Cs[Tf2N]: a second polymorph with a layered structure.
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ABSTRACT:
SUBMITTER: Stritzinger JT
PROVIDER: S-EPMC5946987 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:A second polymorph of the title compound, C21H16N4, is reported. The original polymorph was solved by our group [Matsumoto et al. (2003 ?). Tetra-hedron Lett. 44, 2861-2864] in the monoclinic space group C2/c and refined to R = 0.050. Now the crystal structure of a tetra-gonal polymorph (space group P-421 c) has been solved and refined to R = 0.036. In the crystal, there are no strong inter-molecular inter-actions. Reflecting the high symmetry of the mol-ecular structure, the asymmetric unit is a quarter of the mol-ecule, and the mol-ecule exhibits S4 symmetry along the c axis in the crystal.
| S-EPMC4257413 | biostudies-literature
Project description:Diosgenone [(20S,22R,25R)-spirost-4-en-3-one, C(27)H(40)O(3)] has been proposed as a new therapeutic alternative for the treatment of malaria. The first X-ray structure report for diosgenone was by Piro et al. [(2002). Z. Naturforsch. Teil C, 57, 947-950] in the space group P2(1) (Z' = 2). We now report a new polymorph in the same space group, with two mol-ecules in the asymmetric unit. Both mol-ecules have similar conformations, characterized by a skewed envelope A ring, which contains the C=C bond conjugated with the ketone functionality at C3. The dimorphism results from a modification of the relative orientation of the mol-ecules in the asymmetric unit: two independent mol-ecules were arranged anti-parallel in the Piro report, while they are parallel in the present determination.
| S-EPMC3414291 | biostudies-literature
Project description:The title compound, C13H16N10O5S (systematic name: 1-(4,6-di-meth-oxypyrimidin-2-yl)-3-{[1-methyl-4-(2-methyl-2H-tetra-zol-5-yl)pyrazol-5-yl]sulfonyl}urea), is a second triclinic polymorph of this crystal [for the other, see: Jeon et al., (2015 ?). Acta Cryst. E71, o470-o471]. There are two mol-ecules, A and B, in the asymmetric unit; the dihedral angles between the pyrazole ring and the tetra-zole and di-meth-oxy-pyrimidine ring planes are 72.84?(10) and 37.24?(14)°, respectively (mol-ecule A) and 84.38?(9) and 26.09?(15)°, respectively (mol-ecule B). Each mol-ecule features an intra-molecular N-H?N hydrogen bond. In the crystal, aromatic ?-? stacking inter-actions [centroid-centroid separations = 3.9871?(16), 3.4487?(14) and 3.5455?(16)?Å] link the mol-ecules into [001] chains. In addition, N-H?N, N-H?O, C-H?O and C-H?N hydrogen bonds occur, forming a three-dimensional architecture. We propose that the dimorphism results from differences in conformations and packing owing to different inter-molecular inter-actions, especially aromatic ?-? stacking.
| S-EPMC5050778 | biostudies-literature
Project description:The title compound, C(3)H(3)N(3)S(3), is a triclinic modification. The other reported modification crystallizes with just one mol-ecule in the asymmetric unit, [Guo et al. (2006 ▶). Cryst. Growth Des.6, 846-848] and was solved by power X-ray diffraction data. The present modification has Z' = 2. In the crystal, mol-ecules are linked by strong intra-molecular N-H⋯S hydrogen bonds with set graph-motif R(2) (2)(8). In both mol-ecules, all of the N atoms and two of the S atoms are involved in hydrogen bonding, with an average H⋯S distance of 2.58 Å and N-H⋯S angles in the range 163-167°. π-π stacking inter-actions are not observed. In the solid state, the mol-ecules exist in the thione form. The mol-ecular and supra-molecular properties are similar in both polymorphs.
| S-EPMC3007918 | biostudies-literature
Project description:The title mol-ecular salt, C6H8N(+)·C6H2N3O7 (-) (systematic name: 2-methyl-pyridinium 2,4,6-tri-nitro-phenolate), crystallizes with two cations and two anions in the asymmetric unit. In the crystal, the cations are linked to the anions via bifurcated N-H?(O,O) hydrogen bonds, generating R 1 (2)(6) graph-set motifs. Numerous C-H?O hydrogen bonds are observed between these cation-anion pairs, which result in a three-dimensional network. In addition, weak aromatic ?-? stacking between the 2-methyl-pyridinium rings [inter-centroid distance = 3.8334?(19)?Å] and very weak stacking [inter-centroid distance = 4.0281?(16)?Å] between inversion-related pairs of picrate anions is observed. The title salt is a second triclinic polymorph of the structure (also with Z' = 2) reported earlier [Anita et al. (2006). Acta Cryst. C62, o567-o570; Chan et al. (2014 ?). CrystEngComm, 16, 4508-4538]. In the title compound, the cations and anions display a chequerboard arrangement when viewed down [100], whereas in the first polymorph, (010) layers of alternating cations and anions are apparent in a [100] view. It is inter-esting that the unit-cell lengths are almost identical for the two polymorphs, although the inter-axial angles are quite different.
