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Syntheses of the acyclic amidinium salts, morpholinoformamidinium hexafluoridophosphate [OC4H8N--CH NH2]PF6 or C5H11N2O+·PF6-, 1, and pyrrolidinoformamidinium hexafluoridophosphate [C4H8N--CH NH2]PF6 or C5H11N2 +·PF6-, 2, were carried out by heating either morpholine or pyrrolidine with triethyl orthoformate and ammonium hexafluoridophosphate. Crystals of 1 obtained directly from the reaction mixture contain one cation and one anion in the asymmetric unit. The structure involves cations linked in chains parallel to the b axis by N--H. . .O hydrogen bonds in space group Pbca, with glide-related chains pointing in opposite directions. Crystals of 1 obtained by recrystallization from ethanol, however, showed a similar unit cell and the same basic structure, but unexpectedly, there was positional disorder [occupancy ratio 0.639 (4):0.361 (4)] in one of the cation chains, which lowered the crystal symmetry to the non-centrosymmetric space group Pca21, with two cations and anions in the asymmetric unit. In the pyrrolidino compound, 2, cations and anions are ordered and are stacked separately, with zigzag N--H. . .F hydrogenbonding between stacks, forming ribbons parallel to (101), extended along the baxis direction. Slight differences in the delocalized C N distances between the two cations may reflect the inductive effect of the oxygen atom in the morpholino compound. [ABSTRACT FROM AUTHOR]

The crystal structure and a Hirshfeld surface analysis of the substituted anilinium salt 4-(dimethylazaniumyl)-2-hydroxyanilinium dichloride monohydrate, C8H14N2O+·2Cl- ·H2O, at low temperature (90 K) are presented. The organic cation is essentially planar: the r.m.s. deviation of its non-hydrogen atoms (aside from the two methyl groups) is 0.0045 A °. The methyl carbons are 1.3125 (12) A ° and 1.1278 (12) A ° either side of the mean plane. The crystal packing involves extensive hydrogen bonding of types O--H...Cl, N--H...Cl, N--H...OW, and OW--HW...Cl (where W = water), which arrange into chains of R2 4(12) motifs that combine to form corrugated layers parallel to (101). Atom-atom contacts for the cation primarily involve hydrogen, leading to the most abundant coverage percentages being 51.3% (H...H), 23.0% (H...Cl), 12.9% (H....O), and 9.7% (C...H). [ABSTRACT FROM AUTHOR]

The synthesis, crystal structure and spectroscopic analysis of (E)-1-(2,3-dihydrobenzo[b][1,4]dioxin-6-yl)-3-(4-chlorophenyl)prop-2-en-1-one (C17H13ClO3), a substituted chalcone, are described. The overall geometry of the molecule is largely planar (r.m.s. deviation = 0.1742 JA), but slightly kinked, leading to a dihedral angle between the planes of the benzene rings at either side of the molecule of 8.31 (9)°. In the crystal, only weak interactions determine the packing motifs. These include C--H--O and C--H--Cl hydrogen bonds and n-n overlap of aromatic rings. [ABSTRACT FROM AUTHOR]

The synthesis and crystal structure of a monoclinic polymorph of 2-amino-5-chlorobenzophenone oxime, C13H11ClN2O, are presented. The molecular conformation results from twisting of the phenyl and 2-amino-5-chloro benzene rings attached to the oxime group, which subtend a dihedral angle of 80.53 (4)°. In the crystal, centrosymmetric dimers are formed as a result of pairs of strong O--H--N hydrogen bonds. A comparison is made to a previously known triclinic polymorph, including differences in atom-atom contacts obtained via a Hirshfeld-surface analysis. [ABSTRACT FROM AUTHOR]

The synthesis and crystal structure of a monoclinic polymorph of 2-amino-5-chlorobenzophenone oxime, C13H11ClN2O, are presented. The molecular conformation results from twisting of the phenyl and 2-amino-5-chloro benzene rings attached to the oxime group, which subtend a dihedral angle of 80.53 (4)°. In the crystal, centrosymmetric dimers are formed as a result of pairs of strong O--H⋯N hydrogen bonds. A comparison is made to a previously known triclinic polymorph, including differences in atom-atom contacts obtained via a Hirshfeld-surface analysis. [ABSTRACT FROM AUTHOR]

The synthesis and crystal structure of C3HF3N2OS, systematic name 5-(trifluoromethyl)-1,3,4-thiadiazol-2(3H)-one (5-TMD-2-one), a compound containing the pharmacologically important heterocycle 1,3,4-thiadiazole, is presented. The asymmetric unit comprises six independent molecules (Z0 = 6), all of which are planar. The r.m.s. deviations from each mean plane range from 0.0063 to 0.0381 A °, not including the CF3 fluorine atoms. Within the crystal, two of the molecules form hydrogen-bonded dimers that in turn combine with inversion-related copies to form tetrameric constructs. Similar tetramers, but lacking inversion symmetry, are formed by the remaining four molecules. The tetramers are linked into tape-like motifs by S- - -O and O- - -O close contacts. The environments of each symmetry-independent molecule were compared via a Hirshfeld surface analysis. The most abundant atom-atom contacts are between fluorine atoms, while the strongest result from N--H- - -O hydrogen bonds. [ABSTRACT FROM AUTHOR]

The syntheses and crystal structures of four salts of amitriptynol (C20H25NO) with different carboxylic acids are described. The salts formed directly from solutions of amitriptyline (which first hydrolysed to amitriptynol) and the corresponding acid in acetonitrile to form amitriptynolium [systematic name: (3-{2-hydroxytricyclo[9.4.0.03,8]pentadeca-1(11),3,5,7,12,14-hexaen-2-yl}propyl)dimethylazanium] 4-methoxybenzoate monohydrate, C20H26NO+C8H7O3 -H2O, (I), amitriptynolium 3,4-dimethoxybenzoate trihydrate, C20H26NO+·C9H9O4 -3H2O, (II), amitriptynolium 2-chlorobenzoate, C20H26NO+·C7H4ClO2 -, (III), and amitriptynolium thiophene-2-carboxylate monohydrate, C20H26NO+·C5H3-O2S-H2O, (IV). Compound (III) crystallizes with two cations, two anions and six water molecules in the asymmetric unit. The different conformations of the amitriptynolium cations are determined by the torsion angles in the dimethylamino-propyl chains and the -CH2-CH2- bridge between the benzene rings in the tricyclic ring system, and are complicated by disorder of the bridging unit in II and III. The packing in all four salts is dominated by N-H...O and O- H...O hydrogen bonds. Hirshfeld surface analyses show that the amitriptynolium cations make similar inter-species contacts, despite the distinctly different packing in each salt. [ABSTRACT FROM AUTHOR]

