Gallium tris­(iodate), Ga(IO3)3

Ga(IO₃)₃ crystallizes in the space group P6₃, with the Ga atom at a site with imposed threefold symmetry. The crystal structure consists of slightly distorted GaO₆ octa­hedra that are bridged by I atoms of IO₃⁻ groups, giving rise to a three‐dimensional polar network. The framework contains unoccupied hexa­gonal channels running parallel to the hexa­gonal [001] direction. The iodate groups have their stereochemically active non‐bonded electron pairs pointing in the same direction along [001], which creates the polarity in the structure. The I—O bond distances and O—I—O angles are normal, being in the ranges 1.783 (3)–1.847 (2) Å and 94.68 (11)–99.61 (12)°, respectively.     

Poly[bis(μ‐5‐iodoisophthalato)(methanol)dilead(II)] exhibiting a novel centrosymmetric rhombus‐shaped I4 unit

The asymmetric unit of the title compound, [Pb₂(C₈H₃IO₄)₂(CH₄O)]_n, contains two Pb^II atoms, two 5‐iodoisophthalate (5‐IIP²⁻) ligands and one coordinated methanol molecule. One Pb atom is eight‐coordinated, surrounded by seven carboxylate O atoms from five 5‐IIP²⁻ ligands and one O atom from the terminal methanol ligand. The other Pb atom is seven‐coordinated in a hemidirected geometry, surrounded by seven carboxylate O atoms from five 5‐IIP²⁻ ligands. Both Pb atoms are connected by carboxylate groups to form a one‐dimensional infinite rod along the a axis; neighbouring rods are further linked by the aromatic rings of 5‐IIP²⁻ to generate the final three‐dimensional structure with channels in the a direction. An O—H...O hydrogen bond between the methanol ligand and one of the carboxylate groups of a 5‐IIP²⁻ ligand stablizes the three‐dimensional framework. Interestingly, a centrosymmetric rhombus‐shaped I₄ unit is formed by four 5‐IIP²⁻ ligands, with I...I distances of 3.8841 (8) and 3.9204 (8) Å.     

Poly[[diaqua(μ3‐3‐nitrophthalato)calcium(II)] monohydrate]

The title 3‐nitrophthalate–calcium coordination polymer, {[Ca(C₈H₃NO₆)(H₂O)₂]·H₂O}_n, crystallizes as a one‐dimensional framework. The Ca^II centre has a distorted pentagonal–bipyramidal geometry, being seven‐coordinated by five O atoms from three different 3‐nitrophthalate groups and by two water molecules, resulting in a one‐dimensional zigzag chain along the a‐axis direction by the interconnection of the four O atoms from the two carboxylate groups. There is a D3 water cluster composed of the coordinated and the solvent water molecules within such chains. Adjacent chains are aggregated into two‐dimensional layers via hydrogen bonds in the c‐axis direction. The whole three‐dimensional structure is further stabilized by weak O—H...O hydrogen bonds between the O atoms of the nitro group and the water molecules.     

Comparison of the methyl ester of l‐tyrosine hydrochloride and its methanol monosolvate

Solvent‐free (2S)‐methyl 2‐ammonio‐3‐(4‐hydroxy­phenyl)­propionate chloride, C₁₀H₁₄NO₃⁺·Cl⁻, (I), and its methanol solvate, C₁₀H₁₄NO₃⁺·Cl⁻·CH₃OH, (II), are obtained from different solvents: crystallization from ethanol or propan‐2‐ol gives the same solvent‐free crystals of (I) in both cases, while crystals of (II) were obtained by crystallization from methanol. The structure of (I) is characterized by the presence of two‐dimensional layers linked together by N—H⋯Cl and O—H⋯Cl hydrogen bonds and also by C—H⋯O contacts. Incorporation of the methanol solvent mol­ecule in (II) introduces additional O—H⋯O hydrogen bonds linking the two‐dimensional layers, resulting in the formation of a three‐dimensional network.     

