Two-dimensional Infinite Layers Research Articles

Two-dimensional dysprosium(III) coordination polymer: Structure, single-molecule magnetic behavior, proton conduction, and luminescence.

A new dysprosium (III) coordination polymer [Dy(Hm-dobdc) (H2O)2]·H2O (Dy-CP), was hydrothermal synthesized based on 4,6-dioxido-1,3-benzenedicarboxylate (H4m-dobdc) ligand containing carboxyl and phenolic hydroxyl groups. The Dy(III) center adopts an octa-coordinated [DyO8] geometry, which can be described as a twisted square antiprism (D 4d symmetry). Neighboring Dy(III) ions are interconnected by deprotonated Hm-dobdc3− ligand to form the two-dimensional infinite layers, which are further linked to generate three-dimensional structure through abundant hydrogen bonds mediated primarily by coordinated and lattice H2O molecules. Magnetic studies demonstrates that Dy-CP shows the field-induced slow relaxation of magnetization and the energy barrier U eff/k B and relaxation time τ 0 are 35.3 K and 1.31 × 10–6 s, respectively. Following the vehicular mechanism, Dy-CP displays proton conductivity with σ equal to 7.77 × 10–8 S cm−1 at 353 K and 30%RH. Moreover, luminescence spectra reveal that H4m-dobdc can sensitize characteristic luminescence of Dy(III) ion. Herein, good magnetism, proton conduction, and luminescence are simultaneously achieved, and thus, Dy-CP is a potential multifunctional coordination polymer material.

Singular Limit in Hopf Bifurcation for Doubly Diffusive Convection Equations I: Linearized Analysis at Criticality

A singularly perturbed system for doubly diffusive convection equations, called the artificial compressible system, is considered on a two-dimensional infinite layer for a parameters range where the Hopf bifurcation occurs in the corresponding incompressible system. The spectrum of the linearized operator in a time periodic function space is investigated in detail near the bifurcation point when the singular perturbation parameter is small. The results of this paper are the basis of the study of the nonlinear Hopf bifurcation problem and the singular limit of the time periodic bifurcating solutions.

2-Chlorobenzene-1,4-diaminium bis(dihydrogenphosphate)

The asymmetric unit of the title salt, C6H9ClN2 2+·2H2PO4 −, contains two dihydrogenphosphate anions and one 2-chloro­benzene-1,4-diaminium dication. The H2PO4 − anions are inter­connected through strong O—H⋯O hydrogen bonds to form two-dimensional infinite layers parallel to (001). The organic entities are anchored to the inorganic layers through N—H⋯O hydrogen bonds, and through weak C—Cl⋯O halogen bonds [3.159 (2) Å, 140.48 (7)°]. No π–π stacking inter­actions between neighboring aromatic rings or C—H⋯π inter­actions towards them are observed. Minor disorder is observed for the Cl atom and one hy­droxy group [minor-component occupancy = 3.29 (9)%].

The First Ammoniates of Alkali Metal Fluorides: Cesium Fluoride Ammonia (3/4) [Cs3F3(NH3)4] and Ammonium Cesium Difluoride [NH4CsF2

Two new compounds containing cesium fluoride have been obtained as side-products from the reactions of Cs2CuF6 and Cs2KDyF6 with liquid ammonia. Cs2CuF6 reacts with the solvent forming a still unknown blue substance and the colorless ammoniate Cs3F3(NH3)4 which crystallizes in the cubic space group I 4̄3d (no. 220) with a = 10.273(1) Å and V = 1084.3(2) Å3 at 123 K with Z = 4. Its crystal structure is isopointal to Y3Au3Sb4 and shows an infinite three-dimensional network made up through N-H· · ·F hydrogen bonds. Ammonium cesium difluoride NH4CsF2 crystallizes in the orthorhombic space group Pnma (no. 62) with a = 7.1791(1), b = 4.1244(1), c = 13.6417(2) Å and V = 403.92(1) Å3 at 123 K with Z = 4. The crystal structure displays two-dimensional infinite layers of the composition 2 ∞[(NH4F2)−] with embedded Cs+ ions. Analogous to the structure of the compound Cs3F3(NH3)4, the structural motif is formed through strong N-H· · ·F hydrogen bonds, which seem to be the guiding force. To the best of our knowledge, the title compounds are the first reported ammoniates of alkali metal fluorides.

Synthesis, crystal structure, and luminescence properties of a novel 2D cobalt(II) polymer with 1-naphthalene acetate

The coordination compound [Co(H2O)2(C12H9O2)2]n (I) was prepared by the reaction of 1-naphthaleneacetic acid and cobalt(II) acetate in a basic medium and was fully characterized by X-ray diffraction, elemental analysis, FT-IR, TG, and luminescence spectra. In the complex, the six-coordinated Co(II) ions are linked into a two-dimensional infinite layer with hydrophobic exterior by 1-naphthaleneacetate anions. At room temperature solid complex I exhibits favorable fluorescent emission resulted from the intraligand electronic transfer.

