Errors in the elemental analysis results in the paper by Liu et al. [ Acta Cryst. (2013), C 69 , 1488–1493] are corrected.
First-principles calculations show that strain-induced topological phase transition is auniversalphenomenon in those narrow-gap semiconductors for which the valence band maximum (VBM) and conduction band minimum (CBM) have different parities. The transition originates from the opposite responses of the VBM and CBM, whose magnitudes depend critically on the direction of the applied strain. Our work suggests that strain can play a unique role in tuning the electronic properties of topological insulators for device applications, as well as in the achievement of new topological insulators.
The molecules in (E)-N-(3,4,5-trimethoxybenzylidene)naphthalen-1-amine, C20H19NO3, (I), and its reduction product N-(3,4,5-trimethoxybenzyl)naphthalen-1-amine, C20H21NO3, (II), are both conformationally chiral, but (I) crystallizes in a centrosymmetric space group, while (II) crystallizes with just one conformational enantiomer in each crystal. A combination of two C-H···O hydrogen bonds links the molecules of (I) into sheets containing a single type of R(6)(6)(44) ring, and these sheets are linked into a continuous three-dimensional array by a single π-π stacking interaction. The molecules of (II) are linked into complex sheets by a combination of N-H···O, C-H···O and C-H···π(arene) hydrogen bonds.
A new inorganic-organic hybrid zinc phosphite, [Zn(HPO3)(C6H11NO2)](n), has been synthesized hydrothermally. Protonated piperidin-1-ium-4-carboxylate (PDCA) was generated in situ by hydrolysis of the piperidine-4-carboxamide precursor. The P atom possesses a typical PO3H pseudo-pyramidal geometry. The crystal structure features an unusual (3,4)-connected two-dimensional inorganic zinc-phosphite layer, with organic PDCA ligands appended to the sheets and protruding into the interlayer region. Helical chains of opposite chirality are involved in the construction of a puckered sheet structure.
The X-ray powder diffraction pattern that corresponds to the disordered state of kalsilite (potassium aluminium orthosilicate), KAlSiO4, is investigated. The directionality of (Al,Si)O-4 tetrahedra within single six-membered tetrahedral ring building units (S6R) could not be defined. With equal probability for the directionality of each tetrahedra within one S6R [free apex pointing up (U) or down (D)], an undefined sequence of U and D directionalities is needed to describe the S6R building units. The extinction conditions of disordered kalsilite are also different compared to ordered kalsilite within the space group P6(3). In disordered kalsilite, h0l and hhl reflections with l = 2n + 1 are systematically absent.
Different salts of the 2-phenyl-1,10-phenanthrolin-1-ium cation, (pnpH)(+), are obtained by reacting 2-phenyl-1,10-phenanthroline (pnp), C18H12N2, (I), with a variety of anions, such as hexafluoridophosphate, C18H13N2(+)·PF6(-), (II), trifluoromethanesulfonate, C18H13N2(+)·CF3SO3(-), (III), tetrachloridoaurate, (C18H13N2)[AuCl4], (IV), and bromide (as the dihydrate), C18H13N2(+)·Br(-)·2H2O, (V). Compound (I) crystallizes with Z' = 2, with both independent molecules adopting a coplanar conformation. In (II)-(IV), a hydrogen bond exists between the cation and anion, while one of the lattice water molecules serves as a hydrogen-bonded bridge between the cation and anion in (V). Reaction of (I) with HAuCl4 gives the salt complex (IV); however, reaction with KAuCl4 produces the monodentate complex trichlorido(2-phenyl-1,10-phenanthroline-κN(10))gold(III), [AuCl3(C18H12N2)], (VI). Dichlorido(2-phenyl-1,10-phenanthroline-κ(2)N,N')copper(II), [CuCl2(C18H12N2)], (VII), results from the reaction of CuCl2·2H2O and (I), in which the Cu(II) center adopts a tetrahedrally distorted square-planar geometry. The pendent phenyl ring twists to a bisecting position relative to the phenanthroline plane. The square-planar Pd(II) complex, bromido[2-(phenanthrolin-2-yl)phenyl-κ(3)C(1),N,N']palladium(II), [PdBr(C18H11N2)], (VIII), is obtained from the reaction of (I) with [PdCl2(cycloocta-1,5-diene)], followed by addition of bromine. A coplanar geometry for the pendent ring is adopted as a result of the tridentate bonding motif.
