Syntheses,structures, and optical properties of heteroselenometallic W–Se–Ag polymer compounds {[Et4N][(μ-WSe4)Ag]}n and {[Ln(Me2SO)8][(μ3-WSe4)3Ag3]}n (Ln = Pr,Er)

The one-dimensional linear polymer W–Se–Ag compound {[Et₄N][(μ-WSe₄)Ag]}_n (1) was obtained from the reaction of [Et₄N]₂[WSe₄] and AgNO₃ in a mixed solvent, MeCN/DMF (1:10). Treatment of a solution of 1 in Me₂SO with Ln(NO₃)₃ · 6H₂O resulted in the formation of a helical chain polymer compound {[Ln(Me₂SO)₈][(μ₃-WSe₄)₃Ag₃]}_n (Ln = Pr 2, Er 3). The solid-state structures of the three polymer compounds 1, 2, and 3 have been established by X-ray crystallography. The third-order non-linear optical properties of the linear polymer compound 1 were determined by z-scan techniques with 7 ns pulses at 532 nm.     

The anhydride route to Group 15/16 ligands in oligomeric and polymeric environments: from metal complexes to supraionic chemistry

The aim of this paper is to introduce a synthetic concept suitable for the preparation of a broad variety of compounds. The so-called anhydride route (in this article the term anhydride is used for compounds derived from corresponding acids by formal loss of H2O, H2S and H2Se) has so far led to a range of unusual Group 15/16 ligands in oligomeric and polymeric environments. Commonly, reactions of neutral precursor molecules, for example, [{RP(S)(mu-S)}2] (R=4-anisyl) Lawesson's reagent or [{PhP(Se)(mu-Se)}2] Woollins's reagent and metal salts are performed to result in novel coordination compounds in which ligands and metal atoms form coordination oligomers and polymers. An attempt is made to relate the outcome of the investigations to the type of metal used. By relating the strength of ionic interactions, which correspond to metal-donor distances, to phenomena observed in the solid-state structures, an aspect of supraionic chemistry is described. Chemistry of and beyond novel Group 15/16 anions is further discussed using a novel approach in coordination chemistry where the chemical nature of ligands is unknown prior to the experiment despite the use of a range of similar starting materials.     

The interaction of 1,1'-diisocyanoferrocene with gold: formation of monolayers and supramolecular polymerization of an aurophilic ferrocenophane

The coordination chemistry of 1,1'-diisocyanoferrocene (1) was investigated. Its reaction with Cr(CO)5(THF) (2 equiv) affords (1)[Cr(CO)5]2, which exhibits eclipsed cyclopentadienyl rings with a synclinal arrangement of the two substituents. 1 behaves like an aryl isocyanide in this compound according to IR spectroscopic data, and its oxidation leads to a marked decrease of net electron donor ability. The reaction of 1 with AuCl(SMe2) affords the insoluble coordination polymer [(1)(AuCl)2]infinity. The (1)(AuCl)2 molecules adopt a 3,4-diaura-[6]ferrocenophane structure. They are aggregated in a zipperlike fashion through aurophilic interactions, with Au-Au distances ranging from 3.34 to 3.48 A. The adsorption of 1 from acetonitrile solution on polycrystalline gold affords a self-assembled monolayer. Both isocyanide groups are binding to the surface.     

Rapid determination of total sulfur in fuels using gas chromatography with atomic emission detection

The purpose of this study is to determine whether gas chromatography (GC)-atomic emission detection (AED) can be used in a low-resolution mode for rapid, accurate determinations of total sulfur in fuels at trace levels to complement other popular methods of total sulfur analysis. A method for the rapid determination of total sulfur in fuels (called "fast GC-AED") is developed. The method is tested on gasoline, jet fuel, kerosene, and diesel fuel with sulfur concentrations ranging from 125 mg/L down to 2.5 mg/L. Fast GC-AED shows better performance than traditional GC-AED for total sulfur determinations, especially for complex mixtures containing many different sulfur-containing compounds at trace levels. This method also shows that GC-AED can be used for both rapid determinations of total sulfur and traditional determinations of speciated sulfur without requiring equipment changes. Fast GC-AED is competitive with other popular methods for sulfur analysis. The 5-min program that is developed for fast GC-AED is comparable with the time scale of other methods, such as wavelength dispersive X-ray fluorescence and UV-fluorescence (2 to 5 min). Fast GC-AED also compares favorably with UV-fluorescence for trace sulfur determinations, demonstrating accuracy down to 2.5-mg/L sulfur.     

