Synthesis and structure of iron complex with 1,2-dithiolate-1,2-dicarba-closo-dodecaborane [Li(THF)(4)][Fe(S2C2B10H10)(2)(THF)]

The crystal of complex [Li(THF)(4)][Fe(S2C2B10H10)(2)(THF)] 3 belongs to monoclinic, space group P2(1) with a = 11.964(2), b = 16.527(3), c = 12.554(3) Angstrom,beta = 108.70(3)degrees, V= 2351.3(8) Angstrom(3), Z = 2, M-r = 835.95, D-c = 1.181 g/cm(3), mu (MoKalpha) = 5.30 cm(-1), f(000) = '874, R = 0.0622 and Rw 0.1538 for 1641 observed reflections with I > 2sigma(I). The ionic complex,of 3 contains the square pyramidal anion of [Fe(S2C2B10H10)(2)(THF)](-) and the tetrahedral cation of [Li(THF)(4)](+). The iron is 5-coordinated and located in the square pyramidal configuration. The iron atom and the four sulfur atoms are almost coplanar. The Lithium atom is coordinated with four oxygen atoms of four THF molecules and located in a tetrahedral configuration.

Synthesis, characterization and molecular structure of a novel asymmetrical half-sandwich binuclear iron carborane complex Cp ' Fe-2(2)(CO)(3)(Se2C2B10H10)

The half-sandwich methylcyclopentadlenyl iron carbonyl complex reacted with 1,2-dilithium diselenolate carborane Li2Se2C2B10H10 (1) which was produced by the insertion of element Se into 1, 2-dilithium carborane to give a half-sandwich binuclear iron carborane complex Cp'Fe-2(2)(CO) 3Se2C2B10H10 (3). X-ray structural analysis of complex 3 reveals that one of the iron atoms is chiral.

Chemical bond properties and Mossbauer spectroscopy in REBa2Cu3O7 (RE = Eu, Y)

By using the chemical bond theory of complex crystals, the chemical bond properties of REBa2Cu3O7 (RE = Eu, Y) were calculated. The calculated covalencies for Cu(1)-O and Cu(2)-O bond in REBa2Cu3O7 compounds are 0.41 and 0.28 respectively. Mossbauer isomer shifts of Fe-57 doped, and Sn-119 doped in REBa2Cu3O7-x were calculated by using the chemical environmental factor, h(e), defined by covalency and electronic polarizability. Four valence state tin ion and iron ion sites were identified in Fe-57 and Sn-119 doped REBa2Cu3O7-x superconductors.

Synthesis of tetra-iron substituted sandwich-type pentadecatungstodiarsenate and its multilayers on glassy carbon electrode by self-assembly with electrocatalytic properties

A novel sandwich-type compound, Na-12 [Fe-4 (H2O)(2) (As2W15O56)(2)] . 38H(2)O (denoted as Fe(4)AS(4)W(30)) was synthesized. The compound was well characterized by means of IR, UV-Vis, W-138 NMR and elemental analyses. Redox electrochemistry of the compound has been studied in acid buffer solutions using cyclic voltammetry(CV). The compound containing multilayer films has been fabricated on the 4-aminobenzoic acid(4-ABA) modified glassy carbon electrode(GCE) surface by alternate deposition with a quaternized poly (4-vinylpyridine) partially completed with [Os(bpy)(2)Cl](2+/-) (denoted as QPVP-Os). CV, X-ray photoelectron spectroscopy (XPS) and UV-Vis spectroscopy were used to characterize the asprepared multilayer films. It is proved that the multilayer films are uniform and stable. The electrocatalytic activities of the multilayer films were investigated on the reduction of two substrates of important analytical interest, NO2- and H2O2.

