Weak C—H...N[triple‐bond]C hydrogen bonds in the structures of two poly(cyano)‐substituted ring systems

In benzene‐1,2,3‐tricarbonitrile, C₉H₃N₃, the packing of the two independent molecules is three‐dimensional and complex, involving inter alia bifurcated (C—H)₂...N systems from neighbouring CH groups. In [2.2]paracyclophane‐4,5,12,13‐tetracarbonitrile, C₂₀H₁₂N₄, the [2.2]paracyclophane systems display the usual distortions, namely lengthened C—C bonds and widened sp³ angles in the bridges, narrow angles in the six‐membered rings at the bridgehead atoms, and flattened boat conformations of the rings. The molecules are linked by a series of C—H...N interactions to form layers parallel to the ab plane.     

The effect of Cl...π interactions on the conformations of 4‐chloro‐5‐(2‐phenoxyethoxy)phthalonitrile and 4‐chloro‐5‐[2‐(pentafluorophenoxy)ethoxy]phthalonitrile

4‐Chloro‐5‐(2‐phenoxyethoxy)phthalonitrile, C₁₆H₁₁ClN₂O₂, (I), and 4‐chloro‐5‐[2‐(pentafluorophenoxy)ethoxy]phthalonitrile, C₁₆H₆ClF₅N₂O₂, (II), show different types of electrostatic interaction. In (I), the phenoxy and phthalonitrile (benzene‐1,2‐dicarbonitrile) moieties are well separated in an open conformation and intermolecular C—H...π interactions are observed in the crystal packing. On the other hand, in (II), the pentafluorophenoxy moiety interacts closely with the Cl atom to form a folded conformation containing an intramolecular halogen–π interaction.     

Four N7‐benzyl‐substituted 4,5,6,7‐tetrahydro‐1H‐pyrazolo[3,4‐b]pyridine‐5‐spiro‐1′‐cyclohexane‐2′,6′‐diones as ethanol hemisolvates: similar molecular constitutions but different crystal structures

3‐tert‐Butyl‐7‐(4‐chlorobenzyl)‐4′,4′‐dimethyl‐1‐phenyl‐4,5,6,7‐tetrahydro‐1H‐pyrazolo[3,4‐b]pyridine‐5‐spiro‐1′‐cyclohexane‐2′,6′‐dione ethanol hemisolvate, C₃₀H₃₄ClN₃O₂·0.5C₂H₆O, (I), its 7‐(4‐bromobenzyl)‐ analogue, C₃₀H₃₄BrN₃O₂·0.5C₂H₆O, (II), and its 7‐(4‐methylbenzyl)‐ analogue, C₃₁H₃₇N₃O₂·0.5C₂H₆O, (III), are isomorphous, with the ethanol component disordered across a twofold rotation axis in the space group C2/c. In the corresponding 7‐[4‐(trifluoromethyl)benzyl]‐ compound, C₃₁H₃₄F₃N₃O₂·0.5C₂H₆O, (IV), the ethanol component is disordered across a centre of inversion in the space group P. In each of (I)–(IV), the reduced pyridine ring adopts a half‐chair conformation. The heterocyclic components in (I)–(III) are linked into centrosymmetric dimers by a single C—H...π interaction, with the half‐occupancy ethanol component linked to the dimer by a combination of C—H...O and O—H...π(arene) hydrogen bonds. The heterocyclic molecules in (IV) are linked into chains of centrosymmetric rings by C—H...O and C—H...π hydrogen bonds, again with the half‐occupancy ethanol component pendent from the chain. The significance of this study lies in the isomorphism of the related derivatives (I)–(III), in the stoichiometric hemisolvation by ethanol, where the disordered solvent molecule is linked to the heterocyclic component by a two‐point linkage, and in the differences between the crystal structures of (I)–(III) and that of (IV).     

The `cyclophene' [2.2.2](1,2,4)cyclophan‐9‐ene

In the title compound, C₁₈H₁₆, the [2.2]paracyclophane geometry is restrained to a considerable extent despite the introduction of the extra C=C bridge; typical paracyclophane features, such as the elongated C—C bridges, are still observed. However, the bridgehead atoms of the C=C bridge are forced into unusually close proximity [2.657 (3) Å], which in turn causes the rings to be rotated to an interplanar angle of 13.7 (2)°. The packing involves hexagonally close‐packed layers of molecules parallel to the xy plane, corresponding to the known `7,11' pattern of paracyclophanes, but without significant short intermolecular contacts.     

