The 1:1 adduct of hexa­methyl­ene­tetramine (HMT) with racemic trans‐1,2‐cyclo­hexane­di­carboxylic acid (CDA)

Hexa­methyl­ene­tetramine and rac‐trans‐1,2‐cyclo­hexane­di­carboxylic acid crystallize in a 1:1 ratio as a neutral molecular adduct, C₆H₁₂N₄·C₈H₁₂O₄. Two di­carboxylic acid mol­ecules and two tetr­amine mol­ecules form a hydrogen‐bonded ring, in the shape of a rhombus, which lies on a crystallographic twofold axis bisecting the two diacid mol­ecules. The O—H⋯N hydrogen bonds have lengths 2.6808 (19) and 2.6518 (19) Å, and, in each ring, both acid mol­ecules have the same handedness.     

Hydro­gen‐bonding patterns in 2‐amino‐4,6‐di­methyl­pyrimidinium hydrogen sulfate

In the title compound, C₆H₁₀N₃⁺·HSO₄⁻, the asymmetric unit consists of a hydrogen sulfate anion and a 2‐amino‐4,6‐di­methyl­pyrimidinium cation. The hydrogen sulfate anions self‐assemble through O—H⋯O hydrogen bonds, forming supramolecular chains along the b axis, while the organic cations form base pairs via N—H⋯N hydrogen bonds. The amino­pyrimidinium cations join to the sulfate anions via a pair of hydrogen bonds donated from the pyrimidinium protonation site and from the exo amine group cis to the protonated site.     

catena‐Poly­[[(di‐2‐pyridyl­amine)­silver(I)]‐μ‐nicotinato] and catena‐poly­[[(di‐2‐pyridyl­amine)silver(I)]‐μ‐2,6‐di­hydroxy­benzoato]

In catena‐poly­[[(di‐2‐pyridyl­amine‐κ²N,N′)silver(I)]‐μ‐nico­tinato‐κ²N:O], [Ag(C₆H₄NO₂)(C₁₀H₉N₃)]_n, the Ag^I atom is tetracoordinated by two N atoms from the di‐2‐pyridyl­amine (BPA) ligand [Ag—N = 2.3785 (18) and 2.3298 (18) Å] and by one N atom and one carboxyl­ate O atom from nicotinate ligands [Ag—N = 2.2827 (15) Å and Ag—O = 2.3636 (14) Å]. Bridging by nicotinate N and O atoms generates a polymeric chain structure, which extends along [100]. The carboxyl O atom not bonded to the Ag atom takes part in an intrachain C—H⋯O hydrogen bond, further stabilizing the chain. Pairs of chains are linked by N—H⋯O hydrogen bonds to generate ribbons. There are no π–π interactions in this complex. In catena‐poly­[[(di‐2‐pyridyl­amine‐κ²N,N′)silver(I)]‐μ‐2,6‐di­hydroxy­benzoato‐κ²O¹:O²], [Ag(C₇H₅O₄)(C₁₀H₉N₃)]_n, the Ag^I atom has a distorted tetrahedral coordination, with three strong bonds to two pyridine N atoms from the BPA ligand [Ag—N = 2.286 (5) and 2.320 (5) Å] and to one carboxyl­ate O atom from the 2,6‐di­hydroxy­benzoate ligand [Ag—O = 2.222 (4) Å]; the fourth, weaker, Ag‐atom coordination is to one of the phenol O atoms [Ag⋯O = 2.703 (4) Å] of an adjacent moiety, and this interaction generates a polymeric chain along [100]. Pairs of chains are linked about inversion centers by N—H⋯O hydrogen bonds to form ribbons, within which there are π–π interactions. The ribbons are linked about inversion centers by pairs of C—H⋯O hydrogen bonds and additional π–π interactions between inversion‐related pairs of 2,6‐di­hydroxy­benzoate ligands to generate a three‐dimensional network.     

2‐Pyridone–tartronic acid (1/1), 3‐hydroxy­pyridinium hydrogen tartronate and 4‐hydroxy­pyridinium hydrogen tartronate

Tartronic acid forms a hydrogen‐bonded complex, C₅H₅NO·C₃H₄O₅, (I), with 2‐pyridone, while it forms acid salts, namely 3‐hydroxy­pyridinium hydrogen tartronate, (II), and 4‐hy­droxy­pyridinium hydrogen tartronate, (III), both C₅H₆NO⁺·C₃H₃O₅⁻, with 3‐hydroxy­pyridine and 4‐hydroxy­pyridine, respectively. In (I), the pyridone mol­ecules and the acid mol­ecules form R(8) and R(10) hydrogen‐bonded rings, respectively, around the inversion centres. In (II) and (III), the cations and anions are linked by N—H⋯O and O—H⋯O hydrogen bonds to form a hydrogen‐bonded chain. In each of (I), (II) and (III), an intermolecular hydrogen bond is formed between a carboxyl group and the hydroxyl group attached to the central C atom, and in (I), the hydroxyl group participates in an intramolecular hydrogen bond with a carbonyl group. No intermolecular hydrogen bond is formed between the carboxyl groups in (I), or between the carboxyl and carboxyl­ate groups in (II) and (III).     

