Four 7‐aryl‐substituted pyrido[2,3‐d]pyrimidine‐2,4(1H,3H)‐diones: similar molecular structures but different crystal structures

Molecules of 1,3‐dimethyl‐7‐(4‐methylphenyl)pyrido[2,3‐d]pyrimidine‐2,4(1H,3H)‐dione, C₁₆H₁₅N₃O₂, (I), are linked by paired C—H...O hydrogen bonds to form centrosymmetric R₂²(10) dimers, which are linked into chains by a single π–π stacking interaction. A single C—H...O hydrogen bond links the molecules of 7‐(biphenyl‐4‐yl)‐1,3‐dimethylpyrido[2,3‐d]pyrimidine‐2,4(1H,3H)‐dione, C₂₁H₁₇N₃O₂, (II), into C(10) chains, which are weakly linked into sheets by a π–π stacking interaction. In 7‐(4‐fluorophenyl)‐3‐methylpyrido[2,3‐d]pyrimidine‐2,4(1H,3H)‐dione, C₁₄H₁₀FN₃O₂, (III), an N—H...O hydrogen bond links the molecules into C(6) chains, which are linked into sheets by a π–π stacking interaction. The molecules of 7‐(4‐methoxyphenyl)‐3‐methylpyrido[2,3‐d]pyrimidine‐2,4(1H,3H)‐dione, C₁₅H₁₃N₃O₃, (IV), are also linked into C(6) chains by an N—H...O hydrogen bond, but here the chains are linked into sheets by a combination of two independent C—H...π(arene) hydrogen bonds.     

Design of two series of 1:1 cocrystals involving 4‐amino‐5‐chloro‐2,6‐dimethylpyrimidine and carboxylic acids

Two series of a total of ten cocrystals involving 4‐amino‐5‐chloro‐2,6‐dimethylpyrimidine with various carboxylic acids have been prepared and characterized by single‐crystal X‐ray diffraction. The pyrimidine unit used for the cocrystals offers two ring N atoms (positions N1 and N3) as proton‐accepting sites. Depending upon the site of protonation, two types of cations are possible [Rajam et al. (2017). Acta Cryst. C 73 , 862–868]. In a parallel arrangement, two series of cocrystals are possible depending upon the hydrogen bonding of the carboxyl group with position N1 or N3. In one series of cocrystals, i.e. 4‐amino‐5‐chloro‐2,6‐dimethylpyrimidine–3‐bromothiophene‐2‐carboxylic acid (1/1), 1 , 4‐amino‐5‐chloro‐2,6‐dimethylpyrimidine–5‐chlorothiophene‐2‐carboxylic acid (1/1), 2 , 4‐amino‐5‐chloro‐2,6‐dimethylpyrimidine–2,4‐dichlorobenzoic acid (1/1), 3 , and 4‐amino‐5‐chloro‐2,6‐dimethylpyrimidine–2‐aminobenzoic acid (1/1), 4 , the carboxyl hydroxy group (–OH) is hydrogen bonded to position N1 (O—H…N1) of the corresponding pyrimidine unit (single point supramolecular synthon). The inversion‐related stacked pyrimidines are doubly bridged by the carboxyl groups via N—H…O and O—H…N hydrogen bonds to form a large cage‐like tetrameric unit with an R₄²(20) graph‐set ring motif. These tetrameric units are further connected via base pairing through a pair of N—H…N hydrogen bonds, generating R₂²(8) motifs (supramolecular homosynthon). In the other series of cocrystals, i.e. 4‐amino‐5‐chloro‐2,6‐dimethylpyrimidine–5‐methylthiophene‐2‐carboxylic acid (1/1), 5 , 4‐amino‐5‐chloro‐2,6‐dimethylpyrimidine–benzoic acid (1/1), 6 , 4‐amino‐5‐chloro‐2,6‐dimethylpyrimidine–2‐methylbenzoic acid (1/1), 7 , 4‐amino‐5‐chloro‐2,6‐dimethylpyrimidine–3‐methylbenzoic acid (1/1), 8 , 4‐amino‐5‐chloro‐2,6‐dimethylpyrimidine–4‐methylbenzoic acid (1/1), 9 , and 4‐amino‐5‐chloro‐2,6‐dimethylpyrimidine–4‐aminobenzoic acid (1/1), 10 , the carboxyl group interacts with position N3 and the adjacent 4‐amino group of the corresponding pyrimidine ring via O—H…N and N—H…O hydrogen bonds to generate the robust R₂²(8) supramolecular heterosynthon. These heterosynthons are further connected by N—H…N hydrogen‐bond interactions in a linear fashion to form a chain‐like arrangement. In cocrystal 1 , a Br…Br halogen bond is present, in cocrystals 2 and 3 , Cl…Cl halogen bonds are present, and in cocrystals 5 , 6 and 7 , Cl…O halogen bonds are present. In all of the ten cocrystals, π–π stacking interactions are observed.     

