2‐Bromo‐5‐hydroxy­benz­aldehyde

The mol­ecules of the title compound, C₇H₅BrO₂, form zigzag chains running along the b axis and are stacked in layers perpendicular to the a axis. Intermolecular bonding occurs through hydrogen bonds linking the hydroxyl and carbonyl groups, with an O?O distance of 2.804 (4) Å. The Br atom deviates significantly from the plane of the ring and the aldehyde group is twisted by 7.1 (5)° around the Csp²—C_aryl bond. The geometry of the mol­ecule in the crystal is compared to that given by ab initio quantum mechanical calculations for the isolated mol­ecule, using a molecular orbital Hartree–Fock method and density functional theory.     

2,2,4,4‐Tetra‐tert‐butyl‐1,3,5,2,4‐benzotrioxadisilepine‐7‐carbaldehyde

The mol­ecule of the title compound, C₂₃H₄₀O₄Si₂, features an approximate non‐crystallographic C₂ symmetry axis. The aldehyde group is disordered over two positions with similar occupancies. The geometry of the isolated mol­ecule was studied by ab initio quantum mechanical calculations employing a mol­ecular orbital Hartree–Fock method. The calculations reproduce well the equilibrium geometry but slightly overestimate the value of the Si—O bond lengths of the trioxadisilepine ring.     

R(30) rectangular rings in 2,5‐dioxopiperazine‐1,4‐di­acetic acid

Molecules of the title 2,5‐dioxopiperazinedione derivative, C₈H₁₀N₂O₆, occupy centres of symmetry in the crystal structure. The six‐membered ring has an almost planar conformation, with the substituent on nitrogen nearly perpendicular to the ring. The ideal geometry of the isolated mol­ecule, as determined by ab initio HF–LCAO quantum‐mechanical calculations, is slightly more puckered than that observed in the solid state. In the crystal structure, a strong hydrogen bond joins neighbouring mol­ecules, thus forming a network of rectangular (30) rings.     

Hydrogen‐bonding and C—H⋯π interactions in ethyl 4‐acetyl‐5‐methyl‐3‐phenyl‐1H‐pyrrole‐2‐carboxylate monohydrate

In the title compound, C₁₆H₁₇NO₃·H₂O, the pyrrole ring is distorted slightly from ideal C_2v symmetry. Three strong hydrogen bonds link the substituted pyrrole and water mol­ecules to form infinite chains, in which the hydrogen bonds form rings and chain patterns. Two intermolecular C—H?π interactions maintain the internal cohesion between these chains. The molecular structure differs slightly from that of the isolated mol­ecule calculated by ab initio quantum‐mechanical calculations. In the latter model, the non‐H substituent atoms share the plane of the pyrrole ring, except for the phenyl group, which lies almost perpendicular to this plane.     

2,4‐Dibromo‐3‐methoxy‐6‐nitrobenz­aldeyde: effect of substituents on ring geometry

In the title compound, C₈H₅Br₂NO₄, the endocyclic angles of the ring deviate significantly from the ideal value of 120°. The substituents deviate from the plane of the ring, with large twist angles for the aldehyde, nitro and methoxy groups. The geometry of the mol­ecule in the crystal is compared with that of the isolated mol­ecule, as given by a self‐consistent field molecular‐orbital Hartree–Fock calculation. Only weak hydrogen bonds of the C—H?Br and C—H?O types are present in the crystal structure.     

N‐(o‐Chloro­phenyl)‐2,5‐di­methyl­pyrrole‐3‐carb­aldehyde

Crystal structure analysis of the title compound, C₁₃H₁₂ClNO, reveals three crystallographically independent mol­ecules in the asymmetric unit. The main conformational difference between these mol­ecules is the orientation of the phenyl rings with respect to the pyrrole rings. The coplanar arrangement of the aldehyde groups attached to the pyrrole rings influences the pyrrole‐ring geometry. The C2—C3 and N1—C5 bonds are noticeably longer than the C4—C5 and N1—C2 bonds. Two independent mol­ecules of the title compound form dimers via intermolecular C—H⃛O hydrogen bonds [D⃛A = 3.400 (3) Å and D—H⃛A = 157°]. The perpendicular orientation of the phenyl and pyrrole rings of one independent mol­ecule and its symmetry‐related mol­ecule allows C—H⃛π interactions, with an H⃛centroid distance of 2.85 Å and a C—H⃛π angle of 155°. The distances between the H atom and the pyrrole‐ring atoms indicate that the C—H bond points towards one of the bonds in the pyrrole ring.     