1:1 Adducts of 2,2′‐[isopropylidenebis(p‐phenyleneoxy)]diacetic acid with dimethylammonium and 4,4′‐bipyridine

The title compounds, dimethylammonium 2‐{4‐[1‐(4‐carboxymethoxyphenyl)‐1‐methylethyl]phenoxy}acetate, C₂H₈N⁺·C₁₉H₁₉O₆⁻, (I), and 2,2′‐[isopropylidenebis(p‐phenyleneoxy)]diacetic acid–4,4′‐bipyridine (1/1), C₁₉H₂₀O₆·C₁₀H₈N₂, (II), are 1:1 adducts of 2,2′‐[isopropylidenebis(p‐phenyleneoxy)]diacetic acid (H₂L) with dimethylammonium or 4,4′‐bipyridine. The component ions in (I) are linked by N—H...O, O—H...O and C—H...O hydrogen bonds into continuous two‐dimensional layers parallel to the (001) plane. Adjacent layers are stacked via C—H...O hydrogen bonds into a three‐dimensional network with an –ABAB– alternation of the two‐dimensional layers. In (II), two H₂L molecules, one bipy molecule and two half bipy molecules are linked by O—H...N hydrogen bonds into one‐dimensional chains and rectanglar‐shaped rings. They are assembled viaπ–π stacking interactions and C—H...O hydrogen bonds into an intriguing zero‐dimensional plus one‐dimensional poly(pseudo)rotaxane motif.     

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.     

Hydrogen‐bonded two‐ and three‐dimensional polymeric structures in the ammonium salts of 3,5‐dinitrobenzoic acid, 4‐nitrobenzoic acid and 2,4‐dichlorobenzoic acid

The structures of ammonium 3,5‐dinitrobenzoate, NH₄⁺·C₇H₃N₂O₆⁻, (I), ammonium 4‐nitrobenzoate dihydrate, NH₄⁺·C₇H₄NO₄⁻·2H₂O, (II), and ammonium 2,4‐dichlorobenzoate hemihydrate, NH₄⁺·C₇H₃Cl₂O₂⁻·0.5H₂O, (III), have been determined and their hydrogen‐bonded structures are described. All three salts form hydrogen‐bonded polymeric structures, viz. three‐dimensional in (I) and two‐dimensional in (II) and (III). With (I), a primary cation–anion cyclic association is formed [graph set R₄³(10)] through N—H...O hydrogen bonds, involving a carboxylate group with both O atoms contributing to the hydrogen bonds (denoted O,O′‐carboxylate) on one side and a carboxylate group with one O atom involved in two hydrogen bonds (denoted O‐carboxylate) on the other. Structure extension involves N—H...O hydrogen bonds to both carboxylate and nitro O‐atom acceptors. With structure (II), the primary inter‐species interactions and structure extension into layers lying parallel to (001) are through conjoined cyclic hydrogen‐bonding motifs, viz.R₄³(10) (one cation, an O,O′‐carboxylate group and two water molecules) and centrosymmetric R₄²(8) (two cations and two water molecules). The structure of (III) also has conjoined R₄³(10) and centrosymmetric R₄²(8) motifs in the layered structure but these differ in that the first motif involves one cation, an O,O′‐carboxylate group, an O‐carboxylate group and one water molecule, and the second motif involves two cations and two O‐carboxylate groups. The layers lie parallel to (100). The structures of salt hydrates (II) and (III), displaying two‐dimensional layered arrays through conjoined hydrogen‐bonded nets, provide further illustration of a previously indicated trend among ammonium salts of carboxylic acids, but the anhydrous three‐dimensional structure of (I) is inconsistent with that trend.     

Poly[[tetraaquabis(μ2‐2‐nitroterephthalato‐κ3O1:O4,O4′)(μ2‐piperazine‐κ3N:N′)dicadmium(II)] dihydrate]

In the title complex, {[Cd₂(C₈H₃NO₆)₂(C₄H₁₀N₂)(H₂O)₄]·2H₂O}_n, the Cd^II atoms show distorted octahedral coordination. The two carboxylate groups of the dianionic 2‐nitroterephthalate ligand adopt monodentate and 1,2‐bridging modes. The piperazine molecule is in a chair conformation and lies on a crystallographic inversion centre. The Cd^II atoms are connected via three O atoms from two carboxylate groups and two N atoms from piperazine molecules to form a two‐dimensional macro‐ring layer structure. These layers are further aggregated to form a three‐dimensional structure via rich intra‐ and interlayer hydrogen‐bonding networks. This study illustrates that, by using the labile Cd^II salt and a combination of 2‐nitroterephthalate and piperazine as ligands, it is possible to generate interesting metal–organic frameworks with rich intra‐ and interlayer O—H...O hydrogen‐bonding networks.     

