Hydrogen bonding in 1,2‐diazine–chloranilic acid (2/1) and 1,4‐diazine–chloranilic acid (2/1) determined at 110 K

The crystal structures of the isomeric title compounds [systematic names: pyridazine–2,5‐dichloro‐3,6‐dihydroxy‐p‐benzoquinone (2/1), (I), and pyrazine–2,5‐dichloro‐3,6‐dihydroxy‐p‐benzoquinone (2/1), (II)], 2C₄H₄N₂·C₆H₂Cl₂O₄, have been redetermined at 110 K. The H atom in the intermolecular O...H...N hydrogen bond in each compound was revealed to be disordered; the relative occupancies at the O and N sites are 0.33 (3) and 0.67 (3), respectively, for (I), and 0.56 (4) and 0.44 (4) for (II). The formal charges of the chloranilic acid in (I) and (II) estimated from the occupancy factors are ca−1.3 and −0.8, respectively. The geometries of the centrosymmetric chloranilic acid molecule in (I) and (II) are compared with the neutral, monoanionic and dianionic forms of chloranilic acid optimized by density functional theory (DFT) at the B3LYP/6–311+G(3df,2p) level. The result implies that the chloranilic acid molecule in (I) is close to the monoanionic state, while that in (II) is between neutral and monoanionic, consistent with the result derived from the H‐atom occupancies.     

Ethyl­ammonium and diethyl­ammonium salts of chloranilic acid

In the crystals of two title salts of chloranilic acid (2,5‐di­chloro‐3,6‐di­hydroxy‐p‐benzo­quinone), namely ethyl­ammonium chloranilate, C₂H₈N⁺·C₆HCl₂O₄^?, (I), and diethyl­ammonium chloranilate, C₄H₁₂N⁺·C₆HCl₂O₄^?, (II), the chloranilate ions are present as a hydrogen‐bonded dimer which has an inversion center. The ethyl­ammonium and diethyl­ammonium ions link the dimers through N—H?O hydrogen bonds, forming a three‐dimensional hydrogen‐bond network in (I) and a one‐dimensional chain in (II).     

Hydrogen‐bonded structures of the 1:1 and 1:2 compounds of chloranilic acid with pyrrolidin‐2‐one and piperidin‐2‐one

In the four compounds of chloranilic acid (2,5‐dichloro‐3,6‐dihydroxycyclohexa‐2,5‐diene‐1,4‐dione) with pyrrolidin‐2‐one and piperidin‐2‐one, namely, chloranilic acid–pyrrolidin‐2‐one (1/1), C₆H₂Cl₂O₄·C₄H₇NO, (I), chloranilic acid–pyrrolidin‐2‐one (1/2), C₆H₂Cl₂O₄·2C₄H₇NO, (II), chloranilic acid–piperidin‐2‐one (1/1), C₆H₂Cl₂O₄·C₅H₉NO, (III), and chloranilic acid–piperidin‐2‐one (1/2), C₆H₂Cl₂O₄·2C₅H₉NO, (IV), the shortest interactions between the two components are O—H...O hydrogen bonds, which act as the primary intermolecular interaction in the crystal structures. In (II), (III) and (IV), the chloranilic acid molecules lie about inversion centres. For (III), this necessitates the presence of two independent acid molecules. In (I), there are two formula units in the asymmetric unit. The O...O distances are 2.4728 (11) and 2.4978 (11) Å in (I), 2.5845 (11) Å in (II), 2.6223 (11) and 2.5909 (10) Å in (III), and 2.4484 (10) Å in (IV). In the hydrogen bond of (IV), the H atom is disordered over two positions with site occupancies of 0.44 (3) and 0.56 (3). This indicates that proton transfer between the acid and base has partly taken place to form ion pairs. In (I) and (II), N—H...O hydrogen bonds, the secondary intermolecular interactions, connect the pyrrolidin‐2‐one molecules into a dimer, while in (III) and (IV) these hydrogen bonds link the acid and base to afford three‐ and two‐dimensional hydrogen‐bonded networks, respectively.     

