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.     

Zero‐, one‐ and two‐dimensional hydrogen‐bonded structures in the 1:1 proton‐transfer compounds of 4,5‐dichlorophthalic acid with the monocyclic heteroaromatic Lewis bases 2‐aminopyrimidine,nicotinamide and isonicotinamide

The structures of the anhydrous 1:1 proton‐transfer compounds of 4,5‐dichlorophthalic acid (DCPA) with the monocyclic heteroaromatic Lewis bases 2‐aminopyrimidine, 3‐(aminocarbonyl)pyridine (nicotinamide) and 4‐(aminocarbonyl)pyridine (isonicotinamide), namely 2‐aminopyrimidinium 2‐carboxy‐4,5‐dichlorobenzoate, C₄H₆N₃⁺·C₈H₃Cl₂O₄⁻, (I), 3‐(aminocarbonyl)pyridinium 2‐carboxy‐4,5‐dichlorobenzoate, C₆H₇N₂O⁺·C₈H₃Cl₂O₄⁻, (II), and the unusual salt adduct 4‐(aminocarbonyl)pyridinium 2‐carboxy‐4,5‐dichlorobenzoate–methyl 2‐carboxy‐4,5‐dichlorobenzoate (1/1), C₆H₇N₂O⁺·C₈H₃Cl₂O₄⁻·C₉H₆Cl₂O₄, (III), have been determined at 130 K. Compound (I) forms discrete centrosymmetric hydrogen‐bonded cyclic bis(cation–anion) units having both R₂²(8) and R₁²(4) N—H...O interactions. In (II), the primary N—H...O‐linked cation–anion units are extended into a two‐dimensional sheet structure via amide–carboxyl and amide–carbonyl N—H...O interactions. The structure of (III) reveals the presence of an unusual and unexpected self‐synthesized methyl monoester of the acid as an adduct molecule, giving one‐dimensional hydrogen‐bonded chains. In all three structures, the hydrogen phthalate anions are essentially planar with short intramolecular carboxyl–carboxylate O—H...O hydrogen bonds [O...O = 2.393 (8)–2.410 (2) Å]. This work provides examples of low‐dimensional 1:1 hydrogen‐bonded DCPA structure types, and includes the first example of a discrete cyclic `heterotetramer.' This low dimensionality in the structures of the 1:1 aromatic Lewis base salts of the parent acid is generally associated with the planar DCPA anion species.     

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.     

Three‐dimensional hydrogen‐bonded structures in the hydrated proton‐transfer salts of isonipecotamide with the dicarboxylic oxalic and adipic acid homologues

The structures of the 1:1 hydrated proton‐transfer compounds of isonipecotamide (piperidine‐4‐carboxamide) with oxalic acid, 4‐carbamoylpiperidinium hydrogen oxalate dihydrate, C₆H₁₃N₂O⁺·C₂HO₄⁻·2H₂O, (I), and with adipic acid, bis(4‐carbamoylpiperidinium) adipate dihydrate, 2C₆H₁₃N₂O⁺·C₆H₈O₄²⁻·2H₂O, (II), are three‐dimensional hydrogen‐bonded constructs involving several different types of enlarged water‐bridged cyclic associations. In the structure of (I), the oxalate monoanions give head‐to‐tail carboxylic acid O—H...O_carboxyl hydrogen‐bonding interactions, forming C(5) chain substructures which extend along a. The isonipecotamide cations also give parallel chain substructures through amide N—H...O hydrogen bonds, the chains being linked across b and down c by alternating water bridges involving both carboxyl and amide O‐atom acceptors and amide and piperidinium N—H...O_carboxyl hydrogen bonds, generating cyclic R₄³(10) and R₃²(11) motifs. In the structure of (II), the asymmetric unit comprises a piperidinium cation, half an adipate dianion, which lies across a crystallographic inversion centre, and a solvent water molecule. In the crystal structure, the two inversion‐related cations are interlinked through the two water molecules, which act as acceptors in dual amide N—H...O_water hydrogen bonds, to give a cyclic R₄²(8) association which is conjoined with an R₄⁴(12) motif. Further N—H...O_water, water O—H...O_amide and piperidinium N—H...O_carboxyl hydrogen bonds give the overall three‐dimensional structure. The structures reported here further demonstrate the utility of the isonipecotamide cation as a synthon for the generation of stable hydrogen‐bonded structures. The presence of solvent water molecules in these structures is largely responsible for the non‐occurrence of the common hydrogen‐bonded amide–amide dimer, promoting instead various expanded cyclic hydrogen‐bonding motifs.     