The three‐dimensional hydrogen‐bonded structures in the ammonium and sodium salt hydrates of 4‐aminophenylarsonic acid

The structures of two hydrated salts of 4‐aminophenylarsonic acid (p‐arsanilic acid), namely ammonium 4‐aminophenylarsonate monohydrate, NH₄⁺·C₆H₇AsNO₃⁻·H₂O, (I), and the one‐dimensional coordination polymer catena‐poly[[(4‐aminophenylarsonato‐κO)diaquasodium]‐μ‐aqua], [Na(C₆H₇AsNO₃)(H₂O)₃]_n, (II), have been determined. In the structure of the ammonium salt, (I), the ammonium cations, arsonate anions and water molecules interact through inter‐species N—H...O and arsonate and water O—H...O hydrogen bonds, giving the common two‐dimensional layers lying parallel to (010). These layers are extended into three dimensions through bridging hydrogen‐bonding interactions involving the para‐amine group acting both as a donor and an acceptor. In the structure of the sodium salt, (II), the Na⁺ cation is coordinated by five O‐atom donors, one from a single monodentate arsonate ligand, two from monodentate water molecules and two from bridging water molecules, giving a very distorted square‐pyramidal coordination environment. The water bridges generate one‐dimensional chains extending along c and extensive interchain O—H...O and N—H...O hydrogen‐bonding interactions link these chains, giving an overall three‐dimensional structure. The two structures reported here are the first reported examples of salts of p‐arsanilic acid.     

A novel three‐dimensional heterometallic coordination polymer: poly[[diaquadi‐μ3‐chlorido‐μ2‐chlorido‐tri‐μ3‐nicotinato‐tricopper(I)gadolinium(III)] hemihydrate]

In the title polymeric heterometallic compound, {[Cu₃Gd(C₆H₄NO₂)₃Cl₃(H₂O)₂]·0.5H₂O}_n, comprising copper(I) and gadolinium(III) cations bridged by nicotinate (nic) ligands and chloride anions, the Gd^III centers display a bicapped trigonal prismatic geometry, defined by six carboxylate O atoms and two water molecules. For copper(I), one Cu center is three‐coordinated by three chloride ions and displays a trigonal–planar geometry; the other two Cu centers are four‐coordinated and display a very distorted tetrahedral geometry. The chloride anions act in μ₂‐ and μ₃‐bridging modes, linking the Cu^I ions into an infinite chain. The nic ligand exhibits a tridentate coordination mode, with the carboxylate O atoms linking to two Gd^III ions and the N atom linking to one Cu^I ion. Thus, a novel three‐dimensional heterometallic coordination polymer is constructed from Gd–carboxylate subunits and Cu—Cl chains. In addition, intra‐ and intermolecular O—H...O and O—H...Cl hydrogen bonds are also observed within the three‐dimensional structure. Topologically, the framework represents an unusual 3,6‐connected (4.8²)₃(4¹⁰.6⁵) net.     

{4‐[(Carbamimidoylhydrazono)methyl‐κ2N1,N4]‐5‐hydroxymethyl‐2‐methylpyridinium‐3‐olate‐κO}(methanol‐κO)copper(II) dinitrate

The title compound, [Cu(C₉H₁₃N₅O₂)(CH₄O)](NO₃)₂, consists of square‐planar cationic complex units where the Cu^II centre is coordinated by an N,N′,O‐tridentate pyridoxal–aminoguanidine Schiff base adduct and a methanol molecule. The tridentate ligand is a zwitterion exhibiting an almost planar conformation. The dihedral angles between the mean planes of the pyridoxal ring and the six‐ and five‐membered chelate rings are all less than 2.0°. The charge on the complex cation is neutralized by two nitrate counter‐ions. Extensive N—H...O and C—H...O hydrogen bonding connects these ionic species and leads to the formation of layers. The pyridoxal hydroxy groups are the only fragments that deviate significantly from the flat layer structure; these groups are involved in O—H...O hydrogen bonding, connecting the layers into a three‐dimensional crystal structure.     

