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.     

Di‐μ‐chlorido‐bis[chlorido(4′‐p‐tolyl‐2,2′:6′,2′′‐terpyridine‐κ3N,N′,N′′)nickel(II)]: a supramolecular system constructed by C—H...Cl interactions

The title complex, [Ni₂Cl₄(C₂₂H₁₇N₃)₂], was synthesized solvothermally. The molecule is a centrosymmetric dimer with the unique Ni^II centre in a distorted octahedral N₃Cl₃ coordination environment. The chloride bridges are highly asymmetric. In the 4′‐p‐tolyl‐2,2′:6′,2′′‐terpyridine ligand, the p‐tolyl group is perfectly coplanar with the attached pyridine ring, and this differs from the situation found in previously reported compounds; however, there are no π–π interactions between the ligands. The terminal Cl atom forms four intermolecular C—H...Cl hydrogen bonds with one methyl and three methine groups. The methyl group also forms intermolecular C—H...π interactions with a pyridine ring. These nonclassical hydrogen bonds extend the molecule into a three‐dimensional network.     

An optically resolved crystal of thiomalate: (S)‐1‐phenylethanaminium (R)‐thiomalate

The asymmetric unit of the optically resolved title salt, C₈H₁₂N⁺·C₄H₅O₄S⁻, contains a 1‐phenylethanaminium monocation and a thiomalate (3‐carboxy‐2‐sulfanylpropanoate) monoanion. The absolute configurations of the cation and the anion are determined to be S and R, respectively. In the crystal, cation–anion N—H...O hydrogen bonds, together with anion–anion O—H...O and S—H...O hydrogen bonds, construct a two‐dimensional supramolecular sheet parallel to the ab plane. The two‐dimensional sheet is linked with the upper and lower sheets through C—H...π interactions to stack along the c axis.     

Inter‐ring and endo anomeric effects,and hydrogen‐bonded supramolecular motifs in two 2,4,6,8‐tetraazabicyclo[3.3.0]octane derivatives

In 2,4,6,8‐tetrakis(4‐chlorophenyl)‐2,4,6,8‐tetraazabicyclo[3.3.0]octane, C₂₈H₂₂Cl₄N₄, the imidazolidine rings adopt envelope conformations, which are favoured by two equal endo anomeric effects. The molecule lies on a crystallographic twofold axis and molecules are linked into a three‐dimensional framework via two C—H...Cl hydrogen bonds. In 2,4,6,8‐tetrakis(4‐methoxyphenyl)‐2,4,6,8‐tetraazabicyclo[3.3.0]octane, C₃₂H₃₄N₄O₄, one of the methyl groups is disordered over two sets of sites and the same methyl group participates in an intermolecular C—H...O hydrogen bond, which in turn causes a considerable deviation from the preferred conformation. There are two unequal inter‐ring anomeric effects in the N—C—N groups. Molecules are linked into corrugated sheets by one C—H...π hydrogen bond and two independent C—H...O hydrogen bonds involving methoxy groups.     

Isomeric 3‐ and 4‐chloro‐N‐[1‐(1H‐pyrrol‐2‐yl)ethylidene]aniline

The title isomers, namely 3‐chloro‐N‐[1‐(1H‐pyrrol‐2‐yl)ethylidene]aniline, (I), and 4‐chloro‐N‐[1‐(1H‐pyrrol‐2‐yl)ethylidene]aniline, (II), both C₁₂H₁₁ClN₂, differ in the position of the chlorine substitution. Both compounds have the basic iminopyrrole structure, which shows a planar backbone with similar features. The dihedral angle formed by the planes of the pyrrole and benzene rings is 75.65 (7)° for (I) and 86.56 (8)° for (II). The H atom bound to the pyrrole N atom is positionally disordered and partial protonation occurs at the imino N atom in (I), while this phenomenon is absent from the structure of (II). Packing interactions for both compounds include intermolecular N—H...N hydrogen bonds and C—H...π interactions, forming centrosymmetric dimers for both (I) and (II).     

