Acetic anhydride at 100 K: the first crystal structure determination

Acetic anhydride (ethanoic anhydride), (CH₃CO)₂O, is a widely used acetylation reagent in organic synthesis. The crystal and molecular structure, as determined by single‐crystal X‐ray analysis at 100 K, is reported for the first time. A crystal of the title compound (m.p. 200 K) suitable for X‐ray diffraction was grown from the melt at low temperature. The title compound crystallizes in the orthorhombic space group Pbcn, with Z = 4. In the crystal, the molecule adopts an exact C₂‐symmetric conformation about a crystallographic twofold axis. The molecules are densely packed. Two of the methyl H atoms form short intermolecular contacts to a neighbouring carbonyl O atom, which can be viewed as weak hydrogen bonds.     

Adiponitrile at 100 K

Adiponitrile, C₆H₈N₂, is a key intermediate in the synthesis of the polyamide Nylon 66 and is produced industrially on a large scale. We have determined the crystal and molecular structure of adiponitrile by single‐crystal X‐ray analysis at 100 K, a suitable crystal (m.p. 275 K) having been grown from the melt at low temperature. The compound crystallizes in the monoclinic space group P 2₁/c with Z = 2. In the crystal structure, the molecule adopts an exact C_i‐symmetric gauche –anti –gauche conformation of the C—C—C—C skeleton about an inversion centre. The molecules are densely packed, with short intermolecular contacts between the α‐H and nitrile N atoms.     

Dehydration of raffinose pentahydrate: structures of raffinose 5‐, 4.433‐, 4.289‐ and 4.127‐hydrate at 93 K

Raffinose [or O‐α‐D‐galactopyranosyl‐(1→6)‐α‐D‐glucopyranosyl‐(1→2)‐β‐D‐fructofuranoside] pentahydrate, C₁₈H₃₂O₁₆·5H₂O, (I), and three lower hydrates, namely the 4.433‐, (II), 4.289‐, (III), and 4.127‐hydrated, (IV), forms, obtained in the course of the dehydration of (I), have been studied. The unit cells in the space group P2₁2₁2₁ are of similar dimensions for all the crystals. The conformation of the raffinose molecules remains almost the same across the four crystal structures. The raffinose molecules are linked into a three‐dimensional hydrogen‐bonded network involving all the –OH groups, the ring and glycosidic O atoms, and the water molecules. Six water sites were identified in the structures of (II), (III) and (IV), of which W1, W4 and W6 (W = water) are partially occupied with their populations coupled. W1, W4 and one of the –OH groups of the galactose ring form an infinite hydrogen‐bonding chain around a 2₁ axis parallel to the a axis (denoted chain A), and W6 and the same –OH group form a similar chain (chain A′) disordered with chain A. The occupancy ratio of chain A to chain A′ for N‐hydrates (N is a hydration number between 4 and 5) is (N− 4):(5 −N). The transformation of chain A to chain A′ as part of the dehydration process has little effect on the rest of the structure. Thus, the dehydration proceeds without significant impact on the crystal structure.     

Hydroxytropylium chloride: the first crystal structure of an unfunctionalized hydroxytropylium ion

The crystal structure of hydroxytropylium chloride, C₇H₆OH⁺·Cl⁻, the hydrochloride salt of tropone, is described, which represents the first crystallographic characterization of an unfunctionalized hydroxytropylium ion. Crystals were obtained serendipitously from a sample of chlorotropylium chloride after partial hydrolysis. This highlights the role of hydroxytropylium ions as an intermediate in the hydrolytic decomposition of halotropylium halides to tropone. The solid‐state structure consists of layers, in which the hydroxytropylium and chloride ions interact via both strong hydrogen bonds formed by the hydroxy protons and weaker hydrogen bonds formed by the tropylium protons to produce a two‐dimensional network.     

