A new polymorph of bis(2‐aminopyridinium) fumarate–fumaric acid (1/1) from powder X‐ray diffraction

A new polymorph of bis(2‐aminopyridinium) fumarate–fumaric acid (1/1), 2C₅H₇N₂⁺·C₄H₂O₄²⁻·C₄H₄O₄, was obtained and its crystal structure determined by powder X‐ray diffraction. The new polymorph (form II) crystallizes in the triclinic system (space group P), while the previous reported polymorph [form I; Ballabh, Trivedi, Dastidar & Suresh (2002). CrystEngComm, 4 , 135–142; Büyükgüngör, Odabaşoğlu, Albayrak & Lönnecke (2004). Acta Cryst. C 60 , o470–o472] is monoclinic (space group P2₁/c). In both forms I and II, the asymmetric unit consists of one 2‐aminopyridinium cation, half a fumaric acid molecule and half a fumarate dianion. The fumarate dianion is involved in hydrogen bonding with two neighbouring 2‐aminopyridinium cations to form a hydrogen‐bonded trimer in both forms. In form II, the hydrogen‐bonded trimers are interlinked across centres of inversion via pairs of N—H...O hydrogen bonds, whereas such trimers are joined via single N—H...O hydrogen bonds in form I, leading to different packing modes for forms I and II. The results demonstrate the relevance and application of the powder diffraction method in the study of polymorphism of organic molecular materials.     

2‐Amino­pyridinium–fumarate–fumaric acid (2/1/1)

The title complex, 2C₅H₇N₂⁺·C₄H₂O₄²⁻·C₄H₄O₄, contains cyclic eight‐membered hydrogen‐bonded rings involving 2‐­aminopyridinium and fumarate ions. The fumaric acid mol­ecules and fumarate ions lie on inversion centers and are linked into zigzag chains by O—H⋯O hydrogen bonds. The dihedral angle between the pyridinium ring and the hydrogen‐bonded fumarate ion is 7.60 (4)°. The fumarate anion is linked to the pyridinium cations by intermolecular N—H⋯O hydrogen bonds. The heterocycle is fully protonated, thus enabling amine–imine tautomerization.     

Tris[(1‐methylimidazol‐2‐yl)methyl]amine–boric acid (1/1)

Cocrystallization of a poly­imidazole compound with boric acid results in the formation of the title compound, C₁₅H₂₁N₇·B(OH)₃, which has an extensive hydrogen‐bonding network. The O?N(im) separations (im is imidazole) range from 2.6991 (15) to 2.7914 (14) Å, with O—H?N angles ranging from 170.6 (18) to 175 (2)°. In addition, symmetry‐related boric acid mol­ecules form intermolecular hydrogen bonds, with an O?O distance of 2.7582 (14) Å, and symmetry‐related imidazole groups form π–π stacks, with a centroid‐to‐centroid separation of 3.533 Å.     

Hydrogen‐bonded one‐dimensional networks in 1:1 complexes of N,N′‐bis(2‐pyridyl)aryldiamines with anilic acid

The 1:1 complexes N,N′‐bis(2‐pyridyl)­benzene‐1,4‐di­amine–anilic acid (2,5‐di­hydroxy‐1,4‐benzo­quinone) (1/1), C₁₆H₁₄N₄·C₆H₄O₄, (I), and N,N′‐bis(2‐pyridyl)­bi­phenyl‐4,4′‐di­amine–anilic acid (1/1), C₂₂H₁₈N₄·C₆H₄O₄, (II), have been prepared and their solid‐state structures investigated. The component mol­ecules of these complexes are connected via conventional N—H?O and O—H?N hydrogen bonds, leading to the formation of an infinite one‐dimensional network generated by the cyclic motif R(9). The anilic acid molecules in both crystal structures lie around inversion centres and the observed bond lengths are typical for the neutral mol­ecule. Nevertheless, the pyridine C—N—C angles [120.9 (2) and 120.13 (17)° for complexes (I) and (II), respectively] point to a partial H‐atom transfer from anilic aicd to the bispyridyl­amine, and hence to H‐atom disorder in the OHN bridge. The bispyridyl­amine mol­ecules of (I) and (II) also lie around inversion centres and exhibit disorder of their central phenyl rings over two positions.     

