Polymorphism in 3‐acetyl‐4‐hydroxy‐2H‐chromen‐2‐one

A new polymorph (denoted polymorph II) of 3‐acetyl‐4‐hydroxy‐2H‐chromen‐2‐one, C₁₁H₈O₄, was obtained unexpectedly during an attempt to recrystallize the compound from salt–melted ice, and the structure is compared with that of the original polymorph (denoted polymorph I) [Lyssenko & Antipin (2001). Russ. Chem. Bull. 50 , 418–431]. Strong intramolecular O—H...O hydrogen bonds are observed equally in the two polymorphs [O...O = 2.4263 (13) Å in polymorph II and 2.442 (1) Å in polymorph I], with a slight delocalization of the hydroxy H atom towards the ketonic O atom in polymorph II [H...O = 1.32 (2) Å in polymorph II and 1.45 (3) Å in polymorph I]. In both crystal structures, the packing of the molecules is dominated and stabilized by weak intermolecular C—H...O hydrogen bonds. Additional π–π stacking interactions between the keto–enol hydrogen‐bonded rings stabilize polymorph I [the centres are separated by 3.28 (1) Å], while polymorph II is stabilized by interactions between α‐pyrone rings, which are parallel to one another and separated by 3.670 (5) Å.     

3‐(1‐Hydroxy­ethyl­idene)‐1‐phenyl­pyrrolidine‐2,4‐dione

Analysis of C₁₂H₁₁NO₃ revealed a coplanar N‐substituted phenyl group on a pyrrolidine ring with two keto moieties and a hydroxy­ethyl­idene functionality. The hydroxy group forms part of a hydrogen‐bonding network characterized by a short intramolecular H?O distance of 1.81 (3) Å, and a longer intermolecular interaction with an H?O distance of 2.38 (3) Å. Both keto groups form additional intra‐ and intermolecular C—H?O contacts with H?O distances ranging from 2.26 to 2.41 Å.     

Halogen bonds on demand: I...S contacts in cocrystals of trans‐bis(thiocyanato‐κN)tetrakis(4‐vinylpyridine‐κN)nickel(II) and 2,3,5,6‐tetrafluoro‐1,4‐diiodobenzene

Hydrogen bonds are considered a powerful organizing force in designing supramolecular architectures because they are directional, selective and reversible at room temperature. trans‐Dithiocyanatotetrakis(4‐vinylpyridine)nickel(II) is a popular host for the inclusion of small molecules and 2,3,5,6‐tetrafluoro‐1,4‐diiodobenzene (TFDIB) represents a strong halogen‐bond donor. These constituents cocrystallize in a 1:1 stoichiometry, [Ni(NCS)₂(C₇H₇N)₄]·C₆F₄I₂, in the tetragonal space group I4₁/a. Both residues occupy special positions, i.e. the pseudo‐octahedral Ni^II complex is located on a twofold axis and the TFDIB molecule sits about a crystallographic centre of inversion. The components interact via a short S...I contact of 3.2891 (12) Å between the thiocyanate S atom of the host and the iodine substituent at the perhalogenated aromatic ring of the smaller guest molecule. This interaction meets the commonly accepted criteria for a halogen bond. Such halogen bonds to sulfur are significantly less common than to smaller electronegative atoms.     

Polymorphism of 3‐(5‐phenyl‐1,3,4‐oxadiazol‐2‐yl)‐ and 3‐[5‐(pyridin‐4‐yl)‐1,3,4‐oxadiazol‐2‐yl]‐2H‐chromen‐2‐ones