(1S,2R,2′S)‐ and (1S,2S,2′S)‐1‐phenyl‐2‐phenyl­thio‐2‐(tetra­hydro­pyran‐2′‐yl­thio)­ethanol diastereoisomers at 193 K

In the synthesis of 1‐phenyl‐2‐phenyl­thio‐2‐(tetra­hydro­pyran‐2‐yl­thio)­ethanol, C₁₉H₂₂O₂S₂, four diastereoisomers are formed. Two non‐centrosymmetric enantiomeric forms which crystallize in space groups P2₁2₁2₁ and Pna2₁ are presented. The former has an intramolecular hydrogen bond between the hydroxyl group and the O atom of the tetra­hydro­pyran ring. In the latter isomer, the hydroxyl group forms an intermolecular hydrogen bond to the O atom of the tetra­hydro­pyran­yl group of a neighbouring mol­ecule, joining the mol­ecules into chains in the c‐axis direction; the O?O distances are 2.962 (4) and 2.764 (3) Å, respectively. The tetra­hydro­pyran rings are in chair conformations in both isomers and the S side chain has an equatorial orientation in the former, but an axial orientation in the latter mol­ecule.     

Ethyl 3,5‐dimethyl‐4‐phenyl‐1H‐pyrrole‐2‐carboxylate

In the title compound, C₁₅H₁₇NO₂, the ethoxy­carbonyl group is anti with respect to the pyrrole N atom. The angle between the planes of the phenyl and pyrrole rings is 48.26 (9)°. The mol­ecules are joined into dimeric units by a strong hydrogen bonds between pyrrole N—H groups and carbonyl O atoms. The geometry of the isolated mol­ecule was studied by ab initio quantum mechanical calculations, employing both molecular orbital Hartree–Fock (MO–HF) and density functional theory (DFT) methods. The minimum energy was achieved for a conformation where the angle between the planes of the phenyl and pyrrole rings is larger, and that between the ethoxy­carbonyl and pyrrole planes is smaller than in the solid‐state mol­ecule.     

tert‐Butyl (3S,6R,9R)‐(5‐oxo‐3‐{[1(R)‐phenyl­ethyl]­carbamoyl}‐1,2,3,5,6,7,8,8a‐octa­hydro­indolizin‐6‐yl)­carbamate monohydrate at 95 K

The asymmetric unit of the title compound, C₂₂H₃₁N₃O₄·H₂O, incorporates one water mol­ecule, which is hydrogen bonded to the 3‐oxo O atom of the indolizidinone system. The two rings of the peptidomimetic mol­ecule are trans‐fused, with the six‐membered ring having a slightly distorted half‐chair conformation and the five‐membered ring having a perfect envelope conformation. The structure is stabilized by intermolecular O—H?O interactions between the water and adjacent peptide mol­ecules, and by N—H?O interactions between the peptide mol­ecules, which link the mol­ecules into infinite chains.     

The gossypol–cyclo­dodecanone (1/2) inclusion complex

Gossypol and cyclo­dodecanone crystallize at room temperature as an inclusion complex in a 1:2 molar ratio. This complex, viz. 1,1′,6,6′,7,7′‐hexa­hydroxy‐5,5′‐diiso­pro­pyl‐3,3′‐di­methyl‐2,2′‐bi­naphthalene‐8,8′‐di­carbox­aldehyde–cyclo­do­deca­none (1/2), C₃₀H₃₀O₈·2C₁₂H₂₂O, is unusual in that there is limited intermolecular hydrogen bonding within the structure. Each cyclo­dodecanone mol­ecule accepts a hydrogen bond from a gossypol mol­ecule, but there are no gossypol‐to‐gossypol hydrogen‐bond interactions. The gossypol mol­ecules form a framework structure enclosing channels, and the cyclo­dodecanone mol­ecules lie in these channels. In terms of the number of non‐H guest atoms, this is the largest gossypol inclusion complex reported to date.     