Hydrogen‐bonded and π‐interaction assembly in two 8‐alkoxycarbonyl‐1,8‐diazabicyclo[5.4.0]undec‐7‐enium chloride salts

The crystal structures of 8‐phenoxycarbonyl‐1,8‐diazabicyclo[5.4.0]undec‐7‐enium chloride, C₁₆H₂₁N₂O₂⁺·Cl⁻, (I), and 8‐methoxycarbonyl‐1,8‐diazabicyclo[5.4.0]undec‐7‐enium chloride monohydrate, C₁₁H₁₉N₂O₂⁺·Cl⁻·H₂O, (II), recently reported by Carafa, Mesto & Quaranta [Eur. J. Org. Chem. (2011), pp. 2458–2465], are analysed and discussed with a focus on crystal interaction assembly. Both compounds crystallize in the space group P2₁/c. The crystal packings are characterized by dimers linked through π–π stacking interactions and intermolecular nonclassical hydrogen bonds, respectively. Additional intermolecular C—H...Cl interactions [in (I) and (II)] and classical O—H...Cl hydrogen bonds [in (II)] are also evident and contribute to generating three‐dimensional hydrogen‐bonded networks.     

Bis{2‐[(phenylimino)ethyl]‐1H‐pyrrol‐1‐ido‐κ2N,N′}nickel(II): a supramolecular structure formed by C—H...π hydrogen bonds

In the title compound, [Ni(C₁₂H₁₁N₂)₂], the Ni^II cation lies on an inversion centre and has a square‐planar coordination geometry. This transition metal complex is composed of two deprotonated N,N′‐bidentate 2‐[(phenylimino)ethyl]‐1H‐pyrrol‐1‐ide ligands around a central Ni^II cation, with the pyrrolide rings and imine groups lying trans to each other. The Ni—N bond lengths range from 1.894 (3) to 1.939 (2) Å and the bite angle is 83.13 (11)°. The Ni—N(pyrrolide) bond is substantially shorter than the Ni—N(imino) bond. The planes of the phenyl rings make a dihedral angle of 78.79 (9)° with respect to the central NiN₄ plane. The molecules are linked into simple chains by an intermolecular C—H...π interaction involving a phenyl β‐C atom as donor. Intramolecular C—H...π interactions are also present.     

Two novel ferrocenyl dipeptide‐like compounds generated via the Ugi four‐component reaction

The Ugi four‐component reaction, a powerful method for the synthesis of diverse dipeptide‐like derivatives in combinatorial chemistry, was used to synthesize (S)‐1′‐{N‐[1‐(anthracen‐9‐yl)‐2‐(tert‐butylamino)‐2‐oxoethyl]‐N‐(4‐methoxyphenyl)carbamoyl}ferrocene‐1‐carboxylic acid dichloromethane disolvate, [Fe(C₆H₅O₂)(C₃₃H₃₁N₂O₃)]·2CH₂Cl₂, (I), and (S)‐2‐(anthracen‐9‐yl)‐N‐tert‐butyl‐2‐[N‐(4‐methylphenyl)ferrocenylformamido]acetamide, [Fe(C₅H₅)(C₃₃H₃₁N₂O₂)], (II). They adopt broadly similar molecular conformations, with near‐eclipsed cyclopentadienyl rings and near‐perpendicular amide planes in their dipeptide‐like chains, one of which is almost coplanar with its attached cyclopentadienyl ring but perpendicular to the aromatic ring bound to the N atom. In the supramolecular structure of (I), a two‐dimensional network is constructed based on molecular dimers and a combination of intermolecular O—H...O, N—H...O and C—H...O hydrogen bonds, forming R₂²(11), R₂²(16), R₂²(22) and C(9) motifs. These two‐dimensional networks are connected by C—H...O and C—H...Cl contacts to create a three‐dimensional framework, where one dichloromethane solvent molecule acts as a bridge between two neighbouring networks. In the packing of (II), classical hydrogen bonds are absent and an infinite one‐dimensional chain is generated via a combination of C—H...O hydrogen bonds and C—H...π interactions, producing a C(7) motif. This work describes a simple synthesis and the supramolecuar structures of ferrocenyl dipeptide‐like compounds and is significant in the development of redox‐active receptors.     