The three‐dimensional hydrogen‐bonded framework structure in the 1:1 proton‐transfer compound of the drug quinacrine with 5‐sulfosalicylic acid

For the hydrated proton‐transfer compound 6‐chloro‐9‐[(4‐diethylammonio‐2‐methylbutyl)amino]‐2‐methoxyacridinium 3‐carboxylato‐4‐hydroxybenzenesulfonate dihydrate, C₂₃H₃₂ClN₃O²⁺·C₇H₄O₆S²⁻·2H₂O, (I), the conformational features, specifically those of the extended side chain at the 9‐position of the acridine parent, have been compared with those of quinacrinium dichloride dihydrate (the drug atabrine or mepacrine). Racemic compound (I) has a three‐dimensional hydrogen‐bonded framework structure similar to atabrine but also involves the water molecules and both the carboxylate and sulfonate groups of the anion in structure extension. The comparable conformational features found in this uncommon derivative of quinacrine indicate that (I) has potential as a possible pharmaceutical substitute for atabrine.     

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.     

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.     

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.     

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.     

Phenyl‐ring rotational disorder in the two‐dimensional hydrogen‐bonded structure of the 1:1 proton‐transfer salt of the diazo‐dye precursor 4‐(phenyldiazenyl)aniline (aniline yellow) with l‐tartaric acid

In the structure of the 1:1 proton‐transfer compound from the reaction of l ‐tartaric acid with the azo‐dye precursor aniline yellow [4‐(phenyldiazenyl)aniline], namely 4‐(phenyldiazenyl)anilinium (2R,3R)‐3‐carboxy‐2,3‐dihydroxypropanoate, C₁₂H₁₂N₃⁺·C₄H₅O₆⁻, the asymmetric unit contains two independent 4‐(phenyldiazenyl)anilinium cations and two hydrogen l ‐tartrate anions. The structure is unusual in that all four phenyl rings of the two cations have identical rotational disorder with equal occupancy of the conformations. The two hydrogen l ‐tartrate anions form independent but similar chains through head‐to‐tail carboxyl–carboxylate O—H...O hydrogen bonds [graph set C(7)], which are then extended into a two‐dimensional hydrogen‐bonded sheet structure through hydroxy O—H...O hydrogen‐bonded links. The anilinium groups of the 4‐(phenyldiazenyl)anilinium cations are incorporated into the sheets and also provide internal hydrogen‐bonded extensions, while their aromatic tails are layered in the structure without significant association except for weak π–π interactions [minimum ring centroid separation = 3.844 (3) Å]. The hydrogen l ‐tartrate residues of both anions exhibit the common short intramolecular hydroxy–carboxylate O—H...O hydogen bonds. This work provides a solution to the unusual disorder problem inherent in the structure of this salt, as well as giving another example of the utility of the hydrogen tartrate anion in the generation of sheet substructures in molecular assembly processes.     

4,6‐Diaminopyrimidine‐2(1H)‐thione hemihydrate: a three‐dimensional hydrogen‐bonded framework

In the title compound, C₄H₆N₄S·0.5H₂O, there are two independent pyrimidinethione units, both of which lie across mirror planes in the space group Cmca. Hence, the H atoms bonded to the ring N atoms in each molecule are disordered over two symmetry‐related sites, each having an occupancy of 0.5. The water molecule lies across a twofold rotation axis parallel to [010]. The molecular components of (I) are linked by seven independent hydrogen bonds, of N—H...N, N—H...S, N—H...O and O—H...S types. A combination of disordered N—H...N hydrogen bonds and ordered N—H...S hydrogen bonds links the pyrimidinethione units into a continuous tubular structure. The water molecule acts as both a double donor of hydrogen bonds and a double acceptor, forming hydrogen bonds with components of four distinct pyrimidinethione tubes, thus linking these tubes into a three‐dimensional structure.     