The synthesis and crystal structure of the title compound, C12H16FNO3S, which is related to the herbicide flufenacet, are presented. The dihedral angle between the amide group and the fluorinated benzene ring is 87.30 (5)° and the N-C-C-S torsion angle defining the orientation of the methylsulfonyl substituent relative to the amide group is 106.91 (11)°. In the crystal, inversion-related molecules form dimers as a result of pairwise C-H...O hydrogen bonds, which appear to be reinforced by short O···π - contacts [O...Cg = 3.0643 (11) A °]. A Hirshfeld surface analysis was used to quantify the various types of intermolecular contacts, which are dominated by H atoms. [ABSTRACT FROM AUTHOR]

Crystal structures described as concomitant triclinic (I) and monoclinic (II) polymorphs of meso‐(E,E)‐1,1′‐[1,2‐bis(4‐chlorophenyl)ethane‐1,2‐diyl]bis(phenyldiazene) [Mohamed et al. (2016). Acta Cryst. C72, 57–62] have been re‐investigated. The published model for II was distorted due to forcing the symmetry of space group C2/c on an incomplete structure model. It is shown here to be a likely three‐component superposition of S,S and R,R enantiomers with a lesser amount of the meso form. A detailed analysis of how the improbable distortion in the published model aroused suspicion and the subsequent construction of undistorted chemically and crystallographically plausible alternatives having the symmetry of Cc and C2/c is presented. For the sake of completeness, an improved model for the triclinic P structure of the meso isomer I, revised to include a minor disorder component, is also given. [ABSTRACT FROM AUTHOR]

This paper compares variations on a structure model derived from an X-ray diffraction data set from a solid solution of chalcogenide derivatives of cis-1,2-bis(diphenylphosphanyl)ethylene, namely, 1,2-(ethene-1,2-diyl)bis(diphenylphoshpine sulfide/selenide), C26H22P2S1.13Se0.87. A sequence of processes are presented to ascertain the composition of the crystal, along with strategies for which aspects of the model to inspect to ensure a chemically and crystallographically realistic structure. Criteria include mis-matches between Fobs² and Fcalc², plots of |Fobs| vs |Fcalc|, residual electron density, checkCIF alerts, pitfalls of the OMIT command used to suppress ill-fitting data, comparative size of displacement ellipsoids, and critical inspection of interatomic distances. Since the structure is quite small, solves easily, and presents a number of readily expressible refinement concepts, we feel that it would make a straightforward and concise instructional piece for students learning how to determine if their model provides the best fit for the data and show students how to critically assess their structures. [ABSTRACT FROM AUTHOR]

Syntheses and X-ray crystal structures of four 4-(4-methoxyphenyl)piperazin-1-ium (MeOPP) salts, with 2,2,2-trifluoroacetate, C11H17N2O+πC2F3O2- (I), 2,3,4,5,6-pentafluorobenzoate, C11H17N2O+πC7F5O2-πH2O (II), 4-iodobenzoate C11H17N2O+πC7H4IO2-πH2O (III), and 4-methylbenzoate, C11H17N2O+π- C8H7O2-πH2O (IV) anions are presented. The salts form directly from equimolar quantities of N-(4-methoxyphenyl)piperazine and the corresponding organic acid in methanol and crystallize from 1:1 methanol/ethyl acetate. Salt I is anhydrous whereas II, III, and IVare all monohydrates. In all cases, the MeOPP cation conformation is determined by the torsion about the N--C bond between the piperazinium and 4-methoxybenzene rings. Crystal packing in each structure is largely dictated by N--Hπ π πO and (in II, III, and IV) O--Hπ π πO hydrogen bonds, although each also features weak C--Hπ π πO-type hydrogen bonds. Salt II also has π-π-stacking interactions between cation and anion arene rings, and III exhibits Iπ π πI close contacts. [ABSTRACT FROM AUTHOR]

The syntheses and crystal structures are presented for four organic salts of the 4-(4-nitrophenyl)piperazinium cation, namely, 4-(4-nitrophenyl)piperazinium hydrogen succinate, C10H14N3O2+·C4H5O4- (I), 4-(4-nitrophenyl)piperazinium 4-aminobenzoate monohydrate, C10H14N3O2+·C7H6NO2-·H2O (II), 4-(4-nitrophenyl)piperazinium 2-(4-chlorophenyl)acetate, C10H14N3O2+·C8H6ClO2- (III) and 4-(4-nitrophenyl)piperazinium 2,3,4,5,6-pentafluorobenzoate, C10H14N3O2+·C7F5O2- (IV). The salts form from mixtures of N-(4-nitrophenyl)piperazine and the corresponding acid [succinic acid (I), 4-aminobenzoic acid (II), 2-(4-chlorophenyl)acetic acid (III) and 2,3,4,5,6-pentafluorobenzoic acid (IV)] in mixed solvents of methanol and ethyl acetate. Salts I, III, and IV are anhydrous, whereas II is a monohydrate. In each structure, the overall conformation of the cation is determined by the disposition of the exocyclic N--C bond of the piperazine ring (either axial or equatorial) and twists about the N--C bond between the piperazine ring and its attached 4-nitrophenyl ring. The packing motifs in each structure are quite different, though all are dominated by strong N--H⋯O hydrogen bonds, which are augmented in I and II by O--H⋯O hydrogen bonds, and in III by a π-π stacking interaction between inversion-related 4-nitrophenyl groups. [ABSTRACT FROM AUTHOR]