Hydrogen‐bonded 1,2‐bis(4‐pyridyl)ethylene and maleic acid

The title compound (systematic name: 4,4′‐ethyl­ene­dipyridinium dimaleate), C₁₂H₁₂N₂²⁺·2C₄H₃O₄^?, is a 1:2 adduct of 1,2‐bis(4‐pyridyl)­ethyl­ene (BPE) and maleic acid (MA). The interaction between the two components in the molecular complex is due to intermolecular hydrogen bonding via an N⁺—H?O^? hydrogen bond.     

Hydrogen‐bonded zigzag chains in 2,2′‐dithiodibenzoic acid–1,3‐di‐4‐pyridylpropane (1/1)

The title 1:1 cocrystal, C₁₄H₁₀O₄S₂·C₁₃H₁₄N₂ or H₂L·bpp, has the two components connected by O—H...N hydrogen bonds to generate a one‐dimensional zigzag chain running along the crystallographic a direction. These chains are further stacked into a three‐dimensional supramolecular network by weak C—H...O and C—H...π contacts. Comparison of the structural differences with previous findings suggests that deprotonated forms, hydrogen‐bonding sites and flexible ligand conformations become significant factors that influence the topological arrangement and binding stoichiometry of the resulting cocrystals.     

Hydrogen‐bonded networks in 1‐(4‐methoxyphenyl)‐2,2‐dimethylpropan‐1‐ol

The asymmetric unit of the title compound, C₁₂H₁₈O₂, contains two independent molecules. They differ only slightly in conformation but form completely different intermolecular hydrogen‐bonded arrays. One molecule exhibits disorder in the hydroxy group region, but this does not influence the formation of hydrogen bonds. The bulky tert‐butyl group on one side of the carbinol C atom and the benzene ring on the other side promote the formation of discrete dimeric motifs via hydrogen‐bridged hydroxy groups. Dimers are further joined by strong hydroxy–methoxy O—H...O bonds to form chains with dangling alcohol groups. Weaker intermolecular C—H...O interactions mediate the formation of a two‐dimensional network.     

Bis(2‐aminopyridinium) maleate

Two cyclic eight‐membered hydrogen‐bonded rings exist in the title compound, 2C₅H₇N₂⁺·C₄H₂O₄²⁻, involving the 2‐amino­pyridinium and maleate ions. The dihedral angle between the two pyridinium rings hydrogen bonded to the maleate ion is 74.80 (4)°. The maleate anion lies on a twofold axis and is linked to the pyridinium cations by intermolecular N—H⃛O hydrogen bonds. The heterocycle is fully proton­ated, which enables amino–imino tautomerization.     

2‐Aminopyridinium–succinate–succinic acid (2/1/1)

In the title compound, 2C₅H₇N₂⁺·C₄H₄O₄^2?·C₄H₆O₄, cyclic eight‐membered hydrogen‐bonded rings exist involving 2‐amino­pyridinium and succinate ions. The succinic acid and succinate moieties lie on inversion centres. Succinic acid mol­ecules and succinate ions are linked into zigzag chains by O—H?O hydrogen bonds, with O?O distances of 2.6005 (16) Å.     

2‐Aminopyrimidine–3,3,3‐triphenylpropanoic acid (1/1)

The title bimolecular compound, C₄H₅N₃·C₂₁H₁₈O₂, constructed from 2‐aminopyrimidine and 3,3,3‐triphenylpropanoic acid, forms a tetramolecular hydrogen‐bonded motif via O—H...N, N—H...O and N—H...N contacts. This aggregate organizes to give crystal‐packing motifs with hydrophilic and hydrophobic regions.     

The acid adducts hydrazinium 2‐hydroxybenzoate–2‐hydroxybenzoic acid (1/1) and hydrazinium 3‐hydroxy‐2‐naphthoate–3‐hydroxy‐2‐naphthoic acid (1/1)

The title molecular salts, N₂H₅⁺·C₇H₅O₃⁻·C₇H₆O₃ and N₂H₅⁺·C₁₁H₇O₃⁻·C₁₁H₈O₃, are acid adducts containing a hydrazinium cation, one molecule of a deprotonated acid and one molecule of a neutral acid. The two compounds contain essentially identical hydrogen‐bond networks between the hydrazinium cation and the acid molecules, which define closely comparable two‐dimensional layers in the structures. The planes of the aromatic rings within both structures are approximately parallel and the layers are stacked with comparable intermolecular interactions.     

