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.     

Zeta Potential of Pyrophyllite in Aqueous Solutions of Alkaline and Alkaline Earth Metal Cations and Low‐Molecular‐Weight Organic Anions

Electrokinetic behavior of pyrophyllite in aqueous solutions of K⁺, Na⁺, Mg²⁺, and Ca²⁺ ions and effect of low‐molecular‐weight organic anions like acetate (C₂H₃O₂ ^?), oxalate (C₂O₄ ^2?), and citrate (C₆H₅O₇ ^3?) on the zeta potential was investigated. Pyrophyllite has higher negative zeta potential values in the presence of alkaline metal cations than in water, and it comes close to positive values in the presence of alkaline earth metal cations at low pH values. Results revealed that presence of low‐molecular‐weight organic anions led to a decrease in the zeta potential in the order of acetate>citrate>oxalate.     

Sodium di­hydrogen tris­(cyclo­propane­carboxyl­ate)

The title acid salt, Na⁺·C₄H₅O₂^?·2C₄H₆O₂, contains finite anions in which two cyclo­propanoic acid mol­ecules are hydrogen bonded to a cyclo­propanoate residue. Each such anion interacts with four different Na⁺ cations.     

Polynuclear coordination compounds of alkali metal ions with organic chromophores

The crystal structures of sodium 4‐({4‐[N,N‐bis(2‐hydroxy­ethyl)­amino]­phenyl}diazenyl)­benzoate 3.5‐hydrate, Na⁺·C₁₇H₁₈N₃O₄^?·3.5H₂O, (I), and potassium 4‐({4‐[N,N‐bis(2‐hydroxy­ethyl)­amino]­phenyl}diazenyl)­benzoate dihydrate, K⁺·C₁₇H₁₈N₃O₄^?·2H₂O, (II), are described. The results indicate an octahedral coordination around sodium in (I) and a trigonal prismatic coordination around potassium in (II). In both cases, coordination around the metal cation is achieved through O atoms of the water mol­ecules and hydroxy groups of the chromophore. The organic conjugated part of the chromophore is approximately planar in (I), while a dihedral angle of 30.7 (2)° between the planes of the phenyl rings is observed in (II).     

Impact of the anion and chalcogen on the crystal structure and properties of 4,6‐dimethyl‐2‐pyrimido(thio)nium halides

By the reaction of urea or thiourea, acetylacetone and hydrogen halide (HF, HBr or HI), we have obtained seven new 4,6‐dimethyl‐2‐pyrimido(thio)nium salts, which were characterized by single‐crystal X‐ray diffraction, namely, 4,6‐dimethyl‐2‐oxo‐2,3‐dihydropyrimidin‐1‐ium bifluoride, C₆H₉N₂O⁺·HF₂^? or (dmpH)F₂H, 4,6‐dimethyl‐2‐oxo‐2,3‐dihydropyrimidin‐1‐ium bromide, C₆H₉N₂O⁺·Br^? or (dmpH)Br, 4,6‐dimethyl‐2‐oxo‐2,3‐dihydropyrimidin‐1‐ium iodide, C₆H₉N₂O⁺·I^? or (dmpH)I, 4,6‐dimethyl‐2‐oxo‐2,3‐dihydropyrimidin‐1‐ium iodide–urea (1/1), C₆H₉N₂O⁺·I^?·CH₄N₂O or (dmpH)I·ur, 4,6‐dimethyl‐2‐sulfanylidene‐2,3‐dihydropyrimidin‐1‐ium bifluoride–thiourea (1/1), C₆H₉N₂S⁺·HF₂^?·CH₄N₂S or (dmptH)F₂H·tu, 4,6‐dimethyl‐2‐sulfanylidene‐2,3‐dihydropyrimidin‐1‐ium bromide, C₆H₉N₂S⁺·Br^? or (dmptH)Br, and 4,6‐dimethyl‐2‐sulfanylidene‐2,3‐dihydropyrimidin‐1‐ium iodide, C₆H₉N₂S⁺·I^? or (dmptH)I. Three HCl derivatives were described previously in the literature, namely, 4,6‐dimethyl‐2‐oxo‐2,3‐dihydropyrimidin‐1‐ium chloride, (dmpH)Cl, 4,6‐dimethyl‐2‐sulfanylidene‐2,3‐dihydropyrimidin‐1‐ium chloride monohydrate, (dmptH)Cl·H₂O, and 4,6‐dimethyl‐2‐sulfanylidene‐2,3‐dihydropyrimidin‐1‐ium chloride–thiourea (1/1), (dmptH)Cl·tu. Structural analysis shows that in 9 out of 10 of these compounds, the ions form one‐dimensional chains or ribbons stabilized by hydrogen bonds. Only in one compound are parallel planes present. In all the structures, there are charge‐assisted N⁺—H…X^? hydrogen bonds, as well as weaker C_Ar⁺—H…X^? and π⁺…X^? interactions. The structures can be divided into five types according to their hydrogen‐bond patterns. All the compounds undergo thermal decomposition at relatively high temperatures (150–300 °C) without melting. Four oxopyrimidinium salts containing a π⁺…X^?…π⁺ sandwich‐like structural motif exhibit luminescent properties.     