Comparison of the structure of (E)‐2‐(2‐benzylidenehydrazinylidene)quinoxaline with those of its chloro‐ and bromobenzylidene analogues

(E)‐2‐(2‐Benzylidenehydrazinylidene)quinoxaline, C₁₅H₁₂N₄, crystallized with two molecules in the asymmetric unit. The structures of six halogen derivatives of this compound were also investigated: (E)‐2‐[2‐(2‐chlorobenzylidene)hydrazinylidene]quinoxaline, C₁₅H₁₁ClN₄; (E)‐2‐[2‐(3‐chlorobenzylidene)hydrazinylidene]quinoxaline, C₁₅H₁₁ClN₄; (E)‐2‐[2‐(4‐chlorobenzylidene)hydrazinylidene]quinoxaline, C₁₅H₁₁ClN₄; (E)‐2‐[2‐(2‐bromobenzylidene)hydrazinylidene]quinoxaline, C₁₅H₁₁BrN₄; (E)‐2‐[2‐(3‐bromobenzylidene)hydrazinylidene]quinoxaline, C₁₅H₁₁BrN₄; (E)‐2‐[2‐(4‐bromobenzylidene)hydrazinylidene]quinoxaline, C₁₅H₁₁BrN₄. The 3‐Cl and 3‐Br compounds are isomorphous, as are the 4‐Cl and 4‐Br compounds. In all of these compounds, it was found that the supramolecular structures are governed by similar predominant patterns, viz. strong intermolecular N—H...N(pyrazine) hydrogen bonds supplemented by weak C—H...N(pyrazine) hydrogen‐bond interactions in the 2‐ and 3‐halo compounds and by C—H...Cl/Br interactions in the 4‐halo compounds. In all compounds, there are π–π stacking interactions.     

Redetermination of the cobaltocene crystal structure at 100 K and 297 K: Comparison with ferrocene and nickelocene

The molecular and crystal structures of the monoclinic modification of cobaltocene Cp₂Co (P2₁/n, Z=2) was determined at 100 K and 297 K with new sets of X-ray diffraction data (MoK radiation, 3995 and 6534 reflections, refinement toR = 0.026 and 0.030 using 1061 and 1299 independent observable reflections, respectively). At 297 K the structure is disordered (similar to the isomorphous ferrocene and nickelocene) with two distinct orientations of the ring, differing in occupancy factors (80% and 20%) and by a rotation angle in the ring plane of approximately 34°. Just as for nickelocene but in contrast to ferrocene, no sharp phase transition was found on cooling Cp₂Co to 100 K, but an essential ordering of the Cp-ring position was detected with a decrease of the contribution of the second minor orientation to nearly 10%. On the basis of a careful analysis of the molecular geometry, crystal packing, and anisotropic atomic displacement parameters, a dynamic temperature-dependent nature of the disorder in Cp₂Co is assumed.     

Synthesis and crystal structures of the potential tyrosinase inhibitors N‐(4‐acetylphenyl)‐2‐chloroacetamide and 2‐(4‐acetylanilino)‐2‐oxoethyl cinnamate

Substituted benzoic acid and cinnamic acid esters are of interest as tyrosinase inhibitors and the development of such inhibitors may help in diminishing many dermatological disorders. The tyrosinase enzyme has also been linked to Parkinson's disease. In view of hydroxylated compounds having ester and amide functionalities to potentially inhibit tyrosinase, we herein report the synthesis and crystal structures of two amide‐based derivatives, namely N‐(4‐acetylphenyl)‐2‐chloroacetamide, C₁₀H₁₀ClNO₂, (I), and 2‐(4‐acetylanilino)‐2‐oxoethyl cinnamate, C₁₉H₁₇NO₄, (II). In compound (I), the acetylphenyl ring and the N—(C=O)—C unit of the acetamide group are almost coplanar, with a dihedral angle of 7.39 (18)°. Instead of esterification, a cheaper and more efficient synthetic method has been developed for the preparation of compound (II). The molecular geometry of compound (II) is a V‐shape. The acetamide and cinnamate groups are almost planar, with mean deviations of 0.088 and 0.046 Å, respectively; the dihedral angle between these groups is 77.39 (7)°. The carbonyl O atoms are positioned syn and anti to the amide carbonyl O atom. In the crystals of (I) and (II), N—H…O, C—H…O and C—H…π interactions link the molecules into a three‐dimensional network.     