Crystal structure of pharmaceutical cocrystals of 2,6‐diaminopyridine with piracetam and theophylline

Pharmaceutical cocrystals are crystalline solids formed by an active pharmaceutical ingredient and a cocrystal former. The cocrystals 2,6‐diaminopyridine (DAP)–piracetam [PIR; systematic name: 2‐(2‐oxopyrrolidin‐1‐yl)acetamide] (1/1), C₅H₇N₃·C₆H₁₀N₂O₂, (I), and 2,6‐diaminopyridine–theophylline (TEO; systematic name: 1,3‐dimethyl‐7H‐purine‐2,6‐dione) (1/1), C₅H₇N₃·C₇H₈N₄O₂, (II), were prepared by the solvent‐assisted grinding method and were characterized by IR spectroscopy and powder X‐ray diffraction. Cocrystal (I) crystallized in the orthorhombic space group Pbca and showed a 1:1 stoichiometry. The DAP and PIR molecules are linked by an N—H…O hydrogen‐bond interaction. Self‐assembly of PIR molecules forms a sheet of C (4) and C (7) chains. Cocrystal (II) crystallized in the monoclinic P 2₁/c space group and also showed a 1:1 stoichiometry. The DAP and TEO molecules are connected by N—H…N and N—H…O hydrogen bonds, forming an R ₂²(9) heterosynthon. A bidimensional supramolecular array is formed by interlinked DAP–TEO tetramers, producing a two‐dimensional sheet.     

Phthal­imide at 120 K: perforated molecular ribbons containing three different ring motifs

Molecules of phthal­imide [1H‐iso­indole‐1,3(2H)‐dione], C₈H₅NO₂, are linked by N—H?O hydrogen bonds [H?O 2.02 Å, N?O 2.8781 (16) Å and N—H?O 167°] and by C—H?O hydrogen bonds [H?O 2.54 and 2.56 Å, C?O 3.3874 (18) and 3.4628 (19) Å, and C—H?O 149 and 159°] into molecular ribbons, which are pierced by three different ring motifs; there are two centrosymmetric R(8) rings, each containing a single hydrogen bond, N—H?O in one case and C—H?O in the other, and R(9) rings containing all three hydrogen bonds.     

Mechanochemical synthesis and X‐ray structural characterization of three 3‐nitrophenol cocrystals with three aminal cage azaadamantanes: the role of the stereoelectronic effect on intermolecular hydrogen‐bonding patterns