This study of 3‐(5‐phenyl‐1,3,4‐oxadiazol‐2‐yl)‐2H‐chromen‐2‐one, C₁₇H₁₀N₂O₃, 1 , and 3‐[5‐(pyridin‐4‐yl)‐1,3,4‐oxadiazol‐2‐yl]‐2H‐chromen‐2‐one, C₁₆H₉N₃O₃, 2 , was performed on the assumption of the potential anticancer activity of the compounds. Three polymorphic structures for 1 and two polymorphic structures for 2 have been studied thoroughly. The strongest intermolecular interaction is stacking of the `head‐to‐head' type in all the studied crystals. The polymorphic structures of 1 differ with respect to the intermolecular interactions between stacked columns. Two of the polymorphs have a columnar or double columnar type of crystal organization, while the third polymorphic structure can be classified as columnar‐layered. The difference between the two structures of 2 is less pronounced. Both crystals can be considered as having very similar arrangements of neighbouring columns. The formation of polymorphic modifications is caused by a subtle balance of very weak intermolecular interactions and packing differences can be identified only using an analysis based on a study of the pairwise interaction energies.     

Hydro­gen‐bonded adducts of ferrocene‐1,1′‐diyl­bis­(di­phenyl­methanol): a finite cyclic 1:1 adduct with 2,2′‐dipyridyl­amine

In ferrocene‐1,1′‐diyl­bis­(di­phenyl­methanol)–2,2′‐dipyridyl­amine (1/1), [Fe(C₁₈H₁₅O)₂]·C₁₀H₉N₃, (I), there is an intramolecular O—H?O hydrogen bond [H?O 2.03 Å, O?O 2.775 (2) Å and O—H?O 147°] in the ferrocenediol component, and the two neutral molecular components are linked by one O—H?N hydrogen bond [H?N 1.96 Å, O?N 2.755 (2) Å and O—H?N, 157°] and one N—H?O hydrogen bond [H?O 2.26 Å, N?O 3.112 (2) Å and N—H?O 164°] forming a cyclic R(8) motif. One of the pyridyl N atoms plays no part in the intermolecular hydrogen bonding, but participates in a short intramolecular C—H?N contact [H?N 2.31 Å, C?N 2.922 (2) Å and C—H?N 122°].     

2‐Amino‐5‐chloro‐1,3‐benzoxazol‐3‐ium 2‐(3,4‐di­chloro­phenoxy)­acetate

The 1:1 organic salt of the title compound, C₇H₆ClN₂O⁺·C₈H₅Cl₂O₃^? or [(2‐ABOX)(3,4‐D)], comprises the two constituent mol­ecules associated by an R₂²(8) graph‐set interaction through the carboxyl­ate group of 3,4‐D across the protonated N/N sites of 2‐ABOX [N?O 2.546 (3) and 2.795 (3) Å]. Cation/anion pairs associate across an inversion centre forming discrete tetramers via an additional three‐centre hydrogen‐bonding association from the latter N amino proton to a phenoxy O atom [N?O 3.176 (3) Å] and a carboxyl­ate O atom [N?O 2.841 (3) Å]. This formation differs from the polymeric hydrogen‐bonded chains previously observed for adduct structures of 2‐ABOX with carboxyl­ic acids.     

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.     

The first crystal structures of six‐ and seven‐membered tellurium‐ and nitrogen‐containing (Te—N) heterocycles: 2H‐1,4‐benzotellurazin‐3(4H)‐one and 2,3‐dihydro‐1,5‐benzotellurazepin‐4(5H)‐one

There is a paucity of data concerning the structures of six‐ and seven‐membered tellurium‐ and nitrogen‐containing (Te—N) heterocycles. The title compounds, C₈H₇NOTe, (I), and C₉H₉NOTe, (II), represent the first structurally characterized members of their respective classes. Both crystallize with two independent molecules in the asymmetric unit. When compared to their sulfur analogs, they exhibit slightly greater deviations from planarity to accommodate the larger chalcogenide atom, with (II) adopting a pronounced twist‐boat conformation. The C—Te—C angles of 85.49 (15) and 85.89 (15)° for the two independent molecules of (I) were found to be somewhat smaller than those of 97.4 (2) and 97.77 (19)° for the two independent molecules of (II). The C—Te bond lengths [2.109 (4)–2.158 (5) Å] are in good agreement with those predicted by the covalent radii. Intermolecular N—H...O hydrogen bonding in (I) forms centrosymmetric R₂²(8) dimers, while that in (II) forms chains. In addition, intermolecular Te...O contacts [3.159 (3)–3.200 (3) Å] exist in (I).     