The crystal structure of ethiprole {systematic name: 5-amino-1-[2,6-dichloro- 4-(trifluoromethyl)phenyl]-4-ethanesulfinyl-1H-imidazole-3-carbonitrile}, C13H9Cl2F3N4OS, a phenylpyrazole-based insecticide, is presented. The pyrazole ring carries four substituents: an N-bound 2,6-dichloro-4-trifluoromethylphenyl ring and C-bound amine, ethanesulfinyl, and cyano groups. The sulfur atom of the ethanesulfinyl group is trigonal--pyramidal and stereogenic. The structure exhibits whole-molecule configurational disorder due to superposition of enantiomers. The crystal packing is dominated by strong N--H • • • O and N--H • • • N hydrogen bonds, which form R44(18) and R2 2(12) ring motifs. Since the ethiprole molecule is quite small, and structure solution and refinement were straightforward, the structure presents a convenient instructional example for modelling whole-body disorder of a non-rigid molecule. To this end, a step-bystep overview of the model-building and refinement process is also given. The structure could form the basis of a useful classroom, practical, or workshop-style example. [ABSTRACT FROM AUTHOR]

The crystal structures of three salts, namely N-(4-methoxyphenyl)piperazin-1-ium ethoxybenzoate monohydrate (I), N-(4-methoxyphenyl)piperazin-1-ium methoxybenzoate monohydrate (II) and N-(4-methoxyphenyl)piperazin-1-ium hydroxybenzoate monohydrate (III), have been determined and compared. In each of them, the ionic components and the water molecules are linked by a combination of N—H···O and O—H···O hydrogen bonds to form infinite chains of edge-fused centrosymmetric rings running parallel to the [100] direction. The C—H···O, C—H···π(arene) interactions and O—H···O in (III) are responsible for the further propagation of the aforementioned chains into di-periodic layers or tri-periodic networks. From an energetic point of view, all structures are primarily di-periodic; the very strong ionic interactions determine the periodicity. For comparison purposes, quantum chemical calculations were performed to show the difference between the ionic and neutral components. The energy of the hydrogen-bonded ring motifs was also estimated. [ABSTRACT FROM AUTHOR]

Three organic salts of sparfloxacin, a difluorinated third-generation fluoroquinolone antibiotic, have been synthesized and their crystal structures determined. The salts, sparfloxacinium 4-nitrobenzoate dihydrate, C19H23F2N4O3 +·C7H4NO4 -·2H2O (I), sparfloxacinium 2-phenylacetate, C19H23F2N4O3 +·C8H7O2- (II), and sparfloxacinium 4-methylbenzoate trihydrate, C19H23F2N4O3 +·C8H7O2O (III), exhibit similar inter-species packing interactions. The overall crystal structures each, however, have their own distinct characteristics, which are described here along with a Hirshfeld surface analysis of the various atom-atom contacts involving the sparfloxacinium cations. In the crystal structure of III, an extended supramolecular tape of edgefused hydrogen-bonded water pentagons was found. These pentagonal water and tape motifs are compared to related constructs in a broad selection of structure types, ranging from macromolecules to small molecules, clathrates, and exotic 'ice' formations on clean metal surfaces. [ABSTRACT FROM AUTHOR]-·3H2O (III), exhibit similar inter-species packing interactions. The overall crystal structures each, however, have their own distinct characteristics, which are described here along with a Hirshfeld surface analysis of the various atom-atom contacts involving the sparfloxacinium cations. In the crystal structure of III, an extended supramolecular tape of edgefused hydrogen-bonded water pentagons was found. These pentagonal water and tape motifs are compared to related constructs in a broad selection of structure types, ranging from macromolecules to small molecules, clathrates, and exotic 'ice' formations on clean metal surfaces. [ABSTRACT FROM AUTHOR]

The structure of 2-chloro-1-(3-hydroxyphenyl)ethanone, C8H7ClO2, an α-haloketone is described. The molecule is planar (r.m.s. deviation = 0.0164 A °) and in the crystal, inversion-symmetric dimers are formed as a result of pairs of strong O--H···O and weak C--H···O hydrogen bonds. A brief comparison is made with structurally related compounds deposited in the CSD. In addition, the synthesis and some spectroscopic details are presented. [ABSTRACT FROM AUTHOR]

The structure of the title compound, C15H8N4Cl2F6OS, a phenylpyrazole-based insecticide related to ethiprole, fipronil, and derivatives thereof is presented. The pyrazole ring has four chemically diverse substituents, namely a nitrogenbound 2,6-dichloro-4-trifluoromethylphenyl and carbon-bound cyano, ethylsulfanyl, and 2,2,2-trifluoroacetamide groups. The pyrazole and phenyl rings are perpendicular, subtending a dihedral angle of 89.80 (5)°. In the crystal, strong N--H···O hydrogen bonds link the molecules into chains that extend parallel to the a-axis. [ABSTRACT FROM AUTHOR]

Synthesis and crystal structures of 1-benzoyl-4-(4-nitrophenyl)piperazine, C17H17N3O3, (I) and 1-(4-bromobenzoyl)-4-phenylpiperazine, C17H17BrN2O, (II) are described. Compounds I and II crystallize in the orthorhombic and monoclinic crystal systems with space groups Pna21 (Z = 2, I) and P21 (Z = 1, II), respectively. The crystal of II was a two-component aggregate, treated as a 'twin' for data-acquisition purposes. There are no conventional hydrogen bonds in either I or II, but there are weaker C--H--O contacts. Each molecule consists of a central piperazine ring in a chair conformation, with either benzoyl and nitrophenyl (I) or 4-bromobenzoyl and phenyl (II) groups attached to different nitrogen atoms of the piperazine. The various atom-atom contact coverages as quantified by Hirshfeld surface analysis fingerprint plots are given. [ABSTRACT FROM AUTHOR]

Benzyl N'-[(E)-2-hydroxybenzylidene]hydrazinecarboxylate, C15H14N2O3 (I) and benzyl N'-[(E)-5-bromo-2-hydroxybenzylidene]hydrazinecarboxylate (II), C15H13BrN2O3, have been synthesized by the reaction of either 2-hydroxybenzaldehyde or 5-bromo-2-hydroxybenzaldehyde with benzyl carbazate, respectively. Both the compounds crystallize in the monoclinic crystal system with space groups Pn (Z' = 1, I) and P21/c (Z' = 2, II). Molecular conformations in each structure are similar, and both structures feature strong intramolecular O--H--N hydrogen bonds, which form S(6) ring motifs. There are also strong N--H--O and weak C--H--O hydrogen bonds in both structures, but their modes of packing within their respective crystals are markedly different. Some comparisons are made with the structures of a few related compounds. [ABSTRACT FROM AUTHOR]