Lagoden dimethylformamide hemisolvate dihydrate: absolute configuration,dipolar interactions and hydrogen‐bonding interactions

Lagoden (L·3H₂O, where L is Na⁺·C₂₀H₃₃O₆⁻; sodium 3β,16,18‐trihydroxy‐8,13‐epi‐9,13‐epoxylabdan‐15‐oate trihydrate) is widely used as an effective haemostatic agent. It has been crystallized from dimethylformamide (DMF) as sodium 3β,16,18‐trihydroxy‐8,13‐epi‐9,13‐epoxylabdan‐15‐oate dimethylformamide hemisolvate dihydrate, Na⁺·C₂₀H₃₃O₆⁻·0.5C₃H₇NO·2H₂O or L₂·DMF·4H₂O, and the asymmetric unit contains two of the latter formulation. The four symmetry‐independent Na⁺ cations and lagoden anions, one DMF molecule and six of the eight symmetry‐independent water molecules assemble into a one‐dimensional polymeric structure via dipolar and hydrogen‐bonding interactions. The lagoden anions coordinate to the Na⁺ cations via the carboxylate groups and the two primary hydroxy groups, whereas the secondary OH groups are solely involved in hydrogen bonding. Two of the four symmetry‐independent lagoden anions act in a chelating mode, forming seven‐membered chelate rings. The absolute structure, based on anomalous dispersion data collected at 130 K with Cu Kα radiation, confirms an inverted configuration at chiral centres C8 and C13 (labdane numbering) relative to the labdane skeleton.     

Direct Determination of Phosphite in Fertilizers by Flow‐Injection Amperometry

A sensor based on graphite electrode modified with palladium‐platinum‐palladium film is proposed for phosphite determination by flow‐injection amperometry. The modified electrode was prepared by a sequential cathodic deposition of Pd, Pt and Pd on a graphite electrode from 0.5% m/v PdCl₂+28% m/v NH₄OH and 2% m/v H₂PtCl₆+10% v/v H₂SO₄ solutions. After suitable conditioning, the electrode showed catalytic activity for phosphite oxidation when 0.15 V was applied. The proposed system handles approximately 50 samples per hour (0.01–0.05 mol L^?1 Na₂HPO₃; R²=0.9997), consuming ca. 70 μL of sample per determination. The limit of detection and amperometric sensibility were 5×10^?4 mol L^?1 and 1.5 mA L mol^?1, respectively. The proposed method was applied to analysis of fertilizer samples without pre‐treatment. Results are in agreement with those obtained by spectrophotometry and titrimetry at 95% confidence level and good recoveries (96–109%) of spiked samples were found. Relative standard deviation (n= 12) of a 0.01 mol L^?1 Na₂HPO₃ sample was 2%. The useful lifetime of modified electrode was around 220 determinations. For routine purposes it means that this electrode can be continuously used for 5 hours.     

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.     

The design of novel metronidazole benzoate structures: exploring stoichiometric diversity