Intra‐ and intermolecular Se...X (X = Se,O) interactions in selenium‐containing heterocycles: 3‐benzoylimino‐5‐(morpholin‐4‐yl)‐1,2,4‐diselenazole

In the selenium‐containing heterocyclic title compound {systematic name: N‐[5‐(morpholin‐4‐yl)‐3H‐1,2,4‐diselenazol‐3‐ylidene]benzamide}, C₁₃H₁₃N₃O₂Se₂, the five‐membered 1,2,4‐diselenazole ring and the amide group form a planar unit, but the phenyl ring plane is twisted by 22.12 (19)° relative to this plane. The five consecutive N—C bond lengths are all of similar lengths [1.316 (6)–1.358 (6) Å], indicating substantial delocalization along these bonds. The Se...O distance of 2.302 (3) Å, combined with a longer than usual amide C=O bond of 2.252 (5) Å, suggest a significant interaction between the amide O atom and its adjacent Se atom. An analysis of related structures containing an Se—Se...X unit (X = Se, S, O) shows a strong correlation between the Se—Se bond length and the strength of the Se...X interaction. When X = O, the strength of the Se...O interaction also correlates with the carbonyl C=O bond length. Weak intermolecular Se...Se, Se...O, C—H...O, C—H...π and π–π interactions each serve to link the molecules into ribbons or chains, with the C—H...O motif being a double helix, while the combination of all interactions generates the overall three‐dimensional supramolecular framework.     

Polymorphism and phase transformation in the dimethyl sulfoxide solvate of 2,3,5,6‐tetrafluoro‐1,4‐diiodobenzene

A new polymorph (form II) is reported for the 1:1 dimethyl sulfoxide solvate of 2,3,5,6‐tetrafluoro‐1,4‐diiodobenzene (TFDIB·DMSO or C₆F₄I₂·C₂H₆SO). The structure is similar to that of a previously reported polymorph (form I) [Britton (2003). Acta Cryst. E 59 , o1332–o1333], containing layers of TFDIB molecules with DMSO molecules between, accepting I…O halogen bonds from two TFDIB molecules. Re‐examination of form I over the temperature range 300–120 K shows that it undergoes a phase transformation around 220 K, where the DMSO molecules undergo re‐orientation and become ordered. The unit cell expands by ca 0.5 Å along the c axis and contracts by ca 1.0 Å along the a axis, and the space‐group symmetry is reduced from Pnma to P2₁2₁2₁. Refinement of form I against data collected at 220 K captures the (average) structure of the crystal prior to the phase transformation, with the DMSO molecules showing four distinct disorder components, corresponding to an overlay of the 297 and 120 K structures. Assessment of the intermolecular interaction energies using the PIXEL method indicates that the various orientations of the DMSO molecules have very similar total interaction energies with the molecules of the TFDIB framework. The phase transformation is driven by interactions between DMSO molecules, whereby re‐orientation at lower temperature yields significantly closer and more stabilizing interactions between neighbouring DMSO molecules, which lock in an ordered arrangement along the shortened a axis.     

Diphenyl(2‐thioxo‐1,3‐dithiole‐4,5‐di­thiolato‐S,S′)plumbane at 295 K and diphenyl(2‐thioxo‐1,3‐dithiole‐4,5‐di­thiolato‐S,S′)stannane at 150 K

Molecules of di­phenyl(2‐thio­xo‐1,3‐di­thiole‐4,5‐di­thiol­ato‐S,S′)­plumbane, [Pb(C₃S₅)(C₆H₅)₂], are linked into sheets via two intermolecular Pb?S_thione interactions of 3.322 (4) and 3.827 (4) Å; the Pb centre has a distorted octahedral geometry. In contrast, mol­ecules of ­di­phenyl(2‐thio­xo‐1,3‐di­thiole‐4,5‐di­thiol­ato‐S,S′)­stannane, [Sn(C₃S₅)(C₆H₅)₂], are linked into chains via a single intermolecular Sn—S_thione interaction of 2.8174 (9) Å; the Sn centre has a distorted trigonal‐bipy­ramidal geometry.     