Ein neues Selten-Erd-Metall(III)-Oxidchlorid-Oxotellurat(IV): Nd5O4Cl3[TeO3]2 / A New Rare Earth-Metal(III) Oxide Chloride Oxotellurate(IV): Nd5O4Cl3[TeO3]2

Pale violet, plate-like single crystals of the title compound, neodymium(III) oxide chloride oxotellurate( IV) Nd5O4Cl3[TeO3]2, can be obtained by the reaction of Nd2O3 with NdCl3 and TeO2 in equimolar ratios in evacuated silica ampoules within five days at 775 °C with an excess of CsCl added as fluxing agent. Nd5O4Cl3[TeO3]2 crystallizes in the monoclinic space group C2/m (no. 12) with the lattice parameters a = 1270.61(9), b = 562.70(4), c = 1008.97(8) pm, β = 90.784(3)°and Z = 2, and is thus isostructural to the lanthanoid(III) oxide halide oxoselenates(IV) Tb5O4Cl3[SeO3]2 and Gd5O4Br3[SeO3]2. The crystal structure exhibits three crystallographically different Nd3+ cations, of which (Nd1)3+ has a purely oxidic coordination sphere of eight oxide anions building up a square prism. (Nd2)3+ and (Nd3)3+ are both coordinated by oxide and chloride anions. The coordination polyhedron around (Nd2)3+ is a trigonal prism of oxide anions that is capped by one chloride anion to give a coordination number of seven. (Nd3)3+ resides in an eightfold coordination of five oxide and three chloride anions forming a square antiprism. All (O1)2 − anions are surrounded tetrahedrally by Nd3+ cations as [ONd4]10+ units. These tetrahedra share common edges and vertices to generate two-dimensional infinite layers of the composition ∞ 2 {[O4Nd5]7+ }, which extend parallel to the (001) plane. The chloride anions (Cl1) − are connecting those slabs via Nd3-Cl1-Nd3 bridges along the [001] direction, while the (Cl2)− anions alternate with the Te4+ cations above and below the layers. The three-dimensional crystal structure of Nd5O4Cl3[TeO3]2 is completed by Te4+ cations, which are bonded to one (O2)2 − and two (O3)2 − anions to form ψ1-tetrahedra [TeO3]2 − with a nonbinding, stereochemically active electron pair (“lone pair”) pointing into the free space between the chloride-decorated ∞ 2 {[O4Nd5]7+ } layers

A new dinuclear CuII–SmIIIcomplex with a salen-type Schiff base ligand

The title complex (systematic name: diaqua­{6,6′-dimeth­oxy-2,2′-[1,2-ethanediylbis(nitrilo­methyl­idyne)]­diphenolato}­di­nitrato­samarium(III)copper(II) nitrate), [CuSm(C18H18N2O4)(NO3)2(H2O)2]NO3, is composed of a discrete dinuclear cation with a salen-type Schiff base ligand and one uncoordinated nitrate anion. The copper and samarium are doubly bridged by two phenolate O atoms provided by the Schiff base ligand. There are some classical inter­molecular hydrogen bonds (O—H⋯O), and some weak O⋯Cu and N⋯Cu inter­actions are also observed. These inter­actions generate a two-dimensional infinite layer.

Crystal structure of digadolinium(III) oxide disulfide, Gd2OS2

AbstractGd2OS2, monoclinic, P121/c1 (No. 14), a = 8.3365(6) Å, b = 6.9872(5) Å, c = 6.9231(5) Å, β = 99.463(6)°, V = 397.8Å3, Z = 4, Rgt(F) = 0.022, wRref(F2) = 0.047, T = 293 K.

Thermal instability in a three-dimensional rigid container with prescribed heat flux at lower boundary

The Bénard–Marangoni convection is studied in a three-dimensional container with thermally insulated lateral walls and prescribed heat flux at lower boundary. The upper surface of the incompressible, viscous fluid is assumed to be flat with temperature dependent surface tension. A Galerkin–Tau method with odd and even trial functions satisfying all the essential boundary conditions except the natural boundary conditions at the free surface has been used to solve the problem. The critical Marangoni and Rayleigh numbers are determined for the onset of steady convection as a function of aspect ratios x 0 and y 0 for the cases of Bénard–Marangoni, pure Marangoni and pure Bénard convections. It is observed that critical parameters are decreasing with an increase in aspect ratios. The flow structures corresponding to the values of the critical parameters are presented in all the cases. It is observed that the critical parameters are higher for case with heat flux prescribed than those corresponding to the case with prescribed temperature. The critical Marangoni number for pure Marangoni convection is higher than critical Rayleigh number corresponding to pure Bénard convection for a given aspect ratio whereas the reverse was observed for two-dimensional infinite layer.