Synthesis of Tetraoxygenated Terephthalates via a Dichloroquinone Route: Characterization of Cross‐Conjugated Liebermann Betaine Intermediates

Cross‐conjugated quinoid betaines 4 (2,5‐bis(alkoxycarbonyl)‐3,6‐dioxo‐4‐(1‐pyridinium‐1‐yl)cyclohexa‐1,4‐dien‐1‐olates; Liebermann betaines) were synthesized from 2,5‐dichloro‐3,6‐dioxocyclohexa‐1,4‐diene‐1,4‐dicarboxylates ( 2 ) and pyridines in acetone containing H₂O. Their structure was secured by NMR spectroscopy and by X‐ray diffraction analysis of 4f (alkoxy = EtO, pyridine = 4‐Me₂N–C₅H₄N). Betaines 4 show comparatively high reactivity towards nucleophiles as a consequence of their cross‐conjugated character. Betaine 4a and hydroxy‐3,4‐methylenedioxybenzene (sesamol) condense to give a pyridinium quinolate salt 14 which has a bifurcate H‐bond from a pyridinium N⁺–H donor to both carbonyl (C=O) and olate (C–O⁻) acceptors in the solid state. Betaine 4b hydrolyzes in aqueous solution to give diethyl 2,5‐dihydroxy‐3,6‐dioxocyclohexa‐1,4‐diene‐1,4‐dicarboxylate ( 11 ) as a pyridinium salt, or as polymeric zinc(II) complex of the dianion of 11 in the presence of ZnCl₂. Dihydroxyquinone 11 was analytically differentiated from its independently prepared hydroquinone form, diethyl 2,3,5,6‐tetrahydroxyterephthalate ( 12 ), by NMR analysis in solution and X‐ray crystal structure determination of both compounds.     

Hydrogen‐bonded dimers in 3‐amino‐4‐anilino‐1H‐isochromen‐1‐one and a hydrogen‐bonded sheet in 3‐amino‐4‐[methyl(phenyl)amino]‐1H‐isochromen‐1‐one

The molecules of 3‐amino‐4‐anilino‐1H‐isochromen‐1‐one, C₁₅H₁₂N₂O₂, (I), and 3‐amino‐4‐[methyl(phenyl)amino]‐1H‐isochromen‐1‐one, C₁₆H₁₄N₂O₂, (II), adopt very similar conformations, with the substituted amino group PhNR, where R = H in (I) and R = Me in (II), almost orthogonal to the adjacent heterocyclic ring. The molecules of (I) are linked into cyclic centrosymmetric dimers by pairs of N—H...O hydrogen bonds, while those of (II) are linked into complex sheets by a combination of one three‐centre N—H...(O)₂ hydrogen bond, one two‐centre C—H...O hydrogen bond and two C—H...π(arene) hydrogen bonds.     

4‐Aminopyridinium 4‐aminobenzoate dihydrate and 4‐aminopyridinium nicotinate

In the title compounds, 4‐aminopyridinium 4‐aminobenzoate dihydrate, C₇H₆NO₂⁻·C₅H₇N₂⁺·2H₂O, (I), and 4‐aminopyridinium nicotinate, C₅H₇N₂⁺·C₆H₄NO₂⁻, (II), the aromatic N atoms of the 4‐aminopyridinium cations are protonated. In (I), the asymmetric unit is composed of two 4‐aminopyridinium cations, two 4‐aminobenzoate anions and four water molecules, and the compound crystallizes in a noncentrosymmetric space group. The two sets of independent molecules of (I) are related by a centre of symmetry which is not part of the space group. In (I), the protonated pyridinium ring H atoms are involved in bifurcated hydrogen bonding with carboxylate O atoms to form an R₁²(4) ring motif. The water molecules link the ions to form a two‐dimensional network along the (10) plane. In (II), an intramolecular bifurcated hydrogen bond generates an R₁²(4) ring motif and inter‐ion hydrogen bonding generates an R₄²(16) ring motif. The packing of adduct (II) is consolidated via N—H...O and N—H...N hydrogen bonds to form a two‐dimensional network along the (10) plane.     

Two‐dimensional networks in 2‐methylanilinium picrate and 2,5‐dichloroanilinium picrate

Both the title molecular adducts of 2‐methylaniline or 2,5‐dichloroaniline with picric acid are 1:1 organic salts, namely 2‐methylanilinium picrate, C₇H₁₀N⁺·C₆H₂N₃O₇⁻, (I), and 2,5‐dichloroanilinium picrate, C₆H₆Cl₂N⁺·C₆H₂N₃O₇⁻, (II). In both structures, the phenoxide O atoms accept two N—H hydrogen bonds in a bifurcated acceptor fashion, which link the component ions by N—H...O hydrogen bonds into continuous two‐dimensional zigzag layers, running parallel to the (100) plane in (I) and the (010) plane in (II). A π–π interaction is observed between symmetry‐related anilinium cations in (I), while in (II), Cl...O_nitro and Cl...Cl interactions are observed. This study indicates that a substitution on aniline can exert a pivotal influence on the construction of its supramolecular structure.     