| S-EPMC4645006 | biostudies-other
Project description:The crystal structure of the title compound, C(17)H(28)O(5), reported here is a polymorph of the structure first reported by El-Feraly, Al-Yahya, Orabi, McPhail & McPhail [J. Nat. Prod. (1992). 55, 878-883]. It is a derivative of the anti-malaria compound artemisinin and consists primarily of three substituted ring systems fused together. A cyclo-hexane ring (distorted chair conformation) fused to a tetra-hydro-pyran group (distorted chair) is adjacent to an oxacyclo-heptane unit containing an endo-peroxide bridge, giving the mol-ecule its particular three-dimensional arrangement. The crystal packing is stabilized by inter-molecular C-H?O inter-actions between an O atom from the endo-peroxide bridge and H atoms from both the cyclo-hexane and seven-membered oxacyclo-heptane fused rings, as well as between an O atom and H atom from adjacent tetra-hydro-pyran rings. The two polymorphs have the same space group and similar cell parameters for the a and b axes, but significantly different values for the c axis.
| S-EPMC2960847 | biostudies-other
Project description:The title alkali propano-ates poly[(?5-propano-ato)alkali(I)], M +(C2H5COO)-, with alkali/M + = Na+, K+, Rb+ and Cs+, show close structural similarity, which is manifested by the coordination of the cations by six oxygen atoms in a chessboard motif, forming a bilayer. This bilayer is situated between hydro-phobic layers composed of dangling ethyl chains from the carboxyl-ate groups. Stacking of these two-dimensional sandwiches, which are parallel to (001), forms the title structures. Each metal cation is coordinated by six O atoms in the form of a distorted trigonal prism. One pair of these oxygen atoms belongs to a bridging, bidentately coordinating carboxyl-ate anion, while each of the other four oxygen atoms belongs to different carboxyl-ate groups, which are in a bridging monodentate mode. Despite the close similarity, each of the studied alkali propano-ates crystallizes in a different space group. The atoms are in general positions, except for the cation in K+(C2H5COO)-, which is situated on a mirror plane. Positional disorder of the methyl groups that are disordered over two positions is present in the Na+ and K+ propano-ates, in contrast to the Rb+ and Cs+ propano-ates. In the Na+ compound, the occupational parameters of the disordered methyl groups are different compared to the K+ compound where they are equal. This difference results in doubling of the a unit-cell parameter of the Na+ compound with respect to that of the K+ compound, otherwise the structures are homeotypic. In Cs+ propano-ate, a disorder of the methyl H atoms is observed.
| S-EPMC7472758 | biostudies-literature
Project description:The title compound, C(15)H(22)N(2)O(3), was obtained as a by-product of oxidative cleavage of 1,3-dicyclo-hexyl-(3-oxo-2,3-dihydro-benzofuran-2-yl)imidazolidine-2,4-dione. Herein, we report the crystal structure of a second polymorph, which was obtained by crystallization from an ethanol solution at 253?K, instead of slow evaporation of the same solvent at room temperature. While the first polymorph [Talhi et al. (2011). Acta Cryst. E67, o3243] crystallized in the non-centrosymmetric space group P2(1)2(1)2(1), this second polymorph crystallizes in the centrosymmetric space group P2(1)/n. Compared to the first polymorph, in the crystal no C=O?C=O inter-actions were found (C?O inter-molecular distance longer than 3.15?Å) and instead, close packing of individual mol-ecular units is mediated by C-H?? and weak C-H?O inter-actions.
| S-EPMC3515314 | biostudies-literature
Project description:A second monoclinic polymorph of methyl 4-hydroxy-benzoate, C(8)H(8)O(3), is reported. The unit-cell dimensions are different from those of the previously reported monoclinic form [Vujovic & Nassimbeni (2006 ?). Cryst. Growth Des.6, 1595-1597]. The asymmetric unit contains three crystallographically independent mol-ecules, as observed in the previous form. The crystal structure is stabilized by inter-molecular O-H?O and C-H?O hydrogen bonds and C-H?? inter-actions, which link the mol-ecules into a three-dimensional network.
| S-EPMC2961691 | biostudies-literature
Project description:The history of human settlement in Southeast Asia has been complex and involved several distinct dispersal events. Here we report the analyses of 1825 individuals from Southeast Asia including new genome-wide genotype data for 146 individuals from three Mainland Southeast Asian (Burmese, Malay and Vietnamese) and four Island Southeast Asian (Dusun, Filipino, Kankanaey and Murut) populations. While confirming the presence of previously recognized major ancestry components in the Southeast Asian population structure, we highlight the Kankanaey Igorots from the highlands of the Philippine Mountain Province as likely the closest living representatives of the source population that may have given rise to the Austronesian expansion. This conclusion rests on independent evidence from various analyses of autosomal data and uniparental markers.
2016-02-04 | GSE77508 | GEO