The title bimolecular structure, [Cu4Cl6O(C4H8O)3(H2O)]2[Cu4Cl6O(C4H8O)4]·4C4H8O, at 100 K has monoclinic (P21/c) symmetry. The structure contains nine symmetry-independent molecules expressed in simplest molecular form as 6[Cu4Cl6O(C4H8O)3(H2O)·2(C4H8O)]:3Cu4Cl6O(C4H8O)4. The compound exhibits a supercell (smaller than the unit cell based on weak reflections) structure due to pseudotranslational symmetry. The structure displays O—H...O hydrogen bonding between bound water ligands and tetrahydrofuran (THF) solvent molecules. The structure exhibits disorder for 12 of the THF molecules, of which seven are ligated to Cu and five are hydrogen bonded to H2O ligands.
In the title salt, C14H18N2(2+) · 2C9H5N4O(-), the 1,1'-diethyl-4,4'-bipyridine-1,1'-diium dication lies across a centre of inversion in the space group P21/c. In the 1,1,3,3-tetracyano-2-ethoxypropenide anion, the two independent -C(CN)2 units are rotated, in conrotatory fashion, out of the plane of the central propenide unit, making dihedral angles with the central unit of 16.0(2) and 23.0(2)°. The ionic components are linked by C-H...N hydrogen bonds to form a complex sheet structure, within which each cation acts as a sixfold donor of hydrogen bonds and each anion acts as a threefold acceptor of hydrogen bonds.
The title compound, [Ag(C15H11N4O2S)]n, was synthesized by the reaction of 4-{[(1-phenyl-1H-tetrazol-5-yl)sulfanyl]methyl}benzoic acid (Hptmba) with silver nitrate and triethylamine at room temperature. The asymmetric unit contains one crystallographically independent Ag(I) cation and one ptmba(-) ligand. Each Ag(I) cation is tricoordinated by two carboxylate O atoms and one tetrazole N atom from three different ptmba(-) ligands, displaying a distorted T-shaped geometry. Three Ag(I) cations are linked by tris-monodentate bridging ptmba(-) ligands to form a one-dimensional double chain along the c axis, which is further consolidated by an intrachain π-π contact with an offset face-to-face distance of 4.176 (3) Å between the centroids of two adjacent aromatic rings in neighbouring benzoate groups. The one-dimensional chains are linked into a three-dimensional supramolecular framework by additional π-π interchain interactions, viz. of 3.753 (3) Å between two phenyl substituents of the tetrazole rings and of 4.326 (2) Å between a benzoate ring and a tetrazole ring. Thermogravimetric analysis and the fluorescence spectrum of the title compound reveal its good thermal stability and a strong green luminescence at room temperature.
A novel neutral polymer, {[Co2(C7H3NO4)2(H2O)4]·2H2O}n, was hydrothermally synthesized using pyridine-2,5-dicarboxylate (2,5-PDC(2-)) as the organic linker. It features a two-dimensional layer structure constructed from one-dimensional {[Co(2,5-PDC)2](2-)}n chains interlinked by [Co(H2O)4](+) units. The two Co(II) cations occupy special positions, sitting on inversion centres. Each 2,5-PDC(2-) anion chelates to one Co(II) cation via the pyridine N atom and an O atom of the adjacent carboxylate group, and links to two other Co(II) cations in a bridging mode via the O atoms of the other carboxylate group. In this way, the 2,5-PDC(2-) ligand connects three neighbouring Co(II) centres to form a two-dimensional network. The two-dimensional undulating layers are linked by extensive hydrogen bonds to form a three-dimensional supramolecular structure, with the uncoordinated solvent molecules occupying the interlamellar region.