A three‐dimensional hydrogen‐bonded framework in 2‐amino‐6‐(N‐methylanilino)pyrimidin‐4(3H)‐one and a ribbon of fused hydrogen‐bonded rings in 2‐amino‐6‐(N‐methylanilino)‐5‐nitropyrimidin‐4(3H)‐one

The molecular dimensions of both 2‐amino‐6‐(N‐methylanilino)pyrimidin‐4(3H)‐one, C₁₁H₁₂N₄O, (I), and 2‐amino‐6‐(N‐methylanilino)‐5‐nitropyrimidin‐4(3H)‐one, C₁₁H₁₁N₅O₃, (II), are consistent with considerable polarization of the molecular–electronic structures. The molecules of (I) are linked into a three‐dimensional framework by a combination of one N—H...N hydrogen bond, two independent N—H...O hydrogen bonds and one C—H...π(arene) hydrogen bond. The molecules of (II) are linked into ribbons containing three types of edge‐fused ring by the combination of two independent three‐centre N—H...(O)₂ hydrogen bonds.     

Five 2‐aryl‐substituted tetrahydro‐1,4‐epoxy‐1‐benzazepines: isolated molecules and hydrogen‐bonded chains and sheets

(2SR,4RS)‐2‐exo‐Phenyl‐2,3,4,5‐tetrahydro‐1H‐1,4‐epoxy‐1‐benzazepine, C₁₆H₁₅NO, (I), (2SR,4RS)‐2‐exo‐(4‐chlorophenyl)‐2,3,4,5‐tetrahydro‐1H‐1,4‐epoxy‐1‐benzazepine, C₁₆H₁₄ClNO, (II), and (2SR,4RS)‐2‐exo‐(3‐methylphenyl)‐2,3,4,5‐tetrahydro‐1H‐1,4‐epoxy‐1‐benzazepine, C₁₇H₁₇NO, (III), all crystallize with Z′ = 2, in the space groups Cc, P2₁/n and P2₁/c, respectively. In each of (II) and (III), the conformations of the two independent molecules are significantly different. The molecules in (I) are linked by C—H...π(arene) hydrogen bonds to form two independent chains, each containing only one type of molecule. The molecules in (II) are linked into sheets by a combination of C—H...O, C—H...(N,O) and C—H...π(arene) hydrogen bonds, all of which link pairs of molecules related by inversion, while in (III), the molecules are linked into sheets by a combination of C—H...N, C—H...O and C—H...π(arene) hydrogen bonds. There are no direction‐specific intermolecular interactions of any kind in the structure of (2SR,4RS)‐7‐bromo‐2‐exo‐phenyl‐2,3,4,5‐tetrahydro‐1H‐1,4‐epoxy‐1‐benzazepine, C₁₆H₁₄BrNO, (IV), but in the structure of (2SR,4RS)‐2‐exo‐(4‐bromophenyl)‐7‐chloro‐2,3,4,5‐tetrahydro‐1H‐1,4‐epoxy‐1‐benzazepine, C₁₆H₁₃BrClNO, (V), a combination of one C—H...N hydrogen bond and one C—H...O hydrogen bond links the molecules into sheets of alternating centrosymmetric R²₂(14) and R⁶₆(22) rings. Comparisons are made with the structures of a number of related compounds.     

An X‐ray crystallographic and density functional theory study of (3Z)‐4‐(5‐ethylsulfonyl‐2‐hydroxyanilino)pent‐3‐en‐2‐one and (3Z)‐4‐(5‐tert‐butyl‐2‐hydroxyanilino)pent‐3‐en‐2‐one