Dichloro(2,2′‐diamino‐4,4′‐bi‐1,3‐thiazole‐N3,N3′)copper(II)

The title complex, [CuCl₂(C₆H₆N₄S₂)], has a flattened tetrahedral coordination. The Cu^II atom is located on a twofold rotation axis and is coordinated by two N atoms from a chelating 2,2′‐di­amino‐4,4′‐bi‐1,3‐thia­zole ligand and by two Cl atoms. Intramolecular hydrogen bonding exists between the amino groups of the 2,2′‐di­amino‐4,4′‐bi‐1,3‐thia­zole ligand and the Cl atoms. The intermolecular separation of 3.425 (1) Å between parallel bi­thia­zole rings suggests there is a π–π interaction between them.     

1′‐Acetyl­ferrocene‐1‐carboxyl­ic acid: an instance of hydrogen bonding in the rare dimeric acid‐to‐ketone mode

The title compound, [Fe(C₆H₅O₂)(C₇H₇O)], adopts a conformation involving partial staggering of its rings and aggregates in the solid as acid‐to‐ketone hydrogen‐bonding dimers [O?O = 2.720 (4) Å and O—H?O = 164°] having centro­symmetrically related components. Close intermolecular C—H?O contacts were found to both carboxyl O atoms.     

3‐[(Diphenylphosphinothioyl)oxy]‐N‐methylpropan‐1‐aminium diphenylphosphanylthioate

The title salt, C₁₆H₂₁NOPS⁺·C₁₂H₁₀OPS, was synthesized from the reaction between 3‐(methylamino)propan‐1‐ol and PPh₂(S)Cl in the presence of Et₃N. Its structure has been identified using spectroscopic methods and X‐ray analysis. Single crystals were obtained from ethanol by slow evaporation. In the asymmetric unit, a cation–anion pair is formed through an intermolecular N—H...O [N...O = 2.6974 (18) Å] hydrogen bond. The molecules are packed through N—H...O and N—H...S hydrogen bonds in the crystal and these hydrogen bonds are responsible for the high melting point. The P atoms of the anion and cation both have distorted tetrahedral environments.     

Non‐Isomorphic Chlorine—Bromine Substitution in the Copper(I) Halide π‐Complexes with 1‐Allyl‐4‐aminopyridinium

By alternating‐current electrochemical synthesis crystals of {Cu[H₂NC₅H₄N(C₃H₅)]Br₂} ˙ H₂O ( I ), {Cu[H₂NC₅H₄N(C₃H₅)]Br_0.65Cl_1.35} ˙ H₂O ( II ) and {Cu[H₂NC₅H₄N(C₃H₅)]Cl₂} ( III ) π‐complexes have been obtained and structurally investigated. The I and II compounds are isostructural and crystallize in a monoclinic sp. gr. P2₁/c, I : a = 7.359(2)Å, b = 12.3880(6)Å, c = 13.637(3)Å, β = 107.03(1)°, V = 1188.7(4)ų, Z = 4 for C₈H₁₃N₂OBr₂Cu composition, R = 0.0293 for 2140 reflections. II : a = 7.2771(6)Å, b = 12.3338(3)Å, c = 13.4366(7)Å, β = 107.632(2)°, V = 1149.3(1)ų, Z = 4 for C₈H₁₃N₂Br_0.65Cl_1.35Cu composition, R = 0.0463 for 2185 reflections. Metal and halogen atoms form centrosymmetric Cu₂X₄ dimers. Each copper atom is surrounded by three halogen atoms and by a weakly bonded C=C‐group of the onium moiety. Isolated {Cu[H₂NC₅H₄N(C₃H₅)]}₂X₄ dimers are combined into a three‐dimensional network due to a bridging function of water molecules via a system of rather strong hydrogen bonds. Chlorine derivative III crystallizes in another structure type: sp. gr. C2/c, a = 21.568(7)Å, b = 7.260(2)Å, c = 13.331(3)Å, β = 95.65(2)°, V = 2077(2)ų, Z = 8 for C₈H₁₁N₂Cl₂Cu composition. Copper atom, included in CuCl₂^— isolated fragment, is coordinated to a C=C‐bond of ligand moiety. N‐H…Cl hydrogen bonds unite Cu[H₂NC₅H₄N(C₃H₅)]Cl₂ subunits into infinite ribbons. π‐Interaction in III appears to be more effective than in I and II .     

