One-dimensional Double Chain Research Articles

Structural diversity in the Cu(pyrazinecarboxylate)2/CdCl2 system: new one-, two- and three-dimensional mixed metal coordination polymers

Four new inorganic–organic polymeric materials have been synthesized by reacting the metal containing building block, Cu(pyzca)2, with cadmium chloride. All resulting polymers have both metals incorporated in the structure and display a variety of structural motifs, ranging from one-dimensional chains to complicated three-dimensional networks. The first compound, [Cu(Pyzca)2(H2O)CdCl2(H2O)·H2O]n (1) is a one-dimensional double chain. The next two compounds, [Cu(Pyzca)2(H2O)2Cd2Cl4(H2O)2]n (2) and [Cu(Pyzca)2(H2O)Cd2Cl4(H2O)2·3H2O]n (3), assemble in a two-dimensional brick-wall network, while the fourth, [Cu(Pyzca)2Cd2Cl4]n (4), features an intricate three-dimensional network. Synthesis, X-ray structure determinations, and the influence of water molecules coordinated to the copper centers on the coordination geometry and overall extended structure are discussed.

{M(C5H4N)CH(OH)PO3}(H2O) (M = Mn, Fe, Co): layered compounds based on [hydroxy(4-pyridyl)methyl]phosphonate

This paper describes the syntheses and characterization of three novel phosphonate compounds M{(C5H4N)CH(OH)PO3}(H2O) [M = Mn (1), Fe (2), Co (3)] with isomorphous layered structures. Each {MO4N} trigonal bipyramid in the structure is corner-shared with three {CPO3} tetrahedra from three equivalent [hydroxy(4-pyridyl)methyl]phosphonate ligands, forming a one-dimensional inorganic double chain. These inorganic chains are linked together via the organic groups of the ligand, leading to a two-dimensional layer structure. The layers are further connected to each other through extensive hydrogen bonds, thus generating a three-dimensional supramolecular network. The magnetic properties show that weak antiferromagnetic interactions are mediated between the metal centers in all three compounds.

Preparation, Structure and Optical Properties of [CH3SC(NH2)2]3SnI5, [CH3SC(NH2)2][HSC(NH2)2]SnBr4, (CH3C5H4NCH3)PbBr3, and [C6H5CH2SC(NH2)2]4Pb3I10

Abstract The preparation, crystal structure and optical absorption spectra of [CH3SC(NH2)2]3SnI5 (1), [CH3SC(NH2)2][HSC(NH2)2]SnBr4 (2), (CH3C5H4NCH3)PbBr3 (3), and [C6H5CH2SC-(NH2)2]4Pb3I10 (4) are reported. The compounds 1, 2, 3 consist of MX6-octahedra (M = Sn, Pb, X = I, Br) forming one-dimensional single chains (compounds 1, 3) or double chains (compound 2). The compound 4 forms a two-dimensional inorganic network via corner sharing of three face sharing octahedral units. Because of their low-dimensional character, a blue shift of the excitonic absorption bands, in comparison to those of higher dimensionality systems, is observed.

A one-dimensional model of friction at nanometric scale

A simple one-dimensional double chain model is used to simulate tribology effects at the nanometric level, via a classical molecular dynamics simulation. The two chain modulate each other and, when pulled parallel to their common direction, slide and pull the modulation along on the other chain. The equilibrium velocity as a function of the pulling force amplitude shows several different regions, either “smooth” or “rough” depending on the stability of the velocity.

Crystal structure and dielectric properties of the[(CH3)2NH2]3Sb2(1-x)Bi2xCl9 (DMACAB) mixedcrystals

Phase transitions in[(CH3)2NH2]3Sb2(1-x)Bi2xCl9 (DMACAB) mixedsalts in the composition range 0⩽x⩽0.41 have beeninvestigated by the pyroelectric method and dielectric measurementsover the frequency range from 75 kHz to 900 MHz. The phase situationis additionally confirmed by the differential scanning calorimetry(DSC) and dilatometric techniques. A transition from theparaelectric (PE) to the ferroelectric (FE) phase is observed forcrystals with 0⩽x⩽0.14. Pyroelectric measurementssupport the presence of polar phases. The dynamic dielectricbehaviour of ferroelectric systems is found to be determined by theexistence of two independent relaxators. The low-frequencyrelaxator reveals a critical slowing down of its dynamics in theclose vicinity of the PE→FE transition. For compositionsin the range 0.17⩽x⩽0.41 a new sequence of phasetransitions appears without any polar phases being present. Thedisappearance of ferroelectric properties is related to thefundamental changes in the crystal structure of the mixed compounds.The characteristic feature of the ferroelectric mixed crystals (0.0⩽x⩽0.14) is the presence of polyanionic (M2Cl93-)n(M = Sb, Bi) layers, whereas non-ferroelectric ones arecharacterized by a different anionic sublattice composed ofpolyanionic one-dimensional double chains.

A novel coordination polymer [Co(NCS) 2(bpms) 2] n (bpms=1,2-bis(4-pyridylmethyl)disulfenyl): synthesis, crystal structure and third-order nonlinear optical properties

A new 4,4′-bipyridyl-based ‘building block’, 1,2-bis(4-pyridylmethyl)disulfenyl (bpms) was synthesized. Treatment of the ‘building block’ with Co(NO 3) 2 and KSCN afforded a new type of one-dimensional (1-D) double zigzag chain coordination polymer [Co(NCS) 2(bpms) 2] n . Each Co ion is symmetrically bridged by four bpms ligands and also coordinates with two NCS − anions. The [Co(NCS) 2(bpms) 2] n can be regarded as a layered structure in the solid state. The 1-D parallel chains are stacked ABAB with a rotation of 90° between A and B. [Co(NCS) 2(bpms) 2] n in DMF solution also shows very strong third-order nonlinear optical (NLO) properties, its third-order susceptibility χ (3) is 1.07×10 −11 esu in a 2.8×10 −3 g cm −3 DMF solution. The data are comparable to those of C60, phthalocyanine derivations and inorganic clusters. To our knowledge, this is the first reported coordination polymer showing strong third-order NLO properties.

