Hydrogen‐bonded structures of the isomeric compounds of quinoline with 2‐chloro‐5‐nitrobenzoic acid, 3‐chloro‐2‐nitrobenzoic acid, 4‐chloro‐2‐nitrobenzoic acid and 5‐chloro‐2‐nitrobenzoic acid

The structures of four isomeric compounds, all C₇H₄ClNO₄·C₉H₇N, of quinoline with chloro‐ and nitro‐substituted benzoic acid, namely, 2‐chloro‐5‐nitrobenzoic acid–quinoline (1/1), (I), 3‐chloro‐2‐nitrobenzoic acid–quinoline (1/1), (II), 4‐chloro‐2‐nitrobenzoic acid–quinoline (1/1), (III), and 5‐chloro‐2‐nitrobenzoic acid–quinoline (1/1), (IV), have been determined at 185 K. In each compound, a short hydrogen bond is observed between the pyridine N atom and a carboxyl O atom. The N...O distances are 2.6476 (13), 2.5610 (13), 2.5569 (12) and 2.5429 (12) Å for (I), (II), (III) and (IV), respectively. Although in (I) the H atom in the hydrogen bond is located at the O site, in (II), (III) and (IV) the H atom is disordered in the hydrogen bond over two positions with (N site):(O site) occupancies of 0.39 (3):0.61 (3), 0.47 (3):0.53 (3) and 0.65 (3):0.35 (3), respectively.     

2‐Ammonio‐5‐chloro‐4‐methylbenzenesulfonate,its 1‐methyl‐2‐pyrrolidone and dimethyl sulfoxide monosolvates and a corrected structure of 2,2′‐(1,4‐phenylene)di(4,5‐dihydroimidazolium) bis(4‐aminobenzenesulfonate) dihydrate

2‐Ammonio‐5‐chloro‐4‐methylbenzenesulfonate, C₇H₈ClNO₃S, (Ia), is an intermediate in the synthesis of lake red azo pigments. The present structure determination from single‐crystal data confirms the results of a previous powder diffraction determination [Bekö, Thoms, Brüning, Alig, van de Streek, Lakatos, Glaubitz & Schmidt (2010). Z. Kristallogr. 225 , 382–387]. The zwitterionic tautomeric form is confirmed. During a polymorph screening, two additional pseudopolymorphs were obtained, viz. 2‐ammonio‐5‐chloro‐4‐methylbenzenesulfonate 1‐methyl‐2‐pyrrolidone monosolvate, C₇H₈ClNO₃S·C₅H₉NO, (Ib), and 2‐ammonio‐5‐chloro‐4‐methylbenzenesulfonate dimethyl sulfoxide monosolvate, C₇H₈ClNO₃S·C₂H₆OS, (Ic). The molecules of (Ib) have crystallographic m symmetry. The 1‐methyl‐2‐pyrrolidone solvent molecule has an envelope conformation and is disordered around the mirror plane. The structure shows hydrogen‐bonded ladders of molecules [graph‐set notation C₂²(6)R₂²(12)] in the [010] direction. The benzene groups of adjacent ladders are also stacked in this direction. A different type of hydrogen‐bonded ladder [graph‐set notation C(6)R₂²(4)R₄⁴(12)] occurs in (Ic). In (Ia), (Ib) and (Ic), the molecules correspond to the zwitterionic tautomer. The structure of the cocrystal of 4‐aminobenzenesulfonic acid with 1,4‐bis(4,5‐dihydroimidazol‐2‐yl)benzene [Shang, Ren, Wang, Lu & Yang (2009). Acta Cryst. E 65 , o2221–o2222] is corrected; it actually contains 4‐aminobenzenesulfonate anions and 2,2′‐(1,4‐phenylene)di(dihydroimidazolium) dications, i.e. 2,2′‐(1,4‐phenylene)di(4,5‐dihydroimidazolium) bis(4‐aminobenzenesulfonate) dihydrate, C₁₂H₁₆N₄²⁺·2C₆H₆NO₃S⁻·2H₂O. Hence, all known structures of aminobenzenesulfonic acid complexes contain ionic or zwitterionic molecules; there is no known structure with a neutral aminobenzenesulfonic acid molecule.     