Three‐dimensional hydrogen‐bonded structures in the 1:1 proton‐transfer compounds of l‐tartaric acid with the associative‐group monosubstituted pyridines 3‐aminopyridine, 3‐carboxypyridine (nicotinic acid) and 2‐carboxypyridine (picolinic acid)

The 1:1 proton‐transfer compounds of l ‐tartaric acid with 3‐aminopyridine [3‐aminopyridinium hydrogen (2R,3R)‐tartrate dihydrate, C₅H₇N₂⁺·C₄H₅O₆⁻·2H₂O, (I)], pyridine‐3‐carboxylic acid (nicotinic acid) [anhydrous 3‐carboxypyridinium hydrogen (2R,3R)‐tartrate, C₆H₆NO₂⁺·C₄H₅O₆⁻, (II)] and pyridine‐2‐carboxylic acid [2‐carboxypyridinium hydrogen (2R,3R)‐tartrate monohydrate, C₆H₆NO₂⁺·C₄H₅O₆⁻·H₂O, (III)] have been determined. In (I) and (II), there is a direct pyridinium–carboxyl N⁺—H...O hydrogen‐bonding interaction, four‐centred in (II), giving conjoint cyclic R₁²(5) associations. In contrast, the N—H...O association in (III) is with a water O‐atom acceptor, which provides links to separate tartrate anions through O_hydroxy acceptors. All three compounds have the head‐to‐tail C(7) hydrogen‐bonded chain substructures commonly associated with 1:1 proton‐transfer hydrogen tartrate salts. These chains are extended into two‐dimensional sheets which, in hydrates (I) and (III) additionally involve the solvent water molecules. Three‐dimensional hydrogen‐bonded structures are generated via crosslinking through the associative functional groups of the substituted pyridinium cations. In the sheet struture of (I), both water molecules act as donors and acceptors in interactions with separate carboxyl and hydroxy O‐atom acceptors of the primary tartrate chains, closing conjoint cyclic R₄⁴(8), R₃⁴(11) and R₃³(12) associations. Also, in (II) and (III) there are strong cation carboxyl–carboxyl O—H...O hydrogen bonds [O...O = 2.5387 (17) Å in (II) and 2.441 (3) Å in (III)], which in (II) form part of a cyclic R₂²(6) inter‐sheet association. This series of heteroaromatic Lewis base–hydrogen l ‐tartrate salts provides further examples of molecular assembly facilitated by the presence of the classical two‐dimensional hydrogen‐bonded hydrogen tartrate or hydrogen tartrate–water sheet substructures which are expanded into three‐dimensional frameworks via peripheral cation bifunctional substituent‐group crosslinking interactions.     

Characterization and gas adsorption of a novel three‐dimensional metal–organic framework (MOF) generated from a new polydentate fluorene‐bridged ligand

A polydentate ligand bridged by a fluorene group, namely 9,9‐bis(2‐hydroxyethyl)‐2,7‐bis(pyridin‐4‐yl)fluorene (L), has been prepared under solvothermal conditions in acetonitrile. Crystals of the three‐dimensional metal–organic framework (MOF) poly[[[μ₃‐9,9‐bis(2‐hydroxyethyl)‐2,7‐bis(pyridin‐4‐yl)fluorene‐κ³N:N′:O]bis(methanol‐κO)(μ‐sulfato‐κ²O:O′)nickel(II)] methanol disolvate], {[Ni(SO₄)(C₂₇H₂₄N₂O₂)(CH₃OH)]·2CH₃OH}_n, (I), were obtained by the solvothermal reaction of L and NiSO₄ in methanol. The ligand L forms a two‐dimensional network in the crystallographic bc plane via two groups of O—H…N hydrogen bonds and neighbouring two‐dimensional planes are completely parallel and stack to form a three‐dimensional structure. In (I), the Ni^II ions are linked by sulfate ions through Ni—O bonds to form inorganic chains and these Ni‐containing chains are linked into a three‐dimensional framework via Ni—O and Ni—N bonds involving the polydentate ligand L. With one of the hydroxy groups of L coordinating to the Ni^II atom, the torsion angle of the hydroxyethyl group changes from that of the uncoordinated molecule. In addition, the adsorption properties of (I) with carbon dioxide were investigated.     