The low (90 K) and room (298 K) temperature crystal structures of topiramate azidosulfate [systematic name 2,3:4,5-bis-O-(1-methylethylidene)-ß-D-fructopyranose azidosulfate], C12H19N3O8S, an intermediate in the synthesis of the anti-convulsant drug topiramate, are described. Topiramate azidosulfate (I) finds use as a reference impurity standard for topiramate. A modified synthesis and some spectroscopic details are also presented. [ABSTRACT FROM AUTHOR]

The structure of ebastinium hydrogen fumarate {systematic name: 1-[4-(4-tertbutylphenyl)-4-oxobutyl]-4-(diphenylmethoxy)piperidin-1-ium (E)-3-carboxy-1-hydroxyprop-2-en-1-olate}, C32H40NO2 +⋅C4H3O4, a 1:1 salt formed in the reaction between ebastine and fumaric acid is presented. All examined crystals were found to be twinned by pseudo-merohedry. The structure is extensively disordered, with over half (20 out of 35) its non-hydrogen atoms modelled as lying over two sets of sites. In the crystal, cation-anion pairs are linked by a strong N--H⋅ ⋅ ⋅O hydrogen bond [N⋅ ⋅ ⋅O = 2.697 (11) A ° ]. These units interact via weaker C--H⋅ ⋅ ⋅O and C--H⋅ ⋅ ⋅⋅ contacts to form layers lying parallel to the bc plane. The hydrogen fumarate anions are linked by a very short O--H⋅ ⋅ ⋅O hydrogen bond [O⋅ ⋅ ⋅O = 2.5402 (17) A ° ], augmented by weak C--H⋅ ⋅ ⋅O contacts into pairs of R2 2(6) ring motifs to form chains that extend parallel to the b-axis direction. Comparisons to similar crystal structures are presented. [ABSTRACT FROM AUTHOR]

Crystal structures are reported for two mol­ecular salts containing the 4-(4-nitro­phen­yl)piperazin-1-ium cation. Co-crystallization from methanol/ethyl acetate solution of N-(4-nitro­phen­yl)piperazine with benzoic acid gives the benzoate salt, which crystallizes as a monohydrate, C10H14N3O2·C7H5O2·H2O, (I), and similar co-crystallization with 3,5-di­nitro­salicylic acid yields the 2-carb­oxy-4,6-di­nitro­phenolate salt, C10H14N3O2·C7H3N2O7, (II). In the structure of (I), a combination of O--H...O, N--H...O and C--H...O hydrogen bonds links the components into sheets, while in the structure of (II), the supra­molecular assembly, generated by hydrogen bonds of the same types as in (I), is three dimensional. Comparisons are made with the structures of some related compounds. [ABSTRACT FROM AUTHOR]

The title compound, C16H20N22+·2Br−·H2O (1) is a member of the class of compounds called viologens. Viologens are quaternary salts of di­pyridyls and are especially useful as redox indicators as a result of their large negative one-electron reduction potentials. Compound 1 consists of a dication composed of a pair of 4-methyl­pyridine rings mutually joined at the 2-position, with a dihedral angle between the pyridine rings of 62.35 (4)°. In addition, the rings are tethered via the pyridine nitro­gen atoms by a tetra­methyl­ene bridge. Charge balance is provided by a pair of bromide anions, which are hydrogen bonded to a single water mol­ecule [DO...Br = 3.3670 (15) and 3.3856 (15) Å]. The crystal structure of 1, details of an improved synthesis, and a full analysis of its NMR spectra are presented. [ABSTRACT FROM AUTHOR]

Threefold twinning in 1‐{(R)‐1‐[(3‐oxo‐2‐isoindolinoyl)methyl]‐2‐propenyl}‐5‐methyl‐2,3‐indolinedione, C21H16N2O4, has been reported recently [Trost et al. (2020). Org. Lett.22, 2584–2589] but the twin characterization was not published. This twinning presents several interesting features. The crystal structure is monoclinic, but its lattice is metrically strongly pseudo‐orthorhombic and underpins a strongly pseudo‐hexagonal sublattice. Several possible twin laws are compatible with these metric specializations, among which the one found experimentally corresponds to a trichromatic point group. Twinning is by reticular pseudo‐merohedry with twin index 2 and zero obliquity but a non‐zero twin misfit. The twin lattice coincides with the pseudo‐hexagonal sublattice of the individual domain, which justifies the adoption of the unconventional setting B21 of the space group. [ABSTRACT FROM AUTHOR]

Polychlorinated biphenyls (PCBs) are environmental pollutants implicated in a variety of adverse health effects, including cancer and noncancer diseases in animals and humans. PCBs are metabolized to hydroxylated compounds, and some of these PCB metabolites are more toxic than the parent PCBs. Unfortunately, most PCB metabolites needed for toxicological studies are not available from commercial sources. Moreover, it is challenging to synthesize PCB metabolites because starting materials with suitable substitution patterns are not readily available. Here, we report the novel synthesis of a variety of mono- and dimethoxyarene derivatives from commercially available fluoroarenes via nucleophilic aromatic substitution with sodium methoxide. This reaction provided good to excellent yields of the desired methoxylated products. Suzuki coupling of selected mono- and dimethoxy haloarenes with chlorinated phenylboronic acids yielded methoxylated derivatives of PCB 11, 12, 25, 35, and 36 in low to good yields. Crystal structures of 3,3′-dichloro-2,5-dimethoxy-1,1′-biphenyl and 3′,5-dichloro-2,3-dimethoxy-1,1′-biphenyl confirmed the substitution pattern of both compounds. This synthesis strategy provides straightforward access to a range of mono- and dimethoxylated PCB derivatives that were not readily accessible previously. [ABSTRACT FROM AUTHOR]

Flunixin [2-(3-trifluoromethyl-2-methyl-phenylamino)-nicotinic acid, FLX], a potent nonsteroidal anti-inflammatory drug widely used in veterinary medicine, was found to exist in at least two crystal forms (I and II), in contrast to clonixin [2-(3-chloro-2-methyl-phenylamino)-nicotinic acid, CLX], which exists in four solvent-free forms and multiple solvates. Form I was harvested from a variety of solvents and characterized by single-crystal X-ray diffraction, PXRD, FT-IR, and Raman spectroscopy. Its crystal structure is sustained on the strong acid–pyridine hydrogen bond. Form II was generated by thermal treatment of form I. Other aspects of this polymorphic system were investigated both experimentally and theoretically. Quantum chemistry calculations were performed to shed light on the lack of polymorphism from solution-phase crystallization. Conformational scan of the dihedral angle C2–N7–C8–C9 (τ) revealed two stable conformations, one with τ near 170°, and the other near 70°, corresponding to the molecule in the crystal. Hirshfeld analysis accounted for the major intermolecular interactions contributing to the overall stability of the crystal. [ABSTRACT FROM AUTHOR]

