Ammonium N‐(6‐amino‐3,4‐di­hydro‐3‐methyl‐5‐nitro­so‐4‐oxopyrimidin‐2‐yl)­glycinate monohydrate forms hydrogen‐bonded bilayers

In the title compound, NH₄⁺·C₇H₈N₅O₄⁻·H₂O, the independent components are linked into bilayers by an extensive series of two‐centre N—H⃛O hydrogen bonds [H⃛O = 1.85–1.96 Å, N⃛O = 2.776 (2)–2.840 (2) Å and N—H⃛O = 149–172°], and by asymmetric three‐centre N—H⃛(O)₂, O—H⃛(N,O) and O—H⃛(O)₂ hydrogen bonds.     

trans‐4‐Acetylcyclo­hexane­carboxyl­ic acid and ()‐trans‐2‐acetyl­cyclo­hexane­carboxyl­ic acid: hydrogen‐bonding patterns in two isomeric keto acids

Both title compounds, C₉H₁₄O₃, display carboxyl‐dimer hydrogen‐bonding patterns. The 4‐acetyl isomer adopts a chiral conformation with negligible disordering of the methyl and carboxyl groups and forms centrosymmetric dimers across the b and c edges of the chosen cell [O?O = 2.667 (3) Å and O—H?O = 175°]. Intermolecular C—H?O close contacts were found for both carbonyl groups. In the 2‐acetyl isomer, there is no intramolecular interaction between the carboxyl and acetyl groups and the hydrogen bonding involves centrosymmetric carboxyl dimerization across the ab and ac faces of the chosen cell [O?O = 2.668 (2) Å and O—H?O = 173°]. The carboxyl group is negligibly disordered, but significant rotational disordering was found for the acetyl methyl group. An intermolecular C—H?O close contact was found involving the ketone group.     

(R)‐1‐Phenyl­ethyl­ammonium 6‐amino‐5‐nitro­pyrimidine‐2,4(1H,3H)‐dionate (R)‐1‐phenyl­ethyl­amine hemisolvate: hydrogen‐bonded sheets of ions with pendent solvent mol­ecules

In the title compound, 2C₈H₁₂N⁺·2C₄H₃N₄O₄⁻·C₈H₁₁N, the anions are linked by paired N—H⋯N hydrogen bonds [H⋯N = 2.07 and 2.11 Å, N⋯N = 2.942 (3) and 2.978 (3) Å and N—H⋯N = 173 and 170°] and by paired N—H⋯O hydrogen bonds [H⋯O = 1.98 and 2.05 Å, N⋯O = 2.855 (3) and 2.917 (3) Å, and N—H⋯O = 173 and 167°] into chains of rings. These chains are linked into sheets by further N—H⋯O hydrogen bonds in which all of the donors are provided by the cations [H⋯O = 1.83–2.17 Å, N⋯O = 2.747 (3)–2.965 (3) Å and N—H⋯O = 141–168°]. The neutral amine molecule is pendent from the sheet and is linked to it by a single N—H⋯N hydrogen bond [H⋯N = 2.00 Å, N⋯N = 2.901 (3) Å and N—H⋯N = 175°].     

(+)‐3‐Oxo‐4‐pregnene‐20β‐carboxyl­ic acid: catemeric hydrogen bonding in a steroidal keto acid

The title keto acid, (+)‐23,24‐dinor‐3‐oxo­chol‐4‐en‐22‐oic acid, C₂₂H₃₂O₃, forms carboxyl‐to‐ketone hydrogen‐bonding catemers [O?O = 2.699 (4) Å and O—H?O = 173°], linking mol­ecules screw‐related in b. The four mol­ecules in the cell form two parallel counter‐directional chains, screw‐related in a. Intermolecular C—H?O=C close contacts to different neighboring mol­ecules were found for the ketone and the acid.     

(+)‐3,11‐Dioxoandrost‐4‐ene‐17β‐carboxyl­ic acid: catemeric hydrogen bonding in a steroidal keto acid

The title keto acid, C₂₀H₂₆O₄, forms carboxyl‐to‐ketone hydrogen‐bonding catemers [O?O = 2.653 (5) Å and O—H?O = 172 (5)°], linking translationally related mol­ecules via the A‐ring ketone. The two mol­ecules in the cell form two parallel counter‐directional chains, screw‐related in b. A total of four intermolecular C—H?O=C close contacts was found, involving both ketone functions.     

(+)‐2‐(1,2,3,4,4a,5,6,7‐Octa­hydro‐4a,8‐di­methyl‐7‐oxo‐2‐naphthyl)­propionic acid: catemeric hydrogen bonding in a bicyclic sesquiterpenoid keto acid

The title compound, C₁₅H₂₂O₃, derived from a naturally occurring sesquiterpenoid, has two mol­ecules in the asymmetric unit, differing principally in the rotational conformation of the carboxyl group. Each species aggregates separately as a carboxyl‐to‐ketone hydrogen‐bonding catemer [O?O = 2.752 (4) and 2.682 (4) Å, and O—H?O = 161 (4) and 168 (4)°], producing two crystallographically independent single‐strand hydrogen‐bonding helices, with opposite end‐to‐end orientations, passing through the cell in the b direction. Three intermolecular C—H?O=C close contacts exist for the ketone.     

