W-183 NMR characterization of rare earth heteropolymetalates in aqueous solution

W-183 NMR spectra were obtained for [La(AsW11O39)(2)](11-), [La(As2W17O61)(2)](17-), [La(SiW9Mo2O39)(2)](13-), [LaSb9W21O86](16-), [LaAs4W40O140](25-) and alpha-, beta-[(CeO)(3) . (SiW9O34)(2)](14-) complexes, Tungsten NMR studies showed that the C-s symmetry of the square antiprism for [La(ASW(11)O(39))(2)](11-) and [La(As2W17O61)(2)](17-) anions keep constant in aqueous solution; the lanthanide accupied the central S-1 site in [LnSb(9)W(21)O(86)](16-) and [LnAs(4)W(40)O(140)](25-) complexes, respectively, and lanthanide metal cations gave [(CeO)(3) . (SiW9O34)(3)](14-) type of complexes with SiW9O3410-.

Dawson结构杂多阴离子~（183）W NMR谱的研究──“极位”W原子~（183）W NMR谱化学位移值的预测

本文研究了Ｄａｗｓｏｎ结构取代原子数与相应的１８３ＷＮＭＲ谱中“极位’Ｗ原子的化学位移值间的关系，预测广α－１，２－［Ｐ２Ｗ１６Ｎｂ２Ｏ６２］８－α－１－２，３－［Ｐ２Ｗ１５ＭｏＮｂ２Ｏ６２］８－“极位”Ｗ原子１８３ＷＮＭＲ谱化学位移们，结果α－１，２－［Ｐ２Ｗ１６Ｎｂ２Ｏ６２］８－中与取代Ｎｂ相连“极位”Ｗ原子的化学位移值为－８８ｐｐｍ，与取代Ｎｂ书对称“极位”Ｗ原了的化学位移值为－１４４．７ｐｐｍ，与取代Ｎｂ不对称“极位”Ｗ原子的化学位移值为－１３０．５ｐｐｍ，α－１－２，３－［Ｐ２Ｗ１５ＭｏＮｂ２Ｏ６２］８－中与取代Ｍｏ对称“极位”Ｗ原子的化学位移值为－１３４．７ｐｐｍ，与取代Ｎｂ对称“极位”Ｗ原子的化学位移值为－１４５．６ｐｐｍ．

稀土杂多化合物在溶液中的￣（183）W核磁共振表征

~（１８３）Ｗ核磁共振研究确认，Ｌａ（ＡｓＷ_（１１））_２、Ｌａｍ（Ａｓ_２Ｗ_（１７））_２在溶液中仍保持其四方反棱柱的Ｃ_３结构，Ｌａ（ＳｉＷ_９ＭＯ_２）_２阴离子中，２个Ｍｏ原子取代了２个等价的Ｗ原子，在穴状杂多阴离子ＬｎＡｓ_４Ｗ_（１０）和ＬｎＳｂ_９Ｗ_（２１）中，稀土离子占据中心Ｓ_１位置，ＳｉＷ_９与稀土离子生成（ＬｎＯ）_３（ＳｉＷ_９）_２型杂多阴离子。

Synthesis, characterization and fabrication on a glassy carbon electrode of a tetra-iron substituted sandwich-type pentadecatungstodiarsenate heteropolyanion

A novel sandwich-type compound, Na-12[Fe-4(H2O)(2)(As2W15O56)2].41H(2)O, has been synthesized. The compound was well-characterized by means of IR, UV-vis, W-183 NMR and elemental analyses. The compound crystallizes in the triclinic, P (1) over bar symmetry group. The structure of the compound is similar to that of Na-16[M-4(H2O)(2)(As2W15O56)(2)].nH(2)O (M = Cu, Zn, Co, Ni, Mn, Cd), and consists of an oxo-aqua tetranuclear iron core, [(Fe4O14)-O-III(H2O)(2)], sandwiched by two trivacant alpha-Wells-Dawson structural moieties, alpha-[As2W15O56]. Redoxelectrochemistry of the compound has been studied in buffer solutions at pH = 4.7 using polarography and cyclic voltammetry ( CV). The compound exhibited four one-electron couples associated with the Fe(III) center followed by three four-electron redox processes attributed to the tungsten-oxo framework. The compound-containing monolayer and multilayer films have been fabricated on a 4-aminobenzoic acid modified glassy carbon electrode surface by alternating deposition with a quaternized poly(4-vinylpyridine) partially complexed with [Os(bpy)(2)Cl](2+/-). CV, X-ray photoelectron spectroscopy (XPS), UV-vis spectroscopy and atomic force microscopy (AFM) have been used to characterize the multilayer films.

