N—H...O and O—H...O hydrogen‐bonded supramolecular networks in 4‐chloroanilinium, 2‐hydroxyanilinium and 3‐hydroxyanilinium hydrogen phthalates

The title salts, 4‐chloroanilinium hydrogen phthalate (PCAHP), C₆H₇ClN⁺·C₈H₅O₄⁻, 2‐hydroxyanilinium hydrogen phthalate (2HAHP), C₆H₈NO⁺·C₈H₅O₄⁻, and 3‐hydroxyanilinium hydrogen phthalate (3HAHP), C₆H₈NO⁺·C₈H₅O₄⁻, all crystallize in the space group P2₁/c. The asymmetric unit of 2HAHP contains two independent ion pairs. The hydrogen phthalate ions of 2HAHP and 3HAHP show a short intramolecular O—H...O hydrogen bond, with O...O distances ranging from 2.3832 (15) to 2.3860 (14) Å. N—H...O and O—H...O hydrogen bonds, together with short C—H...O contacts in PCAHP and 3HAHP, generate extended hydrogen‐bond networks. PCAHP forms a two‐dimensional supramolecular sheet extending in the (100) plane, whereas 2HAHP has a supramolecular chain running parallel to the [100] direction and 3HAHP has a two‐dimensional network extending parallel to the (001) plane.     

Cyclic heterotetrameric and low‐dimensional hydrogen‐bonded polymeric structures in the morpholinium salts of ring‐substituted benzoic acid analogues

The morpholinium (tetrahydro‐2H‐1,4‐oxazin‐4‐ium) cation has been used as a counter‐ion in both inorganic and organic salt formation and particularly in metal complex stabilization. To examine the influence of interactive substituent groups in the aromatic rings of benzoic acids upon secondary structure generation, the anhydrous salts of morpholine with salicylic acid, C₄H₁₀NO⁺·C₇H₅O₃⁻, (I), 3,5‐dinitrosalicylic acid, C₄H₁₀NO⁺·C₇H₃N₂O₇⁻, (II), 3,5‐dinitrobenzoic acid, C₄H₁₀NO⁺·C₇H₃N₂O₆⁻, (III), and 4‐nitroanthranilic acid, C₄H₁₀NO⁺·C₇H₅N₂O₄⁻, (IV), have been prepared and their hydrogen‐bonded crystal structures are described. In the crystal structures of (I), (III) and (IV), the cations and anions are linked by moderately strong N—H…O_carboxyl hydrogen bonds, but the secondary structure propagation differs among the three, viz. one‐dimensional chains extending along [010] in (I), a discrete cyclic heterotetramer in (III), and in (IV), a heterotetramer with amine N—H…O hydrogen‐bond extensions along b, giving a two‐layered ribbon structure. With the heterotetramers in both (III) and (IV), the ion pairs are linked though inversion‐related N—H…O_carboxylate hydrogen bonds, giving cyclic R₄⁴(12) motifs. With (II), in which the anion is a phenolate rather than a carboxylate, the stronger assocation is through a symmetric lateral three‐centre cyclic R₁²(6) N—H…(O,O′) hydrogen‐bonding linkage involving the phenolate and nitro O‐atom acceptors of the anion, with extension through a weaker O—H…O_carboxyl hydrogen bond. This results in a one‐dimensional chain structure extending along [100]. In the structures of two of the salts [i.e. (II) and (IV)], there are also π–π ring interactions, with ring‐centroid separations of 3.5516 (9) and 3.7700 (9) Å in (II), and 3.7340 (9) Å in (IV).     

New pharmaceutical salts containing pyridoxine

Two mixed crystals were obtained by crystallizing the active pharmaceutical ingredient pyridoxine [systematic name: 4,5‐bis(hydroxymethyl)‐2‐methylpyridin‐3‐ol, PN] with (E )‐3‐(4‐hydroxy‐3‐methoxyphenyl)prop‐2‐enoic acid (ferulic acid) and 4‐hydroxy‐3,5‐dimethoxybenzoic acid (syringic acid). PN and the coformers crystallize in the form of pharmaceutical salts in a 1:1 stoichiometric ratio, namely 3‐hydroxy‐4,5‐bis(hydroxymethyl)‐2‐methylpyridin‐1‐ium (E )‐3‐(4‐hydroxy‐3‐methoxyphenyl)prop‐2‐enoate, C₈H₁₂NO₃⁺·C₉H₉O₅⁻, and 3‐hydroxy‐4,5‐bis(hydroxymethyl)‐2‐methylpyridin‐1‐ium 4‐hydroxy‐3,5‐dimethoxybenzoate monohydrate, C₈H₁₂NO₃⁺·C₁₀H₁₁O₅⁻·H₂O, the proton exchange between PN and the acidic partner being supported by the differences of the pK _a values of the two components and by the C—O bond lengths of the carboxylate groups. Besides complex hydrogen‐bonding networks, π–π interactions between aromatic moieties have been found to be important for the packing architecture in both crystals. Hirshfeld surface analysis was used to explore the intermolecular interactions in detail and compare them with the interactions found in similar pyridoxine/carboxylic acid salts.     

