1,721,034 research outputs found
Layered ω-Substituted Alkylpyridinium Salts with Inorganic Anions: Effects of H-Bonding Patterns on the Layer Thickness
No full textThe synthesis and characterization of a carboxy-substituted alkylpyridinium cation with inorganic counterions is reported. Structural evidence points to the formation of a layered structure with mutual recognition of cations through strong O-(HO)-O-... bonding when halides X- (X = Cl, Br) are chosen. Variation of the anionic component to complex metal ions of [MX4](2-) type affords a different layer motif with weaker cation-anion O-(HX)-X-...-M interactions and interdigitation of functionalized alkyl chains
Macrocyclic Metallomesogens: Thermotropic Double-chained Silver Amphiphiles
No full textMesomorphic [Ag(2)][TfO] (TfO=CF3SO3) and [Ag(2)][TsO] (TsO=p-CH3C6H4SO3) have been prepared by silver complexation of the novel N,N'-bis(hexadecanoyl)-1,10-diaza-4,7,13,16-tetrathiacyclooctadecane, 2. The phase behaviour of the silver complexes is described and a lamellar mesophase is proposed for [Ag(2)][TfO] by means of X-ray evidence
Crystal architecture and mesophase structure of long-chain N-alkylpyridinium tetrachlorometallates
No full textThe N-hexadecylpyridinium derivatives [C16-Py]2[MCl4] (M=Cd (1), Zn (2)) were prepared and structurally characterized by X-ray diffraction methods. The crystal structure of 1 reveals a layered arrangement with alternation of monolayers of interdigitated cations with layers of isolated [CdCl4]2- anions. C-H⋯Cl-Cd interactions reinforce the association between anions and cations in the polar region of the supramolecular structure. Both 1 and 2 display a thermotropic smectic A phase in addition to some high-temperature crystalline modifications. The thermal polymorphism of the salts was studied by X-ray powder diffraction, differential scanning calorimetry (DSC), and thermal optical microscopy. The structural and mesomorphic characteristics of 1 and 2 are compared with those of the analogous salts along the series [C16-Py]2[MCl4] (M=Co, Ni, kCu, Zn, Pd, Cd)
On the thermal behaviour of palladium(II) macrocyclic polycatenars
No full textPolycatenar saturated macrocycles 1,10-bis[3,4,5-tris(4-dodecyloxy)benzoyl]-1,10-diaza-4,7,13,16-tetrathiacyclo-octadecane (3b) and 1,10-bis[3,4-bis(4-dodecyloxy)benzoyl]-1,10-diaza-4,7,13,16-tetrathiacyclo-octadecane (3d) reacted with [Pd(MeCN)(4)][BF4](2) led to the cationic complexes [4b][BF4](2) and [4d][BF4](2), respectively. Complexes [4b][BF4](2) and [4d][BF4](2) showed smectic mesomorphism on heating as confirmed by small angle X-ray diffraction. A concurrent, irreversible structural change of the complex cations was observed and a tentative explanation is suggested
Structural Studies on Layered Alkylpyridinium Iodopalladate Networks
No full textThe reaction of alkylpyridinium (C(n)H(2n+1)NC5H5, hereafter Cn-Py) iodide salts in aqueous acetonitrile with a preformed palladium iodide precursor afforded two different types of organic-inorganic phases depending on the molar ratio. A 2:1 ratio yielded the phase [Cn-Py]2[PdI4] (3, n = 14, 16), which crystallized in the triclinic crystal system. The X-ray crystal structure of 3, (n = 14), refined in the space group P1 (a = 8.918(3) Å, b = 9.894(3) Å, c = 29.062(12) Å, α = 93.51(3)°, β = 94.17(3)°, γ = 115.60(3)°, and Z = 2), consists of interdigitated bilayers with a basal spacing of 29.0 Å. The aliphatic chains of the cations, which run almost parallel to the stacking direction, are fully stretched between polar planes built on isolated. [PdI4]2- anions and cation headgroups. Changing the organic cation to palladium ratio to 1:1 led to a new phase [Cn-Py]2[Pd2I6] (4, n = 14, 16), which crystallizes in the triclinic P1 space group (a = 9.399(4) Å, b = 14.264(6) Å, c = 29.415(13) Å, α = 92.11(4)°, β = 90-07(4)°, γ = 104.53(3)°, Z = 3 for 4(n = 14); a = 9.417(2) Å, b = 14.215(3) Å, c = 31.552(6) Å, α = 87.96(3)°, β = 87.63(3)°, γ = 75.67(3)°, Z = 3 for 4(n = 16)). The layered structure is basically of a continuously interdigitated single-layer type, with a bilayer sublattice superimposed. Isolated [Pd2I6]2- anions contribute to the inorganic planes. A high degree of interdigitation and tilting of the aliphatic chains lead to basal spacings of 29.4 and 31.5 Å for 4(n = 14) and 4(n = 16), respectively. The [Cn-Py]2[PdI4] and [Cn-Py]2[Pd2I6] phases were characterized by thermal analysis. Mesomorphic behavior was observed only for 3(n = 16), which was confirmed by variable-temperature powder XRD and optical microscopy
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
3,6-BIS(2'-PYRIDYL)PYRIDAZINE DINUCLEAR COMPLEXES - PALLADIUM(II), PLATINUM(II) AND 1ST ROW TRANSITION METAL(II) MIXED COMPLEXES
No full textNew Pd(II) and Pt(II) 3,6-bis(2′-pyridyl)pyridazine (dppn) mononuclear complexes of the type M(dppn)Cl2 were prepared and characterized. From M(dppn)Cl2, the bimetallic homonuclear complexes M(dppn)MCl4 were prepared by reaction with Pd(PhCN)2Cl2 or K2PtCl4. Bimetallic heteronuclear species of the type M(dppn)M′Cl4, were prepared reacting the mononuclear complexes with the stoichiometric amount of M′Cl2 (M′ = Cu, Co, Ni). All the described reaction give product in high yield. The isolated compounds, almost completely insoluble in most organic solvents, were characterized by elemental analysis, IR, ESR, reflectance spectra, and magnetic moment measurements. On the basis of these data the geometries around the metals are discussed
Iridium(I) insertion into an aromatic C-H bond. Synthesis and structure of [Ir(H)(CO)(bq)(PPh3)2]PF6 (bq=7,8-benzoquinolinato)
No full textIonic Metallomesogens. Lamellar Mesophases in Copper(I) Azamacrocyclic Complexes
No full textA series of nonmesogenic N-acylated derivatives (2) of 1,10-diaza-4,7,13,16-tetrathiacyclooctadecane (1) affords stable cationic complexes upon reaction with [Cu(MeCN)4][PF6]. The products [Cu(2)] [PF6] show thermotropic mesomorphism as a result of copper(I) complexation. Optical microscopy, calorimetry, and low-resolution powder X-ray diffraction were used to characterize the liquid-crystalline order. The presence in all complexes of a single mesophase with a lamellar structure is proposed and discussed
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