Hydrogen‐bonded structures of the isomeric compounds of phthalazine with 3‐chloro‐2‐nitrobenzoic acid, 4‐chloro‐2‐nitrobenzoic acid and 4‐chloro‐3‐nitrobenzoic acid

The structures of three isomeric compounds, C₇H₄ClNO₄·C₈H₆N₂, of phthalazine with chloro‐ and nitro‐substituted benzoic acid, namely, 3‐chloro‐2‐nitrobenzoic acid–phthalazine (1/1), (I), 4‐chloro‐2‐nitrobenzoic acid–phthalazine (1/1), (II), and 4‐chloro‐3‐nitrobenzoic acid–phthalazine (1/1), (III), have been determined at 190 K. In the asymmetric unit of each compound, there are two crystallographically independent chloronitrobenzoic acid–phthalazine units, in each of which the two components are held together by a short hydrogen bond between an N atom of the base and a carboxyl O atom. In one hydrogen‐bonded unit of (I) and in two units of (II), a weak C—H...O interaction is also observed between the two components. The N...O distances are 2.5715 (15) and 2.5397 (17) Å for (I), 2.5655 (13) and 2.6081 (13) Å for (II), and 2.613 (2) and 2.589 (2) Å for (III). In both hydrogen‐bonded units of (I) and (II), the H atoms are each disordered over two positions with (N site):(O site) occupancies of 0.35 (3):0.65 (3) and 0.31 (3):0.69 (3) for (I), and 0.32 (3):0.68 (3) and 0.30 (3):0.70 (3) for (II). The H atoms in the hydrogen‐bonded units of (III) are located at the O‐atom sites.     

2:1 Complexes of 2‐chloro‐4‐nitro­benzoic acid and 2‐chloro‐5‐nitro­benzoic acid with pyrazine

2‐Chloro‐4‐nitro­benzoic acid and 2‐chloro‐5‐nitro­benzoic acid form O—H?N hydrogen bonds with pyrazine to afford 2:1 complexes of 2C₇H₄ClNO₄·C₄H₄N₂, (I) and (II), respectively, that are located on inversion centers. The 2C₇H₄ClNO₄·­C₄H₄N₂ units in both complexes are connected by weak C—H?O hydrogen bonds; the units build a three‐dimensional hydrogen‐bond network in (I) and a ribbon structure in (II).     

The 1:1 proton‐transfer compounds of 4‐(phenyldiazenyl)aniline (aniline yellow) with 3‐nitrophthalic, 4‐nitrophthalic and 5‐nitroisophthalic acids

The structures of the anhydrous 1:1 proton‐transfer compounds of the dye precursor aniline yellow [4‐(phenyldiazenyl)aniline], namely isomeric 4‐(phenyldiazenyl)anilinium 2‐carboxy‐6‐nitrobenzoate, C₁₂H₁₂N₃⁺·C₈H₄NO₆⁻, (I), and 4‐(phenyldiazenyl)anilinium 2‐carboxy‐4‐nitrobenzoate, C₁₂H₁₂N₃⁺·C₈H₄NO₆⁻, (II), and 4‐(phenyldiazenyl)anilinium 3‐carboxy‐5‐nitrobenzoate monohydrate, C₁₂H₁₂N₃⁺·C₈H₄NO₆⁻·H₂O, (III), have been determined at 130 K. In (I) the cation has longitudinal rotational disorder. All three compounds have substructures comprising backbones formed through strong head‐to‐tail carboxyl–carboxylate hydrogen‐bond interactions [graph set C(7) in (I) and (II), and C(8) in (III)]. Two‐dimensional sheet structures are formed in all three compounds by the incorporation of the 4‐(phenyldiazenyl)anilinium cations into the substructures, including, in the cases of (I) and (II), infinite H—N—H to carboxylate O—C—O group interactions [graph set C(6)], and in the case of (III), bridging through the water molecule of solvation. The peripheral alternating aromatic ring residues of both cations and anions give only weakly π‐interactive step features which lie between the sheets.     

Channel‐forming solvates of 6‐chloro‐2,5‐dihydroxypyridine and its solvent‐free tautomer 6‐chloro‐5‐hydroxy‐2‐pyridone