Three‐dimensional hydrogen‐bonded framework structures in flunarizinium nicotinate and flunarizinediium bis(4‐toluenesulfonate) dihydrate

The structures of two salts of flunarizine, namely 1‐bis[(4‐fluorophenyl)methyl]‐4‐[(2E)‐3‐phenylprop‐2‐en‐1‐yl]piperazine, C₂₆H₂₆F₂N₂, are reported. In flunarizinium nicotinate {systematic name: 4‐bis[(4‐fluorophenyl)methyl]‐1‐[(2E)‐3‐phenylprop‐2‐en‐1‐yl]piperazin‐1‐ium pyridine‐3‐carboxylate}, C₂₆H₂₇F₂N₂⁺·C₆H₄NO₂⁻, (I), the two ionic components are linked by a short charge‐assisted N—H...O hydrogen bond. The ion pairs are linked into a three‐dimensional framework structure by three independent C—H...O hydrogen bonds, augmented by C—H...π(arene) hydrogen bonds and an aromatic π–π stacking interaction. In flunarizinediium bis(4‐toluenesulfonate) dihydrate {systematic name: 1‐[bis(4‐fluorophenyl)methyl]‐4‐[(2E)‐3‐phenylprop‐2‐en‐1‐yl]piperazine‐1,4‐diium bis(4‐methylbenzenesulfonate) dihydrate}, C₂₆H₂₈F₂N₂²⁺·2C₇H₇O₃S⁻·2H₂O, (II), one of the anions is disordered over two sites with occupancies of 0.832 (6) and 0.168 (6). The five independent components are linked into ribbons by two independent N—H...O hydrogen bonds and four independent O—H...O hydrogen bonds, and these ribbons are linked to form a three‐dimensional framework by two independent C—H...O hydrogen bonds, but C—H...π(arene) hydrogen bonds and aromatic π–π stacking interactions are absent from the structure of (II). Comparisons are made with some related structures.     

Three‐dimensional hydrogen‐bonded structures in the guanidinium salts of the monocyclic dicarboxylic acids rac‐trans‐cyclohexane‐1,2‐dicarboxylic acid (2:1, anhydrous), isophthalic acid (1:1, monohydrate) and terephthalic acid (2:1, trihydrate)

The structures of bis(guanidinium) rac‐trans‐cyclohexane‐1,2‐dicarboxylate, 2CH₆N₃⁺·C₈H₁₀O₄²⁻, (I), guanidinium 3‐carboxybenzoate monohydrate, CH₆N₃⁺·C₈H₅O₄⁻·H₂O, (II), and bis(guanidinium) benzene‐1,4‐dicarboxylate trihydrate, 2CH₆N₃⁺·C₈H₄O₄²⁻·3H₂O, (III), all reveal three‐dimensional hydrogen‐bonded framework structures. In anhydrous (I), both guanidinium cations form classic cyclic R₂²(8) N—H...O,O′_carboxylate and asymmetric cyclic R₂¹(6) hydrogen‐bonding interactions, while one cation forms an unusual enlarged cyclic interaction with O‐atom acceptors of separate ortho‐related carboxylate groups [graph set R₂²(11)]. Cations and anions also associate across inversion centres, giving cyclic R₄²(8) motifs. In the 1:1 guanidinium salt, (II), the cation forms two separate cyclic R₂¹(6) interactions, one with a carboxyl O‐atom acceptor and the other with the solvent water molecule. The structure is unusual in that both carboxyl groups form short interanion O...H...O contacts, one across a crystallographic inversion centre [O...O = 2.483 (2) Å] and the other about a twofold axis of rotation [O...O = 2.462 (2) Å], representing shared sites on these elements for the single acid H atom. The water molecule links the cation–anion ribbon structures into a three‐dimensional framework. In (III), the repeating molecular unit comprises a benzene‐1,4‐dicarboxylate dianion which lies across a crystallographic inversion centre, two guanidinium cations and two solvent water molecules (each set related by twofold rotational symmetry), and a single water molecule which lies on a twofold axis. Each guanidinium cation forms three types of cyclic interaction with the dianions: one R₂¹(6), the others R₃²(8) and R₃³(10) (both of these involving the water molecules), giving a three‐dimensional structure through bridges down the b‐cell direction. The water molecule at the general site also forms an unusual cyclic R₂²(4) homodimeric association across an inversion centre [O...O = 2.875 (2) Å]. The work described here provides further examples of the common cyclic guanidinium–carboxylate hydrogen‐bonding associations, as well as featuring other less common cyclic motifs.     

