The use of half-sandwich iridium dithiolate and diselenolate complexes, Cp*Ir(L)(ER)(2) (L = CO, PMe3, PPh3; ER = SPh, SePh, SeMe), for the synthesis of heterodimetallic compounds. The molecular structure of Cp*Ir(CO)(mu-SePh)(2)[Mo(CO)(4)]

Carbonyl-iridium half-sandwich compounds, Cp*Ir(CO)(EPh)(2) (E = S, Se), were prepared by the photo-induced reaction of Cp*Ir(CO)(2) with the diphenyl dichalcogenides, E2Ph2, and used as neutral chelating ligands in carbonylmetal complexes such as Cp*Ir(CO)(mu-EPh)(2)[Cr(CO)(4)], Cp*Ir(CO)(mu-EPh)(2)[Mo(CO)(4)] and Cp*Ir(CO)(mu-EPh)(2)[Fe(CO)(3)], respectively. A trimethylphosphane - iridium analogue, Cp*Ir(PMe3)(mu-SeMe)(2)[Cr(CO)(4)], was also obtained. The new heterodimetallic complexes were characterized by IR and NMR spectroscopy, and the molecular geometry of Cp*Ir(CO)(mu-SePh)(2)[Mo(CO)(4)] has been determined by a single crystal X-ray structure analysis. According to the long Ir...Mo distance (395.3(1) Angstrom), direct metal-metal interactions appear to be absent. (C) 1998 Elsevier Science S.A. All rights reserved.

Intramolecular energy transfer mechanism between ligands in ternary rare earth complexes with aromatic carboxylic acids and 1,10-phenanthroline

A series of binary and ternary rare earth (Gd, Eu, Tb) complexes with aromatic acids and 1,10-phenanthroline have been synthesized. The lowest triplet state energies of ligands have been obtained by measuring the phosphorescence spectra of binary gadolinium complexes. By comparing the phosphorescence spectra of binary complexes with those of ternary ones, it is found that there exists another intramolecular energy transfer process from the aromatic acids to 1,10-phenanthroline besides the intramolecular energy transfer process between the aromatic acids and the central rare earth ions. The intramolecular energy transfer efficiencies have been calculated by determining phosphorescence lifetimes of binary and ternary gadolinium complexes. The luminescence properties of corresponding europium and terbium complexes are in agreement with the prediction based on energy transfer mechanism. (C) 1998 Elsevier Science S.A. All rights reserved.

Structure, electric and magnetic properties of new compounds CdYMWO7 (M = Cr and Mn)

Two new compounds with the formula of CdYMWO7 (M = Cr, Mn) were prepared by solid state reaction. They crystallized with orthorhombic structure with the cell parameters of a = 11.7200 Angstrom, b = 7.1779 Angstrom, c = 6.9805 Angstrom (CdYCrWO7), and a = 11.7960 Angstrom, b = 6.1737 Angstrom, c = 7.6530 Angstrom (CdYMnWO7). These compounds are insulators with high resistivities at room temperature. The temperature dependence of the magnetic susceptibility of CdYMWO7 (M = Cr and Mn) show Curie-Weiss Law's behaviors from 80 to 300 K. The magnetic moments at room temperature fit very well with those corresponding to Cr3+ and Mn3+ ions. This suggests that both Cr and Mn ions exist in + 3 oxidation state in CdYMWO7 compounds. (C) 1998 Elsevier Science Ltd. All rights reserved.

Spectroscopic study of luminescence and energy transfer of binary and ternary complexes of rare earth with aromatic carboxylic acids and 1,10-phenanthroline

A series of rare earth (Gd, Eu, Tb) complexes with different substituent group carboxylic acids (ortho-hydroxylbenzioc acid, ortho-aminobenzoic acid and ortho-methoxy benzoic acid) and 1,10-phenanthroline were synthesized. The spectroscopic studies of the photophysical properties such as luminescence properties, energy match and intramolecular energy transfer were carried out. The lowest triplet state energies of ligands and the intramolecular energy transfer efficiencies were determined with the measurement of low phosphorescence spectra and lifetimes of Gd complexes.

Catalysis of hydrotalcite-like compounds in liquid phase oxidation: (II) - Oxidation of p-cresol to p-hydroxybenzaldehyde

Hydrotalcite-like compounds (HTLcs): CoMAlCO3-HTLcs (M=Cu2+, Ni2+, Mn2+, Cr3+, Fe3+), were synthesized by coprecipitation and characterized with XRD and IR. The catalysis of these HTLcs and their calcined products were studied in the p-cresol oxidation, and the effects of the temperature of HTLcs calcination, the ratio of Co/Cu, different promoters, reaction temperatures and reaction times on reaction activities were investigated. It has been found that calcined HTLcs have higher activity than uncalcined samples and mechanical mixed oxides in this reaction. The best yield was obtained from the CoCuAlCO3-HTLc (Co/Cu/Al=3:1:1) calcined at 450 degrees C. A tentative reaction mechanism was also proposed. (C) 1998 Elsevier Science B.V.