The role of different nonspecific interactions and halogen contacts in the crystal structure organization of 5‐chloroisatoic anhydride

The crystal structure of 6‐chloro‐2,4‐dihydro‐1H‐3,1‐benzoxazine‐2,4‐dione (5‐chloroisatoic anhydride), C₈H₄ClNO₃, has been determined and analysed in terms of connectivity and packing patterns. The compound crystallizes in the noncentrosymmetric space group Pna2₁ with one molecule in the asymmetric unit. The role of different weak interactions is discussed with respect to three‐dimensional network organization. Molecules are extended into one‐dimensional helical arrangements, making use of N—H…O hydrogen bonds and π–π interactions. The helices are further organized into monolayers via weak C—H…O and lone pair–π interactions, and the monolayers are packed into a noncentrosymmetric three‐dimensional architecture by C—Cl…π interactions and C—H…Cl and Cl…Cl contacts. A Hirshfeld surface (HS) analysis was carried out and two‐dimensional (2D) fingerprint plots were generated to visualize the intermolecular interactions and to provide quantitative data for their relative contributions. In addition, tests of the antimicrobial activity and in vitro cytotoxity effects against fitoblast L929 were performed and are discussed.     

Effect of the position of a methoxy substituent on the antimicrobial activity and crystal structures of 4‐methyl‐1,6‐diphenylpyrimidine‐2(1H)‐selenone derivatives

Derivatives of pyrimidine‐2(1H)‐selenone are a group of compounds with very strong antimicrobial activity. In order to study the effect of the position of the methoxy substituent on biological activity, molecular geometry and intermolecular interactions in the crystal, three derivatives were prepared and evaluated with respect to their antimicrobial activities, and their crystal structures were determined by X‐ray diffraction. The investigated compounds, namely, 1‐(X‐methoxyphenyl)‐4‐methyl‐6‐phenylpyrimidine‐2(1H)‐selenones (X = 2, 3 and 4 for 1 , 2 and 3 , respectively), C₁₈H₁₆N₂OSe, showed very strong activity against selected strains of Gram‐positive bacteria and fungi. Two compounds, 1 and 2 , crystallize in the monoclinic space group P2₁/c, while 3 crystallizes in the space group P2₁/n; 1 has two molecules in the asymmetric unit and the other two ( 2 and 3 ) have one molecule. The geometries of the investigated compounds differ slightly in the mutual orientations of the aromatic and pyrimidineselenone rings. The O atom in 1 stabilizes the conformation of the molecules via intramolecular C—H…O hydrogen bonding. The packing of molecules is determined by weak C—H…N and C—H…Se intermolecular interactions and additionally in 1 and 2 by C—H…O intermolecular interactions. The introduction of the methoxy substituent results in greater selectivity of the investigated compounds.     

Hirshfeld surface analysis of sulfameter (polymorph III), sulfameter dioxane monosolvate and sulfameter tetrahydrofuran monosolvate,all at 296 K

The ability of the antibacterial agent sulfameter (SMT) to form solvates is investigated. The X‐ray crystal structures of sulfameter solvates have been determined to be conformational polymorphs. Both 1,4‐dioxane and tetrahydrofuran form solvates with sulfameter in a 1:1 molar ratio. 4‐Amino‐N‐(5‐methoxypyrimidin‐2‐yl)benzenesulfonamide (polymorph III), C₁₁H₁₂N₄O₃S, (1), has two molecules of sulfameter in the asymmetric unit cell. 4‐Amino‐N‐(5‐methoxypyrimidin‐2‐yl)benzenesulfonamide 1,4‐dioxane monosolvate, C₁₁H₁₂N₄O₃S·C₄H₈O₂, (2), and 4‐amino‐N‐(5‐methoxypyrimidin‐2‐yl)benzenesulfonamide tetrahydrofuran monosolvate, C₁₁H₁₂N₄O₃S·C₄H₈O, (3), crystallize in the imide form. Hirshfeld surface analyses and fingerprint analyses were performed to study the nature of the interactions and their quantitative contributions towards the crystal packing. Finally, Hirshfeld surfaces, fingerprint plots and structural overlays were employed for a comparison of the two independent molecules in the asymmetric unit of (1), and also for a comparison of (2) and (3) in the monoclinic crystal system. A three‐dimensional hydrogen‐bonding network exists in all three structures, involving one of the sulfone O atoms and the aniline N atom. All three structures are stabilized by strong intermolecular N—H...N interactions. The tetrahydrofuran solvent molecule also takes part in forming significant intermolecular C—H...O interactions in the crystal structure of (3), contributing to the stability of the crystal packing.     