The use of supramolecular synthons as a strategy to control crystalline structure is a crucial factor in developing new solid forms with physicochemical properties optimized by design. However, to achieve this objective, it is necessary to understand the intermolecular interactions in the context of crystal packing. The feasibility of a given synthon depends on its flexibility to combine the drug with a variety of coformers. In the present work, the imidazole–hydroxy synthon is investigated using as the target molecule benzoylmetronidazole [BZMD; systematic name 2‐(2‐methyl‐5‐nitro‐1H‐imidazol‐1‐yl)ethyl benzoate], whose imidazole group seems to be a suitable acceptor for hydrogen bonds. Thus, coformers with carboxylic acid and phenol groups were chosen. According to the availability of binding sites presented in the coformer, and considering the proposed synthon and hydrogen‐bond complementarity as major factors, different drug–coformer stoichiometric ratios were explored (1:1, 2:1 and 3:1). Thirteen new solid forms (two salts and eleven cocrystals) were produced, namely BZMD–benzoic acid (1/1), C₁₃H₁₃N₃O₄·C₇H₆O₂, BZMD–β‐naphthol (1/1), C₁₃H₁₃N₃O₄·C₁₀H₈O, BZMD–4‐methoxybenzoic acid (1/1), C₁₃H₁₃N₃O₄·C₈H₈O₃, BZMD–3,5‐dinitrobenzoic acid (1/1), C₁₃H₁₃N₃O₄·C₇H₄N₂O₆, BZMD–3‐aminobenzoic acid (1/1), C₁₃H₁₃N₃O₄·C₇H₇NO₂, BZMD–salicylic acid (1/1), C₁₃H₁₃N₃O₄·C₇H₆O₃, BZMD–maleic acid (1/1) {as the salt 1‐[2‐(benzoyloxy)ethyl]‐2‐methyl‐5‐nitro‐1H‐imidazol‐3‐ium 3‐carboxyprop‐2‐enoate}, C₁₃H₁₄N₃O₄⁺·C₄H₃O₄^?, BZMD–isophthalic acid (1/1), C₁₃H₁₃N₃O₄·C₈H₆O4, BZMD–resorcinol (2/1), 2C₁₃H₁₃N₃O₄·C₆H₆O₂, BZMD–fumaric acid (2/1), C₁₃H₁₃N₃O₄·0.5C₄H₄O₄, BZMD–malonic acid (2/1), 2C₁₃H₁₃N₃O₄·C₃H₂O₄, BZMD–2,6‐dihydroxybenzoic acid (1/1) {as the salt 1‐[2‐(benzoyloxy)ethyl]‐2‐methyl‐5‐nitro‐1H‐imidazol‐3‐ium 2,6‐dihydroxybenzoate}, C₁₃H₁₄N₃O₄⁺·C₇H₅O₄^?, and BZMD–3,5‐dihydroxybenzoic acid (3/1), 3C₁₃H₁₃N₃O₄·C₇H₆O₄, and their crystalline structures elucidated, confirming the robustness of the selected synthon.     

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.     

Chiral anionic layers in tartramide spiroborate salts and variable solvation for [NR4][B(TarNH2)2] (R = Et,Pr or Bu)

The spiroborate anion, namely, 2,3,7,8‐tetracarboxamido‐1,4,6,9‐tetraoxa‐5λ⁴‐boraspiro[4.4]nonane, [B(TarNH₂)₂]^?, derived from the diol l ‐tartramide TarNH₂, [CH(O)(CONH₂)]₂, shows a novel self‐assembly into two‐dimensional (2D) layer structures in its salts with alkylammonium cations, [NR₄]⁺ (R = Et, Pr and Bu), and sparteinium, [HSpa]⁺, in which the cations and anions are segregated. The structures of four such salts are reported, namely, the tetrapropylazanium salt, C₁₂H₂₈N⁺·C₈H₁₂BN₄O₈^?, the tetraethylazanium salt hydrate, C₈H₂₀N⁺·C₈H₁₂BN₄O₈^?·6.375H₂O, the tetrabutylazanium salt as the ethanol monosolvate hemihydrate, C₁₆H₃₆N⁺·C₈H₁₂BN₄O₈^?·C₂H₅OH·0.5H₂O, and the sparteinium (7‐aza‐15‐azoniatetracyclo[7.7.1.0^2,7.0^10,15]heptadecane) salt as the ethanol monosolvate, C₁₅H₂₇N₂⁺·C₈H₁₂BN₄O₈^?·C₂H₅OH. The 2D anion layers have preserved intermolecular hydrogen bonding between the amide groups and a typical metric repeat of around 10 × 15 Å. The constraint of matching the interfacial area organizes the cations into quite different solvated arrangements, i.e. the [NEt₄] salt is highly hydrated with around 6.5H₂O per cation, the [NPr₄] salt apparently has a good metric match to the anion layer and is unsolvated, whilst the [NBu₄] salt is intermediate and has EtOH and H₂O in its cation layer, which is similar to the arrangement for the chiral [HSpa]⁺ cation. This family of salts shows highly organized chiral space and offers potential for the resolution of both chiral cations and neutral chiral solvent molecules.     

