Resolution of 3,3 '-dioxo-1,1 '(3H,3 ' H)spirobi[isobenzofuran]-5,6,5 ' 6 '-tetracarboxylic acid and Optically active Polyimides thereof

3,3'-Dioxo-1.1'(3H.3'H)spirobi[isobenzofuran]-5,6,5',6 acid 1 was resolved successfully and the corresponding optically active polyimides PI were synthesized. The properties of the optically active PI and the racemic one were investigated. The results showed that the specific rotation of(-)-PI was about two times to that of the: (+)-PI, and the regularity of the optically active PI was higher than that of the racemic one.

X-ray crystal structure and molecular mechanics calculations of (2,6-iso-dipropyl-phenylamide) dimethyl (tetra-methylcyclopenta-dienyl) silane titanium dichloride

Crystal and molecular structure of (2.6-dipropylphenylamide) dimethyl (tetra-methyl cyclopentadienyl) silane titanium dichloride (I) was fully characterized by X-ray diffraction. The crystal is obtained from a mixture of ether/hexane as orthorhombic. with a = 12.658 (3) Angstrom. b = 16.62 (3) Angstrom. c = 11.760 (2) Angstrom. V = 2474.2 (9) Angstrom(3). Z = 4, space group Pnma. R = 0.0399; Componud I compose of the pi-bounded ring with its dimethylsilyl-dipropyl phenyl amido group and the two terminal chloride atoms coordinated to central metal to form a so-called constrained geometry catalyst (CGC) structure. The result of molecular mechanics (MM) calculations on compound I shows that bond lengths and bond angles from the MM calculation are comparable to the data obtained from the X-ray diffraction study. The relation of the structure of CGCs and their catalytic activity by MM calculations is also discussed.

Synthesis and crystal structure of a new supermolecular compound: [C12H24O6][H3PMo12O40]center dot 22H(2)O (C12H24O6=18-crown-6)

The title compound, [C12H24O6][H3PMo12O40]. 22H(2)O, was synthesized by the self-assembly of 18-crown-6 (abbreviated as C12H24O6 or 18C6) and H3PMo12O40 in the mixed solvent of CH3OH and CH3CN, and was characterized by IR, H-1 NMR and Xray diffraction for the first time. Crystal data: Triclinic, P (1) over bar, a = 13.428(3) Angstrom, b = 13.557(3)A, c = 14.642(3) Angstrom, a = 105.39(3)degrees, beta = 90.06(3)degrees, gamma = 119.56(5)degrees, V = 2207.5(8) Angstrom(3), Z = 1, R1 = 0.0719, wR2 = 0.1990. It has a disordered alpha-Keggin PMo12O403- anion, which contains the strong alternating short (mean 1.844 Angstrom) and long (mean 1.958 Angstrom) Mo-O-Mo bonds. In the unit cell, crown ethers and molybdophosphates are alternatively arranged in good order along c-axis. An oxonium ion is located at the center of a crown ether molecule., Oxonium ion interacts with 18C6 by the means of hydrogen bonds (mean 2.7771 Angstrom), which are electrostatic or resonant. The observations show the existence of [H3O(C12H24O6)](+) (C) 2000 Elsevier Science B.V. All rights reserved.

Synthesis, structure characterization and biological activity of a novel amino acid salt (HAla)(8)(H3O)(10)[PMo12O40](6) center dot 22H(2)O

A novel compound was synthesized and characterized by means of elemental analysis, IR and UV spectra, TG, CV and single crystal X-ray diffraction. The compound crystallized in an orthorhombic space group C222 with a=1. 622 4(3) nm, b=3. 498 4(7) nm, c=1. 301 5(3) nm, V=7. 387 (3) nm(3), Z=6, R-1= 0. 037 3, wR(2)=0. 114 0. The Ala (Ala = alanine) molecules were protonated at the amino nitrogen N (1) and the C (2) of Ala group with the terminal oxygen atom O(15), O(14), O(26) and O(27) of the polyoxometalates participating in the hydrogen bond network. The anti-tumor activity of the title compound was estimated against Hela and Pc-3m cancer cells.

P-6(7/2)-excited-state decay mechanism and energy-transfer processes in KMgF3 : Eu2+ and KMgF3 : EuX (X = Gd, Ce, Cr)

A four-level decay model in KMgF3:Eu2+ is proposed. The decay profiles of the P-6(7/2) excited state of Eu2+ are biexponential, and the physical implication of each term in the fit equation responsible for the model is interpreted. The evidence obtained spectroscopically for supporting the model is presented. A new method to study energy transfer between Eu2+ and X3+ in KMgF3:Eu-X (X = Gd, Ce, Cr) is established on the basis of the proposed model.