Single-crystal X-ray structure and properties of K-10[Ni-4(H2O)(2)(AsW9O34)(2)]center dot 4H(2)O

The rational synthesis and the structural and magnetic characterization of a nickel cluster are presented. The compound comprises a rhomblike Ni4O16 group encapsulated between two-heptadentate tungstoarsenate ligands [AsW9O34](9-). The crystal structure of K-10[Ni-4(H2O)(2)(AsW9O34)(2)](.)4H(2)O was solved in monoclinic, P2(1)/n symmetry, with a = 12.258(3) Angstrom, b = 21.232(4) Angstrom, c = 15.837(3) Angstrom, beta = 92.05(3)degrees, V = 4119.1(14) Angstrom(3), Z = 2, and R = 0.0862. The crystal structure of the Ni(II) derivative was compared with that of the Cu(II), Zn(II), Co(II) and Mn(II) derivatives. The Ni4O14(H2O)(2) unit in the compound shows no Jahn-Teller distortion. On the other hand, the Ni(II) derivative shows ferromagnetic exchange interactions within the Ni4O16 group (J = 7.8 cm(-1), J' = 13.7 cm(-1)) and an S = 4 ground state, the highest spin state reported in a heteropoly complex. Its redox electrochemistry has been studied in acid buffer solutions using cyclic voltammetry. It exhibited two steps of one-electron redox waves attributed to redox processes of the tungsten-oxo framework. The new catalyst showed an electrocatalytic effect on the reduction of NO2-.

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.

Synthesis and characterization of sandwiched heteropolycompound

New complex K5O4Na4H5 [Sn-3(PW9O34)(2)]. 16N(2)O was prepared and its structure was determined by elemental analysis, IR, P-31, W-183 NMR, polarography, XPS and X-ray crystallography. The anion has A-alpha-Keggin structure. The new complex crystallize is the monoclinic, P2(1)/n with a = 1.3625 (3) nm, b = 2.3625 (5) nm, c = 2.9306 (6) nm, alpha = 90 degrees, beta = 99.67 (3)degrees, gamma = 90 degrees, V = 9.299 nm(3), Z = 4.

Synthesis and structure of alpha-B-Keggin type heteropoly complex K5H[Co-4(VW9O33)(2)]center dot 5H(2)O

A new complex K5H[Co-4(VW9O33)(2)]. 5H(2)O was prepared and its structure was determined by X - ray diffraction analysis. The anion has alpha - beta - Keggin structure. Two (VW9O33)(7-) moieties (alpha - B isomers) are linked via four Co(11)O-6 groups. The single crystal of the title complex is monoclinic P2(1/n) with a = 1.2307(3) nm, b = 2.1250(4) nm, c = 1.5817(3) nm, beta = 91.86(3)degrees, V = 4.1343 (14) nm(3), R = 0.0895, R-w = 0.2180.

Synthesis and structural characterization of V(IV) and V(V) containing mixed-valence heteropolytungstogermanates

V(IV) and V(V) containing mixed-valence heteropolytungstogermanates have been prepared by controlled potential reduction of corresponding GeW9V3O407-, their electronic spectra have been recorded. The ESR spectra of one-electron-reduced anions in solution at 340K consist of more than 40 equally spaced lines, showing that the three VO6 octahedra in both alpha- and beta-forms are corner-shaped and one of the bridging oxygen atoms is protonated at pH 4.7.

SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF THE DAWSON-TYPE TUNGSTOPHOSPHATE HETEROPOLY COMPLEXES SUBSTITUTED BY NIOBIUM

Eight new complexes alpha(2)-M(7-m)H(m)[P2W17NbO62]. H2O and alpha-1, 2, 3-M(g-m)H(m) [P2W15Nb3O62]. XH(2)O(M=K, TMA, TEA, TBA) were synthesized and characterized by IR and UV spectroscopy, polarography, XPS and XRD methods. P-31 and W-183 NMR studies show that the niobium atoms in the anions are on the polar sites. The crystal of alpha-1, 2, 3-K7H2 [P2W15Nb3O62]. 30H(2)O is hexagonal, its cell parameters: a=1.9836(4), b=1.9836(9), c=1.5498(6)nm, alpha=beta=90 degrees, gamma=120 degrees.

SYNTHESIS AND CHARACTERIZATION OF ALPHA,BETA-TRIINDIUM SUBSTITUTED HETEROPOLYTUNGSTATES

The complexes of alpha,beta-K(a)H(b)XW(9)O(37)(InH2O)(3) . xH(2)O (X = Si, Ge; a+b = 7) were synthesized from their lacunary precursors alpha,beta-XW(9)O(34)(10-) (X = Si, Ge) and characterized by elemental analysis, W-183 NMR, IR and UV spectroscopy and polarography. W-183 NMR spectra of the title complexes consist of two lines with intensity ratio 2:1, as expected for the C-3 nu structure of trisubstituted A alpha- and A beta-Keggin anions.

SYNTHESIS AND PROPERTIES OF ALPHA-MOLYBDOTUNGSTONIOBIC DIPHOSPHATES

Four kinds of new molybdotungstoniobic diphosphates with the Dawson structure, formulated as alpha-P2W15Mo2Nb62(7-), are prepared and characterized by IR, UV spectra, polarography and W-183 NMR which show that the same ''polar'' W atoms in the Dawson frames-are substituted. The mean value of W-183 chemical shifts of the ''polar'' group varies linearly with the number of substituted atoms in the opposite polar group.

Dawson结构钨铌磷杂多配合物~(183)W NMR谱的研究

过渡金属离子取代的杂多钨酸盐,具有金属叶啉的类似结构,在烯烃环氧化反应中具有比金属叶啉更优异的催化活性和选择性,特别重要的是其抗氧化性能强,在烯烃基质存在下比金属叶啉稳定,催化寿命持久,并称其为无机金属叶啉,因而引起人们的极大关注.

Kinetic and Size Control of Polystyrene and Polyacrylic Octadecyl Ester Lattices Via Polymerization in O/W Microemulsions

The kinetic studies of the acrylic octadecyl ester and styrene polymerization in microemulsion systems, (1) cetyl pyridine bromide (CPDB)/t-butanol/styrene/water; (2) CPDB/t-butanol/toluene + acrylic octadecyl ester (1:1, w/v)/ water; (3) cetyl pyridine bromide/styrene/formamide, were made by using dynamic laser light scattering techniques (DLS). The mechanisms of nucleation of latex particles were discussed. The most possible nucleation location of the styrene and acrylic octadecyl ester microlatex particles in aqueous microemulsion system is in aqueous phase via homogeneous nucleation. Meanwhile, parts of microlatex particles are possibly produced via swollen micelles (microemulsions) and monomer droplets nucleation. On the other hand, the most possible nucleation location of the styrene microlatex particles in nonaqueous microemulsion system is inside monomer droplets. The relationship between the amount of monomer and the size of microlatex was also investigated. It has been found that the size of microlatex particles could be controlled by changing the amount of monomer. (C) 2002 Elsevier Science B.V. All rights reserved.

三组元W/O乳化液的表面张力和雾化特性

研究了W／O型乳化液的表面张力，压力雾化喷嘴的乳化液雾化特性与乳化液的组分、乳化剂的黏度以及喷油压力的关系．实验结果表明：乳化液的表面张力接近柴油，但喷雾滴径均大于柴油，而且喷嘴的启喷压力、乳化液组分和乳化剂黏度对乳化液平均滴径均有显著影响．随着启喷压力升高，喷雾滴径明显减小；若启喷压力相同，随着乳化液中水相含量增加(不高于50％)，乳化液喷雾滴径随之增加；采用高黏度、低HLB值乳化剂配制的乳化液的喷雾滴径相对较大；内相界面特性和界面上的乳化剂会对滴径分布有重要影响．