On crystallization from CHCl₃, CCl₄, CH₂ClCH₂Cl and CHCl₂CHCl₂, 6‐chloro‐5‐hydroxy‐2‐pyridone, C₅H₄ClNO₂, (I), undergoes a tautomeric rearrangement to 6‐chloro‐2,5‐dihydroxypyridine, (II). The resulting crystals, viz. 6‐chloro‐2,5‐dihydroxypyridine chloroform 0.125‐solvate, C₅H₄ClNO₂·0.125CHCl₃, (IIa), 6‐chloro‐2,5‐dihydroxypyridine carbon tetrachloride 0.125‐solvate, C₅H₄ClNO₂.·0.125CCl₄, (IIb), 6‐chloro‐2,5‐dihydroxypyridine 1,2‐dichloroethane solvate, C₅H₄ClNO₂·C₂H₄Cl₂, (IIc), and 6‐chloro‐2,5‐dihydroxypyridine 1,1,2,2‐tetrachloroethane solvate, C₅H₄ClNO₂·C₂H₂Cl₄, (IId), have I4₁/a symmetry, and incorporate extensively disordered solvent in channels that run the length of the c axis. Upon gentle heating to 378 K in vacuo, these crystals sublime to form solvent‐free crystals with P2₁/n symmetry that are exclusively the pyridone tautomer, (I). In these sublimed pyridone crystals, inversion‐related molecules form R²₂(8) dimers via pairs of N—H...O hydrogen bonds. The dimers are linked by O—H...O hydrogen bonds into R⁴₆(28) motifs, which join to form pleated sheets that stack along the a axis. In the channel‐containing pyridine solvate crystals, viz. (IIa)–(IId), two independent host molecules form an R²₂(8) dimer via a pair of O—H...N hydrogen bonds. One molecule is further linked by O—H...O hydrogen bonds to two 4₁ screw‐related equivalents to form a helical motif parallel to the c axis. The other independent molecule is O—H...O hydrogen bonded to two related equivalents to form tetrameric R⁴₄(28) rings. The dimers are π–π stacked with inversion‐related dimers, which in turn stack the R⁴₄(28) rings along c to form continuous solvent‐accessible channels. CHCl₃, CCl₄, CH₂ClCH₂Cl and CHCl₂CHCl₂ solvent molecules are able to occupy these channels but are disordered by virtue of the site symmetry within the channels.     

Supramolecular hydrogen‐bonded networks in cytosinium succinate and cytosinium 4‐nitrobenzoate cytosine monohydrate

In cytosinium succinate (systematic name: 4‐amino‐2‐oxo‐2,3‐dihydropyrimidin‐1‐ium 3‐carboxypropanoate), C₄H₆N₃O⁺·C₄H₅O₄⁻, (I), the cytosinium cation forms one‐dimensional self‐assembling patterns by intermolecular N—H...O hydrogen bonding, while in cytosinium 4‐nitrobenzoate cytosine monohydrate [systematic name: 4‐amino‐2‐oxo‐2,3‐dihydropyrimidin‐1‐ium 4‐nitrobenzoate 4‐aminopyrimidin‐2(1H)‐one solvate monohydrate], C₄H₆N₃O⁺·C₇H₄NO₄⁻·C₄H₅N₃O·H₂O, (II), the cytosinium–cytosine base pair, held together by triple hydrogen bonds, leads to one‐dimensional polymeric ribbons via double N—H...O hydrogen bonds. This study illustrates clearly the different alignment of cytosine molecules in the crystal packing and their ability to form supramolecular hydrogen‐bonded networks with the anions.     

Two‐component molecular crystals from N‐heteroaromatics and nitro­benzoic acids

Five two‐component molecular crystals, benzimidazolium 3‐nitro­benzoate, C₇H₇N₂⁺·C₇H₄NO₄^?, (I), benzimidazolium 4‐nitro­benzoate, C₇H₇N₂⁺·C₇H₄NO₄^?, (II), 1H‐benzotriazole–3‐nitro­benzoic acid (1/1), C₆H₅N₃·C₇H₅NO₄, (III), imidazol­ium 3‐nitro­benzoate, C₃H₅N₂⁺·C₇H₄NO₄^?, (IV), and imid­azolium 4‐nitro­benzoate, C₃H₅N₂⁺·C₇H₄NO₄^?, (V), were prepared with the aim of making chiral crystals. Only (I) crystallizes in a chiral space group. The mol­ecules of (I) and (II) are linked by hydrogen bonds to form 2₁ spiral chains. In (III), (IV) and (V), macrocyclic structures are formed from two acid and two base components, by an alternate arrangement of the acid and base moieties.     

Hydrogen bonding in two benzene‐1,2‐diaminium pyridine‐2‐carboxylate salts and a cocrystal of benzene‐1,2‐diamine and benzoic acid

The isostructural salts benzene‐1,2‐diaminium bis(pyridine‐2‐carboxylate), 0.5C₆H₁₀N₂²⁺·C₆H₄NO₂^?, (1), and 4,5‐dimethylbenzene‐1,2‐diaminium bis(pyridine‐2‐carboxylate), 0.5C₈H₁₄N₂²⁺·C₆H₄NO₂^?, (2), and the 1:2 benzene‐1,2‐diamine–benzoic acid cocrystal, 0.5C₆H₈N₂·C₇H₆O₂, (3), are reported. All of the compounds exhibit extensive N—H…O hydrogen bonding that results in interconnected rings. O—H…N hydrogen bonding is observed in (3). Additional π–π and C—H…π interactions are found in each compound. Hirshfeld and fingerprint plot analyses reveal the primary intermolecular interactions and density functional theory was used to calculate their strengths. Salt formation by (1) and (2), and cocrystallization by (3) are rationalized by examining pK_a differences. The R₂²(9) hydrogen‐bonding motif is common to each of these structures.     