Sol-gel-derived carbon ceramic electrode containing 9,10-phenanthrenequinone, and its electrocatalytic activity toward iodate

9,10-Phenanthrenequinone (PQ) supported on graphite powder by adsorption was dispersed in propyltrimethoxysilane-derived gels to yield a conductive composite which was used as electrode material to fabricate a PQ-modified carbon ceramic electrode. In this configuration, PQ acts as a catalyst, graphite powder guarantees conductivity by percolation, the silicate provides a rigid porous backbone, and the propyl groups endow hydrophobicity and thus limit the wetting region of the modified electrode. Square-wave voltammetry was exploited to investigate the pH-dependent electrochemical behavior of the composite electrode and an almost Nernstian response was obtained from pH 0.42 to 6.84. Because the chemically modified electrode can electrocatalyze the reduction of iodate in acidic aqueous solution (pH 2.45), it was used as an amperometric sensor for the determination of iodate in table salt. The advantages of the electrode are that it can be polished in the event of surface fouling, it is simple to prepare, has excellent chemical and mechanical stability, and the reproducibility of surface-renewal is good.

Synthesis and characterization of polynuclear half-sandwich lanthanoid complexes [Na(THF)(6)](2)[(Cp6Sm6Se13)-Sm-t] and [Li(LHF4](2)[Cp6Nd6Se13]

The half-sandwich tert-butyl cyclopentadienyl lanthanoid complexes {[Cp ' Ln(THF)](2)(mu (2)-Cl)(2)(mu (3)-Cl)(3)Na(THF)}(n) [Cp ' = eta (5)-' BuC5H4; Ln = Nd (1a), Sm (1b), Gd (1c), Yb (1d)] are prepared by the reaction of anhydrous lanthanoid trichloride, LnCl(3), with NaCp ' in THF solution. Complex 1b reacts with Na2Se5 to give hexanuclear samarium polyselenide complexes [Na(THF)(6)](2)[Cp-6' SM6(mu (6)-Se)(mu -Se-2)(6)] (2). An analogous cyclopentadienyl neodymium polyselenide complex [Li(THF)(4)](2)[Cp6Nd6(mu (6)-Se)(mu -Se-2)(6)] (3) is synthesized by the reaction of [CpNdCl2. 2LiCl . 5THF] with Na2Se5 in THF solution. The molecular structures of 1a and 2 were determined by X-ray crystal structure analysis. Complex 2 contains an interstitial selenium atom which is coordinated with six samarium atoms. (C) 2001 Elsevier Science BN. All rights reserved.

Synthesis and crystal structure of [Nd(eta(6)-1,3,5-C6H3Me3)(AlCl4)(3)]( C6H6) and structural comparison of Ln(eta(6)-arene)(AlCl4)(3)

Reaction of NdCl3, with AlCl3 and mesitylene in benzene gives complex [Nd(eta (6)-1,3,5-C6H3Me3) (AlCl4)(3)] (C6H6) (1) which was characterized by elemental analysis, IR spectra, MS and X-lay diffractions. The X-ray determination indicates that 1 has a distorted pentagonal bipyramidal geometry and crystallizes in the monoclinic, space group P2(1)/n with a = 0.9586(2), b = 1.1717(5), c = 2.8966(7) nm, beta = 90.85 (2)degrees, V = 3.2529(6) nm(3), D-c = 1.573 g/cm(3), Z = 4. A comparison of bond parameters for all the reported Ln(eta (6)-Ar) (AlCl4)(3) complexes indicates that the bond distance of Ln-C is shortened with the increasing of methyl group on benzene and with the decreasing of radius of lanthanide ions.

Reactive blending of polyamide 6,6 and Vectra A

In this paper, blends of Nylon 6,6 with the liquid crystal polymer Vectra A950 are considered; specifically we focused our attention on Nylon 6,6 modifications by interchange reactions that can occur in the melt, as a function of mixing conditions and blend compositions. Two matrix samples have been used, characterised by a slightly different relative amount of amine and carboxylic end groups, being the latter predominant in both cases. The dried polymers Nylon 6,6/Vectra, combined in weight ratios between 95/5 and 50/50, were subjected to reactive blending with different methods (single-screw extruder, Brabender, pyrex reactor). Pure Nylon samples have been also investigated as reference materials. The soluble Nylon 6,6-rich fraction of each blend was separated from the insoluble Vectra-rich one and used for molecular and spectroscopic characterisations. Thermal and morphological analyses, as well as testing of tensile properties, were carried out on the blends. Evidences of the occurrence of interchange reactions are given and the most probable ones are suggested. (C) 2001 Elsevier Science Ltd. All rights reserved.