4‐Pyridone–terephthalic acid–water (2/1/2) and bis(3‐hydroxypyridinium) terephthalate

4‐Hydroxypyridine and terephthalic acid cocrystallize as a hydrate, 4‐pyridone–terephthalic acid–water (2/1/2), 2C₅H₅NO·C₈H₆O₄·2H₂O, from a methanol–water solution. The molecules form a two‐dimensional hydrogen‐bonded network resulting in sheets of hydrogen‐bonded molecules that lie parallel to the (10) plane. In contrast, 3‐hydroxypyridine and terephthalic acid form the salt bis(3‐hydroxypyridinium) terephthalate, 2C₅H₆NO⁺·C₈H₄O₄²⁻, giving rise to two‐dimensional hydrogen‐bonded sheets extending through the lattice parallel to the (10) plane.     

6‐Propyl‐2‐thiouracil versus 6‐methoxymethyl‐2‐thiouracil: enhancing the hydrogen‐bonded synthon motif by replacement of a methylene group with an O atom

The understanding of intermolecular interactions is a key objective of crystal engineering in order to exploit the derived knowledge for the rational design of new molecular solids with tailored physical and chemical properties. The tools and theories of crystal engineering are indispensable for the rational design of (pharmaceutical) cocrystals. The results of cocrystallization experiments of the antithyroid drug 6‐propyl‐2‐thiouracil (PTU) with 2,4‐diaminopyrimidine (DAPY), and of 6‐methoxymethyl‐2‐thiouracil (MOMTU) with DAPY and 2,4,6‐triaminopyrimidine (TAPY), respectively, are reported. PTU and MOMTU show a high structural similarity and differ only in the replacement of a methylene group (–CH₂–) with an O atom in the side chain, thus introducing an additional hydrogen‐bond acceptor in MOMTU. Both molecules contain an ADA hydrogen‐bonding site (A = acceptor and D = donor), while the coformers DAPY and TAPY both show complementary DAD sites and therefore should be capable of forming a mixed ADA/DAD synthon with each other, i.e. N—H…O, N—H…N and N—H…S hydrogen bonds. The experiments yielded one solvated cocrystal salt of PTU with DAPY, four different solvates of MOMTU, one ionic cocrystal of MOMTU with DAPY and one cocrystal salt of MOMTU with TAPY, namely 2,4‐diaminopyrimidinium 6‐propyl‐2‐thiouracilate–2,4‐diaminopyrimidine–N,N‐dimethylacetamide–water (1/1/1/1) (the systematic name for 6‐propyl‐2‐thiouracilate is 6‐oxo‐4‐propyl‐2‐sulfanylidene‐1,2,3,6‐tetrahydropyrimidin‐1‐ide), C₄H₇N₄⁺·C₇H₉N₂OS⁻·C₄H₆N₄·C₄H₉NO·H₂O, (I), 6‐methoxymethyl‐2‐thiouracil–N,N‐dimethylformamide (1/1), C₆H₈N₂O₂S·C₃H₇NO, (II), 6‐methoxymethyl‐2‐thiouracil–N,N‐dimethylacetamide (1/1), C₆H₈N₂O₂S·C₄H₉NO, (III), 6‐methoxymethyl‐2‐thiouracil–dimethyl sulfoxide (1/1), C₆H₈N₂O₂S·C₂H₆OS, (IV), 6‐methoxymethyl‐2‐thiouracil–1‐methylpyrrolidin‐2‐one (1/1), C₆H₈N₂O₂S·C₅H₉NO, (V), 2,4‐diaminopyrimidinium 6‐methoxymethyl‐2‐thiouracilate (the systematic name for 6‐methoxymethyl‐2‐thiouracilate is 4‐methoxymethyl‐6‐oxo‐2‐sulfanylidene‐1,2,3,6‐tetrahydropyrimidin‐1‐ide), C₄H₇N₄⁺·C₆H₇N₂O₂S⁻, (VI), and 2,4,6‐triaminopyrimidinium 6‐methoxymethyl‐2‐thiouracilate–6‐methoxymethyl‐2‐thiouracil (1/1), C₄H₈N₅⁺·C₆H₇N₂O₂S⁻·C₆H₈N₂O₂S, (VII). Whereas in (I) only an AA/DD hydrogen‐bonding interaction was formed, the structures of (VI) and (VII) both display the desired ADA/DAD synthon. Conformational studies on the side chains of PTU and MOMTU also revealed a significant deviation for cocrystals (VI) and (VII), leading to the desired enhancement of the hydrogen‐bond pattern within the crystal.     