The structures of the cocrystalline adducts of 3‐nitrophenol (3‐NP) with 1,3,5,7‐tetraazatricyclo[3.3.1.1^3,7]decane [HMTA, ( 1 )] as the 2:1:1 hydrate, 2C₆H₅NO₃·C₆H₁₂N₄·H₂O, ( 1a ), with 1,3,6,8‐tetraazatricyclo[4.3.1.1^3,8]undecane [TATU ( 2 )] as the 2:1 cocrystal, 2C₆H₅NO₃·C₇H₁₄N₄, ( 2a ), and with 1,3,6,8‐tetraazatricyclo[4.4.1.1^3,8]dodecane [TATD, ( 3 )] as the 2:1 cocrystal, 2C₆H₅NO₃·C₈H₁₆N₄, ( 3a ), are reported. In the binary crystals ( 2a ) and ( 3a ), the 3‐nitrophenol molecules are linked via O—H…N hydrogen bonds into aminal cage azaadamantanes. In ( 1a ), the structure is stabilized by O—H…N and O—H…O hydrogen bonds, and generates ternary cocrystals. There are C—H…O hydrogen bonds present in all three cocrystals, and in ( 1a ), there are also C—H…O and C—H…π interactions present. The presence of an ethylene bridge in the structures of ( 2 ) and ( 3 ) defines the formation of a hydrogen‐bonded motif in the supramolecular architectures of ( 2a ) and ( 3a ). The differences in the C—N bond lengths of the aminal cage structures, as a result of hyperconjugative interactions and electron delocalization, were analysed. These three cocrystals were obtained by the solvent‐free assisted grinding method. Crystals suitable for single‐crystal X‐ray diffraction were grown by slow evaporation from a mixture of hexanes.     

Supramolecular hydrogen‐bonding patterns in two cocrystals of the N(7)–H tautomeric form of N6‐benzoyladenine: N6‐benzoyladenine–3‐hydroxypyridinium‐2‐carboxylate (1/1) and N6‐benzoyladenine–DL‐tartaric acid (1/1)

Two novel cocrystals of the N(7)—H tautomeric form of N⁶‐benzoyladenine (BA), namely N⁶‐benzoyladenine–3‐hydroxypyridinium‐2‐carboxylate (3HPA) (1/1), C₁₂H₉N₅O·C₆H₅NO₃, (I), and N⁶‐benzoyladenine–DL‐tartaric acid (TA) (1/1), C₁₂H₉N₅O·C₄H₆O₆, (II), are reported. In both cocrystals, the N⁶‐benzoyladenine molecule exists as the N(7)—H tautomer, and this tautomeric form is stabilized by intramolecular N—H...O hydrogen bonding between the benzoyl C=O group and the N(7)—H hydrogen on the Hoogsteen site of the purine ring, forming an S(7) motif. The dihedral angle between the adenine and phenyl planes is 0.94 (8)° in (I) and 9.77 (8)° in (II). In (I), the Watson–Crick face of BA (N6—H and N1; purine numbering) interacts with the carboxylate and phenol groups of 3HPA through N—H...O and O—H...N hydrogen bonds, generating a ring‐motif heterosynthon [graph set R₂²(6)]. However, in (II), the Hoogsteen face of BA (benzoyl O atom and N7; purine numbering) interacts with TA (hydroxy and carbonyl O atoms) through N—H...O and O—H...O hydrogen bonds, generating a different heterosynthon [graph set R₂²(4)]. Both crystal structures are further stabilized by π–π stacking interactions.     

Hydrogen bonding in 2‐amino‐4,6‐dimethoxypyrimidine, 2‐benzylamino‐4,6‐bis(benzyloxy)pyrimidine and 2‐amino‐4,6‐bis(N‐pyrrolidino)pyrimidine: chains of fused rings and a centrosymmetric dimer

Molecules of 2‐amino‐4,6‐di­methoxy­pyrimidine, C₆H₉N₃O₂, (I), are linked by two N—H?N hydrogen bonds [H?N 2.23 and 2.50 Å, N?N 3.106 (2) and 3.261 (2) Å, and N—H?N 171 and 145°] into a chain of fused rings, where alternate rings are generated by centres of inversion and twofold rotation axes. Adjacent chains are linked by aromatic π–π‐stacking interactions to form a three‐dimensional framework. In 2‐­benzylamino‐4,6‐bis(benzyloxy)pyrimidine, C₂₅H₂₃N₃O₂, (II), the mol­ecules are linked into centrosymmetric R(8) dimers by paired N—H?N hydrogen bonds [H?N 2.13 Å, N?N 2.997 (2) Å and N—H?N 170°]. Molecules of 2‐amino‐4,6‐bis(N‐pyrrolidino)­pyrimidine, C₁₂H₁₉N₅, (III), are linked by two N—H?N hydrogen bonds [H?N 2.34 and 2.38 Å, N?N 3.186 (2) and 3.254 (2) Å, and N—H?N 163 and 170°] into a chain of fused rings similar to that in (I).     

