Sheet-like Network Research Articles

Novel Electron Acceptors Bearing a Heteroquinonoid System. II. Synthesis and Conductive Complexes of 2,5-Bis(dicyanomethylene)-2,5-dihydrothieno[3,2-b]thiophene, 2,6-Bis(dicyanomethylene)-2,6-dihydrodithieno[3,2-b:2′,3′-d]thiophene, and Their Derivatives

Abstract Novel heteroquinonoid compounds as potential electron acceptors, 2,5-bis(dicyanomethylene)-2,5-dihydrothieno[3,2-b]thiophene (4a), 3,6-dibromo derivative, 2,6-bis(dicyanomethylene)-2,6-dihydrodithieno[3,2-b:2′,3′-d]thiophene, 3,5-dibromo derivative, and 4,4-dioxide were synthesized by the action of tetracyanoethylene oxide or by a Pd(0)-catalyzed substitution reaction with sodium dicyanomethanide on the corresponding α,α′-dihalo-substituted fused thiophenes. They show effectively diminished on-site Coulomb repulsion owing to the extensive conjugation, and most of their molecular complexes with various electron donors exhibit very high electrical conductivities up to metallic region. In addition, X-ray crystallographic analysis of the complex of 4a with bis(ethylenedithio)tetrathiafulvalene has elucidated that sulfur atoms embedded in 4a molecule are capable of inducing a significant intermolecular interaction, forming a sheet-like network structure.

Peripheral vascularization of the dermal laminae of the equine hoof.

The vascular architecture of the dermal laminae was studied by scanning electron microscopy of vascular corrosion casts. Ultrastructurally, the laminar vasculature consisted of arterioles, capillaries, venules and veins, arranged in a sheet-like network. Through the laminae, arterioles ran parallel to the solar surface and branched at two levels to form a continuous arteriolar arcade, parallel to the hoof wall. Capillaries originating from these arcades formed hairpin loops joining the marginal vein prior to forming an axially situated venous network. Additional capillaries were also given off by the arterioles, forming an abaxially arranged capillary plexus.

Crystal structures and physico-chemical properties of thiophene-fused TCNQ acceptors and their TTF complexes

Four isomeric benzodithiophene analogues of TCNQ have been prepared and their physico-chemical properties were investigated. Two isomers, which exhibited low reduction potentials in cyclic voltammetry, formed highly conducting 1:1 charge-transfer complexes with TTF. The crystal structures of these complexes were determined by an X-ray method, revealing a novel mixed stack of DD-AA-DD- with a sheet-like network comprised of the side-by-side arrangement of the donor and acceptor molecules.

Crystal Structure of 2,5-Bis(dicyanomethylene)-2,5-dihydrothieno[3,2-b]thiophene and Bis(ethylenedithio)tetrathiafulvalene Complex

Abstract The crystal structure of 2,5-bis(dicyanomethylene)-2,5-dihydrothienot [3,2-b]thiophene and bis(ethylenedithio) tetrathiafulvalene complex showed a weak face to face interaction and sheet-like networks with intermolecular N···S and S···S interactions, and the shortest S···S contact is 3.48 Å between the acceptors.

Deep-etch structure of astrocytes at the superficial glia limitans, with special emphasis on the internal and external organization of their plasma membranes.

The cytoskeletal system in rat subpial astrocytes and the relationship between astrocytic plasma membrane and basal lamina or cytoplasmic components were examined with a quick-freeze deep-etch technique, mainly using chemically fixed tissues. Attention was focused on the way intramembrane particles (IMPs), particularly orthogonal arrays, are organized in the membranes and related to extramembrane components. The basal lamina was composed of a sheet-like network of strands (4-9 nm thick), some, which we have called 'trabecular' strands, extending through the lamina lucida to touch the astrocytic membrane at irregular intervals. The trabecular strands usually formed a bulbous structure where they touched the membrane, but sometimes appeared to intrude directly into the external lipid layer. The orthogonal arrays did not extend to the outer true surface, and no special structure was detectable in association with them. Small spherical protrusions (7-9 nm in diameter), related to neither the trabecular strands nor the arrays, were observed in the outer surface. Judging from their size and distribution, these are probably tops of tall globular IMPs. In the inner or cytoplasmic true surface, protrusions were relatively numerous; some were large, 15-20 nm in diameter, while others were small (8-10 nm). Some of the small protrusions were identified as transmembrane components. Although protrusions were more conspicuous in the inner than in the outer surface, none of them provided images related or similar to the orthogonal arrays. Some protrusions in the inner surface were connected with thin (4-5 nm) or thick (approximately 10 nm) filaments constituting the underlying network. The thin filaments were also anchored to the intermediate filaments which lay parallel with the astrocytic membranes. In the cytoplasm, the intermediate filaments were firmly packed to form bundles. Because the orthogonal arrays are probably embedded within the astrocytic membrane, they may not serve as a transmembrane channel but rather contribute to some stabilizing function for the membrane.

Crystal Structures of 2,7-Bis(methylthio)-1,6-dithiapyrene (MTDTPY) and 2,3:7,8-Bis(ethanedithio)-1,6-dithiapyrene (ETDTPY). Sheet-Like Networks of Dimeric Pairs

Abstract The crystal structures of methylthio and ethanedithio substituted peri-condensed Weitz type donors, bis(methylthio)dithiapyrene and bis(ethanedithio)dithiapyrene, showed sheet-like networks of dimeric pairs of the donor molecules.