Catalysis of hydrotalcite-like compounds in liquid phase oxidation: (I) phenol hydroxylation

Hydrotalcite-like compounds (HTLcs): (CuMAlCO3)-Al-II-HTLcs, where M-II=Co2+, Ni2+, Cu2+, Zn2+ and Fe2+, were synthesized by coprecipitation and characterized with XRD and IR. The catalysis of these HTLcs was studied in the phenol hydroxylation by H2O2 in liquid phase; then the effects of the ratio of Cu/Al, reaction temperature, solvent and pH of medium were investigated. It has been found that the uncalcined HTLcs have higher activities than those of calcined samples in this reaction. The catalyst CuAlCO3-HTLcs having Cu/Al=3 efficiently oxidized phenol and gave high yields of the corresponding diphenols in appropriate reaction conditions. A tentative reaction mechanism is also proposed. (C) 1998 Elsevier Science B.V.

A study of catalysis of copper-aluminium hydrotalcite-like compounds in the phenol hydroxylation

Copper-Aluminium Hydrotalcite-like compounds are synthesized by coprecipitation and characterized with XRD and IR. Catalysis of the above mentioned HTLcs are investigated in the phenol hydroxylation, good results are obtained. Meanwhile, the effects of the ratio of Cu/Al, reaction temperature, reaction medium and pH of reaction system are discussed, The reaction mechanism is also proposed.

Structure, luminescence and magnetic properties of AgLnW(2)O(8) (Ln = Eu, Gd, Tb and Dy) compounds

Four new compounds AgLnW(2)O(8) (Ln = Eu, Gd, Tb and Dy) are prepared by solid-state reactions. They crystallize with a scheelite-related monoclinic symmetry. Infrared (IR) spectra show complicated absorption transitions in the region of 1000-400 cm(-1) that are similar to those of AgLnMo(2)O(8). Broad excitation and emission bands of the tungstate group are observed in AgGdW2O8 and AgTbW2O8 with a large Stokes shift, 12 573 and 12 387 cm(-1), respectively. Excitation and emission spectra of AgLnW(2)O(8) (Ln = Eu, Gd and Tb) show that energy transfer from the tungstate to EU3+, Gd3+ and Tb3+ occurs and that Eu3+ ions occupy a single crystallographic site with the C-2 Site symmetry. (C) 1997 Elsevier Science Ltd. All rights reserved.

Synthesis, luminescence and intramolecular energy transfer of binary and ternary rare earth complexes with aromatic carboxylic acids and 1,10-phenanthroline

A series of binary and ternary rare earth complexes with para-substitued benzoic acids and 1,10-phenanthroline were synthesized. The phosphorescence spectra were measured and the lowest tripler state energies of ligands were determined, the phosphorescence lifetimes were obtained and intramolecular energy transfer mechanism between ligands was studied. The luminescence properties were also measured and were in agreement with the prediction. The energy match and intramolecular energy transfer process in these binary and ternary complexes were discussed in detail.

Gas separation with organo-soluble high performance aromatic polyimide films

An organo-soluble polyimide based on 4,4'-(1,4-phenylenedioxy)diphthalic anhydride and 2,2'-dimethyl-4,4'-methylenedianiline was synthesized by two-step polycondensation accompanied by chemical imidization. Polyimide films were prepared by spray casting onto glass substrates. The study focused on the separation of carbon dioxide (CO2) from natural gas and the enrichment of methane (CH4) from butane (C4H18). The permeability and permselectivity coefficients of these gases were determined.

Polymerization of ethylene by zirconocene-B(C6F5)(3) catalysts with aluminum compounds

Ethylene polymerization by zirconocene-B(C6F5)(3) catalysts with various aluminum compounds has been investigated. It is found that the catalytic activity depended on zirconocenes used, and especially on the type of aluminum compounds. For Et(H(4)Ind)(2)ZrCl2 (H(4)Ind : tetrahydroindenyl), the activity decreases in the following order: Me3Al > i-Bu3Al > Et3Al much greater than Et2AlCl. While for Cp2ZrCl2(Cp : cyclopentadienyl), it varies as follows: i-Bu3Al > Me3Al much greater than Et3Al. Furthermore, the activity is significantly affected by the addition mode of the catalytic components, which may imply that the formation of active centers is associated with an existing concentration of catalytic components. Results of thermal behavior of polyethylene (PE) studied by differential scanning calorimetry(DSC) show that crystallinity of the polymer prepared with Et3Al is higher than that with Me3Al or i-Bu3Al. It is also found that the number-average molecular weight ((M) over bar) of the polymers prepared with Me3Al or i-Bu3Al is much higher than that with Et3Al. H-1-NMR studies substantiate that i-Bu3Al is a more efficient alkylation agent of Cp2ZrCl2 in comparison with Me3Al. (C) 1997 John Wiley & Sons, Inc.