9,9′‐Biacridine N,N′‐dioxide: a novel potential bridging ligand bearing the bulky acridine N‐oxide skeleton

The title compound, C₂₆H₁₆N₂O₂, is a potential linear bridging O‐donor ligand comprising bulky acridine N‐oxide ring systems. Weak intermolecular C—H...O hydrogen‐bonding interactions link adjacent molecules to form extended chains. The structure also contains intermolecular C—H...π interactions.     

Three‐dimensional networks in bis(imidazolium) 2,2′‐dithiodibenzoate and 4‐methylimidazolium 2‐[(2‐carboxyphenyl)disulfanyl]benzoate

Cocrystallization of imidazole or 4‐methylimidazole with 2,2′‐dithiodibenzoic acid from methanol solution yields the title 2:1 and 1:1 organic salts, 2C₃H₅N₂⁺·C₁₄H₁₀O₄S₂²⁻, (I), and C₄H₇N₂⁺·C₁₄H₁₀O₄S₂⁻, (II), respectively. Compound (I) crystallizes in the monoclinic C2/c space group with the mid‐point of the S—S bond lying on a twofold axis. The component ions in (I) are linked by intermolecular N—H...O hydrogen bonds to form a two‐dimensional network, which is further linked by C—H...O hydrogen bonds into a three‐dimensional network. In contrast, by means of N—H...O, N—H...S and O—H...O hydrogen bonds, the component ions in (II) are linked into a tape and adjacent tapes are further linked by π–π, C—H...O and C—H...π interactions, resulting in a three‐dimensional network.     

4‐Iodoquinoline

Nearly planar molecules of the title compound, C₉H₆IN, are packed in inclined stacks along the short crystallographic b axis and molecules in adjacent stacks are packed to form antiparallel zigzag chains. Short intermolecular N...I contacts [3.131 (3) Å] are observed between molecules in adjacent stacks. A network of C—H...π hydrogen bonds [2.821 (5) and 3.083 (3) Å] between molecules in adjacent stacks is also present. These motif‐generating interactions, including the weak C—H...π interactions, are of relevance in crystal engineering and design.     

An iron(III) complex salt containing pyrazole as both ligand and counter‐ion: bis(1H‐pyrazol‐2‐ium) pentacyanido(1H‐pyrazole‐κN2)ferrate(III)

The title compound, (C₃H₅N₂)₂[Fe(CN)₅(C₃H₄N₂)], is composed of a mononuclear [Fe(CN)₅(pyrazole)]²⁻ dianion and two 1H‐pyrazol‐2‐ium cations. A three‐dimensional supramolecular network is formed through a rich scheme of N—H...N hydrogen bonds and C—H...π interactions among the cations and anions.     

2,12‐Dichloro‐10,20‐diphenyl‐5,7,15,17‐tetrahydro‐6H,16H‐dibenzo[d,l][1,9,2,6,10,14]dioxotetraazacyclohexadecine‐6,16‐dione dioxane solvate as a potential macrocyclic hexadentate ligand

The macrocyclic title compound crystallizes as a dioxane solvate, C₃₀H₂₂Cl₂N₄O₄·C₄H₈O₂, with two independent formula units in the unit cell. The observed syn conformation is controlled by both intramolecular N—H...O hydrogen bonds and intermolecular C—H...π interactions. The relative macrocyclic inner bore is estimated to be 4.19 Å. In the crystal structure, molecules form dimers via intermolecular C—H...π interactions, and these dimers are, in turn, linked to form columns along the a axis by intermolecular C—H...O hydrogen bonds. Both X‐ray diffraction analysis and density functional theory (DFT) calculations reveal that the macrocycle possesses very high flexibility. This property, as well as the presence of six donor atoms accessible for coordination, makes the title macrocycle a very promising ligand for complexation with the majority of transition metals.     

Probing the relationships between molecular conformation and intermolecular contacts in N,N‐dibenzyl‐N′‐(furan‐2‐carbonyl)thiourea

In the crystal structure of the title compound, C₂₀H₁₈N₂O₂S, molecules are linked by bifurcated C—H...O hydrogen‐bond interactions, giving rise to chains whose links are composed of alternating centrosymmetrically disposed pairs of molecules and characterized by R₂²(10) and R₂²(20) hydrogen‐bonding motifs. Also, N—H...S hydrogen bonds form infinite zigzag chains along the [010] direction, which exhibit the C(4) motif. Hirshfeld surface and fingerprint plots were used to explore the intermolecular interactions in the crystal structure. This analysis confirms the important role of C—H...O hydrogen bonds in the molecular conformation and in the crystal structure, providing a potentially useful tool for a full understanding of the intermolecular interactions in acylthiourea derivatives.     