2‐Aminopyridinium–succinate–succinic acid (2/1/1)

In the title compound, 2C₅H₇N₂⁺·C₄H₄O₄^2?·C₄H₆O₄, cyclic eight‐membered hydrogen‐bonded rings exist involving 2‐amino­pyridinium and succinate ions. The succinic acid and succinate moieties lie on inversion centres. Succinic acid mol­ecules and succinate ions are linked into zigzag chains by O—H?O hydrogen bonds, with O?O distances of 2.6005 (16) Å.     

2‐Amino­pyridinium–fumarate–fumaric acid (2/1/1)

The title complex, 2C₅H₇N₂⁺·C₄H₂O₄²⁻·C₄H₄O₄, contains cyclic eight‐membered hydrogen‐bonded rings involving 2‐­aminopyridinium and fumarate ions. The fumaric acid mol­ecules and fumarate ions lie on inversion centers and are linked into zigzag chains by O—H⋯O hydrogen bonds. The dihedral angle between the pyridinium ring and the hydrogen‐bonded fumarate ion is 7.60 (4)°. The fumarate anion is linked to the pyridinium cations by intermolecular N—H⋯O hydrogen bonds. The heterocycle is fully protonated, thus enabling amine–imine tautomerization.     

Tris­(methyl­ammonium) hydrogen­phosphate di­hydrogenphosphate

The title compound, 3CH₆N⁺·HPO₄²⁻·H₂PO₄⁻, aggregates with the moieties interconnected by O—H⋯O and N—H⋯O hydrogen bonds, with O⋯O and N⋯O distances in the ranges 2.5366 (16)–2.5785 (14) and 2.7437 (16)–2.9967 (18) Å, respectively. Three C—H⋯O hydrogen bonds are also present, with C⋯O distances in the range 3.2310 (18)–3.3345 (17) Å. All H atoms are ordered. Structures with ordered hydrogenphosphate and di­hydrogen­phosphate components are rare.     

Symmetric hydrogen bonding in dimethyl­ammonium hydrogen diphenyl­diphospho­nate

In the title compound, C₂H₈N⁺·C₁₂H₁₁O₅P₂⁻, pairs of hydrogen diphenyl­diphospho­nate anions form dimers across a twofold axis, with two symmetric O⋯H⋯O hydrogen bonds [O⋯O = 2.406 (3) and 2.418 (3) Å]. The 12‐membered ring thus formed has crystallographic 2 and quasi‐222 symmetry. Cations on either side of the ring form N—H⋯O hydrogen bonds to the four extraannular O atoms, with N⋯O distances of 2.765 (2) and 2.748 (3) Å.     

Cocrystallization of melaminium levulinate monohydrate

Crystals of 2,4,6‐tri­amino‐1,3,5‐triazin‐1‐ium levulinate (4‐oxo­pentanoate) monohydrate, C₃H₇N₆⁺·C₅H₇O₃⁻·H₂O, are formed via self‐assembled hydrogen bonding by cocrystallization of mel­amine and levulinic acid. Two N—H⋯N hydrogen bonds and four N—H⋯O hydrogen bonds connect two melaminium entities such that each of two pairs of N—H⋯O bonds bridges two H atoms belonging to the amine groups of two different melaminium cations via the carbonyl O atom of one levulinate mol­ecule.     

Ferrocene compounds. XXXIV. 1′‐(tert‐Butoxycarbonylamino)ferrocene‐1‐carboxylic acid

Heteroannularly substituted ferrocene derivatives can act as model systems for various hydrogen‐bonded assemblies of biomol­ecules formed, for instance, by means of O—H⋯O and N—H⋯O hydrogen bonding. The crystal structure analysis of 1′‐(tert‐butoxy­carbonyl­amino)­ferrocene‐1‐carbox­ylic acid, [Fe(C₁₀H₁₄NO₂)(C₆H₅O₂)] or (C₅H₄COOH)Fe(C₅­H₄NHCOOC(CH₃)₃, reveals two independent mol­ecules within the asymmetric unit, and these are joined into discrete dimers by two types of intermolecular hydrogen bonds, viz. O—H⋯O and N—H⋯O. The –COOH and –NHCOOR groups are archetypes for dimer formation via two eight‐membered rings. The O—H⋯O hydrogen bonds [2.656 (3) and 2.663 (3) Å] form a cyclic carboxylic acid dimer motif. Another eight‐membered ring is formed by N—H⋯O hydrogen bonds [2.827 (3) and 2.854 (3) Å] between the N—H group and an O atom of another carbamoyl moiety. The dimers are assembled in a herring‐bone fashion in the bc plane.     