Purine 3′:5′‐cyclic nucleotides with the nucleobase in a syn orientation: cAMP,cGMP and cIMP

Purine 3′:5′‐cyclic nucleotides are very well known for their role as the secondary messengers in hormone action and cellular signal transduction. Nonetheless, their solid‐state conformational details still require investigation. Five crystals containing purine 3′:5′‐cyclic nucleotides have been obtained and structurally characterized, namely adenosine 3′:5′‐cyclic phosphate dihydrate, C₁₀H₁₂N₅O₆P·2H₂O or cAMP·2H₂O, (I), adenosine 3′:5′‐cyclic phosphate 0.3‐hydrate, C₁₀H₁₂N₅O₆P·0.3H₂O or cAMP·0.3H₂O, (II), guanosine 3′:5′‐cyclic phosphate pentahydrate, C₁₀H₁₂N₅O₇P·5H₂O or cGMP·5H₂O, (III), sodium guanosine 3′:5′‐cyclic phosphate tetrahydrate, Na⁺·C₁₀H₁₁N₅O₇P⁻·4H₂O or Na(cGMP)·4H₂O, (IV), and sodium inosine 3′:5′‐cyclic phosphate tetrahydrate, Na⁺·C₁₀H₁₀N₄O₇P⁻·4H₂O or Na(cIMP)·4H₂O, (V). Most of the cyclic nucleotide zwitterions/anions [two from four cAMP present in total in (I) and (II), cGMP in (III), cGMP⁻ in (IV) and cIMP⁻ in (V)] are syn conformers about the N‐glycosidic bond, and this nucleobase arrangement is accompanied by C_rib—H…N_pur hydrogen bonds (rib = ribose and pur = purine). The base orientation is tuned by the ribose pucker. An analysis of data obtained from the Cambridge Structural Database made in the context of syn–anti conformational preferences has revealed that among the syn conformers of various purine nucleotides, cyclic nucleotides and dinucleotides predominate significantly. The interactions stabilizing the syn conformation have been indicated. The inter‐nucleotide contacts in (I)–(V) have been systematized in terms of the chemical groups involved. All five structures display three‐dimensional hydrogen‐bonded networks.     

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).     

Proton‐transfer compounds of isonipecotamide with the aromatic dicarboxylic acids 4‐nitrophthalic, 4,5‐dichlorophthalic, 5‐nitroisophthalic and terephthalic acid

The structures of the 1:1 proton‐transfer compounds of isonipecotamide (piperidine‐4‐carboxamide) with 4‐nitrophthalic acid [4‐carbamoylpiperidinium 2‐carboxy‐4‐nitrobenzoate, C₆H₁₃N₂O₈⁺·C₈H₄O₆⁻, (I)], 4,5‐dichlorophthalic acid [4‐carbamoylpiperidinium 2‐carboxy‐4,5‐dichlorobenzoate, C₆H₁₃N₂O₈⁺·C₈H₃Cl₂O₄⁻, (II)] and 5‐nitroisophthalic acid [4‐carbamoylpiperidinium 3‐carboxy‐5‐nitrobenzoate, C₆H₁₃N₂O₈⁺·C₈H₄O₆⁻, (III)], as well as the 2:1 compound with terephthalic acid [bis(4‐carbamoylpiperidinium) benzene‐1,2‐dicarboxylate dihydrate, 2C₆H₁₃N₂O₈⁺·C₈H₄O₄²⁻·2H₂O, (IV)], have been determined at 200 K. All salts form hydrogen‐bonded structures, viz. one‐dimensional in (II) and three‐dimensional in (I), (III) and (IV). In (I) and (III), the centrosymmetric R₂²(8) cyclic amide–amide association is found, while in (IV) several different types of water‐bridged cyclic associations are present [graph sets R₄²(8), R₄³(10), R₄⁴(12), R₃³(18) and R₆⁴(22)]. The one‐dimensional structure of (I) features the common `planar' hydrogen 4,5‐dichlorophthalate anion, together with enlarged cyclic R₃³(13) and R₄³(17) associations. In the structures of (I) and (III), the presence of head‐to‐tail hydrogen phthalate chain substructures is found. In (IV), head‐to‐tail primary cation–anion associations are extended longitudinally into chains through the water‐bridged cation associations, and laterally by piperidinium–carboxylate N—H...O and water–carboxylate O—H...O hydrogen bonds. The structures reported here further demonstrate the utility of the isonipecotamide cation as a synthon for the generation of stable hydrogen‐bonded structures. An additional example of cation–anion association with this cation is also shown in the asymmetric three‐centre piperidinium–carboxylate N—H...O,O′ interaction in the first‐reported structure of a 2:1 isonipecotamide–carboxylate salt.     