Electronic fine tuning of the structures of reduced rare-earth metal halides.

Electronic band-structure calculations on Pr3I3Ru and Y3I3Ru have been performed in order to analyze the large structural differences found in these isoelectronic compounds. These constitute two structural extremes within the family of monoclinic Re3I3Ru phases (RE = rare-earth metal) that exhibit distortions ranging from one-dimensional double chains of trans-edge-sharing octahedra (bioctahedral chains, BOH) to one-dimensional chains of trans-edge-sharing square pyramidal units bonded base to base (bisquare pyramidal chains, BSP). The structure of La3I3Ru was established by single-crystal X-ray diffraction (monoclinic, P2(1)/m, Z = 4, a = 9.343(1) A, b = 4.3469(8) A, c = 12.496(3) A, beta = 93.42(2) degrees) and found to be isomorphous with the BOH Pr3I3Ru. It is determined that the structural variation in this RE3I3Z family of materials depends largely on the differences in orbital energies between the corresponding rare-earth metal and the interstitial. These bonding considerations can be generalized to account for structural variations in a variety of other rare-earth halides as well as several group 4 or 5 reduced metal halide cluster phases.

TWO-DIMENSIONAL SELF-ASSEMBLY OF SUPRAMOLECULAR STRUCTURES

We briefly review recent low temperature scanning tunneling microscopy (STM) investigations performed in our laboratory1–5 on the self-assembly of the dipolar organic molecule 1-nitronaphthalene (NN) adsorbed on the reconstructed Au(111) surface. NN becomes chiral upon planar adsorption on the gold surface. We observe several coverage-driven structural transformations which are associated with simultaneous changes in the enantiomeric composition of the self-assembled molecular structures. At low coverages almost exclusively decamers with an 8:2 ratio of the enantiomers are formed. In a medium coverage range enantiopure one-dimensional molecular double chains prevail on the surface. Subsequently, molecules with opposite handedness are admixed until at monolayer coverage racemic one- and two-dimensional structures coexist. Modeling shows that hydrogen bonding causes the observed self-assembly. A subtle interplay between the electrostatic interactions among the molecules and their interaction with the reconstructed metal surface is the origin of the observed coverage-driven chiral phase transition in two dimensions.

One-dimensional double chain composed of carbamoylmethylthio-substituted TTF-based donor in ion radical salt

Carbamoylmethylthio-substituted TTF-based donors afforded inclusion-type salts with a BF4 counter ion or an F4-TCNQ acceptor. The crystal structures of these salts are characterized by a one-dimensional double chain composed of singly-oxidized donors via SOMO–SOMO interaction and side-by-side S⋯S contacts. Counter ions of BF4 are hydrogen-bonded to the amide groups. On the other hand, F4-TCNQ acceptors are stacked in a channel created by a stair-like arrangement of donor chains. The thermally activating magnetic susceptibility of the F4-TCNQ complex was interpreted in terms of a double-chain frustrated spin system.

Self-assembly of 1-nitronaphthalene on Au(111)

We report low-temperature scanning tunneling microscopy and near-edge X-ray absorption fine structure investigations of the organic molecule 1-nitronaphthalene adsorbed on the reconstructed Au(111) surface. Depending on the coverage, molecular structures of distinct dimensionality are observed. After saturation of the step edges with molecules, clusters form on the substrate terraces at coverages up to 0.15 monolayers (ML). The smallest clusters consist of three molecules and are stable at specific surface reconstruction sites only. In contrast, pinwheel-shaped clusters comprised of ten molecules are observed on various inequivalent sites of the reconstructed Au surface. For coverages larger than 0.2ML one-dimensional molecular double chains prevail. The structure of the decamers and the chains is determined by intermolecular electrostatic forces, whereas their position and orientation are affected by the surface reconstruction. At saturation coverage a periodic two-dimensional close-packed arrangement of molecules that is independent of the surface reconstruction occurs simultaneously with one-dimensional structures along the uniaxial reconstruction domains. The structural features are discussed in terms of competing effects of intermolecular forces and the interaction with the substrate.

(1R,2R)-4-Methylurazole-α-D-pyranosyl-2-deoxyriboside from Reaction of 4-Methylurazole with 2-Deoxy-D-ribose

The crystalline nucleoside formed from an aqueous solution of 4-methylurazole and 2-deoxy-D-ribose was identified unequivocally by its X-ray structure as a single diastereomer, (1R,2R)-4-methylurazole-α-D-pyranosyl-2-deoxyriboside [IUPAC name: (1R,2R)-1-(2-deoxy-α-D-erythro-pentopyranosyl)-4-methyl-1,2,4-triazolidine-3,5-dione; C 8 H 13 N 3 O 5 ]. In its urazole ring, the two hydrazidic N atoms are pyramidal and confer R chirality, the respective pyranosyl and H-atom substituents being substantially out of the ring plane and trans juxtaposed, while the imidic N atom is trigonal planar, its methyl substituent being essentially coplanar with the ring. The intermolecular hydrogen bonding involves pyranose-pyranose and pyranose-urazole interactions producing one-dimensional cross-linked double chains. From this study and our results from the preparation of three related nucleosides, we find that the crystalline nucleosides formed by direct coupling of these nucleobases with 2-deoxyribose are consistently diastereospecific.