6‐Amino‐2‐(3,4‐di­methoxy­benzyl­amino)‐3‐methyl‐5‐nitro­so­pyrimidin‐4(3H)‐one: hydrogen‐bonded sheets form interdigitated bilayers

Molecules of the title compound, C₁₄H₁₇N₅O₄, exhibit a highly polarized molecular–electronic structure. The mol­ecules are linked into sheets by two N—H⋯O hydrogen bonds [H⋯O = 2.03 and 2.02 Å, N⋯O = 2.836 (2) and 2.887 (2) Å, and N—H⋯O = 153 and 168°], augmented by a single C—H⋯O hydrogen bond [H⋯O = 2.47 Å, C⋯O = 3.403 (2) Å and C—H⋯O = 166°]. Pairs of sheets, related by inversion, form bilayers with interdigitated di­methoxy­benzyl substituents, weakly linked by a further C—H⋯O interaction [H⋯O = 2.50 Å, C⋯O = 3.350 (2) Å and C—H⋯O = 146°].     

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].     

2,2′‐Methyl­enebis(3‐hydroxy‐5,5‐di­methyl­cyclo­hex‐2‐en‐1‐one)

The title compound, C₁₇H₂₄O₄, crystallizes with two independent mol­ecules, both lying across twofold rotation axes in space group Pccn, in a unit cell whose dimensions closely mimic those of a tetragonal cell. Each mol­ecule contains paired O—H⋯O hydrogen bonds [H⋯O = 1.81 and 1.83 Å, O⋯O = 2.640 (2) and 2.642 (2) Å, and O—H⋯O = 168 and 162°].     

2‐Amino‐5‐nitro‐4,6‐dipiperidinopyrimidinium hydrogen­sulfate monohydrate: hydrogen‐bonded sheets containing highly distorted cations

In the title compound, C₁₄H₂₃N₆O₂⁺·HSO₄⁻·H₂O, the pyrimidinium ring of the cation adopts a twist‐boat conformation, induced by steric clashes between adjacent ring substituents; the anions and the water mol­ecules are linked by three O—H⃛O hydrogen bonds [H⃛O = 1.70–1.78 Å, O⃛O = 2.548 (2)–2.761 (2) Å and O—H⃛O = 161–168°] into chains of edge‐fused R(12) rings, which are linked into sheets by the cations, via three N—H⃛O hydrogen bonds [H⃛O = 1.96–2.17 Å, N⃛O = 2.820 (2)–2.935 (2) Å and N—H⃛O = 145–173°].     

(±)‐cis‐2‐Methyl‐4‐oxo­cyclo­hexane­carboxyl­ic acid: catemeric hydrogen bonding in a δ‐keto acid derived from Hagemann's ester

The title compound, C₈H₁₂O₃, crystallizes as acid‐to‐ketone hydrogen‐bonding catemers, in which hydrogen bonds progress from the carboxyl group of each mol­ecule to the ketone group of a translationally related neighbor [O⋯O = 2.738 (3) Å and O—H⋯O = 153 (4)°]. Four separate hy­drogen‐bonding chains proceed through the cell in centrosymmetrically related pairs along axes lying in the ab plane. Three intermolecular C—H⋯O close contacts exist involving both carboxyl O atoms. Factors contributing to the choice of hydrogen‐bonding mode are discussed.     

4‐Amino‐2,6‐di­methoxy­pyrimidine: hydrogen‐bonded sheets of R22(8) and R66(28) rings,reinforced by an aromatic π–π‐stacking interaction

Molecules of the title compound, C₆H₉N₃O₂, are linked by an N—H⃛O hydrogen bond [H⃛O = 2.29 Å, N⃛O = 3.169 (2) Å and N—H⃛O = 173°] and an N—H⃛N hydrogen bond [H⃛N = 2.12 Å, N⃛N = 2.999 (2) Å and N—H⃛N = 175°] into sheets containing centrosymmetric R(8) and R(28) rings; the sheets are reinforced by a single aromatic π–π‐stacking interaction.     

2‐Amino­benzimidazolium O‐ethyl malonate: eight independent N—H⋯O hydrogen bonds generate sheets

The title compound, C₇H₈N₃⁺·C₅H₇O₄⁻, crystallizes with Z′ = 2 in space group P2₁/c; eight independent N—H⋯O hydrogen bonds [H⋯O = 1.75–1.88 Å, N⋯O = 2.699 (2)–2.829 (2) Å and N—H⋯O = 147–179°] link the four inde­pendent ions into sheets.     

7‐Methoxy‐3‐(salicyl­idene­amino)­coumarin

The title compound, C₁₇H₁₃NO₄, exists as a planar mol­ecule; adjacent mol­ecules are linked by electrostatic C—H?O [C?O = 3.318 (4) and 3.455 (4) Å] interactions into a linear chain.     