The Synthesis, Crystal Structure, Electrical Conductivity and Band Electronic Structure of (BPDT-TTF)2lCl2

Abstract (BPDT-TTF)2ICl2 is a synthetic metal salt composed of the electron donor molecule bis(propylenedithio)tetrathiafulvalene (BPDT-TTF, C12H12Sk) and the linear iododichloride anion, ICl2 −. The crystal structure of (BPDT-TTF)2ICl2, determined at 298 K and 120 K, closely resembles those of the organic metals and semiconductors based on bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF, C10H8H8), in that all of these materials contain sheetlike donor molecule networks sandwiched between anion layers. In contrast to the (BEDT-TTF)2X salts, however, there is a total absence of S···S contact distances less than ∼3.6 A (the van der Waals radius sum) within the donor-molecule network of (BPDT-TTF)2ICl2. In addition, each stack of BPDT-TTF molecules is also strongly dimerized. The lack of short S···S contact distances at both 298 K and 120 K appears to be a consequence of the bulky propylene groups of BPDTTTF compared to the smaller ethylene groups of the BEDT-TTF molecule. Based upon four-probe a.c. resistiv...

Crystal and Molecular Structure of Bis-1,2,5-thiadiazolotetracyano-quinodimethane. A Noval Acceptor Forming Highly Conductive Complexes

Abstract The crystal structure of bis-1,2,5-thiadiazolotetracyanoquinodimethane showed stacks of two-dimensionally expanded sheet-like networks, in which the roughly coplanar molesules are connected to one another by way of the rhombohedral linkage involving short S–NC contacts of 3.03 Å.

Structural Characterization and Band Electronic Structure of α-(BEDT-TTF)2I3below its 135 K Phase Transition

Abstract The nature of the 135 K metal-insulator (MI) transition in α-(BEDT-TTF)2l3, abbreviated α-(ET)2l3, was examined by determining the crystal structures above (298 K) and below (120 K) the phase transition and also by calculating the band electronic structures at both temperatures. This study demonstrates that both the crystal and band electronic structures of α-(ET)2l3 change only slightly upon passing through the MI transition. Within each sheetlike network of ET radical cations, the magnitudes of interactions between adjacent pairs of ET molecules (i-j) above and below the MI transition temperature (T MI) were evaluated by calculating their interaction energies, β ij = ⟨Ψ, H off|Ψ⟩, where Ψ1); and Ψ1 are the HOMO's of ET molecules i and j, respectively. The band electronic structures calculated by using single-zeta Slater type orbitals show that α-(ET)2l3 is a semiconductor with band gaps of 13 meV (298 K) and 35 meV (120 K). Thus, within the one-electron model, the apparently metallic properties...

Neutron-diffraction evidence for unusual cohesive H-bonding interactions in .beta.-(BEDT-TTF)2X organic superconductors

In order to determine the nature and exact geometries of the interionic interactions that are responsible for crystal cohesion between the sheetlike networks of radical cation molecules and the halide-containing anions in the layered organic conductors of the type ..beta..-(ET)/sub 2/X, the authors have undertaken low-temperature (20 K) neutron diffraction studies of the X/sup -/ = AuI/sub 2//sup -/ and I/sub 3//sup -/ salts. For these synthetic organic superconductors, ..beta..-(ET)/sub 2/AuI/sub 2/ has the highest T/sub c/ (approx. 5K) at ambient pressure, and ..beta..-(ET)/sub 2/I/sub 3/ has the highest T/sub c/ (approx. 8 K) under a nonhydrostatic pressure of 1.3 kbar. The discovery of very short H...I contacts in ..beta..-(ET)/sub 2/AuI/sub 2/ is surprising because such interactions are generally assumed to be weak. There are important implications for the design and synthesis of new ..beta..-(ET)/sub 2/X systems where the X/sub n//sup -/ anions contain halide (I, Br, Cl, F) atoms, namely, that H-bonding interactions of the type H...X play a major role in determining the crystal cohesive forces between donors and anions thereby controlling compound formation.

The crystal structure of a new synthetic sulfosalt, KHgSbS3

Abstract A new sulfosalt, KHgSbS3 is orange in color with tabular shape and crystallizes in the monoclinic space group A 2 a with a=17.084(8), b=8.647(4), c =8.951(3) A , β=105.78(5)°, and z=8. The crystals are obtained as twin, which is related by a 180° rotation of the reciprocal lattice around [100] with (100) twin plane. The structure was determined by three dimensional Patterson synthesis and refined to a final R-value of 0.082 for 737 reflections. The crystal structure consists of trigonal pyramids of SbS3 linked together by Hg atoms to form a two dimensional sheet-like network. The K atoms are located between the sheets, bonded weakly to them.

Fluid Movement in a Channel With Permeable Walls Covered by Porous Media: A Model of Lung Alveolar Sheet

The smallest microscopic blood vessels in the human lung are organized into sheet-like networks. These sheets form the walls of the 300 million alveoli in which air flows due to breathing. Each sheet may be idealized into a channel bounded by two thin layers of porous media. This paper is concerned with the blood flow in the channel and water movement in the porous wall. The Reynolds number in the lung alveolar sheets is very low, so creeping flow is assumed. Analytical and numerical results on the velocity and pressure distribution in the porous layers are presented.