Sol-gel derived carbon ceramic electrode bulk-modified with tris(1,10-phenanthroline-5,6-dione)iron(II) hexafluorophosphate and its use as an amperometric iodate sensor

A surface-renewable tris (1,10-phenanthroline-5, 6-dione) iron (II) hexafluorophosphate (FePD) modified carbon ceramic electrode was constructed by dispersing FePD and graphite powder in methyltrimethoxysilane (MTMOS) based gels. The FePD-modified electrode presented pH dependent voltammetric behavior, and its peak currents were diffusion-controlled in 0.1 mol/L Na2SO4 + H2SO4 solution (pH = 0. 4). In the, presence of iodate, clear electrocatalytic reduction waves were observed and thus the chemically modified electrode was used as an amperometric sensor for iodate in common salt. The linear range, sensitivity, detection limit and response time of the iodate sensor were 5 x 10(-6)-1 x 10(-2) mol/L, 7.448 muA.L/mmol, 1.2 x 10(-6) mol/L and 5 s, respectively. A distinct advantage of this sensor is its good reproducibility of surface-renewal by simple mechanical polishing.

Polymerized unsymmetrical iron post-metallocene catalyst for ethylene polymerization

The unsymmetrical allyl containing post-metallocene complex [ArN = C( Me)] [(ArN)-N-' = C(Me)]C5H3NFeCl2 [Ar = 2,6(i- Pr)(2)C6H3, Ar' = 4-allyl-2,6-(i-Pr)(2)C6H3] (3) has been prepared and characterized. Complex (3) can be co-polymerized with styrene in the presence of radical initiator to produce polymerized post-metallocene catalyst which exhibits high activity for ethylene polymerization (2.5 x 10(6) g PE/mol Fe.h).

Expert system for elucidation of structures of organic compounds (ESESOC) - Algorithm on stereoisomer generation

An algorithm for enumeration of stereoisomers due to asymmetric carbon, C=C double bond and so on has been developed. It consists of three steps. The output of stereoisomers can be represented by 2.5-dimensional connection table.

Investigation of covalency and spectrum shifts in 3d transition-metal compounds

By using a correction factor of d electron effects on bond, PV theory is applied to the calculation of chemical bond;parameters of d transition-metal compounds. Racah parameters and Mossbauer isomer shifts are calculated, and the results are agreement with the experimental values.

Fullerenes-extracted soot: a new adsorbent for collecting volatile organic compounds in ambient air

Fullerenes-extracted soot (FES) is the by-product of fullerenes production. Retention characteristics at different temperatures for 17 volatile organic compounds (VOCs) on FES are measured. The adsorption and desorption efficiencies for VOCs on FES adsorbent tubes range from 40.8 to 117%, most of them being 100+/-20%. The values are compared with Tenax GR, an adsorbent commonly used in environmental analysis. FES can be used as an adsorbent of low cost to collect VOCs in environmental samples. (C) 2000 Elsevier Science B.V. All rights reserved.

Spectroscopy of several beta-diketone compounds and their tautomers

Six beta-diketone compounds, 1,3-bis(4-nitrophenyl)-1,3-propanedione (1), 1-(4-nitrophenyl)-3-(3-nitrophenyl)-1,3-propanedione(2), 1,3-bis(3-nitrophenyl)-1,3-propanedione(3) 1,3-bis(4-amimophenyl)-1,3-propanedione(4), 1-(4-amimophenyl)-3-( 3-amimophenyl)-1,3-propanedione(5) and 1,3-bis (3-amimophenyl)-1,3-propanedione(6) were synthesized, Their structures were characterized by IR, UV-Vis, fluorescence and NMR spectroscopy, The percentage of keto tautomer, enol-keto equilibrium constant and enol tautomer ratio of them were also determined, The percentage of keto tautomer is increased in the order from compound 1 to 3 and decreased in the order from compound 4 to 6, which show the effect of substituent on the tautomer. The results of enol tautomer ratio of compounds 2 and 5 indicated that b-form of enol is slightly more favorable than its a-form.