4‐Amino‐N‐isopropyl­benzamidinium chloride ethanol solvate

The title compound, C₁₀H₁₆N·Cl⁻·C₂H₆O, is an important intermediate in the convergent synthesis of amidine‐substituted polycyclic heterocycles, a class of compounds that shows significant anticancer activity. The molecule of (I) is not planar, having a dihedral angle of 25.00 (7)° between the aniline and amidine (–C—NH=C=NH₂) groups. The proton­ation of the amidine molecular fragment is accompanied by delocalized C—N bond distances of 1.320 (2) and 1.317 (2) Å. The cations and chloride anions are involved in a network of hydrogen bonds, resulting in the formation of infinite chains propagating along the b direction. The chains are further grouped within the ab plane, in such a way that the structure is segregated into layers dominated by hydro­phobic interactions involving N‐isopropyl residues and layers dominated by N—H⋯Cl [N⋯Cl = 3.275 (2)–3.596 (2) Å], O—H⋯Cl [O⋯Cl = 3.229 (3) Å] and N—H⋯O [N⋯O = 2.965 (3) Å] hydrogen bonds.     

2‐Aminopyridinium benzoate

Cyclic eight‐membered hydrogen‐bonded rings exist in the title compound, C₅H₇N₂⁺·C₇H₅O₂⁻, involving the 2‐amino­pyridinium and benzoate ions. Each benzoate ion has two intramolecular hydrogen bonds. 2‐Amino­pyridinium benzoate ion pairs are linked by N—H⋯O hydrogen bonds, with an N⋯O distance of 2.8619 (14) Å.     

Isomorphous crystals of strychninium 4‐chloro­benzoate and strychninium 4‐nitro­benzoate

In strychninium 4‐chloro­benzoate, C₂₁H₂₃N₂O₂⁺·C₇H₄ClO₂⁻, (I), and strychninium 4‐nitro­benzoate, C₂₁H₂₃N₂O₂⁺·C₇H₄NO₄⁻, (II), the strychninium cations form pillars stabilized by C—H⋯O and C—H⋯π hydrogen bonds. Channels between the pillars are occupied by anions linked to one another by C—H⋯π hydrogen bonds. The cations and anions are linked by ionic N—H⁺⋯O⁻ and C—H⋯X hydrogen bonds, where X = O, π and Cl in (I), and O and π in (II).     

7‐Carboxyl­ato‐8‐hydroxy‐2‐methyl­quinolinium monohydrate and 7‐carboxy‐8‐hydroxy‐2‐methyl­quinolinium chloride monohydrate at 100 K

Both 7‐carboxyl­ato‐8‐hydroxy‐2‐methyl­quinolinium monohydrate, C₁₁H₉NO₃·H₂O, (I), and 7‐carboxy‐8‐hydroxy‐2‐methyl­quinolinium chloride monohydrate, C₁₁H₁₀NO₃⁺·Cl⁻·H₂O, (II), crystallize in the centrosymmetric P space group. Both compounds display an intramolecular O—H⋯O hydrogen bond involving the hydroxy group; this hydrogen bond is stronger in (I) due to its zwitterionic character [O⋯O = 2.4449 (11) Å in (I) and 2.5881 (12) Å in (II)]. In both crystal structures, the HN⁺ group participates in the stabilization of the structure via intermolecular hydrogen bonds with water mol­ecules [N⋯O = 2.7450 (12) Å in (I) and 2.8025 (14) Å in (II)]. In compound (II), a hydrogen‐bond network connects the Cl⁻ anion to the carboxylic acid group [Cl⋯O = 2.9641 (11) Å] and to two water mol­ecules [Cl⋯O = 3.1485 (10) and 3.2744 (10) Å].     