Synthesis and crystal structure of a novel amino-acid-containing polyoxometalate: K-6[Cu (Ala)(2) (H2O)(2)](2)[ CU4 (H2O)(2) (AsW9O34)(2)] center dot 16H(2)O

The novel amino-acid-containing polyoxometalate Ka(6) [Cu(Ala)(2) (H2O)(2)](2) [Cu-4 (H2O)(2) . (AsW9O34)(2)] . 16H(2)O was synthesized from the reaction of K-10[Cu-4(H2O)(2)(AsW9O34)(2)] . 20H(2)O with beta -alanine, Its structure has been determined by single crystal X-ray diffraction. It crystallizes in the triclinic space group P (1) over bar, with a=1. 196 3(2) nm, b=1. 536 5(3) nm, c=1. 591 4(3) nm, alpha =93. 97(3)degrees, beta= 110. 88(3)degrees, gamma =101. 07(3)degrees, V=2. 651 8(9) nm(3) and Z=1. Least-squares refinement of the structure leads to R and R-w factors of 0. 067 3 and 0. 162 8, respectively. An unusual structural feature of the compound is that the polyanion [Cu-4(H2O)(2) (AsW9O34)](10-) is linked with the amino-acid complex of Cu2+ by a mu -oxygen atom.

Four-level decay model of P-6(7/2) excited state of Eu2+ ion in KMgF3

A four-level model of P-6(7/2) excited state of Eu2+ ion in KMgF3: Eu2+ has been proposed. The decay profiles of the P-6(7/2) excited sstate of Eu2+ are two exponential and the physical implication of each term in the fit equation responsible for the model is interpreted. The data obtained spectroscopically are in good agreement with the fit results.

Study of energy transfer in KMgF3 : Eu-X (X = Gd, Cr, Ce) by the decay model of P-6(7/2) exited state of Eu2+

Energy transfer processes between Eu2+ and Gd3+, Cr3+, Ce3+ ions in KMgF3, which are difficult to study spectroscopically, have been investigated by using the proposed four-level decay model of the P-6(7/2) excited state of the Eu2+ ion. Gd3+ and Ce3+ transfer its energy to the vibronic transition of the P-6(7/2) --> S-8(7/2) transition of Eu2+, whereas Cr3+ receive energy from Eu2+ via the d-d interaction. The energy transfer from the Eu2+ 4f(6)5d level to the Ce3+ 4f5d state is observed spectroscopically, and the energy transfer mechanism is discussed. (C) 2001 Elsevier Science B.V. All rights reserved.

A manganese molybdenum phosphate with a tunnel: hydrothermal synthesis, structure and catalytic properties of (NH3CH2CH2NH3)(10-)H3O)(3)(H5O2)Na-2[MnMo12O24(OH)(6)(PO4)(4)(PO3OH)(4)]-[MnMo12O24(OH)(6)(PO4)(6)(PO3OH)(2)] center dot 9H(2)O

A manganese molybdenum phosphate, (NH3CH2CH2NH3)(10)(H3O)(3)(H5O)Na-2[MnMo12O24(OH)(6) (PO4)(4)(PO3OH)(4)][MnMo12O24 (OH)(6)(PO4)(6)(PO3OH)(2)]. 9H(2)O, has been hydrothermally synthesized and structurally characterized by single crystal X-ray diffraction. The structure of this compound may be considered to be two [Mo6O12(OH)(3)(PO4)(2)(HPO4)(2)](7-) units bonded together by a manganese atom, although several P-O groups are not protonated on account of coordination to a Na+ cation. One-dimensional tunnels were formed in the solid. A probe reaction of the oxidation of acetaldehyde with H2O2 using this compound as catalyst was carried out in a liquid-solid system, showing that the manganese molybdenum phosphate has high catalytic activity in the reaction.

End-column amperometric detection of 6-mercaptopurine by capillary zone electrophoresis

End-column amperometric detection of 6-mercaptopurine by capillary zone electrophoresis was described with high resolution and speed. The detection conditions were optimized and the electrochemical behavior was observed. Under the optimal conditions: detection potential of 1.2 V ( vs. Ag/AgCl), operating voltage of 15 kV, sample injection of 3 s at 15 kV and 10 mmol/l Na2HPO4 buffer, the detection limit for 6-MP was as low as 1 x 10(-7) mol/L and the linear range was from 5 x 10(-4) to 5 x 10(-6) mol/L with the relative coefficient of 0.995. The RSD of reproducibility for peak current and migration time was 2.5% and 1.2%, respectively. This method was utilized in assay real sample of human mine and bovine serum albumin containing 6-mercaptopurine.

Crystal structure of mixed sodium-potassium paradodecatungstate 6-hydrate

The crystal structure of K7Na3[H2W12O42]3 . 6H(2)O was determined by X-ray crystallography,and refined to R=0.0864 based on 7024 observed reflections (I>2 sigma(I)). The crystallographic parameters are a=11.755(2), b=13.0493(3), c=16.289(3) Angstrom; alpha=77.13(3)degrees, beta=82.92(3)degrees, gamma=89.65(3)degrees, triclinic, space group, P (1) over bar, V=2416.7(8) Angstrom(3), Z=2, M-r=3330.98, D-cal=4.578Mg/m(3), F(000)=2904; mu (MoK alpha)=29.170mm(-1), T=293K. Two independent polyanions are centered respectively at 1,1,1/2 and 1/2, 1/2, 0, approximately perpendicular to each other with dihedral angle between the equatorial planes of the molecules at 96 degrees. K+ and Na+ respectively occupy the clefts of the two discrete polyanions.