Supramolecular hydrogen‐bonding patterns in the organic–inorganic hybrid compound bis(4‐amino‐5‐chloro‐2,6‐dimethylpyrimidinium) tetrathiocyanatozinc(II)–4‐amino‐5‐chloro‐2,6‐dimethylpyrimidine–water (1/2/2)

Zinc thiocyanate complexes have been found to be biologically active compounds. Zinc is also an essential element for the normal function of most organisms and is the main constituent in a number of metalloenzyme proteins. Pyrimidine and aminopyrimidine derivatives are biologically very important as they are components of nucleic acids. Thiocyanate ions can bridge metal ions by employing both their N and S atoms for coordination. They can play an important role in assembling different coordination structures and yield an interesting variety of one‐, two‐ and three‐dimensional polymeric metal–thiocyanate supramolecular frameworks. The structure of a new zinc thiocyanate–aminopyrimidine organic–inorganic compound, (C₆H₉ClN₃)₂[Zn(NCS)₄]·2C₆H₈ClN₃·2H₂O, is reported. The asymmetric unit consist of half a tetrathiocyanatozinc(II) dianion, an uncoordinated 4‐amino‐5‐chloro‐2,6‐dimethylpyrimidinium cation, a 4‐amino‐5‐chloro‐2,6‐dimethylpyrimidine molecule and a water molecule. The Zn^II atom adopts a distorted tetrahedral coordination geometry and is coordinated by four N atoms from the thiocyanate anions. The Zn^II atom is located on a special position (twofold axis of symmetry). The pyrimidinium cation and the pyrimidine molecule are not coordinated to the Zn^II atom, but are hydrogen bonded to the uncoordinated water molecules and the metal‐coordinated thiocyanate ligands. The pyrimidine molecules and pyrimidinium cations also form base‐pair‐like structures with an R₂²(8) ring motif via N—H…N hydrogen bonds. The crystal structure is further stabilized by intermolecular N—H…O, O—H…S, N—H…S and O—H…N hydrogen bonds, by intramolecular N—H…Cl and C—H…Cl hydrogen bonds, and also by π–π stacking interactions.     

Amino­pyrimidine–carboxyl­(ate) interactions in trimethoprim maleate,an antifolate drug

In the title cocrystal, trimethoprim maleate [2,4‐di­amino‐5‐(3,4,5‐tri­methoxy­benzyl)­pyrimidin‐1‐ium maleate], C₁₄H₁₉­N₄O₃⁺·­C₄H₃O₄^?, the trimethoprim mol­ecule is protonated at N1. The carboxyl group of the maleate ion makes a specific double hydrogen bond of type N—H?O with the 2‐amino group and the protonated N1 atom of the trimethoprim cation which is similar to the carboxyl­ate–trimethoprim cation interaction observed in the complex of di­hydro­folate reductase with trimethoprim. The pyrimidine moieties of trimethoprim cations are centrosymmetrically paired through a pair of N—H?N hydrogen bonds involving the 4‐amino group and the pyridinium N3 atom of a symmetry‐related molecule. One of the O atoms at the maleate carboxyl­ate group bridges the 2‐­amino and 4‐amino groups on either side of the paired trimethoprim cations. The other O atom of the carboxyl­ate group forms an intramolecular O—H?O hydrogen bond with the carboxyl group. These characteristic hydrogen bonds result in infinite two‐dimensional aggregation of rings into a supramolecular ladder, which is further crosslinked through weak C—H?O interactions with methoxy groups of neighbouring trimethoprim mol­ecules to form a layered structure.     