Eight salt forms of sulfadiazine

Proton transfer to the sulfa drug sulfadiazine [systematic name: 4‐amino‐N‐(pyrimidin‐2‐yl)benzenesulfonamide] gave eight salt forms. These are the monohydrate and methanol hemisolvate forms of the chloride (2‐{[(4‐azaniumylphenyl)sulfonyl]azanidyl}pyrimidin‐1‐ium chloride monohydrate, C₁₀H₁₁N₄O₂S⁺·Cl⁻·H₂O, (I), and 2‐{[(4‐azaniumylphenyl)sulfonyl]azanidyl}pyrimidin‐1‐ium chloride methanol hemisolvate, C₁₀H₁₁N₄O₂S⁺·Cl⁻·0.5CH₃OH, (II)); a bromide monohydrate (2‐{[(4‐azaniumylphenyl)sulfonyl]azanidyl}pyrimidin‐1‐ium bromide monohydrate, C₁₀H₁₁N₄O₂S⁺·Br⁻·H₂O, (III)), which has a disordered water channel; a species containing the unusual tetraiodide dianion [bis(2‐{[(4‐azaniumylphenyl)sulfonyl]azanidyl}pyrimidin‐1‐ium) tetraiodide, 2C₁₀H₁₁N₄O₂S⁺·I₄²⁻, (IV)], where the [I₄]²⁻ ion is located at a crystallographic inversion centre; a tetrafluoroborate monohydrate (2‐{[(4‐azaniumylphenyl)sulfonyl]azanidyl}pyrimidin‐1‐ium tetrafluoroborate monohydrate, C₁₀H₁₁N₄O₂S⁺·BF₄⁻·H₂O, (V)); a nitrate (2‐{[(4‐azaniumylphenyl)sulfonyl]azanidyl}pyrimidin‐1‐ium nitrate, C₁₀H₁₁N₄O₂S⁺·NO₃⁻, (VI)); an ethanesulfonate {4‐[(pyrimidin‐2‐yl)sulfamoyl]anilinium ethanesulfonate, C₁₀H₁₁N₄O₂S⁺·C₂H₅SO₃⁻, (VII)}; and a dihydrate of the 4‐hydroxybenzenesulfonate {4‐[(pyrimidin‐2‐yl)sulfamoyl]anilinium 4‐hydroxybenzenesulfonate dihydrate, C₁₀H₁₁N₄O₂S⁺·HOC₆H₄SO₃⁻·2H₂O, (VIII)}. All these structures feature alternate layers of cations and of anions where any solvent is associated with the anion layers. The two sulfonate salts are protonated at the aniline N atom and the amide N atom of sulfadiazine, a tautomeric form of the sulfadiazine cation that has not been crystallographically described before. All the other salt forms are instead protonated at the aniline group and on one N atom of the pyrimidine ring. Whilst all eight species are based upon hydrogen‐bonded centrosymetric dimers with graph set R₂²(8), the two sulfonate structures also differ in that these dimers do not link into one‐dimensional chains of cations through NH₃‐to‐SO₂ hydrogen‐bonding interactions, whilst the other six species do. The chloride methanol hemisolvate and the tetraiodide are isostructural and a packing analysis of the cation positions shows that the chloride monohydrate structure is also closely related to these.     

Crystallographic investigations of select cathinones: emerging illicit street drugs known as `bath salts'