3‐Oxa‐6,8‐diaza‐1,2:4,5‐dibenzocycloocta‐1,4‐dien‐7‐one: a three‐dimensional network assembled by hydrogen‐bonding, π–π and edge‐to‐face interactions

The title compound, C₁₃H₁₀N₂O₂, is the first structure in which the urea moiety is incorporated into an eight‐membered ring. Two mol­ecules are found in the asymmetric unit, which are almost identical in their conformation and their hydrogen‐bond pattern. The carbonyl O atom acts as a double acceptor for the NH groups of two adjacent mol­ecules. In this way, infinite tapes are formed, which are connected viaπ–π and edge‐to‐face interactions in the second and third dimension. This hierarchical order of interactions is confirmed by molecular mechanics calculations. Force‐field and semi‐empirical calculations for a single mol­ecule did not find the envelope conformation present in the crystal, indicating instead a C_s conformation. Only with a model consisting of a hydrogen‐bonded dimer or a larger hydrogen‐bonded section was a conformation found that was similar to the one present in the crystal.     

4,8‐Di­methoxy‐1‐naphthalene­methanol

The title compound, C₁₃H₁₄O₃, crystallized in the centrosymmetric space group C2/c with one mol­ecule as the asymmetric unit. Each hydroxyl O atom is involved in hydrogen bonds with two other hydroxyl O atoms. The resulting chains of interactions propagate along [001]. In these interactions, the hydroxyl H atoms are disordered and the O?O distances are 2.648 (2) and 2.698 (2) Å. Two leading intermolecular C—H?O interactions have H?O distances of 2.80 and 2.84 Å and C—H?O angles of 136 and 144°; these interactions form chain and ring patterns. Taken together with the hydrogen bonds, they result in a three‐dimensional network.     

Gallic acid monohydrate

In the crystal structure of the title compound, 3,4,5‐tri­hydroxy­benzoic acid monohydrate, C₇H₆O₅·H₂O, the gallic acid mol­ecule has an intramolecular hydrogen bond involving a pair of hydroxyl groups, and it is also linked to a water mol­ecule by a three‐centre (bifurcated) OW—H?O hydrogen bond. The packing of the mol­ecules is stabilized by intermolecular O—H?O and C—H?O hydrogen bonds.     

A 1:1 adduct of hexa­methylene­tetramine and 4‐hydroxy‐3‐methoxy­benz­aldehyde

In the title complex, C₆H₁₂N₄·C₈H₈O₃, the hexa­methyl­ene­tetramine mol­ecule accepts a single intermolecular O—H?N hydrogen bond from the hydroxy group of the 4‐hydroxy‐3‐methoxy­benz­aldehyde moiety. The non‐centrosymmetric crystal structure is built from alternating molecular sheets of 4‐hydroxy‐3‐methoxy­benz­aldehyde and hexa­methyl­ene­tetramine mol­ecules, and is stabilized by intermolecular O—H?N, C—H?O and C—H?π interactions.     

(24R)‐24,25‐Dihydroxycyclo­artan‐3‐one

In the title compound, C₃₀H₅₀O₃, the three six‐membered rings adopt chair, twist and twist‐boat conformations. The five‐membered ring is in a slightly distorted envelope conformation. The substituent on the five‐membered ring is in an extended conformation, with its two hydroxyl O atoms forming an intramolecular hydrogen bond. One of these O atoms also forms an intermolecular hydrogen bond with the oxy­gen of the carbonyl group in a neighbouring mol­ecule.     