The Schiff base enaminones (3Z)‐4‐(5‐ethylsulfonyl‐2‐hydroxyanilino)pent‐3‐en‐2‐one, C₁₃H₁₇NO₄S, (I), and (3Z)‐4‐(5‐tert‐butyl‐2‐hydroxyanilino)pent‐3‐en‐2‐one, C₁₅H₂₁NO₂, (II), were studied by X‐ray crystallography and density functional theory (DFT). Although the keto tautomer of these compounds is dominant, the O=C—C=C—N bond lengths are consistent with some electron delocalization and partial enol character. Both (I) and (II) are nonplanar, with the amino–phenol group canted relative to the rest of the molecule; the twist about the N(enamine)—C(aryl) bond leads to dihedral angles of 40.5 (2) and −116.7 (1)° for (I) and (II), respectively. Compound (I) has a bifurcated intramolecular hydrogen bond between the N—H group and the flanking carbonyl and hydroxy O atoms, as well as an intermolecular hydrogen bond, leading to an infinite one‐dimensional hydrogen‐bonded chain. Compound (II) has one intramolecular hydrogen bond and one intermolecular C=O...H—O hydrogen bond, and consequently also forms a one‐dimensional hydrogen‐bonded chain. The DFT‐calculated structures [in vacuo, B3LYP/6‐311G(d,p) level] for the keto tautomers compare favourably with the X‐ray crystal structures of (I) and (II), confirming the dominance of the keto tautomer. The simulations indicate that the keto tautomers are 20.55 and 18.86 kJ mol⁻¹ lower in energy than the enol tautomers for (I) and (II), respectively.     

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.     

Three styryl‐substituted tetrahydro‐1,4‐epoxy‐1‐benzazepines: configurations,conformations and hydrogen‐bonded chains

(2SR,4RS)‐7‐Chloro‐2‐exo‐[(E)‐styryl]‐2,3,4,5‐tetrahydro‐1H‐1,4‐epoxy‐1‐benzazepine, C₁₈H₁₆ClNO, (I), crystallizes as a racemic twin in the space group P2₁ and the molecules are linked into a chain of edge‐fused R₃³(9) rings by a combination of C—H...O and C—H...N hydrogen bonds. The diastereoisomer (2RS,4RS)‐7‐chloro‐2‐endo‐[(E)‐styryl]‐2,3,4,5‐tetrahydro‐1H‐1,4‐epoxy‐1‐benzazepine, (II), also crystallizes as a racemic twin, but in the space group P2₁2₁2₁, and a two‐centre C—H...N hydrogen bond and a three‐centre C—H...(O,N) hydrogen bond combine to link the molecules into a complex chain of rings. In (2R,4R)‐7‐fluoro‐2‐endo‐[(E)‐styryl]‐2,3,4,5‐tetrahydro‐1H‐1,4‐epoxy‐1‐benzazepine, C₁₈H₁₆FNO, (III), which is not isomorphous with (II), the molecules are linked by a single C—H...O hydrogen bond into simple chains, but the molecular arrangements in (II) and (III) are nonetheless very similar. The significance of this study lies in its observation of the variations in molecular configuration and conformation, and in the variation in the supramolecular aggregation, consequent upon modest changes in the peripheral substituents.     

Amide hydrogen bonding: control of the molecular and extended structures of two symmetrical pyridine‐2‐carboxamide derivatives

The crystal structures of two symmetrical pyridine‐2‐carboxamides, namely N,N′‐(propane‐1,3‐diyl)bis(pyridine‐2‐carboxamide), C₁₅H₁₆N₄O₂, (I), and N,N′‐(butane‐1,4‐diyl)bis(pyridine‐2‐carboxamide), C₁₆H₁₈N₄O₂, (II), exhibit extended hydrogen‐bonded sequences involving their amide groups. In (I), conventional bifurcated amide–carbonyl (N—H)...O hydrogen bonding favours the formation of one‐dimensional chains, the axes of which run parallel to [001]. Unconventional bifurcated pyridine–carbonyl C—H...O hydrogen bonding links adjacent one‐dimensional chains to form a `porous' three‐dimensional lattice with interconnected, yet unfilled, voids of 60.6 (2) ų which combine into channels that run parallel to, and include, [001]. 4% of the unit‐cell volume of (I) is vacant. Compound (II) adopts a Z‐shaped conformation with inversion symmetry, and exhibits an extended structure comprising one‐dimensional hydrogen‐bonded chains along [100] in which individual molecules are linked by complementary pairs of amide N—H...O hydrogen bonds. These hydrogen‐bonded chains interlock viaπ–π interactions between pyridine rings of neighbouring molecules to form sheets parallel with (010); each sheet is one Z‐shaped molecule thick and separated from the next sheet by the b‐axis dimension [7.2734 (4) Å].     