The name `bath salts', for an emerging class of synthetic cathinones, is derived from an attempt to evade prosecution and law enforcement. These are truly illicit drugs that have psychoactive CNS (central nervous system) stimulant effects and they have seen a rise in abuse as recreational drugs in the last few years since first having been seen in Japan in 2006. The ease of synthesis and modification of specific functional groups of the parent cathinone make these drugs particularly difficult to regulate. MDPV (3,4‐methylenedioxypyrovalerone) is commonly encountered as its hydrochloride salt (C<sub>16</sub>H<sub>21</sub>NO<sub>3</sub>·HCl), in either the hydrated or the anhydrous forms. This `bath salt' has various names in the US, e.g. `Super Coke', `Cloud Nine', and `Ivory Wave', to name just a few. We report here the structures of two forms of the HCl salt, one as a mixed bromide/chloride salt, C<sub>16</sub>H<sub>22</sub>NO<sub>3</sub><sup>+</sup>·0.343Br<sup>−</sup>·0.657Cl<sup>−</sup> [systematic name: 1‐(benzo[d][1,3]dioxol‐5‐yl)‐2‐(pyrrolidin‐1‐ium‐1‐yl)pentan‐1‐one bromide/chloride (0.343/0.657)], and the other with the H<sub>7</sub>O<sub>3</sub><sup>+</sup> cation, as well as the HCl counter‐ion [systematic name: hydroxonium 1‐(benzo[d][1,3]dioxol‐5‐yl)‐2‐(pyrrolidin‐1‐ium‐1‐yl)pentan‐1‐one dichloride, H<sub>7</sub>O<sub>3</sub><sup>+</sup>·C<sub>16</sub>H<sub>22</sub>NO<sub>3</sub><sup>+</sup>·2Cl<sup>−</sup>]. This is one of a very few structures (11 to be exact) in which we have a new example of a precisely determined hydroxonium cation. During the course of researching the clandestine manufacture of MDPV, we were surprised by the fact that a common precursor of this illicit stimulant is known to be the fragrant species piperonal, which is present in the fragrances of orchids, most particularly in the case of the vanilla orchid. We found that MDPV can be made by a Grignard reaction of this heliotropin. This may also explain the unexpected appearance of the bromide counter‐ion in some of the salts we encountered (C<sub>16</sub>H<sub>21</sub>NO<sub>3</sub>·HBr), one of which is presented here [systematic name: 1‐(benzo[d][1,3]dioxol‐5‐yl)‐2‐(pyrrolidin‐1‐ium‐1‐yl)pentan‐1‐one bromide, C<sub>16</sub>H<sub>22</sub>NO<sub>3</sub><sup>+</sup>·Br<sup>−</sup>]. Complexation of MDPV with a forensic crystallizing reagent, HAuCl<sub>4</sub>, yields the tetrachloridoaurate salt of this drug, (C<sub>16</sub>H<sub>22</sub>NO<sub>3</sub>)[AuCl<sub>4</sub>]. The heavy‐metal complexing agent HAuCl<sub>4</sub> has been used for over a century to identify common quarternary nitrogen‐containing drugs via microscopic identification. Another street drug, called ethylone (3,4‐methylenedioxyethylcathinone), is regularly sold and abused as its hydrochloride salt (C<sub>12</sub>H<sub>15</sub>NO<sub>3</sub>·HCl), and its structure is herein described (systematic name: N‐{1‐[(benzo[d][1,3]dioxol‐5‐yl)carbonyl]ethyl}ethanaminium chloride, C<sub>12</sub>H<sub>16</sub>NO<sub>3</sub><sup>+</sup>·Cl<sup>−</sup>). Marketed and sold as a `bath salt', `plant feeder', or `cleaning product', this drug is nothing more than a slight chemical modification of the banned drug methylone (3,4‐methylenedioxymethcathinone). As with previously popular synthetic cathinones, the abuse of ethylone has seen a recent increase due to regulatory efforts on previous generations of cathinones that are now banned.     

Two‐ and three‐dimensional hydrogen‐bonded structures in the 1:1 proton‐transfer compounds of 4,5‐dichlorophthalic acid with the isomeric monoaminobenzoic acids

The crystal structures of the 1:1 proton‐transfer compounds of 4,5‐dichlorophthalic acid with the three isomeric monoaminobenzoic acids, namely the hydrate 2‐carboxyanilinium 2‐carboxy‐4,5‐dichlorobenzoate dihydrate, C₇H₈NO₂⁺·C₈H₃Cl₂O₄⁻·2H₂O, (I), and the anhydrous salts 3‐carboxyanilinium 2‐carboxy‐4,5‐dichlorobenzoate, C₇H₈NO₂⁺·C₈H₃Cl₂O₄⁻, (II), and 4‐carboxyanilinium 2‐carboxy‐4,5‐dichlorobenzoate, C₇H₈NO₂⁺·C₈H₃Cl₂O₄⁻, (III), have been determined at 130 K. Compound (I) has a two‐dimensional hydrogen‐bonded sheet structure, while (II) and (III) are three‐dimensional. All three compounds feature sheet substructures formed through anilinium N⁺—H...O_carboxyl and anion carboxylic acid O—H...O_carboxyl interactions and, in the case of (I), additionally linked through the donor and acceptor associations of the solvent water molecules. However, (II) and (III) have additional lateral extensions of these substructures though cyclic R²₂(8) associations involving the carboxylic acid groups of the cations. Also, (II) and (III) have cation–anion π–π aromatic ring interactions. This work provides further examples illustrating the regular formation of network substructures in the 1:1 proton‐transfer salts of 4,5‐dichlorophthalic acid with the bifunctional aromatic amines.     

Supramolecular hydrogen‐bonding patterns in salts of the antifolate drugs trimethoprim and pyrimethamine