The title compound [systematic name: (1R*, 8S)-2-acetamidooctahydropyrrol-izin-4-ium chloride--N-[(1R,8S)-hexahydro-1H-pyrrolizin-2-yl)acetamide (1/1)], + 2(C9H16N2O)HCl or C9H17N2O+Cl-·C9H16N2O, arose as an unexpected product when 1-exo-acetamidopyrrolizidine (AcAP; C9H16N2O) was dissolved in CHCl3. Within the AcAP pyrrolizidine group, the unsubstituted five- membered ring is disordered over two orientations in a 0.897 (5):0.103 (5) ratio. Two AcAP molecules related by a crystallographic twofold axis link to H and Cl ions lying on the rotation axis, thereby forming N--H ⋯N and N-- H ⋯Cl ⋯H--N hydrogen bonds. The first of these has an unusually short N ⋯N separation of 2.616 (2) Å: refinement of different models against the present data set could not distinguish between a symmetrical hydrogen bond (H atom lying on the twofold axis and equidistant from the N atoms) or static or dynamic disorder models (i.e. N--H⋯N + N ⋯H--N). Computational studies suggest that the disorder model is slightly more stable, but the energy difference is very small. [ABSTRACT FROM AUTHOR]

Imidazolium salts are common building blocks for functional materials and in the synthesis of N-heterocyclic carbene (NHC) as σ-donor ligands for stable metal complexes. The title salt, 1,3-bis­(4-hy­droxy­phen­yl)-1H-imidazol-3-ium chloride (IOH·Cl), C15H13N2O2+·Cl−, is a new imidazolium salt with a hy­droxy functionality. The synthesis of IOH·Cl was achieved in high yield via a two-step procedure involving a di­aza­butadiene precursor followed by ring closure using tri­methylchloro­silane and paraformaldehyde. The structure of IOH·Cl consists of a central planar imidazolium ring (r.m.s. deviation = 0.0015 Å), with out-of-plane phenolic side arms. The dihedral angles between the 4-hy­droxy­phenyl substituents and the imidazole ring are 55.27 (7) and 48.85 (11)°. In the crystal, O—H···Cl hydrogen bonds connect the distal hy­droxy groups and Cl− anions in adjacent asymmetric units, one related by inversion (−x + 1, −y + 1, −z + 1) and one by the n-glide (x − ½, −y + ½, z − ½), with donor–acceptor distances of 2.977 (2) and 3.0130 (18) Å, respectively. The phenolic rings are each π–π stacked with their respective inversion-related [(−x + 1, −y + 1, −z + 1) and (−x, −y + 1, −z + 1)] counterparts, with inter­planar distances of 3.560 (3) and 3.778 (3) Å. The only other noteworthy inter­molecular inter­action is an O...O (not hydrogen bonded) close contact of 2.999 (3) Å between crystallographically different hy­droxy O atoms on translationally adjacent mol­ecules (x + 1, y, x + 1). [ABSTRACT FROM AUTHOR]

The structure of zymonic acid (systematic name: 4-hy­droxy-2-methyl-5-oxo-2,5-di­hydro­furan-2-carb­oxy­lic acid), C6H6O5, which had previously eluded crystallographic determination, is presented here for the first time. It forms by intra­molecular condensation of parapyruvic acid, which is the product of aldol condensation of pyruvic acid. A redetermination of the crystal structure of pyruvic acid (systematic name: 2-oxo­propanoic acid), C3H4O3, at low temperature (90 K) and with increased precision, is also presented [for the previous structure, see: Harata et al. (1977). Acta Cryst. B33, 210–212]. In zymonic acid, the hy­droxy­lactone ring is close to planar (r.m.s. deviation = 0.0108 Å) and the dihedral angle between the ring and the plane formed by the bonds of the methyl and carb­oxy­lic acid carbon atoms to the ring is 88.68 (7)°. The torsion angle of the carb­oxy­lic acid group relative to the ring is 12.04 (16)°. The pyruvic acid mol­ecule is almost planar, having a dihedral angle between the carb­oxy­lic acid and methyl-ketone groups of 3.95 (6)°. Inter­molecular inter­actions in both crystal structures are dominated by hydrogen bonding. The common R2²(8) hydrogen-bonding motif links carb­oxy­lic acid groups on adjacent mol­ecules in both structures. In zymonic acid, this results in dimers about a crystallographic twofold of space group C2/c, which forces the carb­oxy­lic acid group to be disordered exactly 50:50, which scrambles the carbonyl and hydroxyl groups and gives an apparent equalization of the C—O bond lengths [1.2568 (16) and 1.2602 (16) Å]. The other hydrogen bonds in zymonic acid (O—H· · ·O and weak C—H· · ·O), link mol­ecules across a 21-screw axis, and generate an R2²(9) motif. These hydrogen-bonding inter­actions propagate to form extended pleated sheets in the ab plane. Stacking of these zigzag sheets along c involves only van der Waals contacts. In pyruvic acid, inversion-related mol­ecules are linked into R2²(8) dimers, with van der Waals inter­actions between dimers as the only other inter­molecular contacts. [ABSTRACT FROM AUTHOR]

The title compound, C21H25NO3 [systematic name: (1aR,4E,7aS,8E,10aS,10bR)-8-(2-aminobenzylidene)-1a,5-dimethyl-2,3,6,7,7a,8,10a,10b-octahydrooxireno[2',3':9,10]cyclodeca[1,2-b]furan-9(1aH)-one], was synthesized by the reaction of parthenolide [systematic name (1aR,7aS,10aS,10bS,E)-1a,5-dimethyl-8-methylene-2,3,6,7,7a,8,10a,10b-octahydrooxireno[2',3':9,10]cyclodeca[1,2-b]furan-9(1aH)-one] with 2-iodoaniline via Heck reaction conditions. The molecule is composed of fused ten-, five- (lactone), and three-membered (epoxide) rings. The lactone ring shows a flattened envelope-type conformation (r.m.s. deviation from planarity = 0.0477Å), and bears a 2-aminobenzylidene substituent that is disordered over two conformations [occupancy factors 0.901(4) and 0.099(4)]. The ten-membered ring has an approximate chair-chair conformation. The dihedral angle between the 2-aminobenzylidine moiety (major component) and the lactone ring (mean plane) is 59.93(7)°. There are no conventional hydrogen bonds, but there are a number of weaker C--H...O-type interactions. [ABSTRACT FROM AUTHOR]