Hydro­gen‐bonding patterns in two structural isomers of 3,6‐bis(2‐chloro­phenyl)‐1,4‐di­hydro‐1,2,4,5‐tetrazine

Two structural isomers, 3,6‐bis(2‐chloro­phenyl)‐1,4‐di­hydro‐1,2,4,5‐tetrazine, (I), and 3,5‐bis(2‐chloro­phenyl)‐4‐amino‐1H‐1,2,4‐triazole, (II), both C₁₄H₁₀Cl₂N₄, form chain‐like structures in the solid state, stabilized by N—H⋯N and N—H⋯Cl hydrogen bonds. A contribution from weak interactions to the strong hydrogen‐bond network is observed in both structures. The secondary graph sets for intermolecular hydrogen bonds [(11) for (I) and (12) for (II)] indicate the similarity between the networks.     

Three methoxy‐substituted diethyl 4‐­phenyl‐2,6‐di­methyl‐1,4‐di­hydro­pyridine‐3,5‐di­carboxyl­ate compounds

Diethyl 4‐(2,5‐di­methoxy­phenyl)‐2,6‐di­methyl‐1,4‐di­hydro­pyridine‐3,5‐di­carboxyl­ate, C₂₁H₂₇NO₆, (I), diethyl 4‐(3,4‐di­methoxy­phenyl)‐2,6‐di­methyl‐1,4‐di­hydro­pyridine‐3,5‐di­carboxyl­ate, C₂₁H₂₇NO₆, (II), and diethyl 2,6‐di­methyl‐4‐(3,4,5‐tri­methoxy­phenyl)‐1,4‐di­hydro­pyridine‐3,5‐di­carboxyl­ate, C₂₂H₂₉NO₇, (III), crystallize with hydrogen‐bonding networks involving the H atom bonded to the N atom of the 1,4‐di­hydro­pyridine ring and carbonyl O atoms in (I) and (II). Unusually, (III) shows O atoms of methoxy groups serving as hydrogen‐bond acceptors.     

In situ single‐crystal to single‐crystal (SCSC) transformation of the one‐dimensional polymer catena‐poly[[diaqua(sulfato)copper(II)]‐μ2‐glycine] into the two‐dimensional polymer poly[μ2‐glycine‐μ4‐sulfato‐copper(II)]

The one‐dimensional coordination polymer catena‐poly[diaqua(sulfato‐κO)copper(II)]‐μ₂‐glycine‐κ²O:O′], [Cu(SO₄)(C₂H₅NO₂)(H₂O)₂]_n, (I), was synthesized by slow evaporation under vacuum of a saturated aqueous equimolar mixture of copper(II) sulfate and glycine. On heating the same blue crystal of this complex to 435 K in an oven, its aspect changed to a very pale blue and crystal structure analysis indicated that it had transformed into the two‐dimensional coordination polymer poly[(μ₂‐glycine‐κ²O:O′)(μ₄‐sulfato‐κ⁴O:O′:O′′:O′′)copper(II)], [Cu(SO₄)(C₂H₅NO₂)]_n, (II). In (I), the Cu^II cation has a pentacoordinate square‐pyramidal coordination environment. It is coordinated by two water molecules and two O atoms of bridging glycine carboxylate groups in the basal plane, and by a sulfate O atom in the apical position. In complex (II), the Cu^II cation has an octahedral coordination environment. It is coordinated by four sulfate O atoms, one of which bridges two Cu^II cations, and two O atoms of bridging glycine carboxylate groups. In the crystal structure of (I), the one‐dimensional polymers, extending along [001], are linked via N—H...O, O—H...O and bifurcated N—H...O,O hydrogen bonds, forming a three‐dimensional framework. In the crystal structure of (II), the two‐dimensional networks are linked via bifurcated N—H...O,O hydrogen bonds involving the sulfate O atoms, forming a three‐dimensional framework. In the crystal structures of both compounds, there are C—H...O hydrogen bonds present, which reinforce the three‐dimensional frameworks.     

The inner‐salt zwitterion,the dihydrochloride dihydrate and the dimethyl sulfoxide disolvate of 3,6‐bis(pyridin‐2‐yl)pyrazine‐2,5‐dicarboxylic acid