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.     

Supramolecular architectures in the salt trimethoprimium ferrocene‐1‐carboxylate and the cocrystal 4‐amino‐5‐chloro‐2,6‐dimethylpyrimidine–ferrocene‐1‐carboxylic acid (1/1)

In the salt trimethoprimium ferrocenecarboxylate [systematic name: 2,4‐diamino‐5‐(3,4,5‐trimethoxybenzyl)pyrimidin‐1‐ium ferrocene‐1‐carboxylate], (C₁₄H₁₉N₄O₃)[Fe(C₅H₅)(C₆H₄O₂)], (I), of the antibacterial compound trimethoprim, the carboxylate group interacts with the protonated aminopyrimidine group of trimethoprim via two N—H…O hydrogen bonds, generating a robust R ₂²(8) ring motif (heterosynthon). However, in the cocrystal 4‐amino‐5‐chloro‐2,6‐dimethylpyrimidine–ferrocene‐1‐carboxylic acid (1/1), [Fe(C₅H₅)(C₆H₅O₂)]·C₆H₈ClN₃, (II), the carboxyl–aminopyrimidine interaction [R ₂²(8) motif] is absent. The carboxyl group interacts with the pyrimidine ring via a single O—H…N hydrogen bond. The pyrimidine rings, however, form base pairs via a pair of N—H…N hydrogen bonds, generating an R ₂²(8) supramolecular homosynthon. In salt (I), the unsubstituted cyclopentadienyl ring is disordered over two positions, with a refined site‐occupation ratio of 0.573 (10):0.427 (10). In this study, the two five‐membered cyclopentadienyl (Cp) rings of ferrocene are in a staggered conformation, as is evident from the C…Cg …Cg …C pseudo‐torsion angles, which are in the range 36.13–37.53° for (I) and 22.58–23.46° for (II). Regarding the Cp ring of the minor component in salt (I), the geometry of the ferrocene ring is in an eclipsed conformation, as is evident from the C…Cg …Cg …C pseudo‐torsion angles, which are in the range 79.26–80.94°. Both crystal structures are further stabilized by weak π–π interactions.     

2‐Ethyl‐6‐methylpyridin‐3‐ol and its salt bis(2‐ethyl‐3‐hydroxy‐6‐methylpyridinium) succinate

The title compounds, C₈H₁₁NO, (I), and 2C₈H₁₂NO⁺·C₄H₄O₄²⁻, (II), both crystallize in the monoclinic space group P2₁/c. In the crystal structure of (I), intermolecular O—H...N hydrogen bonds combine the molecules into polymeric chains extending along the c axis. The chains are linked by C—H...π interactions between the methylene H atoms and the pyridine rings into polymeric layers parallel to the ac plane. In the crystal structure of (II), the succinate anion lies on an inversion centre. Its carboxylate groups interact with the 2‐ethyl‐3‐hydroxy‐6‐methylpyridinium cations via intermolecular N—H...O hydrogen bonds with the pyridine ring H atoms and O—H...O hydrogen bonds with the hydroxy H atoms to form polymeric chains, which extend along the [01] direction and comprise R₄⁴(18) hydrogen‐bonded ring motifs. These chains are linked to form a three‐dimensional network through nonclassical C—H...O hydrogen bonds between the pyridine ring H atoms and the hydroxy‐group O atoms of neighbouring cations. π–π interactions between the pyridine rings and C—H...π interactions between the methylene H atoms of the succinate anion and the pyridine rings are also present in this network.     

