐1,2,4‐triazin‐5(4H)‐one containing a rare bifurcated N—H⋯N,N hydrogen bond. The structures differ in their mol­ecular stacking and the hydrogen‐bonding patterns.     

6‐Chloro‐2‐oxindole: X‐ray and DFT‐calculated study

The molecule of the title compound (systematic name: 6‐chloroindolin‐2‐one), C₈H₆ClNO, is almost planar, with a dihedral angle of 1.13 (9)° between the planes of the constituent pyrrolidine and benzene rings. Centrosymmetric dimers are formed in the crystal structure by N—H...O hydrogen bonds, and these dimers are additionally linked by Cl...Cl and C—H...O interactions. Density functional theory (DFT) calculations at the B3LYP/6‐31 G(d,p) level of theory were used to optimize the molecular structure and the geometry was best reproduced by optimization of two interacting molecules. The bond orders in the molecule, estimated using the natural bond orbitals (NBO) formalism, are consistent with the observed bond lengths. In particular, the contribution of the lone pair of electrons on the N atom to the N—C bond in the N—C=O group is revealed. The measured IR spectrum of the compound shows a red shift of the N—H stretching frequency compared with the free molecule, due to the formation of the hydrogen bonds.     

meso‐5,5,7,12,12,14‐Hexamethyl‐1,4‐diaza‐8,11‐diazoniacyclotetradecane bis(2‐naphthoate) ethanol disolvate: centrosymmetric five‐component aggregates linked into sheets by C—H⃛π(arene) hydrogen bonding

The title compound is an ethanol‐solvated salt, C₁₆H₃₈N₄²⁺·2C₁₁H₇O₂⁻·2C₂H₆O, in which the cation lies across a centre of inversion in P2₁/c. The ions are linked by N—H⃛O hydrogen bonds [H⃛O = 1.70 and 2.30 Å, N⃛O = 2.624 (2) and 3.136 (2) Å, and N—H⃛O = 178 and 151°], and the ethanol mol­ecule is linked to the anion by an O—H⃛O hydrogen bond [H⃛O = 1.90 Å, O⃛O = 2.728 (2) Å and O—H⃛O = 171°], to form a centrosymmetric five‐component aggregate. C—H⃛O hydrogen bonds and aromatic π–π‐stacking interactions are absent, but the aggregates are linked into sheets by a single C—H⃛π(arene) hydrogen bond.     

Crystallographic study of self‐organization in the solid state including quasi‐aromatic pseudo‐ring stacking interactions in 1‐benzoyl‐3‐(3,4‐dimethoxyphenyl)thiourea and 1‐benzoyl‐3‐(2‐hydroxypropyl)thiourea

1‐Benzoylthioureas contain both carbonyl and thiocarbonyl functional groups and are of interest for their biological activity, metal coordination ability and involvement in hydrogen‐bond formation. Two novel 1‐benzoylthiourea derivatives, namely 1‐benzoyl‐3‐(3,4‐dimethoxyphenyl)thiourea, C₁₆H₁₆N₂O₃S, (I), and 1‐benzoyl‐3‐(2‐hydroxypropyl)thiourea, C₁₁H₁₄N₂O₂S, (II), have been synthesized and characterized. Compound (I) crystallizes in the space group P , while (II) crystallizes in the space group P 2₁/c . In both structures, intramolecular N—H…O hydrogen bonding is present. The resulting six‐membered pseudo‐rings are quasi‐aromatic and, in each case, interact with phenyl rings via stacking‐type interactions. C—H…O, C—H…S and C—H…π interactions are also present. In (I), there is one molecule in the asymmetric unit. Pairs of molecules are connected via two intermolecular N—H…S hydrogen bonds, forming centrosymmetric dimers. In (II), there are two symmetry‐independent molecules that differ mainly in the relative orientations of the phenyl rings with respect to the thiourea cores. Additional strong hydrogen‐bond donor and acceptor –OH groups participate in the formation of intermolecular N—H…O and O—H…S hydrogen bonds that join molecules into chains extending in the [001] direction.