In the inner‐salt zwitterion of 3,6‐bis(pyridin‐2‐yl)pyrazine‐2,5‐dicarboxylic acid, (I), namely 5‐carboxy‐3‐(pyridin‐1‐ium‐2‐yl)‐6‐(pyridin‐2‐yl)pyrazine‐2‐carboxylate, [C₁₆H₁₀N₄O₄, (Ia)], the pyrazine ring has a twist–boat conformation. The opposing pyridine and pyridinium rings are almost perpendicular to one another, with a dihedral angle of 80.24 (18)°, and are inclined to the pyrazine mean plane by 36.83 (17) and 43.74 (17)°, respectively. The carboxy and carboxylate groups are inclined to the mean plane of the pyrazine ring by 43.60 (17) and 45.46 (17)°, respectively. In the crystal structure, the molecules are linked via N—H...O and O—H...O hydrogen bonds, leading to the formation of double‐stranded chains propagating in the [010] direction. On treating (Ia) with aqueous 1 M HCl, the diprotonated dihydrate form 2,2′‐(3,6‐dicarboxypyrazine‐2,5‐diyl)bis(pyridin‐1‐ium) dichloride dihydrate [C₁₆H₁₂N₄O₄²⁺·2Cl⁻·2H₂O, (Ib)] was obtained. The cation lies about an inversion centre. The pyridinium rings and carboxy groups are inclined to the planar pyrazine ring by 55.53 (9) and 19.8 (2)°, respectively. In the crystal structure, the molecules are involved in N—H...Cl, O—H...O_water and O_water—H...Cl hydrogen bonds, leading to the formation of chains propagating in the [010] direction. When (Ia) was recrystallized from dimethyl sulfoxide (DMSO), the DMSO disolvate 3,6‐bis(pyridin‐2‐yl)pyrazine‐2,5‐dicarboxylic acid dimethyl sulfoxide disolvate [C₁₆H₁₀N₄O₄·2C₂H₆OS, (Ic)] of (I) was obtained. Here, the molecule of (I) lies about an inversion centre and the pyridine rings are inclined to the planar pyrazine ring by only 23.59 (12)°. However, the carboxy groups are inclined to the pyrazine ring by 69.0 (3)°. In the crystal structure, the carboxy groups are linked to the DMSO molecules by O—H...O hydrogen bonds. In all three crystal structures, the presence of nonclassical hydrogen bonds gives rise to the formation of three‐dimensional supramolecular architectures.     

Three derivatives of 4‐fluoro‐5‐sulfonylisoquinoline

In 4‐fluoroisoquinoline‐5‐sulfonyl chloride, C₉H₅ClFNO₂S, (I), one of the two sulfonyl O atoms lies approximately on the isoquinoline plane as a result of minimizing the steric repulsion between the chlorosulfonyl group and the neighbouring F atom. In (S)‐(−)‐4‐fluoro‐N‐(1‐hydroxypropan‐2‐yl)isoquinoline‐5‐sulfonamide, C₁₂H₁₃FN₂O₃S, (II), there are two crystallographically independent molecules (Z′ = 2). The molecular conformations of these two molecules differ in that the amine group of one forms an intramolecular bifurcated hydrogen bond with the F and OH groups, whilst the other forms only a single intramolecular N—H...F hydrogen bond. The N—H...F hydrogen bonds correspond to weak coupling between the N(H) and ¹⁹F nuclei, observed in the ¹H NMR solution‐state spectra. In (S)‐(−)‐4‐[(4‐fluoroisoquinolin‐5‐yl)sulfonyl]‐3‐methyl‐1,4‐diazepan‐1‐ium chloride, C₁₅H₁₉FN₃O₂S⁺·Cl⁻, (III), the isoquinoline plane is slightly deformed, suggestive of a steric effect induced by the bulky substituent on the sulfonyl group.     

Two succinic acid derivatives of 2‐ethyl‐6‐methylpyridin‐3‐ol

Crystals of bis(2‐ethyl‐3‐hydroxy‐6‐methylpyridinium) succinate–succinic acid (1/1), C₈H₁₂NO⁺·0.5C₄H₄O₄²⁻·0.5C₄H₆O₄, (I), and 2‐ethyl‐3‐hydroxy‐6‐methylpyridinium hydrogen succinate, C₈H₁₂NO⁺·C₄H₅O₄⁻, (II), were obtained by reaction of 2‐ethyl‐6‐methylpyridin‐3‐ol with succinic acid. The succinate anion and succinic acid molecule in (I) are located about centres of inversion. Intermolecular O—H...O, N—H...O and C—H...O hydrogen bonds are responsible for the formation of a three‐dimensional network in the crystal structure of (I) and a two‐dimensional network in the crystal structure of (II). Both structures are additionally stabilized by π–π interactions between symmetry‐related pyridine rings, forming a rod‐like cationic arrangement for (I) and cationic dimers for (II).     

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.