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.     

Five bicyclo[3.3.0]octa‐2,6‐dienes

A series of five compounds containing the bicyclo[3.3.0]octa‐2,6‐diene skeleton are described, namely tetramethyl cis,cis‐3,7‐dihydroxybicyclo[3.3.0]octa‐2,6‐diene‐2,4‐exo,6,8‐exo‐tetracarboxylate, C₁₆H₁₈O₁₀, (I), tetramethyl cis,cis‐3,7‐dihydroxy‐1,5‐dimethylbicyclo[3.3.0]octa‐2,6‐diene‐2,4‐exo,6,8‐exo‐tetracarboxylate, C₁₈H₂₂O₁₀, (II), tetramethyl cis,cis‐3,7‐dimethoxybicyclo[3.3.0]octa‐2,6‐diene‐2,4‐exo,6,8‐exo‐tetracarboxylate, C₁₈H₂₂O₁₀, (III), tetramethyl cis,cis‐3,7‐dimethoxy‐1,5‐dimethylbicyclo[3.3.0]octa‐2,6‐diene‐2,4‐exo,6,8‐exo‐tetracarboxylate, C₂₀H₂₆O₁₀, (IV), and tetramethyl cis,cis‐3,7‐diacetoxybicyclo[3.3.0]octa‐2,6‐diene‐2,4‐exo,6,8‐exo‐tetracarboxylate, C₂₀H₂₂O₁₂, (V). The bicyclic core is substituted in all cases at positions 2, 4, 6 and 8 with methoxycarbonyl groups and additionally at positions 3 and 7 with hydroxy [in (I) and (II)], methoxy [in (III) and (IV)] or acetoxy [in (V)] groups. The conformations of the methoxycarbonyl groups at positions 2 and 4 are exo for all five compounds. Each C₅ ring of the bicyclic skeleton is almost planar, but the rings are not coplanar, with dihedral angles of 54.93 (7), 69.85 (5), 64.07 (4), 80.74 (5) and 66.91 (7)° for (I)–(V), respectively, and the bicyclooctadiene system adopts a butterfly‐like conformation. Strong intramolecular hydrogen bonds exist between the –OH and C=O groups in (I) and (II), with O...O distances of 2.660 (2) and 2.672 (2) Å in (I), and 2.653 (2) and 2.635 (2) Å in (II). The molecular packing is stabilized by weaker C—H...O(=C) interactions, leading to dimers in (I)–(III) and to a chain structure in (V). The structure series presented in this article shows how the geometry of the cycloocta‐2,6‐diene skeleton changes upon substitution in different positions and, consequently, how the packing is modified, although the intermolecular interactions are basically the same across the series.     

3,3a‐Dihydrocyclo­penta­[b]­chromen‐1(2H)‐ones from the reaction of salicylaldehyde and 2‐cyclo­penten‐1‐one

The two title chromene compounds, 3,3a‐dihydrocyclo­penta­[b]chromen‐1(2H)‐one, C₁₆H₁₂O₂, (I), and 2‐(2‐hydroxy­benzyl­idene)‐3,3a‐dihydrocyclo­penta­[b]chromen‐1(2H)‐one, C₁₉H₁₄O₃, (II), have been determined in the monoclinic space group P2₁/n. Compound (I) is mainly stabilized by C—H⋯π inter­actions. Compound (II) is linked into infinite one‐dimensional chains with a C(3) motif via inter­molecular O—H⋯O hydrogen bonds. The inter­molecular C—H⋯π and π–­π inter­actions also play key roles in stabilizing the crystal packing. Two intra­molecular C—H⋯O hydrogen bonds with S(5) motifs were detected in (II).     

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.     

Two seven‐membered heterocycles with 1,2‐diaza ring N atoms: 3,5,7‐triphenyl‐1,2‐diazacyclohepta‐1(7),2‐diene and 3,7‐bis(2‐hydroxyphenyl)‐5‐phenyl‐1,2‐diazacyclohepta‐1(7),2‐diene

The title compounds, 3,5,7‐triphenyl‐1,2‐diazacyclohepta‐1(7),2‐diene, C₂₃H₂₀N₂, (I), and 3,7‐bis(2‐hydroxyphenyl)‐5‐phenyl‐1,2‐diazacyclohepta‐1(7),2‐diene, C₂₃H₂₀N₂O₂, (II), constitute the first structurally characterized examples of seven‐membered heterocycles with 1,2‐diaza ring N atoms. Compound (I) crystallizes in the space group P, with two independent molecules in the asymmetric unit that differ in the conformation of one of the phenyl rings, while (II) crystallizes in the space group C2/c. The C₅N₂ ring in each of (I) and (II) adopts a twist‐boat conformation. Compound (I) exhibits neither C—H...π interactions nor π–π stacking interactions, whereas (II) shows both intramolecular O—H...N hydrogen bonds and a C—H...π interaction that joins the molecules into an infinite chain in the [010] direction.     