2‐Hydro­xy‐3‐(4,5,6,7‐tetra­hydro‐1H‐imidazo­[4,5‐c]­pyridin‐5‐ium‐4‐yl)­benzoate monohydrate

The title mol­ecule, C₁₃H₁₃N₃O₃·H₂O, is in the form of a mono­hydrated zwitterion. The tetra­hydro­pyridinium ring adopts an envelope conformation and is nearly coplanar with the plane of the imidazoline ring. The water solvate mol­ecule plays an important role as a bridge between zwitterions, forming molecular chains running along the c direction, which are interconnected by N—H?O hydrogen bonds into molecular ribbons. The crystal packing is further stabilized by another N—H?O and one O—H?N hydrogen bond, which interconnect the molecular ribbons.     

3‐Formyl­phenyl­boronic acid

The mol­ecule of the title compound, C₇H₇BO₃, is planar, and the bond lengths and angles are typical. The formyl group is essentially coplanar with the benzene ring but does not influence significantly the distortion of the ring, although the formyl group does have a strong influence on the crystal packing. The geometry of the boronic acid group is typical. In the crystal structure, the mol­ecules are linked by O—H⋯O hydrogen bonds.     

Tetrameric triphenylsilanol, (Ph3SiOH)4, and the adduct (Ph3SiOH)2–di­methyl sulfoxide,both at 120 K,and the adduct (Ph3SiOH)4–1,4‐dioxan at 150 K: interplay of O—H⋯O and C—H⋯π(arene) interactions

The structure of tetrameric tri­phenyl­silanol, C₁₈H₁₆OSi, (I), has been re‐investigated at 120 (2) K. The hydroxyl H atoms were readily located and one of the arene rings is disordered over two closely positioned sets of sites. The mol­ecules are linked into cyclic tetramers, having approximate (S₄) symmetry, via O—H?O hydrogen bonds [H?O 1.81–1.85 Å, O?O 2.634 (3)–2.693 (3) Å and O—H?O 156–166°]. At ambient temperature, there are indications of multiple disorder of the phenyl‐ring sites. In bis­(tri­phenyl­silanol) di­methyl sulfoxide solvate, 2C₁₈H₁₆OSi·C₂H₆OS, (II), the di­methyl sulfoxide component is disordered across a twofold rotation axis in C2/c, and the molecular components are linked by a single O—H?O hydrogen bond [H?O 1.85 Å, O?O 2.732 (2) Å and O—H?O 172°] into three‐mol­ecule aggregates, which are themselves linked into a single three‐dimensional framework by two C—H?π(arene) interactions. In tetrakis­(tri­phenyl­silanol) 1,4‐dioxan solvate, 4C₁₈H₁₆OSi·C₄H₈O₂, (III), the 1,4‐dioxan component lies across an inversion centre in space group P and centrosymmetric five‐mol­ecule aggregates are linked by paired C—H?π(arene) interactions to form molecular ladders.     

The 1:1 adduct of 2,5-dihydroxy-1,4-benzoquinone with 4,4′-bipyridine

2,5-Di­hydroxy-1,4-benzo­quinone (DHBQ) and 4,4′-bi­pyridine (BPY) crystallize in a 1:1 ratio as a neutral molecular adduct, C₆H₄O₄·C₁₀H₈N₂, in space group C2/c, with half of each mol­ecule in the asymmetric unit. The mol­ecules are linked by a strong O—H⃛N hydrogen bond [O⃛N 2.6323 (15) Å] and a weak C—H⃛O hydrogen bond [C⃛O 3.2082 (17) Å] to form infinite stacks of parallel one-dimensional hydrogen-bonded ribbons. The two rings of the bi­pyridine are twisted at 28.3° with respect to each other, and the benzo­quinone ring is inclined at an angle of 18.3° with respect to the plane of the neighbouring pyridine ring. The 4,4′-bi­pyridine mol­ecule lies on a twofold axis and the benzo­quinone mol­ecule lies across an inversion centre.     

N‐Propionyl‐1,2‐benzisoselenazol‐3(2H)‐one

The title compound, C₁₀H₉NO₂Se, crystallizes as flat mol­ecules linked by selenium–oxy­gen interactions [Se?O = 3.189 (4) Å] into a linear chain along the a axis of the triclinic cell. The bond dimensions that are derived from ab initio geometry optimization calculations are similar to those determined from the diffraction measurements.