Four 1‐naphthyl‐substituted tetrahydro‐1,4‐epoxy‐1‐benzazepines: hydrogen‐bonded structures in one,two and three dimensions

(2S*,4R*)‐2‐exo‐(1‐Naphthyl)‐2,3,4,5‐tetrahydro‐1H‐1,4‐epoxy‐1‐benzazepine, C₂₀H₁₇NO, (I), crystallizes with Z′ = 2 in the space group P2₁; the two independent molecules have the same absolute configuration, although this configuration is indeterminate. The molecules of each type are linked by a combination of C—H...O and C—H...π(arene) hydrogen bonds to form two independent sheets, each containing only one type of molecule. (2SR,4RS)‐7‐Methyl‐2‐exo‐(1‐naphthyl)‐2,3,4,5‐tetrahydro‐1H‐1,4‐epoxy‐1‐benzazepine, C₂₁H₁₉NO, (II), crystallizes as a true racemate in the space group P2₁/c, and a combination of C—H...N, C—H...O and C—H...π(arene) hydrogen bonds links the molecules into sheets, each containing equal numbers of the two enantiomorphs. (2S*,4R*)‐2‐exo‐(1‐Naphthyl)‐7‐trifluoromethyl‐2,3,4,5‐tetrahydro‐1H‐1,4‐epoxy‐1‐benzazepine, C₂₁H₁₆F₃NO₂, (III), crystallizes as a single enantiomorph, as for (I), but now with Z′ = 1 in the space group P2₁2₁2₁; again, the absolute configuration is indeterminate. A single C—H...π(arene) hydrogen bond links the molecules of (III) into simple chains. (2S,4R)‐8‐Chloro‐9‐methyl‐2‐exo‐(1‐naphthyl)‐2,3,4,5‐tetrahydro‐1H‐1,4‐epoxy‐1‐benzazepine, C₂₁H₁₈ClNO, (IV), crystallizes as a single enantiomorph of well defined configuration, in the space group P2₁2₁2₁, where two independent C—H...π(arene) hydrogen bonds link the molecules into a single three‐dimensional framework structure.     

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).     

Main‐chain,thermotropic, liquid‐crystalline,hydrogen‐bonded polymers of 4,4′‐bipyridyl with aliphatic dicarboxylic acids

A series of main‐chain, thermotropic, liquid‐crystalline (LC), hydrogen‐bonded polymers or self‐assembled structures based on 4,4′‐bipyridyl as a hydrogen‐bond acceptor and aliphatic dicarboxylic acids, such as adipic and sebacic acids, as hydrogen‐bond donors were prepared by a slow evaporation technique from a pyridine solution and were characterized for their thermotropic, LC properties with a number of experimental techniques. The homopolymer of 4,4′‐bipyridyl with adipic acid exhibited high‐order and low‐order smectic phases, and that with sebacic acid exhibited only a high‐order smectic phase. Like the homopolymer with adipic acid, the two copolymers of 4,4′‐bipyridyl with adipic and sebacic acids (75/25 and 25/75) also exhibited two types of smectic phases. In contrast, the copolymer of 4,4′‐bipyridyl with adipic and sebacic acids (50/50), like the homopolymer with sebacic acid, exhibited only one high‐order smectic phase. Each of them, including the copolymers, had a broad temperature range of LC phases (36–51 °C). The effect of copolymerization for these hydrogen‐bonded polymers on the thermotropic properties was examined. Generally, copolymerization increased the temperature range of LC phases for these polymers, as expected, with a larger decrease in the crystal‐to‐LC transition than in the LC‐to‐isotropic transition. Additionally, it neither suppressed the formation of smectic phases nor promoted the formation of a nematic phase in these hydrogen‐bonded polymers, as usually observed in many thermotropic LC polymers. The thermal transitions for all of them, measured by differential scanning calorimetry, were well below their decomposition temperatures, as measured by thermogravimetric analysis, which were in the temperature range of 193–210 °C. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1282–1295, 2003     

N‐(4‐Nitrobenzoyl)‐N′‐phenylhydrazine: a three‐dimensional hydrogen‐bonded framework

In the title compound (systematic name: N‐anilino‐4‐nitrobenzamide), C₁₃H₁₁N₃O₃, the molecules are linked into a complex three‐dimensional framework structure by a combination of two‐centre N—H...O and C—H...O hydrogen bonds and a three‐centre N—H...(O,N) hydrogen bond.     