Six closely related 4,6‐disubstituted 2‐amino‐5‐formylpyrimidines: different ring conformations,polarized electronic structures,and hydrogen‐bonded assembly in zero,one, two and three dimensions

In each of ethyl N‐{2‐amino‐5‐formyl‐6‐[methyl(phenyl)amino]pyrimidin‐4‐yl}glycinate, C₁₆H₁₉N₅O₃, (I), N‐{2‐amino‐5‐formyl‐6‐[methyl(phenyl)amino]pyrimidin‐4‐yl}glycinamide, C₁₄H₁₆N₆O₂, (II), and ethyl 3‐amino‐N‐{2‐amino‐5‐formyl‐6‐[methyl(phenyl)amino]pyrimidin‐4‐yl}propionate, C₁₇H₂₁N₅O₃, (III), the pyrimidine ring is effectively planar, but in each of methyl N‐{2‐amino‐6‐[benzyl(methyl)amino]‐5‐formylpyrimidin‐4‐yl}glycinate, C₁₆H₁₉N₅O₃, (IV), ethyl 3‐amino‐N‐{2‐amino‐6‐[benzyl(methyl)amino]‐5‐formylpyrimidin‐4‐yl}propionate, C₁₈H₂₃N₅O₃, (V), and ethyl 3‐amino‐N‐[2‐amino‐5‐formyl‐6‐(piperidin‐4‐yl)pyrimidin‐4‐yl]propionate, C₁₅H₂₃N₅O₃, (VI), the pyrimidine ring is folded into a boat conformation. The bond lengths in each of (I)–(VI) provide evidence for significant polarization of the electronic structure. The molecules of (I) are linked by paired N—H...N hydrogen bonds to form isolated dimeric aggregates, and those of (III) are linked by a combination of N—H...N and N—H...O hydrogen bonds into a chain of edge‐fused rings. In the structure of (IV), molecules are linked into sheets by means of two hydrogen bonds, both of N—H...O type, in the structure of (V) by three hydrogen bonds, two of N—H...N type and one of C—H...O type, and in the structure of (VI) by four hydrogen bonds, all of N—H...O type. Molecules of (II) are linked into a three‐dimensional framework structure by a combination of three N—H...O hydrogen bonds and one C—H...O hydrogen bond.     

Three (E)‐2‐[(bromo­phen­yl)imino­meth­yl]‐4‐methoxy­phenols

The title compounds, (E)‐2‐[(2‐bromo­phenyl)imino­methyl]‐4‐methoxy­phenol, C₁₄H₁₂BrNO₂, (I), (E)‐2‐[(3‐bromo­phenyl)­imino­methyl]‐4‐methoxy­phenol, C₁₄H₁₂BrNO₂, (II), and (E)‐2‐[(4‐bromo­phenyl)imino­methyl]‐4‐methoxy­phenol, C₁₄H₁₂BrNO₂, (III), adopt the phenol–imine tautomeric form. In all three structures, there are strong intra­molecular O—H⋯N hydrogen bonds. Compound (I) has strong inter­molecular hydrogen bonds, while compound (III) has weak inter­molecular hydrogen bonds. In addition to these inter­molecular inter­actions, C—H⋯π inter­actions in (I) and (III), and π–π inter­actions in (I), play roles in the crystal packing. The dihedral angles between the aromatic rings are 15.34 (12), 6.1 (3) and 39.2 (14)° for (I), (II) and (III), respectively.     