Nine salts of the antifolate drugs trimethoprim and pyrimethamine, namely, trimethoprimium [or 2,4‐diamino‐5‐(3,4,5‐trimethoxybenzyl)pyrimidin‐1‐ium] 2,5‐dichlorothiophene‐3‐carboxylate monohydrate (TMPDCTPC, 1:1), C₁₄H₁₉N₄O₃⁺·C₅HCl₂O₂S⁻, ( I ), trimethoprimium 3‐bromothiophene‐2‐carboxylate monohydrate, (TMPBTPC, 1:1:1), C₁₄H₁₉N₄O₃⁺·C₅H₂BrO₂S⁻·H₂O, ( II ), trimethoprimium 3‐chlorothiophene‐2‐carboxylate monohydrate (TMPCTPC, 1:1:1), C₁₄H₁₉N₄O₃⁺·C₅H₂ClO₂S⁻·H₂O, ( III ), trimethoprimium 5‐methylthiophene‐2‐carboxylate monohydrate (TMPMTPC, 1:1:1), C₁₄H₁₉N₄O₃⁺·C₆H₅O₂S⁻·H₂O, ( IV ), trimethoprimium anthracene‐9‐carboxylate sesquihydrate (TMPAC, 2:2:3), C₁₄H₁₉N₄O₃⁺·C₁₅H₉O₂⁻·1.5H₂O, ( V ), pyrimethaminium [or 2,4‐diamino‐5‐(4‐chlorophenyl)‐6‐ethylpyrimidin‐1‐ium] 2,5‐dichlorothiophene‐3‐carboxylate (PMNDCTPC, 1:1), C₁₂H₁₄ClN₄⁺·C₅HCl₂O₂S⁻, ( VI ), pyrimethaminium 5‐bromothiophene‐2‐carboxylate (PMNBTPC, 1:1), C₁₂H₁₄ClN₄⁺·C₅H₂BrO₂S⁻, ( VII ), pyrimethaminium anthracene‐9‐carboxylate ethanol monosolvate monohydrate (PMNAC, 1:1:1:1), C₁₂H₁₄ClN₄⁺·C₁₅H₉O₂⁻·C₂H₅OH·H₂O, ( VIII ), and bis(pyrimethaminium) naphthalene‐1,5‐disulfonate (PMNNSA, 2:1), 2C₁₂H₁₄ClN₄⁺·C₁₀H₆O₆S₂²⁻, ( IX ), have been prepared and characterized by single‐crystal X‐ray diffraction. In all the crystal structures, the pyrimidine N1 atom is protonated. In salts ( I )–( III ) and ( VI )–( IX ), the 2‐aminopyrimidinium cation interacts with the corresponding anion via a pair of N—H…O hydrogen bonds, generating the robust R₂²(8) supramolecular heterosynthon. In salt ( IV ), instead of forming the R₂²(8) heterosynthon, the carboxylate group bridges two pyrimidinium cations via N—H…O hydrogen bonds. In salt ( V ), one of the carboxylate O atoms bridges the N1—H group and a 2‐amino H atom of the pyrimidinium cation to form a smaller R₂¹(6) ring instead of the R₂²(8) ring. In salt ( IX ), the sulfonate O atoms mimic the role of carboxylate O atoms in forming an R₂²(8) ring motif. In salts ( II )–( IX ), the pyrimidinium cation forms base pairs via a pair of N—H…N hydrogen bonds, generating a ring motif [R₂²(8) homosynthon]. Compounds ( II ) and ( III ) are isomorphous. The quadruple DDAA (D = hydrogen‐bond donor and A = hydrogen‐bond acceptor) array is observed in ( I ). In salts ( II )–( IV ) and ( VI )–( IX ), quadruple DADA arrays are present. In salts ( VI ) and ( VII ), both DADA and DDAA arrays co‐exist. The crystal structures are further stabilized by π–π stacking interactions [in ( I ), ( V ) and ( VII )–( IX )], C—H…π interactions [in ( IV )–( V ) and ( VII )–( IX )], C—Br…π interactions [in ( II )] and C—Cl…π interactions [in ( I ), ( III ) and ( VI )]. Cl…O and Cl…Cl halogen‐bond interactions are present in ( I ) and ( VI ), with distances and angles of 3.0020 (18) and 3.5159 (16) Å, and 165.56 (10) and 154.81 (11)°, respectively.     

New hydrophobic L‐amino acid salts: maleates of L‐leucine,L‐isoleucine and L‐norvaline

Crystals of maleates of three amino acids with hydrophobic side chains [L‐leucenium hydrogen maleate, C₆H₁₄NO₂⁺·C₄H₃O₄⁻, (I), L‐isoleucenium hydrogen maleate hemihydrate, C₆H₁₄NO₂⁺·C₄H₃O₄⁻·0.5H₂O, (II), and L‐norvalinium hydrogen maleate–L‐norvaline (1/1), C₅H₁₁NO₂⁺·C₄H₃O₄⁻·C₅H₁₂NO₂, (III)], were obtained. The new structures contain C₂²(12) chains, or variants thereof, that are a common feature in the crystal structures of amino acid maleates. The L‐leucenium salt is remarkable due to a large number of symmetrically non‐equivalent units (Z′ = 3). The L‐isoleucenium salt is a hydrate despite the fact that L‐isoleucine is a nonpolar hydrophobic amino acid (previously known amino acid maleates formed hydrates only with lysine and histidine, which are polar and hydrophilic). The L‐norvalinium salt provides the first example where the dimeric cation L‐Nva...L‐NvaH⁺ was observed. All three compounds have layered noncentrosymmetric structures. Preliminary tests have shown the presence of the second harmonic generation (SGH) effect for all three compounds.     