Bis[2,4‐diamino‐5‐(3,4,5‐trimethoxybenzyl)pyrimidin‐1‐ium] dl‐malate

<!?tpct=1pt>Racemic malic acid and trimethoprim [5‐(3,4,5‐trimethoxybenzyl)pyrimidine‐2,4‐diamine] form a 1:2 salt (monoclinic, P2₁/c), 2C₁₄H₁₉N₄O₃⁺·C₄H₄O₅²⁻, in which the malate component is disordered across a centre of inversion. The crystal structure of the salt consists of protonated trimethoprim residues and a malate dianion. The carboxylate group of the malate ion interacts with the trimethoprim cation in a linear fashion through pairs of N—H...O hydrogen bonds to form a cyclic hydrogen‐bonded motif. This is similar to the carboxylate–trimethoprim cation interaction observed earlier in the complex of dihydrofolate reductase with trimethoprim. The structure of the salt of trimethoprim with racemic dl ‐malic acid reported here is the first of its kind. The present study investigates the conformations and the hydrogen‐bonding interactions, which are very important for biological functions. The pyrimidine plane makes a dihedral angle of 78.08 (7)° with the benzene ring of the trimethoprim cation. The cyclic hydrogen‐bonded motif observed in this structure is self‐organized, leading to novel types of hydrogen‐bonding motifs in supramolecular patterns.     

Hydrogen‐bonded network in biphenyl‐4,4′‐diphosphonic acid

The crystal structure of the title compound, C₁₂H₁₂O₆P₂, displays two different regions alternating along the a axis: a hydrogen‐bonded region encompassing the end‐positioned phosphonic acid groups and a hydrophobic region formed by the aromatic spacers. The asymmetric unit contains only half of the biphenyl‐4,4′‐diphosphonic acid (4,4′‐bpdp) molecule, which is symmetric with an inversion centre imposed at the mid‐point between the two aromatic rings. The periodic organization of the molecules is controlled by two strong O—H...O interactions between the phosphonic acid sites. Weak C—H...π interactions are established in the aromatic regions.     

Hydrogen‐bonded layers in the 1:2 cocrystal of 2,2′‐dithiodibenzoic acid with isonicotinohydrazide

Cocrystallization of 2,2′‐dithiodibenzoic acid with isonicotinohydrazide from methanol solution yields the 1:2 cocrystal 2,2′‐dithiodibenzoic acid–isonicotinohydrazide (1/2), C₁₄H₁₀O₄S₂·2C₆H₇N₃O. The component molecules are linked by intermolecular O—H...N, N—H...O, N—H...N and C—H...O hydrogen bonds into layers running parallel to the (010) plane, and these layers are further linked into a three‐dimensional framework structure by means of weak aromatic π–π stacking interactions. As a potential cocrystallization agent, isonicotinohydrazide may be used for effective and versatile synthetic supramolecular strategies utilizing hydrogen bonding of specific molecular building blocks.     

Hydrogen‐bonded frameworks of bis(2‐carboxypyridinium) hexafluorosilicate and bis(2‐carboxyquinolinium) hexafluorosilicate dihydrate

In bis(2‐carboxypyridinium) hexafluorosilicate, 2C₆H₆NO₂⁺·SiF₆²⁻, (I), and bis(2‐carboxyquinolinium) hexafluorosilicate dihydrate, 2C₁₀H₈NO₂⁺·SiF₆²⁻·2H₂O, (II), the Si atoms of the anions reside on crystallographic centres of inversion. Primary inter‐ion interactions in (I) occur via strong N—H...F and O—H...F hydrogen bonds, generating corrugated layers incorporating [SiF₆]²⁻ anions as four‐connected net nodes and organic cations as simple links in between. In (II), a set of strong N—H...F, O—H...O and O—H...F hydrogen bonds, involving water molecules, gives a three‐dimensional heterocoordinated rutile‐like framework that integrates [SiF₆]²⁻ anions as six‐connected and water molecules as three‐connected nodes. The carboxyl groups of the cation are hydrogen bonded to the water molecule [O...O = 2.5533 (13) Å], while the N—H group supports direct bonding to the anion [N...F = 2.7061 (12) Å].     