Poly[μ3‐hydroxido‐μ6‐sulfato‐μ3‐(1,2,4‐triazolato‐κ3N1:N2:N4)‐dicadmium(II)]: a cadmium–triazolate coordination polymer with a pseudo‐cubane‐like tetranuclear cluster

The title complex, [Cd₂(C₂H₂N₃)(OH)(SO₄)]_n, is a three‐dimensional metal–organic framework consisting of pseudo‐cubane‐like tetranuclear cadmium clusters, which are formed by four Cd^II atoms, two sulfate groups and two hydroxide groups. The tetranuclear cadmium clusters are connected into a layered substructure by Cd—O bonds and adjacent layers are linked by triazolate ligands into a three‐dimensional network. A photoluminescent study revealed that the complex exhibits a strong emission in the visible region which probably originates from a π–π* transition.     

Kristallstruktur,Infrarot‐ und Ramanspektren von Kupfertrihydrogenperiodatmonohydrat,CuH3IO6 · H2O

Crystal Structure, Infrared and Raman Spectra of Copper Trihydrogenperiodate Monohydrate, CuH₃IO₆ · H₂O The hitherto unknown compound CuH₃IO₆ · H₂O was studied by X‐ray, IR‐ and Raman spectroscopic methods. The crystal structure was determined by X‐ray single‐crystal studies (space group P2₁2₁2₁, Z = 4, a = 532.60(10), b = 624.00(10), c = 1570.8(3) pm, R1 = 1.85%, 1559 unique reflections (I > 2σ(I))). Isolated, meridionally configurated H₃IO₆^2– ions are coordinated to the copper ions forming double‐ropes in [100]. These ropes are connected in [010] and [001] by hydrogen bonds. The copper ions possess a square pyramidal co‐ordination with the hydrate H₂O on top. The infrared and Raman spectra as well as group theoretical treatment are presented and discussed with respect to the strength of the hydrogen bonds and the co‐ordination of the CuO₅₍₊₁₎ polyhedra and the H₃IO₆^2– ions at the C₁ lattice sites. The hydrogen bonds of the H₂O molecules and H₃IO₆^2– ions (HO–H…O–IO₅H₃ and H₂IO₅O–H…O–IO₅H₃) greatly differ in strength, as shown from both the respective O…O distances: 282.6 and 298.6 pm (H₂O), and 258.8, 259.7, and 270.9 pm (H₃IO₆^2–) and the OD stretching modes of isotopically dilute samples: 2498 and 2564 cm^–1 (90 K) (HDO), and 1786, 2024, and 2188 cm^–1 (H₂DIO₆^2–). The IO stretching modes of the H₃IO₆^2– ions (696–788 cm^–1 and 555–658 cm^–1, 295 K) display the different strength of the respective I–O and I–O(H) bonds (r_I–O: 181.1–188.3 pm and 189.2–194.5 pm).     

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).     

A cyano‐bridged dinuclear 4f–3d array

A cyano‐bridged bimetallic 4f–3d complex, tri­aqua‐1κ³O‐μ‐cyano‐1:2κ²N:C‐penta­cyano‐2κ⁵C‐tetrakis(2‐pyrrolidone‐1κO)­chromium(III)­dysprosium(III) dihydrate, [CrDy(C₄H₇NO)₄(CN)₆(H₂O)₃]·2H₂O, has been prepared and characterized by X‐ray crystallographic analysis. The structure consists of a neutral cyano‐bridged Dy–Cr dimer. A hydrogen‐bonded three‐dimensional architecture is formed through N—H?O, O—H?N and O—H?O hydrogen bonds.     