Hydrogen‐bonding patterns in two aroylthiocarbamates and two aroylimidothiocarbonates

In O‐ethyl N‐benzoylthiocarbamate, C₁₀H₁₁NO₂S, the molecules are linked into sheets by a combination of two‐centre N—H...O and C—H...S hydrogen bonds and a three‐centre C—H...(O,S) hydrogen bond. A combination of two‐centre N—H...O and C—H...O hydrogen bonds links the molecules of O‐ethyl N‐(4‐methylbenzoyl)thiocarbamate, C₁₁H₁₃NO₂S, into chains of rings, which are linked into sheets by an aromatic π–π stacking interaction. In O,S‐diethyl N‐(4‐methylbenzoyl)imidothiocarbonate, C₁₃H₁₇NO₂S, pairs of molecules are linked into centrosymmetric dimers by pairs of symmetry‐related C—H...π(arene) hydrogen bonds, while the molecules of O,S‐diethyl N‐(4‐chlorobenzoyl)imidothiocarbonate, C₁₂H₁₄ClNO₂S, are linked by a single C—H...O hydrogen bond into simple chains, pairs of which are linked by an aromatic π–π stacking interaction to form a ladder‐type structure.     

Bis[2,4‐diamino‐5‐(3,4,5‐trimethoxybenzyl)pyrimidin‐1‐ium] dl‐malate

<!?tpct=1pt>Racemic malic acid and trimethoprim [5‐(3,4,5‐trimethoxybenzyl)pyrimidine‐2,4‐diamine] form a 1:2 salt (monoclinic, P2₁/c), 2C₁₄H₁₉N₄O₃⁺·C₄H₄O₅²⁻, in which the malate component is disordered across a centre of inversion. The crystal structure of the salt consists of protonated trimethoprim residues and a malate dianion. The carboxylate group of the malate ion interacts with the trimethoprim cation in a linear fashion through pairs of N—H...O hydrogen bonds to form a cyclic hydrogen‐bonded motif. This is similar to the carboxylate–trimethoprim cation interaction observed earlier in the complex of dihydrofolate reductase with trimethoprim. The structure of the salt of trimethoprim with racemic dl ‐malic acid reported here is the first of its kind. The present study investigates the conformations and the hydrogen‐bonding interactions, which are very important for biological functions. The pyrimidine plane makes a dihedral angle of 78.08 (7)° with the benzene ring of the trimethoprim cation. The cyclic hydrogen‐bonded motif observed in this structure is self‐organized, leading to novel types of hydrogen‐bonding motifs in supramolecular patterns.     

Regio‐ and stereospecific assembly of dispiro[indoline‐3,3′‐pyrrolizine‐1′,5′′‐thiazolidines] from simple precursors using a one‐pot procedure: synthesis,spectroscopic and structural characterization,and a proposed mechanism of formation

The synthesis and characterization of three new dispiro[indoline‐3,3′‐pyrrolizine‐1′,5′′‐thiazolidine] compounds are reported, together with the crystal structures of two of them. (3RS,1′SR,2′SR,7a′SR)‐2′‐(4‐Chlorophenyl)‐1‐hexyl‐2′′‐sulfanylidene‐5′,6′,7′,7a′‐tetrahydro‐2′H‐dispiro[indoline‐3,3′‐pyrrolizine‐1′,5′′‐thiazolidine]‐2,4′′‐dione, C₂₈H₃₀ClN₃O₂S₂, (I), (3RS,1′SR,2′SR,7a′SR)‐2′‐(4‐chlorophenyl)‐1‐benzyl‐5‐methyl‐2′′‐sulfanylidene‐5′,6′,7′,7a′‐tetrahydro‐2′H‐dispiro[indoline‐3,3′‐pyrrolizine‐1′,5′′‐thiazolidine]‐2,4′′‐dione, C₃₀H₂₆ClN₃O₂S₂, (II), and (3RS,1′SR,2′SR,7a′SR)‐2′‐(4‐chlorophenyl)‐5‐fluoro‐2′′‐sulfanylidene‐5′,6′,7′,7a′‐tetrahydro‐2′H‐dispiro[indoline‐3,3′‐pyrrolizine‐1′,5′′‐thiazolidine]‐2,4′′‐dione, C₂₂H₁₇ClFN₃O₂S₂, (III), were each isolated as a single regioisomer using a one‐pot reaction involving l ‐proline, a substituted isatin and (Z)‐5‐(4‐chlorobenzylidene)‐2‐sulfanylidenethiazolidin‐4‐one [5‐(4‐chlorobenzylidene)rhodanine]. The compositions of (I)–(III) were established by elemental analysis, complemented by high‐resolution mass spectrometry in the case of (I); their constitutions, including the definition of the regiochemistry, were established using NMR spectroscopy, and the relative configurations at the four stereogenic centres were established using single‐crystal X‐ray structure analysis. A possible reaction mechanism for the formation of (I)–(III) is proposed, based on the detailed stereochemistry. The molecules of (I) are linked into simple chains by a single N—H…N hydrogen bond, those of (II) are linked into a chain of rings by a combination of N—H…O and C—H…S=C hydrogen bonds, and those of (III) are linked into sheets by a combination of N—H…N and N—H…S=C hydrogen bonds.     