An unusual conformation of gabapentin (Gpn) in Pyr‐Gpn‐NH‐NH‐Pyr stabilized by weak interactions

The crystal structure of N‐[(1‐{2‐oxo‐2‐[2‐(pyrazin‐2‐ylcarbonyl)hydrazin‐1‐yl]ethyl}cyclohexyl)methyl]pyrazine‐2‐carboxamide monohydrate (Pyr‐Gpn‐NN‐NH‐Pyr·H₂O), C₁₉H₂₃N₇O₃·H₂O, reveals an unusual trans–gauche (tg⁻) conformation for the gabapentin (Gpn) residue around the C^γ—C^β (θ₁) and C^β—C^α (θ₂) bonds. The molecular conformation is stabilized by intramolecular N—H...N hydrogen bonds and weak C—H...O interactions. The packing of the molecules in the crystal lattice shows a network of strong N—H...O and O—H...O hydrogen bonds together with weak C—H...O and π–π inteactions.     

[2‐(2‐Pyridyl)‐1H‐benzimidazole‐κ2N2,N3]bis(p‐toluato‐κ2O,O′)manganese(II)

In the title compound, [Mn(C₈H₇O₂)₂(C₁₂H₉N₃)], the manganese(II) centre is surrounded by three bidentate chelating ligands, namely, one 2‐(2‐pyridyl)benzimidazole ligand [Mn—N = 2.1954 (13) and 2.2595 (14) Å] and two p‐toluate ligands [Mn—O = 2.1559 (13)–2.2748 (14) Å]. It displays a severely distorted octahedral geometry, with cis angles ranging from 58.87 (4) to 106.49 (5)°. Intermolecular C—H...O hydrogen bonds between the p‐toluate ligands link the molecules into infinite chains, and every two neighbouring chains are further coupled by N—H...O and C—H...O hydrogen bonds between the 2‐(2‐pyridyl)benzimidazole and p‐toluate ligands, leading to an infinite ribbon‐like double‐chain packing mode. The complete solid‐state structure can be described as a three‐dimensional supramolecular framework, stabilized by these intermolecular hydrogen‐bonding interactions and possible C—H...π interactions, as well as stacking interactions involving the 2‐(2‐pyridyl)benzimidazole ligands.     

Intra‐ and intermolecular Se...X (X = Se,O) interactions in selenium‐containing heterocycles: 3‐benzoylimino‐5‐(morpholin‐4‐yl)‐1,2,4‐diselenazole

In the selenium‐containing heterocyclic title compound {systematic name: N‐[5‐(morpholin‐4‐yl)‐3H‐1,2,4‐diselenazol‐3‐ylidene]benzamide}, C₁₃H₁₃N₃O₂Se₂, the five‐membered 1,2,4‐diselenazole ring and the amide group form a planar unit, but the phenyl ring plane is twisted by 22.12 (19)° relative to this plane. The five consecutive N—C bond lengths are all of similar lengths [1.316 (6)–1.358 (6) Å], indicating substantial delocalization along these bonds. The Se...O distance of 2.302 (3) Å, combined with a longer than usual amide C=O bond of 2.252 (5) Å, suggest a significant interaction between the amide O atom and its adjacent Se atom. An analysis of related structures containing an Se—Se...X unit (X = Se, S, O) shows a strong correlation between the Se—Se bond length and the strength of the Se...X interaction. When X = O, the strength of the Se...O interaction also correlates with the carbonyl C=O bond length. Weak intermolecular Se...Se, Se...O, C—H...O, C—H...π and π–π interactions each serve to link the molecules into ribbons or chains, with the C—H...O motif being a double helix, while the combination of all interactions generates the overall three‐dimensional supramolecular framework.     