A novel crystal form of metacetamol: the first example of a hydrated form

We report the crystal structure and crystallization conditions of a first hydrated form of metacetamol (a hemihydrate), C₈H₉NO₂·0.5H₂O. It crystallizes from metacetamol‐saturated 1:1 (v/v) water–ethanol solutions in a monoclinic structure (space group P2₁/n) and contains eight metacetamol and four water molecules per unit cell. The conformations of the molecules are the same as in polymorph II of metacetamol, which ensures the formation of hydrogen‐bonded dimers and R₂²(16) ring motifs in its crystal structure similar to those in polymorph II. Unlike in form II, however, these dimers in the hemihydrate are connected through water molecules into infinite hydrogen‐bonded molecular chains. Different chains are linked to each other by metacetamol–water and metacetamol–metacetamol hydrogen bonds, the latter type being also present in polymorph I. The overall noncovalent network of the hemihydrate is well developed and several types of hydrogen bonds are responsible for its formation.     

Cinnamic acid hydrogen bonds to isoniazid and N′‐(propan‐2‐ylidene)isonicotinohydrazide,an in situ reaction product of isoniazid and acetone

A new polymorph of the cinnamic acid–isoniazid cocrystal has been prepared by slow evaporation, namely cinnamic acid–pyridine‐4‐carbohydrazide (1/1), C₉H₈O₂·C₆H₇N₃O. The crystal structure is characterized by a hydrogen‐bonded tetrameric arrangement of two molecules of isoniazid and two of cinnamic acid. Possible modification of the hydrogen bonding was investigated by changing the hydrazide group of isoniazid via an in situ reaction with acetone and cocrystallization with cinnamic acid. In the structure of cinnamic acid–N′‐(propan‐2‐ylidene)isonicotinohydrazide (1/1), C₉H₈O₂·C₉H₁₁N₃O, carboxylic acid–pyridine O—H...N and hydrazide–hydrazide N—H...O hydrogen bonds are formed.     

Crystal structure of the 1 : 4 complex between 18-crown-6 and a polyfunctional guest: 2-hydroxymethyl-4-(1,1,3,3-tetramethylbutyl)phenol

Single crystal X-ray analysis of the 1 : 4 complex between 18-crown-6 and 2-hydroxymethyl-4-(1,1,3,3-tetramethylbutyl)phenol is reported. Crystals of the complex are triclinic witha = 11.929 (2),b = 18.655(2),c = 8.313(1)Å, = 93.14(1), = 94.02(1), = 100.89(1)^o, andD _c = 1.111 g cm^–3 forZ = 1. TheR index is 0.057 for 5935 reflections measured at 293 K. The complex lies on a center of symmetry, the macroring has the Ci symmetry (g ⁺ g ⁺ aag ^– aag ^– ag ^– g ^– aag ⁺ aag ⁺ a). The CH₂-OH group at theortho position to the phenolic OH lies near the benzene ring plane; this conformation differs from the one found for uncomplexed phenol-alcohol molecules. The packing is characterized by layers of hydrogen bonded entities parallel toac; alongb the layers are stabilized by van der Waals interactions.     

