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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]

The article focuses on the phase transition between 190 and 200 K in [Ni(H2O)6](NO3)2·(15-crown-5)·H2O. It states that differential scanning calorimetry (DSC) was conducted to examine the compound's thermal behavior while packings' rotatable overlays were made to compare the transition. Results show that structural changes expand over a wide range of temperature while the transition temperature ranges near the upper end.

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]

The structures of [ M(H2O)2(15-crown-5)](NO3)2, M = Cu, Zn, Mg and Co, and 15-crown-5 = 1,4,7,10,13-pentaoxacyclopentadecane, have been redetermined at 294 and 90 K. The four structures, and a second form of the Cu structure, have been reported in the literature, but are all incorrect in some significant way. The structures, which all have at least two independent formula units ( i.e. Z′≥ 2), are related; each water ligand is hydrogen-bonded to two nitrate anions, while each nitrate anion is hydrogen bonded to the water ligands of two cations. In the tetragonal Co structure the hydrogen-bond pattern is three-dimensional; in the monoclinic Cu, Zn and Mg structures the hydrogen-bond patterns are two-dimensional. In the isostructural Zn and Mg structures Z′ = 3, while in the Cu structure Z′ = 5. The Cu, Zn and Mg structures are modulated variants of a basic structure, which was reported for Cu but which probably does not exist. The conformations of the 11 independent cations are remarkably similar; they all have approximate twofold symmetry and so exist as conformational enantiomers. The most important modulation is imperfect enantiomeric alternation of the cations along the longest cell axis; the independent cations are related by very good pseudotranslation and pseudoinversion operations. The diffraction patterns for all four structures have classes of weak, even very weak, reflections. [ABSTRACT FROM AUTHOR]

The structure of highly twinned pinacol (2,3-dimethyl-2,3-butanediol) monohydrate, the existence of which has been known since 1922, has been determined, and the structures of anhydrous pinacol and its two other known hydrates have been reinvestigated. All the phases are unusual. The anhydrous phase [Jeffrey & Robbins (1978). Acta Cryst. B 34, 3817–3820] is exceptional among molecular crystals in having molecules located on three different symmetry sites (1, and 2). A hexagonal form of pinacol originally described as a second polymorph [Dahlqvist & Sillanpää (2000). J. Mol. Struct. 524, 141–149] has been shown to be a solvate of uncertain composition that is very loosely packed. Pinacol hexahydrate, which was originally reported as tetragonal and highly disordered [Kim & Jeffrey (1970). J. Chem. Phys. 53, 3610–3615], appears to be described better as having an orthorhombic structure that is both disordered and twinned; the diffraction pattern at 90 K shows structured diffuse scattering that suggests short-range correlations of disordered molecules. The occurrence of this unusual set of structures is attributed to the combination of the hydrogen-bonding requirements of the pinacol molecule with its small size and limited conformational flexibility. [ABSTRACT FROM AUTHOR]

Dimers of the partially fluorinated amphiphile 1-(perfluorobutyl)undecanoic acid, CF3(CF2)3(CH2)10COOH, crystallize in the same basic packing arrangement found for many n-alkyl carboxylic acids. The unit cell of the fluorinated compound, however, contains five independent molecules rather than the one found for most n-alkyl carboxylic acids including CH3(CH2)13COOH. The structures of the two C15 acids are compared. The structural modulations that lead to the large value of Z′ can be understood as resulting from the conflict between the necessity of filling space densely and uniformly and the tendency of unlike groups to be segregated spatially. The few other known structures of compounds with both (CF2)n and (CH2)m regions show evidence of the same conflict. [ABSTRACT FROM AUTHOR]