2-((2-ethylphenyl)amino)nicotinic acid (2EPNA) was synthesized and its crystal structure was determined. It was observed that alkylation of the phenyl ring with ethyl group disrupts the planar conformation of the molecule by steric repulsion, resulting in formation of an acid-pyridine heterosynthon (instead of acid-acid homosynthon) in the crystal. Crystallization tendency from the melt state of the polymorph was studied by differential scanning calorimetry (DSC). It was revealed that this compound could form a very stable amorphous phase on melt quenching and not crystallize even on re-heating. The formation of acid-pyridine hydrogen bonding in the amorphous state is believed to be responsible for its good glass forming ability. [ABSTRACT FROM AUTHOR]

The title compound, C28H32N2, (I), is one of a second generation of compounds designed and synthesized based on a very potent and selective α9α10 nicotinic acetylcholine receptor antagonist ZZ161C {1,1'-[[1,1'-biphenyl]-4,4'-diylbis- (prop-2-yne-3,1-diyl)]bis(3,4-dimethylpyridin-1-ium) bromide}, which has shown analgesic effects in a chemotherapy-induced neuropathy animal model. Compound (I) was synthesized by the reaction of 4,4'-bis(3-bromoprop-1-yn-1-yl)-1,1'-biphenyl with piperidine at room temperature in acetonitrile. The singlecrystal used for X-ray analysis was obtained by dissolving (I) in a mixture of dichloromethane and methanol, followed by slow evaporation of the solvent. In the crystal of (I), the biphenyl moiety has a twisted conformation, with a dihedral angle of 25.93 (4)° between the benzene rings. Both piperidine head groups in (I) are in the chair conformation and are oriented so that the N-atom lone pairs of each piperidine group point away from the central biphenyl moiety. [ABSTRACT FROM AUTHOR]

The solid-state properties of 2-[(2,6-dichlorophenyl)amino]-benzaldehyde ( DCABA) were investigated. Unlike its precursor diclofenac acid, for which three polymorphs are currently known, only one crystalline form of DCABA was found. It was further characterized by other spectroscopic and spectrometric methods including IR, Raman, and UV-vis spectroscopy and powder X-ray diffraction ( PXRD). The thermal behavior of the crystalline form was studied by differential scanning calorimetry ( DSC). Theoretical studies, including Hirshfeld surface analysis and conformational energy searches, were performed to provide insight into the factors contributing to the stability of the crystal and to assess the possibility of additional polymorphs. The full characterization of this compound can help fast and accurate identification of DCABA both in dosage forms and in the environment. [ABSTRACT FROM AUTHOR]

5'-Deoxy-5'-iodoguanosine (I) crystals deposited from mixtures of water and methanol grow as nonsolvated hybrids of conformational polymorphs (Ia, Ib) and as a mixed solvate (Ic). Some solvent-free crystals are purely Ia, while others have varying amounts of Ib epitaxially intergrown with Ia. In Ia and Ib the conformations differ primarily by torsion about the C4'-C5' bond (guanosine numbering scheme), which dramatically affects the iodine atom position. Powder diffraction and reconstructed reciprocal-lattice-slice images had small peaks incompatible with Ia. Some solvent-free crystals required lattices for both Ia and Ib to index all observable reflections. Unit-cell dimensions for Ia and Ib suggest the potential for epitaxial intergrowth. Hydrogen-bond networks in Ia and Ib are essentially identical and result in double layers of molecules in the ab plane, with layers of iodine at the layer surfaces. The iodine layers of Ia and Ib are incompatible: in Ia adjacent iodine atom layers interdigitate slightly, whereas in Ib they do not. Theoretical calculations support the conclusion that at room temperature Ia is the thermodynamically more stable polymorph and that Ib represents a kinetic product. [ABSTRACT FROM AUTHOR]

Anthradithiophene chromophores are found in many current high-performance organic semiconductors, even though these materials are typically synthesized as an inseparable mixture of syn and anti isomers. Recent syntheses of pure syn anthradithiophenes have shown no improvement in performance for the more homogeneous system, but similar studies on the pure anti isomer have not been reported. In this work, a simple protocol is described to prepare the pure anti isomer of fluorinated, functionalized anthradithiophenes, and perform detailed analysis of the intermolecular interactions in the crystal that yield increased density and closer chromophore contacts. Studies of the charge-transport properties of these pure isomers, compared to the isomeric mixtures, suggest that the benefit of isomer purity is not consistent; in the syn case, there was minimal difference between the pure isomer and the mixture, while for the anti isomer mobility improved nearly twofold. Analysis of disorder in the crystals suggests a reason for this difference in performance. [ABSTRACT FROM AUTHOR]

The only crystals that could be grown from racemic solutions of the PF6− salt of the resolvable cation [Ru(2,9-dimethyl-1,10-phenanthroline)2(dipyrido[3,2- d:2′,3′- f]quinoxaline)]2+ have translational symmetry only (space group P1), contain nine independent sets of ions, and include numerous independent solvent molecules (11 acetone, one diethyl ether and possibly several water molecules). Layers of hydrophobic cations alternate with layers containing most of the anions and solvent molecules. All nine cations have the same basic conformation, which is distorted by the presence of the methyl substituents on the two 1,10-phenanthroline ligands. Four pairs of enantiomeric cations within a layer are related by approximate inversion centers; the ninth cation, which shows no sign of disorder, makes the layer chiral. Within the cation layers stripes parallel to [110] of six cations alternate with stripes of three; the local symmetry and the cation orientations are different in the two stripes. These stripes are reflected in the organization of the anion/solvent layer. The ca 80:20 inversion twinning found indicates that enantiomeric preference is transmitted less perfectly across the anion/solvent layer than within the cation layer. The structure is exceptional in having nine independent formula units and an unbalanced set (ratio 4:5) of resolvable enantiomers. The difficulty in growing crystals of this material is consistent with its structural complexity. [ABSTRACT FROM AUTHOR]