Kaliumamidotrioxogermanate(IV) – Wasserstoff-Brückenbindungen in K3GeO3NH2 und K3GeO3NH2 · KNH2

Potassium Amido Trioxo Germanates(IV) – Hydrogen Bridge Bonds in K₃GeO₃NH₂ and K₃GeO₃NH₂ · KNH₂ Colorless crystals of K₃GeO₃NH₂ and of K₃GeO₃NH₂ · KNH₂ were obtained by the reaction of KNH₂ with GeO₂ in supercritical ammonia at 450°C and p = 6 kbar in high-pressure autoclaves within 15 resp. 5 days. The crystal structures of both compounds were solved by X-ray single crystal methods. K₃GeO₃NH₂: P1 , a = 6.390(1) Å, b = 6.684(1) Å, c = 7.206(1) Å, α = 96.47(1)°, β = 101.66(1)°, γ = 91.66(1)°, Z = 2, R/R_w = 0.020/0.022, N(I) ≥ 2σ(I) = 3023, N(Var.) = 82 K₃GeO₃NH₂ · KNH₂: P2₁/c, a = 10.982(6) Å, b = 6.429(1) Å, c = 12.256(8) Å, β = 106.12(1)°, Z = 4, R/R_w = 0.022/0.029, N(F) ≥ 3σ(F) = 1745, N(Var.) = 107. In K₃GeO₃NH₂ tetrahedral ions GeO₃NH₂^3? are connected to chains by N? H …? O bridge bonds with 2.18 Å ≤ d(H …? O) ≤ 2.40 Å for d(N? H) ? 1.0 Å and by potassium ions while in K₃GeO₃NH₂ · KNH₂ bridge bonds between NH₂ groups of GeO₃NH₂^3? and NH₂^? ions as acceptors occur with 2.41 Å ≤ d((N? )H …? NH₂^?) ≤ 2.61 Å for d(N? H) ? 1.0 Å.     

4‐Styrylquinolines from cyclocondensation reactions between (2‐aminophenyl)chalcones and 1,3‐diketones: crystal structures and regiochemistry

Structures are reported for two matched sets of substituted 4‐styrylquinolines which were prepared by the formation of the heterocyclic ring in cyclocondensation reactions between 1‐(2‐aminophenyl)‐3‐arylprop‐2‐en‐1‐ones with 1,3‐dicarbonyl compounds. (E)‐3‐Acetyl‐4‐[2‐(4‐methoxyphenyl)ethenyl]‐2‐methylquinoline, C₂₁H₁₉NO₂, (I), (E)‐3‐acetyl‐4‐[2‐(4‐bromophenyl)ethenyl]‐2‐methylquinoline, C₂₀H₁₆BrNO, (II), and (E)‐3‐acetyl‐2‐methyl‐4‐{2‐[4‐(trifluoromethyl)phenyl]ethenyl}quinoline, C₂₁H₁₆F₃NO, (III), are isomorphous and in each structure the molecules are linked by a single C—H…O hydrogen bond to form C(6) chains. In (I), but not in (II) or (III), this is augmented by a C—H…π(arene) hydrogen bond to form a chain of rings; hence, (I)–(III) are not strictly isostructural. By contrast with (I)–(III), no two of ethyl (E)‐4‐[2‐(4‐methoxyphenyl)ethenyl]‐2‐methylquinoline‐3‐carboxylate, C₂₂H₂₁NO₃, (IV), ethyl (E)‐4‐[2‐(4‐bromophenyl)ethenyl]‐2‐methylquinoline‐3‐carboxylate, C₂₁H₁₈BrNO₂, (V), and ethyl (E)‐2‐methyl‐4‐{2‐[4‐(trifluoromethyl)phenyl]ethenyl}quinoline‐3‐carboxylate, C₂₂H₁₈F₃NO₂, (VI), are isomorphous. The molecules of (IV) are linked by a single C—H…O hydrogen bond to form C(13) chains, but cyclic centrosymmetric dimers are formed in both (V) and (VI). The dimer in (V) contains a C—H…π(pyridyl) hydrogen bond, while that in (VI) contains two independent C—H…O hydrogen bonds. Comparisons are made with some related structures, and both the regiochemistry and the mechanism of the heterocyclic ring formation are discussed.     