The effect of amino acid backbone length on molecular packing: crystalline tartrates of glycine, β‐alanine, γ‐aminobutyric acid (GABA) and dl‐α‐aminobutyric acid (AABA)

We report a novel 1:1 cocrystal of β‐alanine with dl ‐tartaric acid, C₃H₇NO₂·C₄H₆O₆, (II), and three new molecular salts of dl ‐tartaric acid with β‐alanine {3‐azaniumylpropanoic acid–3‐azaniumylpropanoate dl ‐tartaric acid–dl ‐tartrate, [H(C₃H₇NO₂)₂]⁺·[H(C₄H₅O₆)₂]⁻, (III)}, γ‐aminobutyric acid [3‐carboxypropanaminium dl ‐tartrate, C₄H₁₀NO₂⁺·C₄H₅O₆⁻, (IV)] and dl ‐α‐aminobutyric acid {dl ‐2‐azaniumylbutanoic acid–dl ‐2‐azaniumylbutanoate dl ‐tartaric acid–dl ‐tartrate, [H(C₄H₉NO₂)₂]⁺·[H(C₄H₅O₆)₂]⁻, (V)}. The crystal structures of binary crystals of dl ‐tartaric acid with glycine, (I), β‐alanine, (II) and (III), GABA, (IV), and dl ‐AABA, (V), have similar molecular packing and crystallographic motifs. The shortest amino acid (i.e. glycine) forms a cocrystal, (I), with dl ‐tartaric acid, whereas the larger amino acids form molecular salts, viz. (IV) and (V). β‐Alanine is the only amino acid capable of forming both a cocrystal [i.e. (II)] and a molecular salt [i.e. (III)] with dl ‐tartaric acid. The cocrystals of glycine and β‐alanine with dl ‐tartaric acid, i.e. (I) and (II), respectively, contain chains of amino acid zwitterions, similar to the structure of pure glycine. In the structures of the molecular salts of amino acids, the amino acid cations form isolated dimers [of β‐alanine in (III), GABA in (IV) and dl ‐AABA in (V)], which are linked by strong O—H…O hydrogen bonds. Moreover, the three crystal structures comprise different types of dimeric cations, i.e. (A…A)⁺ in (III) and (V), and A⁺…A⁺ in (IV). Molecular salts (IV) and (V) are the first examples of molecular salts of GABA and dl ‐AABA that contain dimers of amino acid cations. The geometry of each investigated amino acid (except dl ‐AABA) correlates with the melting point of its mixed crystal.     

4‐Carboxypyridinium perchlorate 18‐crown‐6 dihydrate clathrate and 4‐carboxypyridinium tetrafluoroborate 18‐crown‐6 dihydrate clathrate

Mixtures of 4‐carboxypyridinium perchlorate or 4‐carboxypyridinium tetrafluoroborate and 18‐crown‐6 (1,4,7,10,13,16‐hexaoxacyclooctadecane) in ethanol and water solution yielded the title supramolecular salts, C₆H₆NO₂⁺·ClO₄⁻·C₁₂H₂₄O₆·2H₂O and C₆H₆NO₂⁺·BF₄⁻·C₁₂H₂₄O₆·2H₂O. Based on their similar crystal symmetries, unit cells and supramolecular assemblies, the salts are essentially isostructural. The asymmetric unit in each structure includes one protonated isonicotinic acid cation and one crown ether molecule, which together give a [(C₆H₆NO₂)(18‐crown‐6)]⁺ supramolecular cation. N—H...O hydrogen bonds between the protonated N atoms and a single O atom of each crown ether result in the 4‐carboxypyridinium cations `perching' on the 18‐crown‐6 molecules. Further hydrogen‐bonding interactions involving the supramolecular cation and both water molecules form a one‐dimensional zigzag chain that propagates along the crystallographic c direction. O—H...O or O—H...F hydrogen bonds between one of the water molecules and the anions fix the anion positions as pendant upon this chain, without further increasing the dimensionality of the supramolecular network.     

Differences and similarities among hypoxanthinium nitrate hydrate structures

Crystals of hypoxanthinium (6‐oxo‐1H,7H‐purin‐9‐ium) nitrate hydrates were investigated by means of X‐ray diffraction at different temperatures. The data for hypoxanthinium nitrate monohydrate (C₅H₅N₄O⁺·NO₃^?·H₂O, Hx1 ) were collected at 20, 105 and 285 K. The room‐temperature phase was reported previously [Schmalle et al. (1990). Acta Cryst. C 46 , 340–342] and the low‐temperature phase has not been investigated yet. The structure underwent a phase transition, which resulted in a change of space group from Pmnb to P2₁/n at lower temperature and subsequently in nonmerohedral twinning. The structure of hypoxanthinium dinitrate trihydrate (H₃O⁺·C₅H₅N₄O⁺·2NO₃^?·2H₂O, Hx2 ) was determined at 20 and 100 K, and also has not been reported previously. The Hx2 structure consists of two types of layers: the `hypoxanthinium nitrate monohydrate' layers (HX) observed in Hx1 and layers of Zundel complex H₃O⁺·H₂O interacting with nitrate anions (OX). The crystal can be considered as a solid solution of two salts, i.e. hypoxanthinium nitrate monohydrate, C₅H₅N₄O⁺·NO₃^?·H₂O, and oxonium nitrate monohydrate, H₃O⁺(H₂O)·NO₃^?.     