Unusual centrosymmetric structure of [M(18‐crown‐6)]+ (M = Rb,Cs and NH4) complexes stabilized in an environment of hexachloridoantimonate(V) anions

In (1,4,7,10,13,16‐hexaoxacyclooctadecane)rubidium hexachloridoantimonate(V), [Rb(C₁₂H₂₄O₆)][SbCl₆], (1), and its isomorphous caesium {(1,4,7,10,13,16‐hexaoxacyclooctadecane)caesium hexachloridoantimonate(V), [Cs(C₁₂H₂₄O₆)][SbCl₆]}, (2), and ammonium {ammonium hexachloridoantimonate(V)–1,4,7,10,13,16‐hexaoxacyclooctadecane (1/1), (NH₄)[SbCl₆]·C₁₂H₂₄O₆}, (3), analogues, the hexachloridoantimonate(V) anions and 18‐crown‐6 molecules reside across axes passing through the Sb atoms and the centroids of the 18‐crown‐6 groups, both of which coincide with centres of inversion. The Rb⁺ [in (1)], Cs⁺ [in (2)] and NH₄⁺ [in (3)] cations are situated inside the cavity of the 18‐crown‐6 ring; they are situated on axes and are equally disordered about centres of inversion, deviating from the centroid of the 18‐crown‐6 molecule by 0.4808 (13), 0.9344 (7) and 0.515 (8) Å, respectively. Interaction of the ammonium cation and the 18‐crown‐6 group is supported by three equivalent hydrogen bonds [N...O = 2.928 (3) Å and N—H...O = 162°]. The centrosymmetric structure of [Cs(18‐crown‐6)]⁺, with the large Cs⁺ cation approaching the centre of the ligand cavity, is unprecedented and accompanied by unusually short Cs—O bonds [2.939 (2) and 3.091 (2) Å]. For all three compounds, the [M(18‐crown‐6)]⁺ cations and [SbCl₆]⁻ anions afford linear stacks along the c axis, with the cationic complexes embedded between pairs of inversion‐related anions.     

Sodium hydrogen nitrilo­tri­acetate dihydrate

In the title compound, Na⁺·C₆H₈NO₆^?·2H₂O, the sodium ion is coordinated in a distorted octahedral manner by two carboxyl­ate O atoms and two water O atoms. Each of these water mol­ecules bridges two adjacent Na ions, resulting in two four‐membered rings of the type Na–O–Na–O.     

Stabilization of Substituted Triazenide Oxides: Synthesis and X‐ray Structural Features of Polymeric Potassium 3‐(4‐carboxylatophenyl)‐1‐methyltriazene N‐oxide‐hydrate, {K[O2C‐C6H4‐N(H)NN(CH3)O]·4H2O}n

3‐(4‐carboxyphenyl)‐1‐methyltriazene N‐oxide reacts with KOH in methanol/pyridine to give {K[O₂C‐C₆H₄‐N(H)NN(CH₃)O]·4H₂O}_n, Potassium‐3‐(4‐carboxylatophenyl)‐1‐methyltriazene N‐oxide). The terminal carboxylato group of the anion does not interact with the cation. In the crystal lattice of {K(C₈H₈N₃O₃)·4H₂O}_n each three of the four water molecules interact with two potassium cations, every K⁺ ion being the centre of six bridging K···O interactions. Potassium cations interact further with the terminal N‐oxigen atom of single [C₈H₈N₃O₃]^? anions achieving two parallel {C₈H₈N₃O₃^?K⁺}_n chains, which are linked through water molecules. The resulting polymeric, one‐dimensional chain, is operated by a screw axis 2₁ parallel to the crystallographic direction [010], along and equidistant to the K⁺ centres. The coordination of the K⁺ centres involves a distortion of the boat conformation of elementary sulfur (S₈) with the ideal C_2v symmetry.     

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).