Four tri­fluoro­methyl­nitro­benzene analogues

The crystal structures of four tri­fluoro­methyl­nitro­benzene analogues (CF₃)C₆H₃(NO₂)[C₄H₈N₂]R (where C₄H₈N₂ is piperazinyl and R is ethyl carboxyl­ate, CO₂C₂H₅, or phenyl, C₆H₅), have been determined, and their conformations and packing arrangements are compared. The four compounds are ethyl 4‐[4‐nitro‐2‐(tri­fluoro­methyl)­phenyl]­piperazine‐1‐car­boxyl­ate, (I), and ethyl 4‐[2‐nitro‐4‐(tri­fluoro­methyl)­phen­yl]piper­azine‐1‐carboxyl­ate, (II), both C₁₄H₁₆F₃N₃O₄, and 1‐­[4‐nitro‐2‐(tri­fluoro­methyl)­phenyl]‐4‐phenyl­piperazine, (III), and 1‐[2‐nitro‐4‐(tri­fluoro­methyl)­phenyl]‐4‐phenyl­piperazine, (IV), both C₁₇H₁₆F₃N₃O₂. All mol­ecules adopt a rod‐like conformation, while the asymmetric units of (II) and (IV) contain two unique mol­ecules that pack as monodirectional pairs. All mol­ecules pack with C—H⋯O/F close contacts to all but one of the O atoms and to five of the 18 F atoms.     

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.     

A series of substituted (2E)‐3‐(2‐fluoro‐4‐phenoxyphenyl)‐1‐phenylprop‐2‐en‐1‐ones

In the molecular structures of a series of substituted chalcones, namely (2E)‐3‐(2‐fluoro‐4‐phenoxyphenyl)‐1‐phenylprop‐2‐en‐1‐one, C₂₁H₁₅FO₂, (I), (2E)‐3‐(2‐fluoro‐4‐phenoxyphenyl)‐1‐(4‐fluorophenyl)prop‐2‐en‐1‐one, C₂₁H₁₄F₂O₂, (II), (2E)‐1‐(4‐chlorophenyl)‐3‐(2‐fluoro‐4‐phenoxyphenyl)prop‐2‐en‐1‐one, C₂₁H₁₄ClFO₂, (III), (2E)‐3‐(2‐fluoro‐4‐phenoxyphenyl)‐1‐(4‐methylphenyl)prop‐2‐en‐1‐one, C₂₂H₁₇FO₂, (IV), and (2E)‐3‐(2‐fluoro‐4‐phenoxyphenyl)‐1‐(4‐methoxyphenyl)prop‐2‐en‐1‐one, C₂₂H₁₇FO₃, (V), the configuration of the keto group with respect to the olefinic double bond is s‐cis. The molecules pack utilizing weak C—H...O and C—H...π intermolecular contacts. Identical packing motifs involving C—H...O interactions, forming both chains and dimers, along with C—H...π dimers and π–π aromatic interactions are observed in the fluoro, chloro and methyl derivatives.     

Three 2,5‐dialkoxy‐1,4‐diethynylbenzene derivatives

2,5‐Diethoxy‐1,4‐bis[(trimethylsilyl)ethynyl]benzene, C₂₀H₃₀O₂Si₂, (I), constitutes one of the first structurally characterized examples of a family of compounds, viz. the 2,5‐dialkoxy‐1,4‐bis[(trimethylsilyl)ethynyl]benzene derivatives, used in the preparation of oligo(phenyleneethynylene)s via Pd/Cu‐catalysed cross‐coupling. 2,5‐Diethoxy‐1,4‐diethynylbenzene, C₁₄H₁₄O₂, (II), results from protodesilylation of (I). 1,4‐Diethynyl‐2,5‐bis(heptyloxy)benzene, C₂₄H₃₄O₂, (III), is a long alkyloxy chain analogue of (II). The molecules of compounds (I)–(III) are located on sites with crystallographic inversion symmetry. The large substituents either in the alkynyl group or in the benzene ring have a marked effect on the packing and intermolecular interactions of adjacent molecules. All the compounds exhibit weak intermolecular interactions that are only slightly shorter than the sum of the van der Waals radii of the interacting atoms. Compound (I) displays C—H...π interactions between the methylene H atoms and the acetylenic C atom. Compound (II) shows π–π interactions between the acetylenic C atoms, complemented by C—H...π interactions between the methyl H atoms and the acetylenic C atoms. Unlike (I) or (II), compound (III) has weak nonclassical hydrogen‐bond‐type interactions between the acetylenic H atoms and the ether O atoms.     