Two closely related,and unexpected,quinolinone derivatives: a three‐dimensional hydrogen‐bonded framework structure and a hydrogen‐bonded molecular ribbon of R22(18) and R44(24) rings

1,5‐Bis(4‐chlorophenyl)‐3‐(2‐oxo‐1,2‐dihydroquinolin‐3‐yl)pentane‐1,5‐dione, (Ia), and 1,5‐bis(2‐chlorophenyl)‐3‐(2‐oxo‐1,2‐dihydroquinolin‐3‐yl)pentane‐1,5‐dione, (Ib), crystallize as an 84:16 mixture, 0.84C₂₆H₁₉Cl₂NO₃·0.16C₂₆H₁₉Cl₂NO₃, in the space group I4₁/a, where the molecules of the two isomers occupy very similar sites in the unit cell. A combination of one N—H...O hydrogen bond and one C—H...O hydrogen bond links the molecules, regardless of isomeric form, into a single three‐dimensional framework structure. The molecules of (9RS,10RS)‐8,9‐bis(4‐chlorobenzyl)‐10‐(2‐oxo‐1,2‐dihydroquinolin‐3‐yl)‐5,6,9,10‐tetrahydrophenanthridine, C₃₆H₂₂Cl₂N₂O₄, (II), are linked by two hydrogen bonds, one each of the N—H...O and C—H...O types, into a molecular ribbon in which centrosymmetric rings of R₂²(18) and R₄⁴(24) types alternate. The hydrogen‐bonded ribbons enclose channels, which contain highly disordered solvent molecules.     

2,4‐Dimethyl‐1,3‐thiazole‐5‐carboxylic acid: an X‐ray structural study at 100 K and Hirshfeld surface analysis

The crystal structure of the title thiazolecarboxylic acid derivative, C₆H₇NO₂S, (I), has been determined from single‐crystal X‐ray analysis at 100 K. In the crystal packing, an interplay of O—H...N and C—H...O hydrogen bonds connects the molecules to form C(6)R₂²(8) polymeric chains, which are further linked via weak C—H...O hydrogen bonds into a two‐dimensional supramolecular framework. The relative contributions of different interactions to the Hirshfeld surface in (I) and a few related thiazolecarboxylic acid derivatives indicate that the H...H, N...H and O...H contacts can account for about 50–70% of the total Hirshfeld surface area in this class of compound.     