Theoretical studies of nonlinear optical properties of compounds K(4)Ln(2)(CO3)(3)F-4 (Ln=Pr, Nd, Sm, Eu, Gd)

K(4)Ln(2)(CO3)(3)F-4 (Ln=Pr, Nd, Sm, Eu, Gd) is a special type of frequency doubling compound, whose crystal structure exhibits a scarcity of fluorine ions. This leads to two different coordination polyhedrons in the general position of K(2) atoms: [K(2)O6F(1)(2)F(2)] and [K(21)O6F(1)(2)] in a 2/1 ratio. The chemical bonding structures of all constituent atoms of the compound K4Gd2(CO3)(3)F-4 (KGCOF) are comprehensively studied; moreover, the relationship between the chemical bonding structure and the nonlinear optical (NLO) properties is investigated from the chemical bond viewpoint. The theoretical prediction of the NLO tensor coefficient d(11) of KGCOF is in agreement with experimental observation. Theoretical analyses show that the nonlinearity of this crystal type mainly originates from K-O bonds. In addition, the correlation between the NLO tensor d(11) and the refractive index n(0) of KGCOF is discussed. (C) 2000 American Institute of Physics. [S0021-8979(00)07506-X].

Quantitative structure-property relationship research to the analysis of photoionization sensitivity of organic compounds in gas chromatography

The A(m) index and molecular connectivity index were used for studying the photoionization sensitivity of some organic compounds in gas chromatography. The analysis of structure-property relationship between the photoionization sensitivity of the compounds and the A(m) indices or molecular connectivity indices has been carried out. The genetic algorighm was used to build the correlation model in this field. The results demonstrate that the property of compounds can be described by both A(m) indices and molecular connectivity indices, and the mathematical model obtained by the genetic algorithm was better than that by multivariate regression analysis.

Amperometric tyrosinase biosensor based on a sol-gel-derived titanium oxide-copolymer composite matrix for detection of phenolic compounds

A new type of tyrosinase biosensor was developed for the detection of phenolic compounds, based on the immobilization of tyrosinase in a sol-gel-derived composite matrix that is composed of titanium oxide sol and a grafting copolymer of poly(vinyl alcohol) with 4-vinylpyridine. Tyrosinase entrapped in the composite matrix can retain its activity to a large extent owing to the good biocompatibility of the matrix. The parameters of the fabrication process and the variables of the experimental conditions for the enzyme electrode were optimized. The resulting sensor exhibited a fast response (20 s), high sensitivity (145.5 muA mmol(-1) 1) and good storage stability. A detection limit of 0.5 muM catechol was obtained at a signal-to-noise ratio of 3.

Investigation of the model compounds at 4-aminobenzoic acid modified glassy carbon electrode by scanning electrochemical microscopy

In this paper, we studied the reactions of both potassium ferricyanide and hexaammineruthenium(III) chloride at a 4-aminobenzoic acid (4-ABA) modified glassy carbon electrode (GCE) by scanning electrochemical microscopy (SECM) in different pH solutions. The surface of the modified electrode has carboxyl groups, the dissociation of which are strongly dependent upon the solution pH values. The rate constant kb of the oxidation of ferrocyanide on the modified electrode can be obtained by fitting the experimental tip current-distance (I-T-d) curves with the theoretical values. The surface pK(a) of the 4-ABA modified GCE was estimated from the plot of standard rate constant k(o) versus the solution pH and is equal to 3.2, which is in good agreement with the reported result. The SECM approach curves for Ru(NH3)(6)(3+) both on the bare and the modified electrodes show similar diffusion control processes. These results can be explained by the electrostatic interactions between the modified electrode surface and the model compounds with different charges. (C) 2001 Elsevier Science BN. All rights reserved.

Gold-coated iron (Fe@Au) nanoparticles: Synthesis, characterization, and magnetic field-induced self-assembly

A unique reverse micelle method has been developed to prepare gold-coated iron (Fe@Au) nanoparticles. XRD, UV/vis, TEM, and magnetic measurements are utilized to characterize the nanocomposites. XRD only gives FCC patterns of gold for the obtained nanoparticles. The absorption band of the Fe@Au colloid shifts to a longer wavelength and broadens relative to that of the pure gold colloid. TEM results show that the average size of Fe@Au nanoparticles is about 10 nm, These nanoparticles are self-assembled into chains on micron scale under a 0.5 T magnetic field. Magnetic measurements show that the particles are superparamagnetic with a blocking temperature (T-B) of 42 K, At 300 K (above T-B), no coercivity (Hc) and remanence (M-r) is observed in the magnetization curve, while at 2K (below T-B) He and M, are observed to be 728 Oe and 4.12 emu/g, respectively, (C) 2001 Academic Press.