The substantially disordered structure of 2-biphenylol [Perrin et al. (1987). Acta Cryst. C43, 980-982; Kapon & Reisner (1988). Acta Cryst. C44, 2039] has been reinvestigated as a function of temperature. The structure was determined at 305, 294, 145 and 90 K; crystals were taken to the lowest temperature both rapidly and slowly (0.1 K min-1). The results of the previous room-temperature study were confirmed and no important structural change was found down to 90 K. Comparisons with structures known for other simple 2- and 2,2'-substituted biphenyl derivatives suggest that the molecular stacks found for 2-biphenylol are probable for related molecules. The disorder in 2-biphenylol allows the formation of some O-H···O bonds, but packing efficiency is a more important factor in this structure than is hydrogen bonding. [ABSTRACT FROM AUTHOR]

Flash-cooled crystals of the /222 form of concanavalin. A undergo a sharp non-destructive non-reversible phase transition upon warming to between 160 and 165 K. characterized by an anomalous increase in unit-cell volume, The expansion is anisotropic and primarily affects the p and c axes. Three sets of 1.7 Å X-ray diffraction data were collected from one crystal: immediately after flash-cooling (130 K), after slow warming to 170 K and after re-cooling to 130 K. Measurable changes in reflection width after the transition were apparent. Each data set was collected under very similar conditions (aside from temperature). Structures refined against each data set using a powerful phase-bias reduction algorithm indicate negligible rearrangement of the protein molecule and its first hydration shell. Further away from the protein surface, on the edge of the fully disordered solvent regions, a small number of more dramatic changes were apparent. Little is known about the behaviour of water confined within dimensionally restricted spaces, but solvent cavities and channels in protein crystals provide a rich source of reproducible nanoscale water assemblies. This paper presents information on the behaviour of water continued within protein cavities in relation to the physics of protein crystal annealing. [ABSTRACT FROM AUTHOR]

Investigates the supramolecular aggregation in 4,4'-bipyridin-1,1'-ium dichloride and 4,4'-bipyridin-1,1'-ium dinitrate. Crystal structure; Hydrogen bonds; Molecular interactions.

Crystals of 4-chloro-2'-tiphenylol grown at 263 K and studied at both 293 and 142 K are loosely packed and contain OH…O bonded tetramers composed of four crystallographically independent molecules (Z' = 4). Approximate symmetry relationships between independent molecules are apparent in many, perhaps even most, structures with Z' > 1, but are not obvious in this structure. The inefficient crystal packing, the surprisingly large value of Z' and the absence of pseudosymmetry reflect the difficulty of finding a dense molecular arrangement that also allows for hydrogen-bond formation. Impediments to good packing are the steric congestion around the ortho hydroxyl groups and the difficulty in filling space with significantly twisted biphenyl fragments. The packing arrangement adopted is strongly reminiscent of the structure type found for eight simple 44'-biphenyl derivatives, but one of the four independent 4'-chloro-2-biphenylol molecules has an orientation that is significantly different from the orientations of the other three and that does not fit the 4,4'-XPhPhY pattern. It is suggested that molecules that crystallize with Z'> 1 are good candidates for solid-state compound formation. [ABSTRACT FROM AUTHOR]

Treatment of 1-chloro-6-iodohexane or 1-chloro-10-iododecane with lithium tris(pyrazolyl)methanide, followed by potassium thioacetate, affords bifunctional 1-S(acetyl)-tris(pyrazolyl)alkanes (L) (pz)3C-(CH2)nSAc (n = 6, 1; 10, 2). Magnetic studies of {[(pzTp)FIII-(CN)3]4[NiIIL]4[OTf]4}•solvent (4, L = 1; 5, L = 2) boxes suggest that -(CH2)6 chains (4) limit intermolecular interactions while -(CH2)10 chains in 5 introduce crystallographic disorder and a distribution of relaxation times; 4 and 5 exhibit slow relaxation of the magnetization. [ABSTRACT FROM AUTHOR]

Crystals of the title compound, which is also commonly known as 6- O-acetyl­codeine, C20H23NO4, were obtained by acetyl­ation of codeine and subsequent crystallization of the product from eth­yl acetate. The atoms of the benzene ring are nearly coplanar, whereas the five-memberedring is distorted. The ethanamine ring has a typical chair form conformation, while the cyclohexene ring is in a twisted boat form. [ABSTRACT FROM AUTHOR]