Structural Properties and Topological Diversity of Polymeric Ag(I)-hexamethylenetetramine Complexes: Self-Assembly of Three Novel Two-Dimensional Coordination Networks and Their Supramolecular Interactions

The self-assembly of polymeric open networks from different Ag(I) salts and the potentially tetradentate ligand hexamethylenetetramine (hmt) has revealed a variety of possible structural motifs, depending on the reagent ratios and the counterions, that are discussed in comparison. Three new Ag(I) coordination polymers are here described, namely [Ag2(μ4-hmt)(Tos)2] (Tos=p-toluenesulfonate) (1), [Ag2(μ3-hmt)2(CF3SO3)(H2O)](CF3SO3)·H2O (2), and [Ag3(μ3-hmt)2(H2O)4](PF6)3 (3), that contain two-dimensional infinite layers of different types. Crystal data: 1 C20H26Ag2N4O6S2, monoclinic, C2/c, Z=4, a=9.482(3) Å, b=8.539(3) Å, c=28.461(10) Å, β=91.75(2)°, V=2303.3(13) Å3, R=0.043 (I>2σ(I)); 2 C14H28Ag2F6NO8S2, monoclinic, P21/c, Z=4, a=6.429(2) Å, b=25.247(3) Å, c=16.162(2) Å, β=91.54(2)°, V=2622.4(9) Å3, R=0.050 (I>2σ(I)); 3 C12H32Ag3F18N8O4P3, monoclinic, C2/c, Z=4, a=16.675(4) Å, b=11.102(5) Å, c=18.455(3) Å, β=111.48(2)°, V=3179.2(17) Å3, R=0.040 (I>2σ(I)). Compound 1 is composed of layers of square grids, with the silver ions acting as spacers and interacting with the anions through Ag–O contacts and also via π bonds with the aromatic rings. Compound 2 consists of layers of hexagons, with alternate triconnected Ag(I) ions and tridentate hmt ligands, while compound 3 contains layers of larger hexagonal meshes, with six hmt ligands at the vertices and six biconnected silver atoms as spacers. The latter two species give rise, via hydrogen-bond bridges involving coordinated water molecules, to three-dimensional arrays of new topologies.

Novel Inclusion Compounds of Urea with Tetraalkylammonium Pentaborates

New crystalline inclusion compounds (n-C3H7)4N+[B5O6(OH)4]−·4(NH2)2CO·H2O (1) and (n-C4H9)4N+[B5O6(OH)4]−·2(NH2)2CO·B(OH)3 (2) have been prepared and characterized by X-ray crystallography. Crystal data, MoKα radiation: 1, space group P21, Z = 2, a = 8.343(2), b = 16.037(3), c = 13.343(3) Å, β = 104.75(3)°, RF = 0.079 for 1820 observed data; 2, space group P21/n, Z = 4, a = 11.582(3), b = 17.270(4), c = 17.819(5) Å, β = 96.85(3)°, and RF = 0.056 for 2291 observed data. Compound 1 has a channel-like host lattice built of urea molecules, pentaborate ions and water molecules, and the (n-C3H7)4N+ cations are arranged in a zigzag column within each channel. In compound 2 the host lattice comprises a stack of two-dimensional infinite layers of inter-connected urea molecules, pentaborate ions, and neutral B(OH)3 molecules. The (n-C4H9)4N+ cations are sandwiched between adjacent layers, while another most unusual guest component, namely a hydrogen-bonded planar ribbon formed by B3O3(OH)2 fragments belonging to different pentaborate ions, threads the central holes of macrocycles within the stacked layers.

A Time of Flight Model for Cloud’s Radiative Transfer

A model for fast calculation of path radiance of finite clouds is presented. The calculations are simplified by using the reciprocity principle and the homogenousness property of the incident light. Comparisons with reasonably accurate calculations for spherical cloud and two-dimensional infinite layer were made.

Crystal structures and physical properties of the ternary carbides ScT1–xC2(T = Fe, CO, Ni)

The crystal structures of the title compounds, originally determined for ScCoC2, have been refined from single-crystal X-ray data to residuals of R= 0.037 (154 structure factors), R= 0. 031 (433 F values) and R= 0.049 (161 F values) each with 12 variable parameters, for the Fe, Co and Ni compounds, respectively. The C–C distances in the carbon pairs are 138.1(9), 139.7(3) and 135(2) pm. They are thus close to the double-bond distance of 134 pm in alkenes. The refinement of the occupancy parameters showed that the iron, cobalt and nickel positions are occupied to only 88, 88 and 83% in the crystals used for the structure refinements. In general, interatomic distances in the three compounds are very similar. This is rationalized by the counterbalancing effects of the electron counts and electronegativity of the transition-metal component. The structure consists of two-dimensional infinite layers of composition ScC2 which have a CaC2-like structure. These layers are separated by sheets of the transition elements, possibly with two-dimensional metallic conductivity. Compact polycrystalline samples of the three compounds are very weakly paramagnetic and show semiconducting behaviour.