An oxonium hydrogen sulfate of 3a,6a‐diphenyl­glycoluril

In the title compound, (5‐oxo‐3a,6a‐diphenyl­perhydro­imidazo[4,5‐d]imidazol‐2‐ylidene)oxonium hydrogen sulfate, C₁₆H₁₅N₄O₂⁺·HSO₄⁻, the asymmetric unit contains a hydrogen sulfate anion and a 3a,6a‐diphenyl­glycoluril oxonium cation. The hydrogen sulfate anion is joined to the oxonium cation via a strong O—H⋯O hydrogen bond (H⋯O = 1.69 Å). The crystal packing is mainly dominated by inter­actions involving the hydrogen sulfate anion. The diphenyl­glycoluril oxonium cations also self‐assemble through N—H⋯O hydrogen bonds, forming mol­ecular chains along the [001] vector. Four intra­molecular C—H⋯N hydrogen bonds are observed, having an S(5) motif.     

Supra­molecular hydrogen‐bonding networks in bis­(adeninium) phthalate phthalic acid 1.45‐hydrate

In the title compound, 2C₅H₆N₅⁺·C₈H₄O₄²⁻·C₈H₆O₄·1.45H₂O, the asymmetric unit comprises two adeninium cations, two half phthalate anions with crystallographic C₂ symmetry, one neutral phthalic acid mol­ecule, and one fully occupied and one partially occupied site (0.45) for water mol­ecules. The adeninium cations form N—H⋯O hydrogen bonds with the phthalate anions. The cations also form infinite one‐dimensional polymeric ribbons via N—H⋯N inter­actions. In the crystal packing, hydrogen‐bonded columns of cations, anions and phthalate anions extend parallel to the c axis. The water mol­ecules crosslink adjacent columns into hydrogen‐bonded layers.     

(2‐Hydroxy­ethyl)­hydrazinium(2+) dichloride

The crystal structure of the title compound, C₂H₁₀N₂O²⁺·2Cl⁻, is built up from one 2‐hydroxy­ethyl­hydrazinium(2+) cation and two Cl⁻ anions. The mol­ecular structure is stabilized by O—H⋯Cl and N—H⋯Cl hydrogen bonds. The crystal structure is stabilized by one N—H⋯O and three N—H⋯Cl inter­actions, and the three‐dimensional network of hydrogen bonds stabilizes the crystal packing. All five hydrazinium H atoms are involved in hydrogen bonds to Cl⁻ anions. The Cl⋯H contact distances range from 2.122 (15) to 2.809 (14) Å.     

Two N,N‐dimethylbiguanidium salts displaying double hydrogen bonds to the counter‐ions

The crystal structures of N,N‐di­methyl­biguanidium oxalate monohydrate, C₄H₁₃N₅²⁺·C₂O₄²⁻·H₂O, (I), and N,N‐di­methyl­biguanidium sulfate monohydrate, C₄H₁₃N₅²⁺·SO₄²⁻·H₂O, (II), show that both compounds contain the same N,N‐di­methyl­biguanidium dication. In (I), two independent oxalate ions lie about inversion centres. Strong double hydrogen bonds, with D⋯A distances of 2.658 (2) and 2.830 (3) Å in (I), and 2.722 (3) and 2.815 (3) Å in (II), are present between N atoms of the N,N‐di­methyl­biguanidium moieties and either the carboxyl­ate group of the oxalate anion or the sulfate anion.     

Doxy­laminium tetra­chloro­cuprate(II)

The structure of the title compound, 2-[1-(di­methyl­ammon­ioethoxy)-1-phenyl­ethyl]­pyridinium tetra­chloro­cuprate(II), (C₁₇H₂₄N₂O)[CuCl₄], contains di­hydro cations of doxyl­amine hydrogen bonded to two Cl atoms in two different CuCl₄²⁻ anions, with Cl⃛N distances of 3.101 (9) and 3.253 (10) Å. The ethereal O atom is involved in intramolecular hydrogen bonds, with O⃛N distances of 2.517 (11) and 2.757 (12) Å. The molecular dimensions in the cation are as expected and the CuCl₄²⁻ anion has a flattened tetrahedral geometry.     

Polar hydrogen‐bonded organic chains in 4,4′‐bipyrazolium bromide and perchlorate monohydrates

4,4′‐Bipyrazolium [or 4‐(1H‐pyrazol‐4‐yl)pyrazolium] bromide monohydrate, C₆H₇N₄⁺·Br⁻·H₂O, and 4,4′‐bipyrazolium perchlorate monohydrate, C₆H₇N₄⁺·ClO₄⁻·H₂O, have closely related layered structures involving tight stacks of antiparallel N—H⋯N hydrogen‐bonded polar bipyrazolium chains [N⋯N = 2.712 (3) and 2.742 (2) Å], which are crosslinked by hydrogen bonds with water mol­ecules and counter‐anions.