Supramolecular architectures in two 1:1 cocrystals of 5‐fluorouracil with 5‐bromothiophene‐2‐carboxylic acid and thiophene‐2‐carboxylic acid

In solid‐state engineering, cocrystallization is a strategy actively pursued for pharmaceuticals. Two 1:1 cocrystals of 5‐fluorouracil (5FU; systematic name: 5‐fluoro‐1,3‐dihydropyrimidine‐2,4‐dione), namely 5‐fluorouracil–5‐bromothiophene‐2‐carboxylic acid (1/1), C₅H₃BrO₂S·C₄H₃FN₂O₂, (I), and 5‐fluorouracil–thiophene‐2‐carboxylic acid (1/1), C₄H₃FN₂O₂·C₅H₄O₂S, (II), have been synthesized and characterized by single‐crystal X‐ray diffraction studies. In both cocrystals, carboxylic acid molecules are linked through an acid–acid R ₂²(8) homosynthon (O—H…O) to form a carboxylic acid dimer and 5FU molecules are connected through two types of base pairs [homosynthon, R ₂²(8) motif] via a pair of N—H…O hydrogen bonds. The crystal structures are further stabilized by C—H…O interactions in (II) and C—Br…O interactions in (I). In both crystal structures, π–π stacking and C—F…π interactions are also observed.     

Six closely related 4,6‐disubstituted 2‐amino‐5‐formylpyrimidines: different ring conformations,polarized electronic structures,and hydrogen‐bonded assembly in zero,one, two and three dimensions

In each of ethyl N‐{2‐amino‐5‐formyl‐6‐[methyl(phenyl)amino]pyrimidin‐4‐yl}glycinate, C₁₆H₁₉N₅O₃, (I), N‐{2‐amino‐5‐formyl‐6‐[methyl(phenyl)amino]pyrimidin‐4‐yl}glycinamide, C₁₄H₁₆N₆O₂, (II), and ethyl 3‐amino‐N‐{2‐amino‐5‐formyl‐6‐[methyl(phenyl)amino]pyrimidin‐4‐yl}propionate, C₁₇H₂₁N₅O₃, (III), the pyrimidine ring is effectively planar, but in each of methyl N‐{2‐amino‐6‐[benzyl(methyl)amino]‐5‐formylpyrimidin‐4‐yl}glycinate, C₁₆H₁₉N₅O₃, (IV), ethyl 3‐amino‐N‐{2‐amino‐6‐[benzyl(methyl)amino]‐5‐formylpyrimidin‐4‐yl}propionate, C₁₈H₂₃N₅O₃, (V), and ethyl 3‐amino‐N‐[2‐amino‐5‐formyl‐6‐(piperidin‐4‐yl)pyrimidin‐4‐yl]propionate, C₁₅H₂₃N₅O₃, (VI), the pyrimidine ring is folded into a boat conformation. The bond lengths in each of (I)–(VI) provide evidence for significant polarization of the electronic structure. The molecules of (I) are linked by paired N—H...N hydrogen bonds to form isolated dimeric aggregates, and those of (III) are linked by a combination of N—H...N and N—H...O hydrogen bonds into a chain of edge‐fused rings. In the structure of (IV), molecules are linked into sheets by means of two hydrogen bonds, both of N—H...O type, in the structure of (V) by three hydrogen bonds, two of N—H...N type and one of C—H...O type, and in the structure of (VI) by four hydrogen bonds, all of N—H...O type. Molecules of (II) are linked into a three‐dimensional framework structure by a combination of three N—H...O hydrogen bonds and one C—H...O hydrogen bond.     

2′‐Deoxyimmunosine: a thiazolo[4,5‐d]pyrimidine nucleoside adopting the syn conformation

The title compound [systematic name: 5‐amino‐3‐(2‐deoxy‐β‐d ‐erythro‐pentofuranosyl)thiazolo[4,5‐d]pyrimidine‐2,7‐(3H,6H)‐dione], C₁₀H₁₂N₄O₅S, exhibits a syn glycosylic bond conformation, with a torsion angle χ of 61.0 (3)°. The furanose moiety adopts the N‐type sugar pucker (³T₄), with P = 33.0 (5)° and τ_m = 15.1 (1)°. The conformation at the exocyclic C4′—C5′ bond is +ap (trans), with the torsion angle γ = 176.71 (14)°. The extended structure is a three‐dimensional hydrogen‐bond network involving O—H...O and N—H...O hydrogen bonds.