Synthesis and properties of optically active aromatic polyimides derived from optically pure 1,1'-bi-2-naphthol

A series of new optically active aromatic polyimides containing axially dissymmetric 1,1'-binaphthalene-2,2-diyl units were prepared from optically pure (R)-(+)-or (S)-(-)-2,2'-bis(3,4-dicarboxyphenoxy)-1,1'-binaphthalene dianhydrides and various aromatic diamines via a conventional two-step procedure that included ring-opening polycondensation and chemical cyclodehydration. The optically pure isomer of dianhydride was prepared by a nucleophilic substitution of optically pure (R)-(+)or (S)-(-)1,1'-bi-2-naphthol with 4-nitrophthalonitrile in aprotic polar solvent and subsequent hydrolysis of the resultant tetranitrile derivatives, followed by the dehydration of the corresponding tetracarboxylic acids to obtain the dianhydrides. These polymers were readily soluble in common organic solvents such as N,N-dimethylacetamide, N-methyl-2-pyrrolidone, and m-cresol, etc., and have glass transition temperatures of 251-296 degrees C, and 5% weight loss occurs not lower than 480 degrees C. The specific rotations of the optically active polyimides ranged from +196 degrees to +263 degrees, and the optical stability and chiroptical properties of them were also studied. (C) 1997 John Wiley & Sons, Inc.

Synthesis, luminescence properties and energy transfer of binary and ternary rare earth complexes with aromatic acids and 1,10-phenanthroline

A series of binary and ternary rare earth (Gd, Eu, Tb) complexes with ortho hydroxyl benzoic acid, pam aminobenzoic acid, nicotinic acid and 1,10-phenanthroline were synthesized. Phosphorescence spectra and lifetimes of Gd complexes were measured and the lowest triplet state energies of gadolinium binary complexes end the intramolecular energy transfer efficiencies were determined. The luminescence properties and energy transfer process of Eu3+ and Tb3+ complexes were discussed.

Catalysis of copper-containing transition metal hydrotalcite-like compounds in the phenol hydroxylation with hydrogen peroxide

Hydrotalcite-like compounds containing carbonate ion as the interlayer anion were prepared by coprecipitation under low supersaturation condition by mixing an aqueous solution of metal nitrates with an aqueous solutions of NaOH and Na2CO3, at room temperature, maintaining pH = 8-10 with vigorous stirring, Following the mixing, the resulting heavy slurry was aged at 353 K for 18 h with vigorous stirring, The precipitate was then filtered, washed several times with hot distilled water and dried in air at 353 K overnight, In this way, CuMI AlCO3-HTLcs and M-I AlCO3-HTLcs were synthesized and characterized by means of XRD and IR, The catalysis of the above mentioned HTLcs were investigated in the phenol hydroxylation with H2O2. The results indicated that all of the copper-containing HTLcs had a higher catalytic activity in the reaction, However, those catalysts that did not contain copper had no catalytic activity in this reaction, This means that copper was the active center in the phenol hydroxylation. Meanwhile, the mechanism was also proposed, which could be used to explain the main reason for higher activity for CuCuAlCO3-HTLcs in the phenol hydroxylation and the effect of Mg2+, Zn2+, Co2+, Ni2+ on activity of CuMI AlCO3-HTLcs.

Fragmentations of some bifunctional phenylether compounds by intermediate ion/neutral complexes

The fragmentations of three bifunctional phenylether compounds including 2-(2, 6-dichloro)phenoxyl propionitrile, N-hydroxyl-4-butoxyl phenylacetyl amine(bufexamc) and 2-(1-methylethoxyl) phenol methylcarbamate (Propoxur) under electron impact ionization were reported, Metastable ion(MI) and collision-induced dissociation(CID) at a low energy have been used to study the fragmentation pathways from molecular ions. Apart from the simple bond cleavages, and the unimolecular dissociations via ion/neutral complex intermediate as a competitive mechanism were demonstrated, Moreover, the intramolecular hydrogen transfer and double hydrogen transfers in the fragmentations of these compounds were discussed in detail.