Cocrystallization of adamantane‐1,3‐dicarboxylic acid and 4,4′‐bipyridine

The cocrystallization of adamantane‐1,3‐dicarboxylic acid (adc) and 4,4′‐bipyridine (4,4′‐bpy) yields a unique 1:1 cocrystal, C₁₂H₁₆O₄·C₁₀H₈N₂, in the C2/c space group, with half of each molecule in the asymmetric unit. The mid‐point of the central C—C bond of the 4,4′‐bpy molecule rests on a center of inversion, while the adc molecule straddles a twofold rotation axis that passes through two of the adamantyl C atoms. The constituents of this cocrystal are joined by hydrogen bonds, the stronger of which are O—H...N hydrogen bonds [O...N = 2.6801 (17) Å] and the weaker of which are C—H...O hydrogen bonds [C...O = 3.367 (2) Å]. Alternate adc and 4,4′‐bpy molecules engage in these hydrogen bonds to form zigzag chains. In turn, these chains are linked through π–π interactions along the c axis to generate two‐dimensional layers. These layers are neatly packed into a stable crystalline three‐dimensional form via weak C—H...O hydrogen bonds [C...O = 3.2744 (19) Å] and van der Waals attractions.     

Tetra­aqua(5‐fluoro­uracil‐1‐acetato‐O)copper(II) tetra­hydrate

In the title complex, [Cu(C₆H₄FN₂O₄)₂(H₂O)₄]·4H₂O, the Cu atom is located in the centre of a distorted octahedral geometry. The coordination atoms are six O atoms provided by two carboxyl­ate groups [coordinated in a monodentate mode, with Cu—O = 1.9551 (10) Å] and four water mol­ecules [Cu—O = 1.9241 (13) and 2.5771 (14) Å]. In addition, one intramolecular hydrogen bond and ten intermolecular hydrogen bonds make up a three‐dimensional network.     

Bis­(acetato‐O)­tetrakis­(imidazole‐N3)­nickel(II)

In the title compound, [Ni(C₂H₃O)₂(C₃H₄N₂)₄], the Ni atom is coordinated centrosymmetrically by four N and two O atoms in an octahedral coordination [Ni—N = 1.986 (3) and 2.054 (3) Å; Ni—O = 2.697 (3) Å]. The O atoms of the acetate anions form hydrogen bonds to adjacent imidazole moieties, with the free O atom forming a somewhat shorter bond [N?O = 2.679 (3) and 2.870 (4) Å]. The hydrogen bonds give rise to a two‐dimensional layer structure.     

catena‐Poly­[[di­aqua­cadmium(II)]‐μ‐5‐carboxyimidazole‐4‐carboxylato‐κ4N1,O5:O4,N3]

A new cadmium coordination polymer, [Cd(C₅H₂N₂O₄)(H₂O)₂]_n, possesses a one‐dimensional zigzag chain structure built from Cd^II centers bridged sequentially by pairs of O and N atoms of the 5‐carboxyimidazole‐4‐carboxylate ligand. The Cd^II center is in a distorted octahedral geometry, being coordinated by two O atoms from two coordinated water mol­ecules [Cd—O = 2.322 (7) and 2.364 (7) Å], and by two N atoms [Cd—N = 2.222 (6) and 2.232 (6) Å] and two carboxyl O atoms [Cd—O = 2.383 (6) and 2.414 (6) Å] from two 5‐carboxyimidazole‐4‐carboxylate ligands.     

2‐Amino‐4‐(4‐pyridyl)­pyrimidine and the 1:1 adduct with 4‐amino­benzoic acid

The structure of the title compound, C₉H₈N₄, comprises non‐planar mol­ecules that associate via pyrimidine N—H?N dimer R(8) hydrogen‐bonding associations [N?N 3.1870 (17) Å] and form linear hydrogen‐bonded chains via a pyrimidine N—H?N(pyridyl) interaction [N?N 3.0295 (19) Å]. The dihedral angle between the two rings is 24.57 (5)°. The structure of the 1:1 adduct with 4‐amino­benzoic acid, C₉H₈N₄·C₇H₇NO₂, exhibits a hydrogen‐bond­ing network involving COOH?N(pyridyl) [O?N 2.6406 (17) Å], pyrimidine N—H?N [N?N 3.0737 (19) and 3.1755 (18) Å] and acid N—H?O interactions [N?O 3.0609 (17) and 2.981 (2) Å]. The dihedral angle between the two linked rings of the base is 38.49 (6)° and the carboxyl­ic acid group binds to the stronger base group in contrast to the (less basic) complementary hydrogen‐bonding site.     

Trigonal–planar silver coordination in (3,5‐di­nitro­benzoato)­bis­(tri­phenyl­phosphine)­silver(I)

The three‐coordinate Ag atom in the title compound, [Ag(C₇H₃N₂O₆)(C₁₈H₁₅P)₂], shows trigonal–planar coordination [P—Ag—P = 147.1 (1)° and Σ_Ag = 359.0 (3)°]. Adjacent mol­ecules are linked through the O atoms of adjacent nitro groups [Ag?O = 3.205 (3) and 3.302 (4) Å] into a zigzag chain running parallel to the c axis.