Different hydrogen‐bonded structures in three 2‐thienyl‐substituted tetrahydro‐1,4‐epoxy‐1‐benzazepines

The molecules of (2RS,4SR)‐2‐exo‐(5‐bromo‐2‐thienyl)‐7‐chloro‐2,3,4,5‐tetrahydro‐1H‐1,4‐epoxy‐1‐benzazepine, C₁₄H₁₁BrClNOS, (I), are linked into cyclic centrosymmetric dimers by C—H...π(thienyl) hydrogen bonds. Each such dimer makes rather short Br...Br contacts with two other dimers. In (2RS,4SR)‐2‐exo‐(5‐methyl‐2‐thienyl)‐2,3,4,5‐tetrahydro‐1H‐1,4‐epoxy‐1‐benzazepine, C₁₅H₁₅NOS, (II), a combination of C—H...O and C—H...π(thienyl) hydrogen bonds links the molecules into chains of rings. A more complex chain of rings is formed in (2RS,4SR)‐7‐chloro‐2‐exo‐(5‐methyl‐2‐thienyl)‐2,3,4,5‐tetrahydro‐1H‐1,4‐epoxy‐1‐benzazepine, C₁₅H₁₄ClNOS, (III), built from a combination of two independent C—H...O hydrogen bonds, one C—H...π(arene) hydrogen bond and one C—H...π(thienyl) hydrogen bond.     

Three aryl‐substituted tetrahydro‐1,4‐epoxy‐1‐benzazepines: hydrogen‐bonded structures in two or three dimensions

In (2SR,4RS)‐7‐chloro‐2‐exo‐(4‐chlorophenyl)‐2,3,4,5‐tetrahydro‐1H‐1,4‐epoxy‐1‐benzazepine, C₁₆H₁₃Cl₂NO, (I), the molecules are linked by a combination of C—H...O and C—H...N hydrogen bonds into a chain of edge‐fused R₃³(12) rings. The isomeric compound (2S,4R)‐7‐chloro‐2‐exo‐(2‐chlorophenyl)‐2,3,4,5‐tetrahydro‐1H‐1,4‐epoxy‐1‐benzazepine, (II), crystallizes as a single 2S,4R enantiomer and the molecules are linked into a three‐dimensional framework structure by two C—H...O hydrogen bonds and one C—H...π(arene) hydrogen bond. The molecules of (2S,4R)‐7‐chloro‐2‐exo‐(1‐naphthyl)‐2,3,4,5‐tetrahydro‐1H‐1,4‐epoxy‐1‐benzazepine, C₂₀H₁₆ClNO, (III), are also linked into a three‐dimensional framework structure, here by one C—H...O hydrogen bond and two C—H...π(arene) hydrogen bonds. The significance of this study lies in its observation of the variations in molecular configuration and conformation, and in the variation in the patterns of supramolecular aggregation, consequent upon modest changes in the peripheral substituents.     

A hydrogen‐bonded chain of rings in 5‐amino‐1‐(4‐methoxybenzoyl)‐3‐methylpyrazole and a three‐dimensional hydrogen‐bonded framework in 5‐amino‐3‐methyl‐1‐(2‐nitrobenzoyl)pyrazole

The molecules of 5‐amino‐1‐(4‐methoxybenzoyl)‐3‐methylpyrazole, C₁₂H₁₃N₃O₂, (I), and 5‐amino‐3‐methyl‐1‐(2‐nitrobenzoyl)pyrazole, C₁₁H₁₀N₄O₃, (II), both contain intramolecular N—H...O hydrogen bonds. The molecules of (I) are linked into a chain of rings by a combination of N—H...N and N—H...π(arene) hydrogen bonds, while those of (II) are linked into a three‐dimensional framework structure by N—H...N and C—H...O hydrogen bonds.