Weak C—H...X (X = O,N) hydrogen bonds in the crystal structure of dihydroberberine

Dihydroberberine (systematic name: 9,10‐dimethoxy‐6,8‐dihydro‐5H‐1,3‐dioxolo[4,5‐g]isoquinolino[3,2‐a]isoquinoline), C₂₀H₁₉NO₄, a reduced form of pharmacologically important berberine, crystallizes from ethanol without interstitial solvent. The molecule shows a dihedral angle of 27.94 (5)° between the two arene rings at the ends of the molecule, owing to the partial saturation of the inner quinolizine ring system. Although lacking classical O—H or N—H donors, the packing in the crystalline state is clearly governed by C—H...N and C—H...O hydrogen bonds involving the two acetal‐type C—H bonds of the 1,3‐dioxole ring. Each dihydroberberine molecule is engaged in four hydrogen bonds with neighbouring molecules, twice as donor and twice as acceptor, thus forming a two‐dimensional sheet network that lies parallel to the (100) plane.     

Crystal structures of the anhydrous and two solvated forms of methyl 4‐(4‐fluorophenyl)‐6‐methyl‐2‐oxo‐1,2,3,4‐tetrahydropyrimidine‐5‐carboxylate

Methyl 4‐(4‐fluorophenyl)‐6‐methyl‐2‐oxo‐1,2,3,4‐tetrahydropyrimidine‐5‐carboxylate, ( I ), was found to exhibit solvatomorphism. The compound was prepared using a classic Biginelli reaction under mild conditions, without using catalysts and in a solvent‐free environment. Single crystals of two solvatomorphs and one anhydrous form of ( I ) were obtained through various crystallization methods. The anhydrous form, C₁₃H₁₃FN₂O₃, was found to crystallize in the monoclinic space group C2/c. It showed one molecule in the asymmetric unit. The solvatomorph with included carbon tetrachloride, C₁₃H₁₃FN₂O₃·0.25CCl₄, was found to crystallize in the monoclinic space group P2/n. The asymmetric unit revealed two molecules of ( I ) and one disordered carbon tetrachloride solvent molecule that lies on a twofold axis. A solvatomorph including ethyl acetate, C₁₃H₁₃FN₂O₃·0.5C₄H₈O₂, was found to crystallize in the triclinic space group P with one molecule of ( I ) and one solvent molecule on an inversion centre in the asymmetric unit. The solvent molecules in the solvatomorphs were found to be disordered, with a unique case of crystallographically induced disorder in ( I ) crystallized with ethyl acetate. Hydrogen‐bonding interactions, for example, N—H…O=C, C—H…O=C, C—H…F and C—H…π, contribute to the crystal packing with the formation of a characteristic dimer through N—H…O=C interactions in all three forms. The solvatomorphs display additional interactions, such as C—F…N and C—Cl…π, which are responsible for their molecular arrangement. The thermal properties of the forms were analysed through differential scanning calorimetry (DSC), hot stage microscopy (HSM) and thermogravimetric analysis (TGA) experiments.     

A new CoII complex of diniconazole: synthesis,crystal structure and antifungal activity

A new Co^II complex of diniconazole, namely diaqua[(E)‐(RS)‐1‐(2,4‐dichlorophenyl)‐4,4‐dimethyl‐2‐(1H‐1,2,4‐triazol‐1‐yl‐κN⁴)pent‐1‐en‐3‐ol]cobalt(II) dinitrate dihydrate, [Co(C₁₅H₁₇Cl₂N₃O)₃(H₂O)₂](NO₃)₂·2H₂O, was synthesized and characterized by elemental analysis, IR spectroscopy and single‐crystal X‐ray diffraction. Crystal structural analysis shows that the centrosymmetric Co^II cation is coordinated by four diniconazole ligands and two water molecules, forming a six‐coordinated octahedral structure. There are also two free nitrate counter‐anions and two additional solvent water molecules in the structure. Intermolecular O—H...O hydrogen bonds link the complex cations into a one‐dimensional chain. In addition, the antifungal activity of the complex against Botryosphaeria ribis, Gibberella nicotiancola, Botryosphaeria berengriana and Alternariasolani was studied. The results indicate that the complex shows a higher antifungal activity for Botryosphaeria ribis and Botryosphaeria berengriana than diniconazole, but a lower antifungal activity for Gibberella nicotiancola and Alternariasolani.