Hydrogen‐bonded 1:1 adduct of 1,1′‐(p‐phenylene)dipyridin‐4(1H)‐one with terephthalic acid

Cocrystallization of 1,1′‐(p‐phenylene)dipyridin‐4(1H)‐one (4,4′‐dpy) and terephthalic acid (tpa) affords the hydrogen‐bonded 1:1 title complex, C₁₆H₁₂N₂O₂·C₈H₆O₄. Both mol­ecules are symmetrically disposed about independent symmetry centers. Strong O—H⋯O hydrogen bonds between tpa carboxyl groups and 4,4′‐dpy carbonyl groups produce one‐dimensional zigzag infinite chains. Each chain is linked to four surrounding chains via weak C—H⋯O inter­actions, resulting in a three‐dimensional mol­ecular framework.     

Hydrogen‐bonded molecular ladders in S‐(4‐nitrophenyl)thioglycolic acid

Molecules of the title compound, [(4‐nitro­phenyl)­sulfanyl]­acetic acid, C₈H₇NO₄S, are linked by paired O—H?O hydrogen bonds [H?O 1.81 Å, O?O 2.6456 (15) Å and O—H?O 178°] into centrosymmetric dimers containing an R(8) motif. A single C—H?O hydrogen bond having a nitro O atom as acceptor [H?O 2.47 Å, 3.3018 (19) Å and C—H?O 147°] links the dimers into a molecular ladder, and neighbouring ladders are weakly linked into sheets by aromatic π–π‐stacking interactions.     

Hydrogen‐bond motifs in N‐monosubstituted derivatives of barbituric acid: 5‐allyl‐5‐isopropyl‐1‐methylbarbituric acid (enallylpropymal) and 1,5‐di(but‐2‐enyl)‐5‐ethylbarbituric acid

Both title structures exhibit essentially planar barbiturate rings. The crystal structure of enallylpropymal (5‐allyl‐5‐isopropyl‐1‐methylbarbituric acid), C₁₁H₁₆N₂O₃, is composed of centrosymmetric N—H...O hydrogen‐bonded dimers, while 1,5‐di(but‐2‐enyl)‐5‐ethylbarbituric acid, C₁₄H₂₀N₂O₃, forms N—H...O hydrogen‐bonded helical chains. Each of the ten known crystal structures of closely related N‐monosubstituted derivatives of barbituric acid displays one of the fundamental N—H...O hydrogen‐bonded motifs of the two title structures, i.e. either a dimer or a chain.     

The hydrogen‐bonded adduct 7,16‐diazonia‐18‐crown‐6–4‐aminobenzenesulfonate–water (1/2/2)

In the title hydrated adduct, 1,4,10,13‐tetraoxa‐7,16‐diazo­nia­cyclo­octa­decane bis(4‐amino­benzene­sulfonate) dihydrate, C₁₂H₂₈N₂O₄²⁺·2C₆H₆NO₃S⁻·2H₂O, formed between 7,16‐di­aza‐18‐crown‐6 and the dihydrate of 4‐amino­benzene­sulfonic acid, the macrocyclic cations lie across centres of inversion in the orthorhombic space group Pbca. The anions alone form zigzag chains, and the cations and anions together form sheets that are linked via water mol­ecules and anions to form a three‐dimensional grid.     

Hydrogen‐bonded sheets in 2‐(2‐aminophenyl)‐1H‐benzimidazol‐3‐ium dihydrogen phosphate

The title salt, C₁₃H₁₂N₃⁺·H₂PO₄⁻, contains a nonplanar 2‐(2‐aminophenyl)‐1H‐benzimidazol‐3‐ium cation and two different dihydrogen phosphate anions, both situated on twofold rotation axes in the space group C2. The anions are linked by O—H...O hydrogen bonds into chains of R₂²(8) rings. The anion chains are linked by the cations, via hydrogen‐bonding complementarities and electrostatic interactions, giving rise to a sheet structure with alternating rows of organic cations and inorganic anions. Comparison of this structure with that of the pure amine reveals that the two compounds generate characteristically different sheet structures. The anion–anion chain serves as a template for the assembly of the cations, suggesting a possible application in the design of solid‐state materials.