Crystals of 2-chloro-benzo-1,3,2-dithiarsole have a strongly modulated structure that can be solved and refined with relative ease in a P, Z′ = 17 approximate supercell but that is better described as incommensurate. Two conventional refinements (different superstructure approximations that differ in the placement of their crystallographic inversion centers) and a (3 + 1)-dimensional superspace refinement are all nearly equally successful, at least as measured by the usual agreement factors; the data integration, however, shows that the incommensurate description is preferable. The overall packing is determined by the stacking of the aromatic rings and probably by the segregation of As and Cl atoms to give short As...Cl contacts. A refinement of the average ( Z′ = 1) structure shows that there are two basic orientations of the C6S2 plane, but that those orientations must be correlated in several directions to avoid impossibly short intermolecular contacts. Along the modulation vector q the orientation of the C6S2 plane varies smoothly, but q is not a direction in which the molecules are in contact. Along the directions in which the molecules are in contact the orientation of the C6S2 plane alternates; there are also positional shifts. The single modulation q relieves packing problems in several different directions well enough that crystals that diffract well can be grown. [ABSTRACT FROM AUTHOR]

Abstract: A series of 2,6-diarylethynyl-9,10-dialkoxyanthracenes have been synthesized, characterized, and evaluated for their morphological and electro-optical properties. Compounds with 2′-naphthyl and 2′-anthracyl peripheral substituents were found to have poor solubility, and were not explored in detail. However, compounds bearing 9′-anthracyl peripheral substituents exhibited better solubility, and a series of these compounds containing straight-chain and branched substituents were prepared and analyzed. These compounds were found to undergo two oxidations at +0.57V and +0.76V relative to a Fc/Fc+ reference. The compounds exhibited absorption with a λ onset of 510nm. Based on this, the average solution-phase HOMO–LUMO energies of these compounds were estimated to be −5.37eV and −2.94eV, respectively. The compounds exhibited fluorescent behavior, with an emission maximum at 505nm. Hexoxy and Isobutoxy substituents were optimal for large crystal formation, and crystallographic studies on these two compounds show a herringbone-type arrangement with 1-dimensional pi-stacking. [Copyright &y& Elsevier]

A sequence of four phases has been found for an acetonitrile-solvated co-crystal with 15-crown-5 of the nickel complex [acetonitrilediaqua-κ1 O-nitrato-κ2 O-nitratonickel(II)]. The structure could be determined at intervals of ca 10 K in the range 90-273 K because crystals remain single through the three transitions. In phase (I) ( T≥ ca 240 K; P21/ m, Z′ = ½), there is extensive disorder, which is mostly resolved in phase (III) ( ca 230-145 K; P21/ c, Z′ = 1). Phase (IV) ( ca 145-90 K, and probably below; P, Z′ = 2) is ordered. Phase (II) ( ca 238-232 K) is modulated, but the satellite reflections are too weak to allow the structure to be determined within its stability range by standard methods. Most crystals that were flash-cooled from room temperature to 90 K have a metastable P21, Z′ = 5 superstructure that (at least in a commensurate approximation) was identified as similar to the structure of phase (II) by comparison of reconstructed reciprocal-lattice slices and by analogy with the phase behavior of the very similar compound [Ni(H2O)6](NO3)2·(15-crown-5)·2H2O [Siegler et al. (2011). Acta Cryst. B 67, 486-498]. In the phase (II) structure slab-like regions that are like the disordered phase (I) structure alternate with regions of similar shape and size that are like the more ordered phase (III) structure. [ABSTRACT FROM AUTHOR]

In the range 308-90 K single crystals of [Ni(H2O)6](NO3)2·(15-crown-5)·2H2O continue to diffract well as they undergo three phase transitions. Structures have been determined at 28 different temperatures; data were collected at six more but could not be refined satisfactorily. The transitions identified structurally are in good agreement with those found by thermal analysis. Phase I (above ca 292 K; I2/ m, Z = 2, Z′ = ¼) is disordered because the 15-crown-5 molecule is located on a 2/ m site. Phase II ( ca 292-248 K; P21/ m, Z = 2, Z′ = ½) is less disordered. Phase III ( ca 248-208 K; B21, Z = 28, Z′ = 7 in a commensurate approximation) is modulated with some regions resembling phase II and the rest resembling the fully ordered phase IV ( P21/ c, Z = 4, Z′ = 1) that is stable below ca 208 K. The modulated structure could be determined well because crystals flash-cooled to 90 K usually retain the phase III structure. The unusual phase III may be a consequence of the differing thermal contraction of two types of alternating layers, one composed of neutral 15-crown-5 molecules and the other composed of the cations, anions and lattice water molecules, which form a hydrogen-bonded network. The two kinds of layers are linked by Oether...H2Oaxial-Ni hydrogen bonds. [ABSTRACT FROM AUTHOR]

Abstract: Polychlorinated biphenyls (PCBs) are an important group of environmental pollutants that have been associated with adverse human health effects. Despite recent advances in their synthesis, the availability of PCB congeners in sufficient quantity and purity still represents one obstacle in the investigation of their biological effects. We report herein improved syntheses of PCB congeners (and their metabolites) containing two or more ortho-chlorine substituents. The Suzuki coupling reaction at 110 °C yielded PCB congeners with a 2,2′-substitution pattern in good yields (78–99%), but failed to give PCB congeners with 3 or 4 ortho chlorine substituents. Symmetrically substituted PCB congeners with multiple ortho chlorine substituents were obtained in 20–52% yields using a modified Ullmann coupling reaction. The yield of the coupling increased with increasing degree of chlorination of the starting material. The modified Ullmann coupling reaction employed much milder reaction conditions (copper–bronze/CuCl in N-methylpyrrolidinone, 110 °C) and, therefore, appears to be advantageous compared to the classical Ullmann coupling reaction (copper–bronze, no solvent, 230 °C). PCBs 136 and 155 prepared via the modified Ullmann coupling reaction were nitrated and reduced with Na2S2O4 to the corresponding amino-PCBs. Subsequently, the amino-PCBs were converted into sulfur-containing PCB metabolites or PCB 184 via the corresponding diazonium salt. These modified reaction conditions allow the synthesis of large quantities of pure, non-dioxin-like PCB congeners and their sulfur-containing metabolites for environmental and toxicological studies by overcoming problems associated with classical PCB synthesis strategies. [ABSTRACT FROM AUTHOR]