The structures of ammonium 3,5-dinitrobenzoate, NH4+·C7H3N2O6−, (I), ammonium 4-nitrobenzoate dihydrate, NH4+·C7H4NO4−·2H2O, (II), and ammonium 2,4-dichlorobenzoate hemihydrate, NH4+·C7H3Cl2O2−·0.5H2O, (III), have been determined and their hydrogen-bonded structures are described. All three salts form hydrogen-bonded polymeric structures,viz.three-dimensional in (I) and two-dimensional in (II) and (III). With (I), a primary cation–anion cyclic association is formed [graph setR43(10)] through N—H...O hydrogen bonds, involving a carboxylate group with both O atoms contributing to the hydrogen bonds (denoted O,O′-carboxylate) on one side and a carboxylate group with one O atom involved in two hydrogen bonds (denoted O-carboxylate) on the other. Structure extension involves N—H...O hydrogen bonds to both carboxylate and nitro O-atom acceptors. With structure (II), the primary inter-species interactions and structure extension into layers lying parallel to (001) are through conjoined cyclic hydrogen-bonding motifs,viz.R43(10) (one cation, an O,O′-carboxylate group and two water molecules) and centrosymmetricR42(8) (two cations and two water molecules). The structure of (III) also has conjoinedR43(10) and centrosymmetricR42(8) motifs in the layered structure but these differ in that the first motif involves one cation, an O,O′-carboxylate group, an O-carboxylate group and one water molecule, and the second motif involves two cations and two O-carboxylate groups. The layers lie parallel to (100). The structures of salt hydrates (II) and (III), displaying two-dimensional layered arrays through conjoined hydrogen-bonded nets, provide further illustration of a previously indicated trend among ammonium salts of carboxylic acids, but the anhydrous three-dimensional structure of (I) is inconsistent with that trend.
The crystal structure of a polymorph of 4-aminobenzoic acid (PABA), C 7 H 7 NO 2 , at 100 K is noncentrosymmetric, as opposed to centrosymmetric in the structures of the other known polymorphs. The two crystallographically independent PABA molecules form pseudocentrosymmetric O—H...O hydrogen-bonded dimers that are further linked by N—H...O hydrogen bonds into a three-dimensional network. The benzene rings stack in the b direction. The CO 2 moieties are bent out slightly from the benzene ring plane.
In the structure of (6 R *,11 R *)-5-acetyl-11-ethyl-6,11-dihydro-5 H -dibenzo[ b , e ]azepine-6-carboxylic acid, C 19 H 19 NO 3 , (I), the molecules are linked into sheets by a combination of O—H...O and C—H...O hydrogen bonds; in the structure of the monomethyl analogue (6 RS ,11 SR )-5-acetyl-11-ethyl-2-methyl-6,11-dihydro-5 H -dibenzo[ b , e ]azepine-6-carboxylic acid, C 20 H 21 NO 3 , (II), the molecules are linked into simple C (7) chains by O—H...O hydrogen bonds; and in the structure of the dimethyl analogue (6 RS ,11 SR )-5-acetyl-11-ethyl-1,3-dimethyl-6,11-dihydro-5 H -dibenzo[ b , e ]azepine-6-carboxylic acid, C 21 H 23 NO 3 , (III), a combination of O—H...O, C—H...O and C—H...π(arene) hydrogen bonds links the molecules into a three-dimensional framework structure. None of these structures exhibits the R 2 2 (8) dimer motif characteristic of simple carboxylic acids.
(1E,4E)-1,5-Bis(2,6-difluorophenyl)penta-1,4-dien-3-one, C17H10F4O, (I), dimerizes under sunlight in chloroform solution to form the corresponding cyclobutane derivative, (2E,2'E)-1,1'-[2,4-bis(2,6-difluorophenyl)cyclobutane-1,3-diyl]bis[3-(2,6-difluorophenyl)prop-2-en-1-one], C34H20F8O2, (II). The crystal structure of (I) explains why no topochemical dimerization can occur in the solid state. In the solid, molecules of dimer (II) show the `truxillic acid'-type arrangement of crystallographic centres of inversion, with half a molecule per asymmetric unit and cell dimensions closely related to those of the monomer. Intermolecular interactions in both solids are dominated by C-H···O and C-H···F contacts and also comprise interactions with aromatic systems (C-H···π and π-π).
In poly[[μ2-1,2-bis(pyridin-4-yl)ethene-κ2N:N′][μ2-2,2′-(diazenediyl)dibenzoato-κ3O,O′:O′′]cadmium(II)], [Cd(C14H8N2O4)(C12H10N2)]n, the asymmetric unit contains one CdIIcation, one 2,2′-(diazenediyl)dibenzoate anion (denotedL2−) and one 1,2-bis(pyridin-4-yl)ethene ligand (denoted bpe). Each CdIIcentre is six-coordinated by four O atoms of bridging/chelating carboxylate groups from threeL2−ligands and by two N atoms from two bpe ligands, forming a distorted octahedron. The CdIIcations are bridged byL2−and bpe ligands to give a two-dimensional (4,4) layer. The layers are interlinked through bridging carboxylate O atoms fromL2−ligands, generating a two-dimensional bilayered structure with a 3641362topology. The bilayered structures are further extended to form a three-dimensional supramolecular architectureviaa combination of hydrogen-bonding and aromatic stacking interactions.