One‐dimensional hydrogen‐bonded structures in the 1:1 proton‐transfer compounds of 4,5‐dichlorophthalic acid with 8‐hydroxyquinoline, 8‐aminoquinoline and quinoline‐2‐carboxylic acid (quinaldic acid)

The structures of the 1:1 proton‐transfer compounds of 4,5‐dichlorophthalic acid with 8‐hydroxyquinoline, 8‐aminoquinoline and quinoline‐2‐carboxylic acid (quinaldic acid), namely anhydrous 8‐hydroxyquinolinium 2‐carboxy‐4,5‐dichlorobenzoate, C₉H₈NO⁺·C₈H₃Cl₂O₄⁻, (I), 8‐aminoquinolinium 2‐carboxy‐4,5‐dichlorobenzoate, C₉H₉N₂⁺·C₈H₃Cl₂O₄⁻, (II), and the adduct hydrate 2‐carboxyquinolinium 2‐carboxy‐4,5‐dichlorobenzoate quinolinium‐2‐carboxylate monohydrate, C₁₀H₈NO₂⁺·C₈H₃Cl₂O₄⁻·C₁₀H₇NO₂·H₂O, (III), have been determined at 130 K. Compounds (I) and (II) are isomorphous and all three compounds have one‐dimensional hydrogen‐bonded chain structures, formed in (I) through O—H...O_carboxyl extensions and in (II) through N⁺—H...O_carboxyl extensions of cation–anion pairs. In (III), a hydrogen‐bonded cyclic R₂²(10) pseudo‐dimer unit comprising a protonated quinaldic acid cation and a zwitterionic quinaldic acid adduct molecule is found and is propagated through carboxylic acid O—H...O_carboxyl and water O—H...O_carboxyl interactions. In both (I) and (II), there are also cation–anion aromatic ring π–π associations. This work further illustrates the utility of both hydrogen phthalate anions and interactive‐group‐substituted quinoline cations in the formation of low‐dimensional hydrogen‐bonded structures.     

Structural study of six cycloalkylammonium cinnamate salt structures featuring one‐dimensional columns and two‐dimensional hydrogen‐bonded networks

Six ammonium carboxylate salts, namely cyclopentylammonium cinnamate, C₅H₁₂N⁺·C₉H₇O₂⁻, (I), cyclohexylammonium cinnamate, C₆H₁₄N⁺·C₉H₇O₂⁻, (II), cycloheptylammonium cinnamate form I, C₇H₁₆N⁺·C₉H₇O₂⁻, (IIIa), and form II, (IIIb), cyclooctylammonium cinnamate, C₈H₁₈N⁺·C₉H₇O₂⁻, (IV), and cyclododecylammonium cinnamate, C₁₂H₂₆N⁺·C₉H₇O₂⁻, (V), are reported. Salts (II)–(V) all have a 1:1 ratio of cation to anion and feature three N⁺—H...O⁻ hydrogen bonds forming one‐dimensional hydrogen‐bonded columns consisting of repeating R₄³(10) rings, while salt (I) has a two‐dimensional network made up of alternating R₄⁴(12) and R⁶₈(20) rings. Salt (III) consists of two polymorphic forms, viz. form I having Z′ = 1 and form II with Z′ = 2. The latter polymorph has disorder of the cycloheptane rings in the two cations, as well as whole‐molecule disorder of one of the cinnamate anions. A similar, but ordered, Z′ = 2 structure is seen in salt (IV).     

Molecular structures of 3‐[(2,2,3,3‐tetrafluoropropoxy)methyl]‐ and 3‐[(2,2,3,3,3‐pentafluoropropoxy)methyl]pyridinium saccharinates

The salts 3‐[(2,2,3,3‐tetrafluoropropoxy)methyl]pyridinium saccharinate, C₉H₁₀F₄NO⁺·C₇H₄NO₃S⁻, (1), and 3‐[(2,2,3,3,3‐pentafluoropropoxy)methyl]pyridinium saccharinate, C₉H₉F₅NO⁺·C₇H₄NO₃S⁻, (2), i.e. saccharinate (or 1,1‐dioxo‐1λ⁶,2‐benzothiazol‐3‐olate) salts of pyridinium with –CH₂OCH₂CF₂CF₂H and –CH₂OCH₂CF₂CF₃meta substituents, respectively, were investigated crystallographically in order to compare their fluorine‐related weak interactions in the solid state. Both salts demonstrate a stable synthon formed by the pyridinium cation and the saccharinate anion, in which a seven‐membered ring reveals a double hydrogen‐bonding pattern. The twist between the pyridinium plane and the saccharinate plane in (2) is 21.26 (8)° and that in (1) is 8.03 (6)°. Both salts also show stacks of alternating cation–anion π‐interactions. The layer distances, calculated from the centroid of the saccharinate plane to the neighbouring pyridinium planes, above and below, are 3.406 (2) and 3.517 (2) Å in (1), and 3.409 (3) and 3.458 (3) Å in (2).     