The title compounds, C22H20N2O3S, (I), and C22H22N2O3S, (II), crystallize in space groups P1 and P212121, respectively. The indole rings are planar and the benzene ring of the phenylsulfonyl group makes a dihedral angle with the mean plane of the indole ring of 90.2 (2)° in (I) and 94.0 (2)° in (II). In both molecules, the double bond connecting the aza-bicyclic and indole moieties has a Z geometry. Compound (II) was obtained as an enantiomerically pure crystal and has the 3S configuration. [ABSTRACT FROM AUTHOR]

The dihedral angle between the benzene rings in the title compound, C13H10Cl2O1, is 59.92 (9)°. [ABSTRACT FROM AUTHOR]

The crystal structure of the title compound, C15H17NO2, contains two nearly identical but crystallographically independent mol­ecules, each with a double bond connecting an aza­bicyclic ring system to a 3-methoxy­benzyl­idene moiety. The space group is triclinic P . The benzene ring is twisted by 18.44 (5) and 22.35 (4)° with respect to the plane of the double bond connected to the azabicyclic ring system for the two mol­ecules. In addition to C—H⋯π inter­actions, mol­ecules are held together in the solid state by van der Waals inter­actions. [ABSTRACT FROM AUTHOR]

Crystals of the title compound, C15H16N2S, were obtained from the reaction of benzo­[ b]­thio­phene-3-aceto­nitrile with mechloreth­amine and subsequent crystallization of the product from hexane.. [ABSTRACT FROM AUTHOR]

The title compound, C22H29NO3, was obtained by the reaction of benzylamine with parthenolide. X-ray crystal structure determination revealed that the configuration of the new chiral center at C11 is R, establishing the stereospecificity of the amination reaction. [ABSTRACT FROM AUTHOR]

The asymmetric unit of the racemic form of the title compound, C12H15NOS, contains four crystallographically independent molecules. The olefinic bond connecting the 2-thienyl and 1-azabicyclo[2.2.2]octan-3-ol moieties has Z geometry. Strong hydrogen bonding occurs in a directed co-operative O—H...O—H...O—H...O—H R44(8) pattern that influences the conformation of the molecules. Co-operative C—H...π interactions between thienyl rings are also present. The average dihedral angle between adjacent thienyl rings is 87.09 (4)°. [ABSTRACT FROM AUTHOR]

The molecule of the title compound, [Sn(C6H2Cl3)4], occupies a general position in the crystal structure, but shows an approximate molecular symmetry. [ABSTRACT FROM AUTHOR]

In crystals of the title compound, C23H23N5O3S, the indole system is planar and the phenyl ring of the phenylsulfonyl group makes a dihedral angle with the best plane of the indole system of 77.18 (4)°. The olefinic bond connecting the aza­bicyclic and indole systems has Z geometry. The geometry adopted by the C=O bond with respect to the N—N bond is trans. The O atom of the carbonyl group of each mol­ecule is hydrogen bonded to the hydrazidic H atom of an adjacent mol­ecule to form an eight-membered-ring dimeric structure. [ABSTRACT FROM AUTHOR]

The crystal structure of 2-meth­oxy-3-nitro­phenol, C7H7NO4, is stabilized by hydrogen bonds and π–π stacking inter­actions. [ABSTRACT FROM AUTHOR]

Presents a correction to the paper "Two fluoradene derivatives: pseudosymmetry, eccentric ellipsoids and a phase transition," by Aibing Xia, John P. Selegue and others, published in a 2001 issue of the periodical "Acta Crystallographica."