C—H⋯O,C—H⋯π and π–π inter­actions in three benzofuran‐2‐yl ketone derivatives

The mol­ecules of 2‐benzoyl‐1‐benzofuran, C₁₅H₁₀O₂, (I), inter­act through double C—H⋯O hydrogen bonds, forming dimers that are further linked by C—H⋯O, C—H⋯π and π–π inter­actions, resulting in a three‐dimensional supramolecular network. The dihedral angle between the benzo­yl and benzofuran fragments in (I) is 46.15 (3)°. The mol­ecules of bis­(5‐bromo‐1‐benzofuran‐2‐yl) ketone, C₁₇H₈Br₂O₃, (II), exhibit C₂ symmetry, with the carbon­yl group (C=O) lying along the twofold rotation axis, and are linked by a combination of C—H⋯O and C—H⋯π inter­actions and Br⋯Br contacts to form sheets. The stability of the mol­ecular packing in 3‐mesit­yl‐3‐methyl­cyclo­but­yl 3‐methyl­naphtho[1,2‐b]furan‐2‐yl ketone, C₂₈H₂₈O₂, (III), arises from C—H⋯π and π–π stacking inter­actions. The fused naphthofuran moiety in (III) is essentially planar and makes a dihedral angle of 81.61 (3)° with the mean plane of the trimethyl­benzene ring.     

1,3,5‐Triphenyladamantane and 1,3,5,7‐tetraphenyladamantane

In 1,3,5‐triphenyladamantane, C₂₈H₂₈, (I), and 1,3,5,7‐tetraphenyladamantane, C₃₄H₃₂, (II), the molecules possess symmetries 3 and , and are situated across threefold and fourfold improper axes, respectively. The molecules aggregate by means of extensive C—H...π interactions. In (I), the pyramidal shape of the molecules dictates the formation of dimers through a `sixfold phenyl embrace' pattern. The dimers are linked to six close neighbors and constitute a primitive cubic net [H...π = 2.95 (2) and 3.02 (2) Å]. Compound (II) is isomorphous with tetraphenyl derivatives EPh₄ of group 14 (E = C–Pb) and ionic salts [EPh₄][BPh₄] (E = P, As and Sb). The multiple C—H...π interactions arrange the molecules into chains, with a concerted action of CH (phenyl) and CH₂ (adamantane) groups as donors [H...π = 3.15 (2) and 3.44 (2) Å, respectively]. The additional interactions with the methylene groups (four per molecule) are presumably important for explaining the high melting point and insolubility of (II) compared with the EPh₄ analogs.     

Hydrogen bonding in cyclic imides and amide carboxylic acid derivatives from the facile reaction of cis‐cyclohexane‐1,2‐carboxylic anhydride with o‐ and p‐anisidine and m‐ and p‐aminobenzoic acids

The structures of the open‐chain amide carboxylic acid rac‐cis‐2‐[(2‐methoxyphenyl)carbamoyl]cyclohexane‐1‐carboxylic acid, C₁₅H₁₉NO₄, (I), and the cyclic imides rac‐cis‐2‐(4‐methoxyphenyl)‐3a,4,5,6,7,7a‐hexahydroisoindole‐1,3‐dione, C₁₅H₁₇NO₃, (II), chiral cis‐3‐(1,3‐dioxo‐3a,4,5,6,7,7a‐hexahydroisoindol‐2‐yl)benzoic acid, C₁₅H₁₅NO₄, (III), and rac‐cis‐4‐(1,3‐dioxo‐3a,4,5,6,7,7a‐hexahydroisoindol‐2‐yl)benzoic acid monohydrate, C₁₅H₁₅NO₄·H₂O, (IV), are reported. In the amide acid (I), the phenylcarbamoyl group is essentially planar [maximum deviation from the least‐squares plane = 0.060 (1) Å for the amide O atom] and the molecules form discrete centrosymmetric dimers through intermolecular cyclic carboxy–carboxy O—H...O hydrogen‐bonding interactions [graph‐set notation R₂²(8)]. The cyclic imides (II)–(IV) are conformationally similar, with comparable benzene ring rotations about the imide N—C_ar bond [dihedral angles between the benzene and isoindole rings = 51.55 (7)° in (II), 59.22 (12)° in (III) and 51.99 (14)° in (IV)]. Unlike (II), in which only weak intermolecular C—H...O_imide hydrogen bonding is present, the crystal packing of imides (III) and (IV) shows strong intermolecular carboxylic acid O—H...O hydrogen‐bonding associations. With (III), these involve imide O‐atom acceptors, giving one‐dimensional zigzag chains [graph‐set C(9)], while with the monohydrate (IV), the hydrogen bond involves the partially disordered water molecule which also bridges molecules through both imide and carboxy O‐atom acceptors in a cyclic R₄⁴(12) association, giving a two‐dimensional sheet structure. The structures reported here expand the structural database for compounds of this series formed from the facile reaction of cis‐cyclohexane‐1,2‐dicarboxylic anhydride with substituted anilines, in which there is a much larger incidence of cyclic imides compared to amide carboxylic acids.     