The crystal structure of PCB 77 (3,3′,4,4′-tetrachlorobiphenyl, C12H6Cl4), a dioxin-like PCB congener, is described. The dihedral angle of PCB 77 is 43.94(6)°, which is slightly larger than calculated or experimental dihedral angles of biphenyl derivatives in solution but smaller than experimental dihedral angles in the gas phase. [Copyright &y& Elsevier]

Abstract: The crystal structures for the glycal bolaamphiphiles, 1,12-bis-(2,3-α-d-erythro-hex-2-enopyranosyloxy)-dodecane (1) and 1,12-bis-(2,3-α-d-threo-hex-2-enopyranosyloxy)-dodecane (2), were determined by single-crystal X-ray analysis. The structure for 1 showed that the α:α and α:β diastereomers co-crystallized, with occupancy factors determining an isomeric ratio of 69:31. The pyranose rings for both structures are oriented away from each other and adopt a conventional glycal geometry. The head groups are nearly gauche to the hydrophobic chain, which adopts an all-trans zigzag conformation. Bolaamphiphile 1 packs in anti-parallel layers, while bolaamphiphile 2 displays a parallel arrangement of layers. Both structures display a three-dimensional hydrogen-bonding network involving the hydroxylic substituents on the head groups. The high similarity in large-scale solid state structures between 1 and glucosamide bolaamphiphile 3, and 2 and galactosamide bolaamphiphile 4 suggest a strong dependence on head group stereochemistry, and that only a few, key intermolecular interactions between head groups are necessary in controlling the ultimate structure observed. The solid state results may have implications for understanding the intermolecular forces directing nanoscale self-assembly in solution. [Copyright &y& Elsevier]

We compare the singlet fission dynamics of five pentacene derivatives precipitated to form nanoparticles. Two nanoparticle types were distinguished by differences in their solid-state order and kinetics of triplet formation. Nanoparticles that comprise primarily weakly coupled chromophores lack the bulk structural order of the single crystal and exhibit nonexponential triplet formation kinetics (Type I), while nanoparticles that comprise primarily more strongly coupled chromophores exhibit order resembling that of the bulk crystal and triplet formation kinetics associated with the intrinsic singlet fission rates (Type II). In the highly ordered nanoparticles, singlet fission occurs most rapidly. We relate the molecular packing arrangement derived from the crystal structure of the pentacene derivatives to their singlet fission dynamics and find that slip stacking leads to rapid, subpicosecond singlet fission. We present evidence that exciton delocalization, coincident with an increased relative admixture of charge-transfer configurations in the description of the exciton wave function, facilitates rapid triplet pair formation in the case of single-step singlet fission. We extend the study to include two hexacene derivatives and find that these conclusions are generally applicable. This work highlights acene derivatives as versatile singlet fission chromophores and shows how chemical functionalization affects both solid-state order and exciton interactions and how these attributes in turn affect the rate of singlet fission. [ABSTRACT FROM AUTHOR]

Abstract: Lower chlorinated polychlorinated biphenyls (PCBs) are readily metabolized via hydroxylated metabolites to reactive PCB quinones. Although these PCB metabolites elicit biochemical changes by mechanisms involving cellular target molecules, such as the aryl hydrocarbon receptor, and toxicity by interacting with enzymes like topoisomerases, only few PCB quinones have been synthesized and their conformational properties investigated. Similar to the parent compounds, knowledge of the three-dimensional structure of PCB quinones may therefore be important to assess their fate and risk. To address this gap in our knowledge, the gas phase molecular structure of a series of PCB quinones was predicted using HF/3-21G, B3LYP/6-31G∗∗ and UB3LYP/6-311G∗∗ calculations and compared to the respective solid state structure. All three methods overestimated the Cl–C bond length, but otherwise provided a reasonable approximation of the solid state bond angles and bond lengths. Overall, the UB3LYP/6-311G∗∗ level of theory yielded the best approximation of the molecular structure of PCB quinones in the solid state. Chlorine addition at the ortho position of both rings was found to increase the dihedral angle of the resulting quinone compound, which may have important implications for their interaction with cellular targets and, thus, their toxicity. [Copyright &y& Elsevier]

Highlights: [•] Chlorophenol sulfates were prepared via trichloroethyl-protected sulfate diesters. [•] Ammonium salts of chlorophenol sulfates are stable for several months at −20°C. [•] Crystal structure analysis confirmed molecular structure of selected sulfate esters. [ABSTRACT FROM AUTHOR]

Abstract: A new organic–inorganic hybrid compound, [Zn(bpy)3]1.5[H3W12O40Zn(bpy)2(H2O)]·0.5H2O (bpy=2,2′-bipyridine) has been synthesized hydrothermally from ZnCl2, Na6[H2W12O40], and 2,2′-bipyridine, and has been analyzed using X-ray crystallography, thermogravimetric analysis and UV–Vis spectroscopy. The compound contains an anionic complex [H3W12O40Zn(bpy)2(H2O)]3− in which α-metatungstate ion [H3W12O40]5− coordinated to a [Zn(bpy)2(H2O)]2+ unit through a bridging oxo group. [Copyright &y& Elsevier]

Approaches to control the self‐assembly of aromatic structures to enhance intermolecular electronic coupling are the key to the development of new electronic and photonic materials. Acenes in particular have proven simple to functionalize to induce strong π‐stacking interactions, although finer control of intermolecular π‐overlap has proven more difficult to accomplish. In this report, we describe how very weak hydrogen bonding interactions can exert profound impact on solid‐state order in solubilized pentacenes, inducing self‐assembly in either head‐to‐tail motifs with strong 2‐D π‐stacking, or head‐to‐head orientations with much weaker, 1‐D π‐stacking arrangements. In order to achieve 3‐D π‐stacking useful for photovoltaic applications, we elaborated a series of diethynyl pentacenes to their trimeric dehydro[18]annulene forms. These large, strongly interacting structures did indeed behave as acceptors in polymer photovoltaic devices. [ABSTRACT FROM AUTHOR]