Pressure dependence of the superconducting state parameters of metallic glass superconductor Mg70Zn30

Explicit expressions have been derived for the volume dependence of electron-phonon coupling strength (λ) and the Coulomb pseudopotential (μ^*) considering the variation of Fermi momentum (κ _F) and Debye temperature (θ _D) with volume. Ashcroft’s model pseudopotential and RPA form of dielectric screening have been used for obtaining pressure dependence of transition temperature (T _C) and the logarithmic volume derivative (Φ) of the effective interaction strength (N ₀ V) for metallic glass superconductor Mg₇₀Zn₃₀. It has been observed that T _C of the metallic glass Mg₇₀Zn₃₀ decreases rapidly with increase of pressure and the superconducting phase disappears at about 30% decrease of volume, for which the μ^* curve shows a minimum and an elbow is formed in the Φ graph.     

Rare Earth Chalcogels NaLnSnS4 (Ln = Y,Gd, Tb) for Selective Adsorption of Volatile Hydrocarbons and Gases

The synthesis and characterization of the rare earth chalcogenide aerogels NaYSnS₄, NaGdSnS₄, and NaTbSnS₄ is reported. Rare earth metal ions like Y³⁺, Gd³⁺, and Tb³⁺ react with the chalcogenide clusters [SnS₄]^4– in aqueous formamide solution forming extended polymeric networks by gelation. Aerogels obtained after supercritical drying have BET surface areas of 649 m² · g^–1 (NaYSnS₄), 479 m² · g^–1 (NaGdSnS₄), and 354 m² · g^–1 (NaTbSnS₄). Electron microscopy and physisorption studies reveal that the new materials have pores in the macro (above 50 nm) and meso (2–50 nm) regions. These aerogels show higher adsorption of toluene vapor over cyclohexane vapor and CO₂ over CH₄ or H₂. The notable adsorption capacity for toluene (NaYSnS₄: 1108 mg · g^–1; NaGdSnS₄: 921 mg · g^–1; and NaTbSnS4: 645 mg · g^–1) and high selectivity for gases (CO₂/H₂: 172 and CO₂/CH₄: 50 for NaYSnS₄, CO₂/H₂: 155 and CO₂/CH₄: 37 for NaGdSnS₄, and CO₂/H₂: 75 and CO₂/CH₄: 28 for NaTbSnS₄) indicate potential future use of chalcogels in adsorption‐based gas or hydrocarbon separation processes.     

DFT modeling of silver disorder and mobility in the semiconductor cluster [Ag28S26(P(O)PhOMe)12(PPh3)12

Disorder of silver atoms and high cation mobility are commonly observed and closely coupled features in silver chalcogenides. The ligand-stabilized cluster [Ag28(micro6-S)2{ArP(O)S2}12(PPh3)12] (1) (Ar=4-anisyl), with a total of 666 atoms, displays in its X-ray structure highly localized disorder at two core silver atoms. To explore the nature of this disorder, we have applied density functional methods to its internal structure and flexibility. The pseudo-S6 symmetry of the cluster provides six equivalent pockets to place the pair of silver atoms, and with the exception of populating neighboring sites, all permutations relax to structures with similar cores. The barrier to concerted motion of the central silver atoms from one set of pockets to the next of the Ci-symmetric conformer is estimated to be less than about 26 kJ mol(-1). Cluster 1 can be considered a model for bulk phase cation mobility.     

Synthesis and structures of two new coordination polymers formed by large polyoxometalate fragments and lanthanide cations

The reactions of the polyoxometalate [Mo₃₆O₁₀₈(NO)₄(H₂O)₁₆]^12? with EuCl₃· 6H₂O and Tm₂(SO₄)₃ · 8H₂O afford the coordination polymers with the following composition: (H₃O)_3.67{Eu(H₂O)₄}{Eu(H₂O)₆}₂ {Mo₃₆(NO)₄O₁₀₈(H₂O)₁₆)}Cl_0.67 · 29.5H₂O and (H₃O)₅[{Tm(H₂O)₆}₂{Tm(H₂O)₄} {Mo₃₆(NO)₄ O₁₀₈(H₂O)₁₆}]Cl₂ · 45H₂O, respectively, in which the polyoxometalate fragments are linked to each other by lanthanide cations to form infinite chains.     

Cleavage of P-S bonds and oxygenation by a trinuclear iron carboxylate: synthesis and structures of iron clusters containing group 15/16 anions

The first reactions of the trinuclear oxygen-centred iron carboxylate [Fe(3)(mu(3)-O)(mu(2)-piv)(6)(H(2)O)(3)](piv) (piv=(t)BuCOO(-)) with the neutral ligand precursor [RP(S)(mu-S)](2) (R=4-anisyl) are reported.