The 1:1 inclusion compounds zolmitriptan–benzene and zolmitriptan–phenol

In the benzene and phenol solvates of (S)‐4‐{3‐[2‐(dimethylamino)ethyl]‐1H‐indol‐5‐ylmethyl}oxazolidin‐2‐one, viz. C₁₆H₂₁N₃O₂·C₆H₆, (I), and C₁₆H₂₁N₃O₂·C₆H₅OH, (II), the host molecule has three linked residues, namely a planar indole ring system, an ethylamine side chain and an oxazolidinone system. It has comparable features to that of sumatriptan, although the side‐chain orientations of (I) and (II) differ from those of sumatriptan. Both (I) and (II) have host–guest‐type structures. The host molecule in (I) and (II) has an L‐shaped form, with the oxazolidinone ring occupying the base and the remainder of the molecule forming the upright section. In (I), each benzene guest molecule is surrounded by four host molecules, and these molecules are linked by a combination of N—H...N, N—H...O and C—H...O hydrogen bonds into chains of edge‐fused R₄⁴(33) rings. In (II), two independent molecules are present in the asymmetric unit, with similar conformations. The heterocyclic components are connected through N—H...N, N—H...O and C—H...O interactions to form chains of edge‐fused R₆⁴(38) rings, from which the phenol guest molecules are pendent, linked by O—H...O hydrogen bonds. The structures are further stabilized by extensive C—H...π interactions.     

Structural comparisons between methylated and unmethylated nitrophenyl lophines

The lophine derivative 2‐(2‐nitrophenyl)‐4,5‐diphenyl‐1H‐imidazole, C₂₁H₁₅N₃O₂, (I), crystallized from ethanol as a solvent‐free crystal and from acetonitrile as the monosolvate, C₂₁H₁₅N₃O₂·C₂H₃N, (II). Crystallization of 2‐(4‐nitrophenyl)‐4,5‐diphenyl‐1H‐imidazole from methanol yielded the methanol monosolvate, C₂₁H₁₅N₃O₂·CH₄O, (III). Three lophine derivatives of methylated imidazole, namely, 1‐methyl‐2‐(2‐nitrophenyl)‐4,5‐diphenyl‐1H‐imidazole methanol solvate, C₂₂H₁₇N₃O₂·CH₄O, (IV), 1‐methyl‐2‐(3‐nitrophenyl)‐4,5‐diphenyl‐1H‐imidazole, C₂₂H₁₇N₃O₂, (V), and 1‐methyl‐2‐(4‐nitrophenyl)‐4,5‐diphenyl‐1H‐imidazole, C₂₂H₁₇N₃O₂, (VI), were recrystallized from methanol, acetonitrile and ethanol, respectively, but only (IV) produced a solvate. Compounds (III) and (IV) each crystallize with two independent molecules in the asymmetric unit. Five imidazole molecules in the six crystals differ in their molecular conformations by rotation of the aromatic rings with respect to the central imidazole ring. In the absence of a methyl group on the imidazole [compounds (I)–(III)], the rotation angles are not strongly affected by the position of the nitro group [44.8 (2) and 45.5 (1)° in (I) and (II), respectively, and 15.7 (2) and 31.5 (1)° in the two molecules of (III)]. However, the rotation angle is strongly affected by the presence of a methyl group on the imidazole [compounds (IV)–(VI)], and the position of the nitro group (ortho, meta or para) on a neighbouring benzene ring; values of the rotation angle range from 26.0 (1) [in (VI)] to 85.2 (1)° [in (IV)]. This group repulsion also affects the outer N—C—N bond angle. The packing of the molecules in (I), (II) and (III) is determined by hydrogen bonding. In (I) and (II), molecules form extended chains through N—H...N hydrogen bonds [with an N...N distance of 2.944 (5) Å in (I) and 2.920 (3) Å in (II)], while in (III) the chain is formed with a methanol solvent molecule as the mediator between two imidazole rings, with O...N distances of 2.788 (4)–2.819 (4) Å. In the absence of the imidazole N—H H‐atom donor, the packing of molecules (IV)–(VI) is determined by weaker intermolecular interactions. The methanol solvent molecule in (IV) is hydrogen bonded to imidazole [O...N = 2.823 (4) Å] but has no effect on the packing of molecules in the unit cell.