Supramolecular interaction patterns in the zinc(II) dichloride and tin(IV) tetrachloride complexes with dipyrido[f,h]quinoxaline‐6,7‐dicarbonitrile

This study characterizes the supramolecular synthons that dominate the intermolecular organization of the title compounds, namely dichloridobis(dipyrido[f,h]quinoxaline‐6,7‐dicarbonitrile)zinc(II), [ZnCl₂(C₁₆H₆N₆)₂], (I), and tetrachlorido(dipyrido[f,h]quinoxaline‐6,7‐dicarbonitrile)tin(IV), [SnCl₄(C₁₆H₆N₆)], (II), in their respective crystal structures. Molecules of (I) are located on 2^b axes of rotational symmetry. Their crystal packing is stabilized mostly by π–π stacking and dipole–dipole attractions between the organic ligand fragments of inversion‐related neighbouring species, as well as by weak intermolecular C—H...N hydrogen bonds. On the other hand, Cl...π and N...π interactions seem to direct the crystal packing in (II), which is unusual in the sense that its aromatic fragments are not involved in π–π stacking. Molecules of (II) are located on m^b planes of mirror symmetry. This study confirms the diverse structural chemistry of this organic ligand, which can be involved in a wide range of supramolecular interactions. These include effective coordination to various metal ions via the phenathroline N‐atom sites, π–π stacking and π...halogen contacts through its extended π‐system, and hydrogen bonding and N...π interactions through its nitrile groups. The competing natures of the latter make it difficult to predict a priori the preferred supramolecular motif that may form in a given structure.     

Two three‐dimensional networks in the binary molecular adducts 4‐methylimidazolium hydrogen terephthalate and bis(4‐methylimidazolium) terephthalate

Both the 1:1 and 2:1 molecular adducts of 4‐methylimidazole (4‐MeIm) and terephthalic acid (H₂TPA) are organic salts, viz. C₄H₇N₂⁺·C₈H₅O₄⁻, (I), and 2C₄H₇N₂⁺·C₈H₄O₄²⁻, (II), respectively. The component ions in (I) are linked by N—H...O and O—H...O hydrogen bonds into continuous two‐dimensional layers built from R₆⁴(32) hydrogen‐bond motifs running parallel to the (100) plane. These adjacent two‐dimensional layers are in turn linked by a combination of C—H...O, C—H...π and π–π interactions into a three‐dimensional network. In the crystal structure of (II), with the anion located on an inversion centre, only N—H...O hydrogen bonds result in two‐dimensional layers built from R₈⁸(42) hydrogen‐bond motifs running parallel to the (102) plane. Being similar to those in (I), these layers are also linked by means of C—H...O, C—H...π and π–π interactions, forming a three‐dimensional network. This study indicates that, on occasion, a change of the reactant concentration can exert a pivotal influence on the construction of supramolecular structures based on hydrogen bonds.     

Similar molecular constitutions but different conformations and different supramolecular assemblies in two related fused tetracyclic benzo[b]pyrimido[5,4‐f]azepine derivatives

A simple and effective two‐step approach to tricyclic pyrimidine‐fused benzazepines has been adapted to give the tetracyclic analogues. In (RS)‐8‐chloro‐6‐methyl‐1,2,6,7‐tetrahydropyrimido[5′,4′:6,7]azepino[3,2,1‐hi]indole, C₁₅H₁₄ClN₃, (I), the five‐membered ring adopts an envelope conformation, as does the reduced pyridine ring in (RS)‐9‐chloro‐7‐methyl‐2,3,7,8‐tetrahydro‐1H‐pyrimido[5′,4′:6,7]azepino[3,2,1‐ij]quinoline, C₁₆H₁₆ClN₃, (II). However, the seven‐membered rings in (I) and (II) adopt very different conformations, with the result that the methyl substituent occupies a quasi‐axial site in (I) but a quasi‐equatorial site in (II). The molecules of (I) are linked by C—H...N hydrogen bonds to form C(5) chains and inversion‐related pairs of chains are linked by a π–π stacking interaction. A combination of a C—H...π hydrogen bond and two C—Cl...π interactions links the molecules of (II) into complex sheets. Comparisons are made with some similar fused heterocyclic compounds.