trans‐Bis(dimethyl sulfoxide‐κO)bis(3‐oxo‐3,4‐dihydroquinoxaline‐2‐carboxylato‐κ2N1,O2)copper(II)

The title compound, [Cu(C₉H₅N₂O₃)₂(C₂H₆OS)₂], consists of octahedrally coordinated Cu^II ions, with the 3‐oxo‐3,4‐dihydroquinoxaline‐2‐carboxylate ligands acting in a bidentate manner [Cu—O = 1.9116 (14) Å and Cu—N = 2.1191 (16) Å] and a dimethyl sulfoxide (DMSO) molecule coordinated axially via the O atom [Cu—O = 2.336 (5) and 2.418 (7) Å for the major and minor disorder components, respectively]. The whole DMSO molecule exhibits positional disorder [0.62 (1):0.38 (1)]. The octahedron around the Cu^II atom, which lies on an inversion centre, is elongated in the axial direction, exhibiting a Jahn–Teller effect. The ligand exhibits tautomerization by H‐atom transfer from the hydroxyl group at position 3 to the N atom at position 4 of the quinoxaline ring of the ligand. The complex molecules are linked through an intermolecular N—H...O hydrogen bond [N...O = 2.838 (2) Å] formed between the quinoxaline NH group and a carboxylate O atom, and by a weak intermolecular C—H...O hydrogen bond [3.392 (11) Å] formed between a carboxylate O atom and a methyl C atom of the DMSO ligand. There is a weak intramolecular C—H...O hydrogen bond [3.065 (3) Å] formed between a benzene CH group and a carboxylate O atom.     

Synthesis and single crystal X‐ray determination of the Schiff base 1‐[(2‐isopropyl‐5‐methylphenoxy)hydrazono] ethyl ferrocene

The reaction of acetylferrocene [Fe(η‐C₅H₅)(η‐C₅H₄COCH₃)] (1) with (2‐isopropyl‐5‐methylphenoxy) acetic acid hydrazide [CH₃C₆H₃CH(CH₃)₂OCH₂CONHNH₂] (2) in refluxing ethanol gives the stable light‐orange–brown Schiff base 1‐[(2‐isopropyl‐5‐methylphenoxy)hydrazono] ethyl ferrocene, [CH₃C₆H₃CH(CH₃)₂OCH₂CONHN?C(CH₃)Fe(η‐C₅H₅)(η‐C₅H₄)] (3). Complex 3 has been characterized by elemental analysis, IR, ¹H NMR and single crystal X‐ray diffraction study. It crystallizes in the monoclinic space group P2₁/n, with a = 9.6965(15), b = 7.4991(12), c = 29.698(7) Å, β = 99.010(13) °, V = 2132.8(7) ų, D_calc = 1.346 Mg m^?3; absorption coefficient, 0.729 mm^?1. The crystal structure clearly shows the characteristic [N? H···O] hydrogen bonding between the two adjacent molecules of 3. This acts as a bidentale ligand, which, on treatment with [Ru(CO)₂Cl₂] _n, gives a stable bimetallic yellow–orange complex (4). Copyright © 2002 John Wiley & Sons, Ltd.     