Frovatriptan salts of aliphatic carboxylic acids

The interaction of the antimigraine pharmaceutical agent frovatriptan with acetic acid and succinic acid yields the salts (±)‐6‐carbamoyl‐N‐methyl‐2,3,4,9‐tetrahydro‐1H‐carbazol‐3‐aminium acetate, C₁₄H₁₈N₃O⁺·C₂H₃O₂⁻, (I), (R)‐(+)‐6‐carbamoyl‐N‐methyl‐2,3,4,9‐tetrahydro‐1H‐carbazol‐3‐aminium 3‐carboxypropanoate monohydrate, C₁₄H₁₈N₃O⁺·C₄H₅O₄⁻·H₂O, (II), and bis[(R)‐(+)‐6‐carbamoyl‐N‐methyl‐2,3,4,9‐tetrahydro‐1H‐carbazol‐3‐aminium] succinate trihydrate, 2C₁₄H₁₈N₃O⁺·C₄H₄O₄²⁻·3H₂O, (III). The methylazaniumyl substitutent is oriented differently in all three structures. Additionally, the amide group in (I) is in a different orientation. All the salts form three‐dimensional hydrogen‐bonded structures. In (I), the cations form head‐to‐head hydrogen‐bonded amide–amide catemers through N—H...O interactions, while in (II) and (III) the cations form head‐to‐head amide–amide dimers. The cation catemers in (I) are extended into a three‐dimensional network through further interactions with acetate anion acceptors. The presence of succinate anions and water molecules in (II) and (III) primarily governs the three‐dimensional network through water‐bridged cation–anion associations via O—H...O and N—H...O hydrogen bonds. The structures reported here shed some light on the possible mode of noncovalent interactions in the aggregation and interaction patterns of drug molecule adducts.     

Hydrogen bonding in two ammonium salts of 5‐sulfosalicylic acid: ammonium 3‐carboxy‐4‐hydroxybenzenesulfonate monohydrate and triammonium 3‐carboxy‐4‐hydroxybenzenesulfonate 3‐carboxylato‐4‐hydroxybenzenesulfonate

The structures of two ammonium salts of 3‐carboxy‐4‐hydroxybenzenesulfonic acid (5‐sulfosalicylic acid, 5‐SSA) have been determined at 200 K. In the 1:1 hydrated salt, ammonium 3‐carboxy‐4‐hydroxybenzenesulfonate monohydrate, NH₄⁺·C₇H₅O₆S⁻·H₂O, (I), the 5‐SSA⁻ monoanions give two types of head‐to‐tail laterally linked cyclic hydrogen‐bonding associations, both with graph‐set R₄⁴(20). The first involves both carboxylic acid O—H...O_water and water O—H...O_sulfonate hydrogen bonds at one end, and ammonium N—H...O_sulfonate and N—H...O_carboxy hydrogen bonds at the other. The second association is centrosymmetric, with end linkages through water O—H...O_sulfonate hydrogen bonds. These conjoined units form stacks down c and are extended into a three‐dimensional framework structure through N—H...O and water O—H...O hydrogen bonds to sulfonate O‐atom acceptors. Anhydrous triammonium 3‐carboxy‐4‐hydroxybenzenesulfonate 3‐carboxylato‐4‐hydroxybenzenesulfonate, 3NH₄⁺·C₇H₄O₆S²⁻·C₇H₅O₆S⁻, (II), is unusual, having both dianionic 5‐SSA²⁻ and monoanionic 5‐SSA⁻ species. These are linked by a carboxylic acid O—H...O hydrogen bond and, together with the three ammonium cations (two on general sites and the third comprising two independent half‐cations lying on crystallographic twofold rotation axes), give a pseudo‐centrosymmetric asymmetric unit. Cation–anion hydrogen bonding within this layered unit involves a cyclic R₃³(8) association which, together with extensive peripheral N—H...O hydrogen bonding involving both sulfonate and carboxy/carboxylate acceptors, gives a three‐dimensional framework structure. This work further demonstrates the utility of the 5‐SSA⁻ monoanion for the generation of stable hydrogen‐bonded crystalline materials, and provides the structure of a dianionic 5‐SSA²⁻ species of which there are only a few examples in the crystallographic literature.     

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.