Carboxylicacid–acid hydrogen-bonding dimer and acid–pyridinehydrogen-bonding motif are two competing supramolecular synthons thata molecule possessing both carboxylic acid and pyridine functionalgroups could form in the solid state. Their coexistence has been observedbut for the molecules with the molar ratio of carboxylic acid andpyridine groups being greater than 1:1. In this crystal engineeringstudy, 2-[phenyl(propyl)amino]nicotinic acid with a 1:1 molar ratioof these two functional groups was discovered to have two polymorphs,in which one consists of unique hydrogen-bonded tetramer units bearingboth acid–acid and acid–pyridine hydrogen-bonding motifs,while the other is composed of acid–pyridine hydrogen-bondedchains. Quantum mechanical calculations were employed to unravel theessence of the coexistence of the two vying counterparts as well asthe origins of the tetramer and chain structures. [ABSTRACT FROM AUTHOR]

Abstract: The combination of various dithiols and AsX3 (X=F, Cl) produces the series of cyclized halo-arsenic dithiolate compounds: 2-chloro-1,3,2-dithiarsolane [AsCl(SCH2CH2S)] (1), 2-iodo-1,3,2-dithiarsolane [AsI(SCH2CH2S)] (2), 2-chloro-1,3,2-dithiarsenane [AsCl(SCH2CH2CH2S)] (3), 2-iodo-1,3,2-dithiarsenane [AsI(SCH2CH2CH2S)] (4), 3-chloro-4H,7H-5,6-benz-1,3,2-dithiarsepine [AsCl(SCH2)2(C6H4)] (5), 1,2-bis-dithiarsolan-2-ylmercapto-ethane [As2(SCH2CH2S)2(SCH2CH2S)] (6) and tris-(pentafluorophenylthio)-arsen [As(SC6F5)3] (7). The geometry around As for these compounds is best described as trigonal pyramidal with varying degrees of distortion. Compound 1 crystallizes in two polymorphic forms with similar structural parameters. The compounds have been characterized by IR, 1H, 19F, and 13C NMR, X-ray crystallography and GC–MS. [Copyright &y& Elsevier]

Crystals of the title compound, C15H15NO3, were obtained from a condensation reaction of piperonal with 1-aza­bicyclo­[2.2.2]octan-3-one and subsequent crystallization of the product from ethyl acetate. The geometry about the C=C double bond connecting the 1,3-benzodioxole moiety to the aza­bicylic ring system is Z. [ABSTRACT FROM AUTHOR]

The title compound {systematic name: (1 R,2 R,5 R)-(+)-2-hydr­oxy-2,6,6-trimethyl-3-[(3-pyrid­yl)methyl­imino]­bicyclo[3.1.1]­heptane}, C16H22N2O, was obtained by the condensation reaction of (1 R,2 R,5 R)-(+)-2α-hydroxy­pinan-3-one with 3-(amino­meth­yl)pyridine in the presence of boron trifluoride. The compound was obtained as an enantiomerically pure isomer, and has the 1 R,2 R,5 R configuration. In the crystal structure, mol­ecules are linked together by inter­molecular O—H⋯N hydrogen bonds between the hydr­oxy group of the pinanone group and the N atom of the pyridine ring, forming mol­ecular chains. [ABSTRACT FROM AUTHOR]

The title compound, C15H17NO, has been synthesized by base-catalyzed condensation of 2-methyl­benzaldehyde with 1-aza­bicyclo­[2.2.2]octan-3-one and crystallization of the product with ethyl acetate. The geometry around the C=C bond is Z. [ABSTRACT FROM AUTHOR]

The title compound, C15H17NO, was synthesized by base-catalyzed condensation of 4-methyl­benzaldehyde with 1-aza­bicyclo­[2.2.2]octan-3-one and crystallization of the product from ethyl acetate. The geometry of the C=C bond is Z. [ABSTRACT FROM AUTHOR]

Crystals of the title compound, C12H13NOS, were prepared by base-catalyzed reaction of thio­phene-2-carboxaldehyde with 1-aza­bicyclo­[2.2.2]octan-3-one and subsequent crystallization of the product from ethyl acetate. The olefinic bond connecting the 2-thienyl and 1-aza­bicyclo­[2.2.2]octan-3-one moieties has Z geometry. No thienyl ring flip is observed. [ABSTRACT FROM AUTHOR]