Diaquaiodidotetrasarcosinepotassium: an overview of sarcosine metal halogenide structures

The monoclinic crystal structure of tetrasarcosine potassium iodide dihydrate {or catena‐poly[[potassium‐tetra‐μ‐sarcosine‐κ⁴O:O′;κ⁴O:O] iodide dihydrate]}, {[K(C₃H₇NO₂)₄]I·2H₂O}_n or Sar₄·KI·2H₂O (space group C2/c), comprises two crystallographically different sarcosine molecules and one water molecule on general positions, and one K⁺ cation and one I⁻ anion located on twofold axes. The irregular eight‐coordinated K⁺ polyhedra are connected into infinite chains along [001] via sarcosine molecules. This compound is the first sarcosine metal halogenide salt with a 4:1 ratio. A short overview of other sarcosine metal halogenide salts is presented and relationships to similar glycine salts are discussed.     

Neutral 4‐phenyl‐1‐[phenyl(pyridin‐2‐yl)methylidene]semicarbazide and its salt forms with inorganic anions

Semicarbazones can exist in two tautomeric forms. In the solid state, they are found in the keto form. This work presents the synthesis, structures and spectroscopic characterization (IR and NMR spectroscopy) of four such compounds, namely the neutral molecule 4‐phenyl‐1‐[phenyl(pyridin‐2‐yl)methylidene]semicarbazide, C₁₉H₁₆N₄O, (I), abbreviated as HBzPyS, and three different hydrated salts, namely the chloride dihydrate, C₁₉H₁₇N₄O⁺·Cl^?·2H₂O, (II), the nitrate dihydrate, C₁₉H₁₇N₄O⁺·NO₃^?·2H₂O, (III), and the thiocyanate 2.5‐hydrate, C₁₉H₁₇N₄O⁺·SCN^?·2.5H₂O, (IV), of 2‐[phenyl({[(phenylcarbamoyl)amino]imino})methyl]pyridinium, abbreviated as [H₂BzPyS]⁺·X^?·nH₂O, with X = Cl^? and n = 2 for (II), X = NO₃^? and n = 2 for (III), and X = SCN^? and n = 2.5 for (IV), showing the influence of the anionic form in the intermolecular interactions. Water molecules and counter‐ions (chloride or nitrate) are involved in the formation of a two‐dimensional arrangement by the establishment of hydrogen bonds with the N—H groups of the cation, stabilizing the E isomers in the solid state. The neutral HBzPyS molecule crystallized as the E isomer due to the existence of weak π–π interactions between pairs of molecules. The calculated IR spectrum of the hydrated [H₂BzPyS]⁺ cation is in good agreement with the experimental results.     

Supramolecular association in proton‐transfer adducts containing benzamidinium cations. I. Four molecular salts with uracil derivatives

Four organic salts, namely benzamidinidium orotate (2,6‐dioxo‐1,2,3,6‐tetrahydropyrimidine‐4‐carboxylate) hemihydrate, C₇H₉N₂⁺·C₅H₃N₂O₄⁻·0.5H₂O (BenzamH⁺·Or⁻), (I), benzamidinium isoorotate (2,4‐dioxo‐1,2,3,4‐tetrahydropyrimidine‐5‐carboxylate) trihydrate, C₇H₉N₂⁺·C₅H₃N₂O₄⁻·3H₂O (BenzamH⁺·Isor⁻), (II), benzamidinium diliturate (5‐nitro‐2,6‐dioxo‐1,2,3,6‐tetrahydropyrimidin‐4‐olate) dihydrate, C₇H₉N₂⁺·C₄H₂N₃O₅⁻·2H₂O (BenzamH⁺·Dil⁻), (III), and benzamidinium 5‐nitrouracilate (5‐nitro‐2,4‐dioxo‐1,2,3,4‐tetrahydropyrimidin‐1‐ide), C₇H₉N₂⁺·C₄H₂N₃O₄⁻ (BenzamH⁺·Nit⁻), (IV), have been synthesized by a reaction between benzamidine (benzenecarboximidamide or Benzam) and the appropriate carboxylic acid. Proton transfer occurs to the benzamidine imino N atom. In all four acid–base adducts, the asymmetric unit consists of one tautomeric aminooxo anion (Or⁻, Isor⁻, Dil⁻ and Nit⁻) and one monoprotonated benzamidinium cation (BenzamH⁺), plus one‐half (which lies across a twofold axis), three and two solvent water molecules in (I), (II) and (III), respectively. Due to the presence of protonated benzamidine, these acid–base complexes form supramolecular synthons characterized by N⁺—H...O⁻ and N⁺—H...N⁻ (±)‐charge‐assisted hydrogen bonds (CAHB).     