(M)‐ and (P)‐8‐[(1S,2R)‐2‐hydroxy‐1‐methyl‐2‐phenylethyl]‐8‐methyl‐8,9‐dihydro‐7H‐dinaphth[2,1‐c:1′,2′‐e]azepinium bromide solvates

The title compounds are diastereoisomers with antipodean axial chirality. The M isomer crystallizes as a (1/3) acetone solvate, C₃₂H₃₀NO⁺·Br^?·3C₃H₆O, while the P isomer crystallizes as a (1/1) di­chloro­methane solvate, C₃₂H₃₀NO⁺·Br^?·CH₂Cl₂. In each structure, O—H?Br hydrogen bonds link the cations and anions to give ion pairs. The seven‐membered azepinium ring adopts the usual twisted‐boat conformation and its ring strain causes a slight curvature of the plane of each naphthyl ring.     

Two hydro­chlorides of 7‐methyl‐3,7,11,17‐tetra­aza­bi­cyclo­[11.3.1]­heptadeca‐1(17),13,15‐triene

The X‐ray structure determinations of the two title com­pounds, namely 7‐methyl‐7,17‐di­aza‐3,11‐diazo­niabi­cyclo[11.3.1]­hep­ta­deca‐1(17),13,15‐triene dichloride monohydrate, C₁₄H₂₆N₄²⁺·2Cl^?·H₂O, (I), and 7‐methyl‐17‐aza‐3,7,11‐triazo­niabi­cyclo­[11.3.1]­heptadeca‐1(17),13,15‐triene 2.826‐chloride 0.174‐nitrate, C₁₄H₂₇N₄³⁺·2.826Cl^?·0.174NO₃^?, (II), are re­ported. Protonation occurs at the secondary amine N atoms in (I) and at all three amine N atoms in (II) to which the Cl^? ions are linked via N—H?Cl hydrogen bonds. The macrocyclic hole is quite different in both structures, as is observed by comparing particularly the N3?N4 distances [2.976 (4) and 4.175 (4) Å for (I) and (II), respectively]. In (II), a Cl^? ion alternates with an NO₃^? ion in a disordered structure.     

1‐Methyl­piperazine‐1,4‐diium 4‐nitro­phthalate(2–) 4‐nitro­phthalic acid monohydrate

The title adduct, C₅H₁₄N₂²⁺·C₈H₃NO₆²⁻·C₈H₅NO₆·H₂O, crystallizes in the monoclinic space group P2₁. All O atoms of the 4‐nitro­phthalate anions and neutral 4‐nitro­phthalic acid mol­ecules are involved in hydrogen bonding with the piperazine dication and the water mol­ecule of crystallization.     

1,3‐Propane­di­ammonium bis(3′‐nitro‐trans‐cinnamate) and trans‐1,2‐cyclo­hexane­di­ammonium bis(3′‐nitro‐trans‐cinnamate)

In the title two adducts, C₃H₁₂N₂²⁺·2C₉H₆NO₄^?, (I), and C₆H₁₆N₂²⁺·2C₉H₆NO₄^?, (II), hydrogen bonds between the di­ammonium and carboxyl­ate ions form a two‐dimensional network parallel to the ab plane in (I) and one‐dimensional chains along the c axis in (II). The cyclo­hexane­di­ammonium ion in (II) has a crystallographic twofold axis.     

Strychninium N‐phthaloyl‐β‐alaninate N‐phthaloyl‐β‐alanine and brucinium N‐phthaloyl‐β‐alaninate 5.67‐hydrate

Comparison of the structures of strychninium N‐phthaloyl‐β‐alaninate N‐phthaloyl‐β‐alanine, C₂₁H₂₃N₂O₂⁺·C₁₁H₈NO₄⁻·C₁₁H₉NO₄, and brucinium N‐phthaloyl‐β‐alaninate 5.67‐hydrate, C₂₃H₂₇N₂O₄⁺·C₁₁H₈NO₄⁻·5.67H₂O, reveals that, unlike strychninium cations, brucinium cations display a tendency to produce stacking inter­actions with cocrystallizing guests.     