Synthesis and characterization of (cryptand‐222)potassium (2‐methylimidazolato)(meso‐tetraphenylporphinato)ferrate(II)–2‐methylimidazole–tetrahydrofuran (1/1/2)

Metalloporphyrin complexes containing an additional imidazole ligand can provide information about the effect of deprotonation or hydrogen bonding on the axial histidine unit in heme proteins. The title high‐spin five‐coordinate imidazolate‐ligated iron(II) porphyrinate, [K(C₁₈H₃₆N₂O₆)][Fe(C₄H₅N₂)(C₄₄H₂₈N₄)]·C₄H₆N₂·2C₄H₈O, has been synthesized and investigated. The solvated salt crystallizes with one 2‐methylimidazole molecule, two tetrahydrofuran solvent molecules and a potassium cation chelated inside a cryptand‐222 (4,7,13,16,21,24‐hexaoxa‐1,10‐diazabicyclo[8.8.8]hexacosane) molecule. The imidazolate ligand is ordered. The average Fe—Np (Np is a porphyrin N atom) bond length is 2.113 (11) Å and the axial Fe—N_Im (N_Im is an imidazolate N atom) is 2.0739 (13) Å. The out‐of‐plane displacement of the Fe^II atom from the 24‐atom mean plane is 0.6098 (5) Å, indicating an apparent doming of the porphyrin core.     

2,3:4,6‐Di‐O‐isopropylidene‐α‐l‐sorbofuranose and 2,3‐O‐isopropylidene‐α‐l‐sorbofuranose

In the title compounds, C₁₂H₂₀O₆, (I), and C₉H₁₆O₆, (II), the five‐membered furanose ring adopts a ⁴T₃ conformation and the five‐membered 1,3‐dioxolane ring adopts an E₃ conformation. The six‐membered 1,3‐dioxane ring in (I) adopts an almost ideal ^OC₃ conformation. The hydrogen‐bonding patterns for these compounds differ substantially: (I) features just one intramolecular O—H...O hydrogen bond [O...O = 2.933 (3) Å], whereas (II) exhibits, apart from the corresponding intramolecular O—H...O hydrogen bond [O...O = 2.7638 (13) Å], two intermolecular bonds of this type [O...O = 2.7708 (13) and 2.7730 (12) Å]. This study illustrates both the similarity between the conformations of furanose, 1,3‐dioxolane and 1,3‐dioxane rings in analogous isopropylidene‐substituted carbohydrate structures and the only negligible influence of the presence of a 1,3‐dioxane ring on the conformations of furanose and 1,3‐dioxolane rings. In addition, in comparison with reported analogs, replacement of the –CH₂OH group at the C1‐furanose position by another group can considerably affect the conformation of the 1,3‐dioxolane ring.     

Aqua(dipicolinato‐κ3O,N,O′)(1H‐imidazole‐κN3)(1,10‐phenanthroline‐N,N′)manganese(II)

In the title compound, [Mn(C₇H₃NO₄)(C₃H₄N₂)(C₁₂H₈N₂)(H₂O)], the Mn^II centre is surrounded by one bidentate phenanthroline ligand [Mn—N = 2.383 (3) and 2.421 (3) Å], one tridentate dipicolinate ligand [Mn—N = 2.300 (3) Å, and Mn—O = 2.300 (2) and 2.357 (2) Å], one monodentate imidazole ligand [Mn—N = 2.238 (3) Å] and one water molecule [Mn—O = 2.157 (3) Å]. It displays a distorted pentagonal‐bipyramidal geometry, with neighbouring angles within the equatorial plane ranging from 68.05 (9) to 77.48 (10)°. Intermolecular O—H...O hydrogen bonds link the molecules into infinite chains. The chains are crosslinked by hydrogen bonds involving the carboxyl O atoms of the dipicolinate ligand and the protonated imidazole N atom, leading to an infinite two‐dimensional network sheet packing mode. The complete solid‐state structure can be described as a three‐dimensional supramolecular framework, stabilized by these intermolecular hydrogen‐bonding interactions and π–π stacking interactions involving the phenanthroline rings.