Six two‐ and three‐component ammonium carboxylate salt structures with a ladder‐type hydrogen‐bonding motif,three incorporating neutral carboxylic acid molecules

Six ammonium carboxylate salts are synthesized and reported, namely 2‐propylammonium benzoate, C₃H₁₀N⁺·C₇H₅O₂⁻, (I), benzylammonium (R)‐2‐phenylpropionate, C₆H₁₀N⁺·C₉H₉O₂⁻, (II), (RS)‐1‐phenylethylammonium naphthalene‐1‐carboxylate, C₈H₁₂N⁺·C₁₁H₇O₂⁻, (III), benzylammonium–benzoate–benzoic acid (1/1/1), C₆H₁₀N⁺·C₇H₅O₂⁻·C₇H₆O₂, (IV), cyclopropylammonium–benzoate–benzoic acid (1/1/1), C₃H₈N⁺·C₇H₅O₂⁻·C₇H₆O₂, (V), and cyclopropylammonium–ea‐cis‐cyclohexane‐1,4‐dicarboxylate–ee‐trans‐cyclohexane‐1,4‐dicarboxylic acid (2/1/1), 2C₃H₈N⁺·C₈H₁₀O₄²⁻·C₈H₁₂O₄, (VI). Salts (I)–(III) all have a 1:1 ratio of cation to anion and feature three N⁺—H...O⁻ hydrogen bonds which form one‐dimensional hydrogen‐bonded ladders. Salts (I) and (II) have type II ladders, consisting of repeating R₄³(10) rings, while (III) has type III ladders, in this case consisting of alternating R₄²(8) and R₄⁴(12) rings. Salts (IV) and (V) have a 1:1:1 ratio of cation to anion to benzoic acid. They have type III ladders formed by three N⁺—H...O⁻ hydrogen bonds, while the benzoic acid molecules are pendant to the ladders and hydrogen bond to them via O—H...O⁻ hydrogen bonds. Salt (VI) has a 2:1:1 ratio of cation to anion to acid and does not feature any hydrogen‐bonded ladders; instead, the ionized and un‐ionized components form a three‐dimensional network of hydrogen‐bonded rings. The two‐component 1:1 salts are formed from a 1:1 ratio of amine to acid. To create the three‐component salts (IV)–(VI), the ratio of amine to acid was reduced so as to deprotonate only half of the acid molecules, and then to observe how the un‐ionized acid molecules are incorporated into the ladder motif. For (IV) and (V), the ratio of amine to acid was reduced to 1:2, while for (VI) the ratio of amine to acid required to deprotonate only half the diacid molecules was 1:1.     

Three salts from the reactions of cysteamine and cystamine with L‐(+)‐tartaric acid

Reaction between cysteamine (systematic name: 2‐aminoethanethiol, C₂H₇NS) and L‐(+)‐tartaric acid [systematic name: (2R,3R)‐2,3‐dihydroxybutanedioic acid, C₄H₆O₆] results in a mixture of cysteamine tartrate(1−) monohydrate, C₂H₈NS⁺·C₄H₅O₆⁻·H₂O, (I), and cystamine bis[tartrate(1−)] dihydrate, C₄H₁₄N₂S₂²⁺·2C₄H₅O₆⁻·2H₂O, (III). Cystamine [systematic name: 2,2′‐dithiobis(ethylamine), C₄H₁₂N₂S₂], reacts with L‐(+)‐tartaric acid to produce a mixture of cystamine tartrate(2−), C₄H₁₄N₂S₂²⁺·C₄H₄O₆²⁻, (II), and (III). In each crystal structure, the anions are linked by O—H...O hydrogen bonds that run parallel to the a axis. In addition, hydrogen bonding involving protonated amino groups in all three salts, and water molecules in (I) and (III), leads to extensive three‐dimensional hydrogen‐bonding networks. All three salts crystallize in the orthorhombic space group P2₁2₁2₁.     

Hydro­gen bonding in proton‐transfer compounds of 5‐sulfosalicylic acid with bicyclic heteroaromatic Lewis bases

The crystal structures of quinolinium 3‐carboxy‐4‐hydroxy­benzene­sulfonate trihydrate, C₉H₈N⁺·C₇H₅O₆S⁻·3H₂O, (I), 8‐hydroxy­quinolinium 3‐carboxy‐4‐hydroxy­benzene­sulfonate monohydrate, C₉H₈NO⁺·C₇H₅O₆S⁻·H₂O, (II), 8‐amino­quinolinium 3‐carboxy‐4‐hydroxy­benzene­sulfonate dihydrate, C₉H₉N₂⁺·C₇H₅O₆S⁻·2H₂O, (III), and 2‐carboxy­quinolinium 3‐carboxy‐4‐hydroxy­benzene­sulfonate quinolinium‐2‐carboxylate, C₁₀H₈NO₂⁺·C₇H₅O₆S⁻·C₁₀H₇NO₂, (IV), four proton‐transfer compounds of 5‐sulfosalicylic acid with bicyclic heteroaromatic Lewis bases, reveal in each the presence of variously hydrogen‐bonded polymers. In only one of these compounds, viz. (II), is the protonated quinolinium group involved in a direct primary N⁺—H⋯O(sulfonate) hydrogen‐bonding interaction, while in the other hydrates, viz. (I) and (III), the water mol­ecules participate in the primary intermediate interaction. The quinaldic acid (quinoline‐2‐carboxylic acid) adduct, (IV), exhibits cation–cation and anion–adduct hydrogen bonding but no direct formal heteromolecular interaction other than a number of weak cation–anion and cation–adduct π–π stacking associations. In all other compounds, secondary interactions give rise to network polymer structures.