Supramolecular interactions in carboxylate and sulfonate salts of 2,6‐diamino‐4‐chloropyrimidinium

Two new salts, namely 2,6‐diamino‐4‐chloropyrimidinium 2‐carboxy‐3‐nitrobenzoate, C₄H₆ClN₄⁺·C₈H₄NO₆⁻, (I), and 2,6‐diamino‐4‐chloropyrimidinium p‐toluenesulfonate monohydrate, C₄H₆ClN₄⁺·C₇H₇O₃S⁻·H₂O, (II), have been synthesized and characterized by single‐crystal X‐ray diffraction. In both crystal structures, the N atom in the 1‐position of the pyrimidine ring is protonated. In salt (I), the protonated N atom and the amino group of the pyrimidinium cation interact with the carboxylate group of the anion through N—H…O hydrogen bonds to form a heterosynthon with an R ₂²(8) ring motif. In hydrated salt (II), the presence of the water molecule prevents the formation of the familiar R ₂²(8) ring motif. Instead, an expanded ring [i.e. R ₃²(8)] is formed involving the sulfonate group, the pyrimidinium cation and the water molecule. Both salts form a supramolecular homosynthon [R ₂²(8) ring motif] through N—H…N hydrogen bonds. The molecular structures are further stabilized by π–π stacking, and C=O…π, C—H…O and C—H…Cl interactions.     

4-硝基苯甲醇的低温热容和标准摩尔生成焓

用精密自动绝热量热计测定了4-硝基苯甲醇（4-NBA）在78 ~ 396 K温区的摩尔热容。其熔化温度、摩尔熔化焓及摩尔熔化熵分别为:(336.426 ± 0.088) K, (20.97 ± 0.13) kJ×mol-1 和 (57.24 ± 0.36) J×K-1×mol-1.根据热力学函数关系式,从热容值计算出了该物质在80 ~ 400 K温区的热力学函数值 [HT - H298.15 K] 和[ST - S298.15 K]. 用精密氧弹燃烧量热计测定了该物质在T＝298.15 K的恒容燃烧能和标准摩尔燃烧焓分别为 (C7H7NO3, s)＝- ( 3549.11 ± 1.47 ) kJ×mol-1 和 (C7H7NO3, s)＝- ( 3548.49 ± 1.47 ) kJ×mol-1. 利用标准摩尔燃烧焓和其他辅助热力学数据通过盖斯热化学循环, 计算出了该物质标准摩尔生成焓 (C7H7NO3, s)＝- (206.49 ± 2.52) kJ×mol-1 .     

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.     

Halogen,hydrogen and electrostatic interactions in 2‐amino‐5‐chloro‐1,3‐benzoxazol‐3‐ium nitrate and 2‐amino‐5‐chloro‐1,3‐benzoxazol‐3‐ium perchlorate

In the title compounds, C₇H₆ClN₂O⁺·NO₃⁻ and C₇H₆ClN₂O⁺·ClO₄⁻, the ions are connected by N—H...O hydrogen bonds and halogen interactions. Additionally, in the first compound, co‐operative π–π stacking and halogen...π interactions are observed. The energies of the observed interactions range from a value typical for very weak interactions (1.80 kJ mol⁻¹) to one typical for mildly strong interactions (53.01 kJ mol⁻¹). The iminium cations exist in an equilibrium form intermediate between exo‐ and endocyclic. This study provides structural insights relevant to the biochemical activity of 2‐amino‐5‐chloro‐1,3‐benzoxazole compounds.     

Two‐component molecular crystals composed of chloronitrobenzoic acids and 4‐aminopyridine

The crystal structures of the four isomeric organic salts 4‐amino­pyridinium 2‐chloro‐4‐nitro­benzoate, (I), 4‐amino­pyridinium 2‐chloro‐5‐nitro­benzoate, (II), 4‐amino­pyridinium 5‐chloro‐2‐nitro­benzoate, (III), and 4‐amino­pyridinium 4‐chloro‐2‐nitro­benzoate, (IV), all C₅H₇N₂⁺·C₇H₃ClNO₄^?, are presented. Compound (I) has one intramolecular hydrogen bond, one intermolecular C—H?O hydrogen bond and π–π‐stacking interactions. Compound (II) has N—H?O, C—H?O and C—H?Cl hydrogen bonds, and Cl?O—C electrostatic interactions. Compound (III) has N—H?O and C—H?O hydrogen bonds. Compound (IV) has a π–π‐stacking interaction, but no C—H?O hydrogen bonds.     

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.