The crystal structure of the tetranuclear organotin compound 1,1,3,3,5,5,7,7-octabutyl-7-((E)-2-cyano-3-{9-[2-(2-methoxyethoxy)ethyl]-9H-carbazol-3-yl}prop-2-enoyloxy)-4,8-dimethyl-2,4,6,8-tetroxa-1,3,5,7-tetrastannatricyclo[4.2.0.02,5]oct-3-yl (E)-2-cyano-3-{9-[2-(2-methoxyethoxy)ethyl]-9H-carbazol-3-yl}prop-2-enoate, [Sn4(C4H9)8(C21H19N2O4)2(CH3O)2(μ3-O)2], consists of a core of three fused Sn2O2rings. The central ring consists of two Sn atoms each coordinated by twon-butyl chains, two μ3-bridging O atoms and one μ2-bridging methanolate O atom. The peripheral Sn2O2rings consist of one of the central ring Sn atoms, and an Sn coordinated by one μ3-bridging O atom, one μ2-bridging methanolate O atom, twon-butyl chains and the carboxylate O atom of a (E)-2-cyano-3-{9-[2-(2-methoxyethoxy)ethyl]-9H-carbazol-3-yl}prop-2-enoate ligand (L). Despite an apparent centrosymmetric nature, the complex does not crystallize about an inversion centre. The structure packs with π–π interactions between carbazole moieties on adjacent molecules.
The reaction between 5-chloro-3-methyl-1-phenyl-1H-pyrazole-4-carbaldehyde and phenylhydrazine proceeds via condensation to provide the title compound, C17H15ClN4, (I), rather than via the alternative routes of simple nucleophilic substitution or cyclocondensation. With the exception of the phenyl group bonded directly to the pyrazole ring, the non-H atoms of (I) are nearly coplanar, with an r.m.s. deviation of 0.058 Å. The molecules are linked into C(7) chains by a single N-H···N hydrogen bond, and the chains are linked by π-π stacking interactions to form sheets.
The structures of two anhydrous salt phases of theophylline, namely 1,3-dimethyl-2,6-dioxo-7H-purin-9-ium tetrafluoroborate, C7H9N4O2(+)·BF4(-), and 1,3-dimethyl-2,6-dioxo-7H-purin-9-ium chloride, C7H9N4O2(+)·Cl(-), are reported together with the structures of two monohydrate salt forms, namely 1,3-dimethyl-2,6-dioxo-7H-purin-9-ium chloride monohydrate, C7H9N4O2(+)·Cl(-)·H2O, and 1,3-dimethyl-2,6-dioxo-7H-purin-9-ium bromide monohydrate, C7H9N4O2(+)·Br(-)·H2O. The monohydrate structures are mutually isostructural, with the cations and anions lying on crystallographic mirror planes (Z' = ½). The main intermolecular interaction motif is a hydrogen-bonding network in the same mirror plane. The tetrafluoroborate structure is based on planar hydrogen-bonded theopylline cation dimers; the anions interact with the dimers in a pendant fashion. The anhydrous chloride structure has Z' = 2 and in contrast to the other species it does not form planar hydrogen-bonded constructs, instead one-dimensional chains of cations and anions propagate parallel to the crystallographic c direction. An earlier report claiming to describe an anhydrous structure of theophylline hydrochloride is re-examined in light of these results. It is concluded that the earlier structure has been reported in the wrong space group and that it has been chemically misidentified.
The title complex, 2C12H24N+·C6H3Cl2O−·C6H2Cl3O−·C6H4Cl2O, consists of three different achiral components, dicyclohexylammonium cations, 2,4,6-trichlorophenolate anions and H-atom-bridged 2,4-dichlorophenolate/2,4-dichlorophenol units, held together by O—H...N and O—H...O hydrogen bonds to form a chiral hydrogen-bonded ring. A helical cylinder is established by the packing of these rings along a crystallographic 41screw axes. Helical cylinders may be generated from each other by translation, resulting in the formation of the chiral crystal. Neighbouring parallel helical cylinders are associated by van der Waals interactions only.
