Synthesis, characterization and crystal structures of dibenzo-18-crown-6 sodium isopolytungstates

Two novel dibenzo-18-crown-6 sodium isopolytungstates, [(DB18C6)(CH3OH)Na](2)W(6)O(19)(.)DB18C6(.)H(2)O 1 and [(DB18C6)(DMF)(2)Na](4)W(10)O(32)(.)2DMF(.)2H(2)O 2, have been synthesized in mixed methanol and acetonitrile solvents and characterized by elemental analysis, TGA, IR and single crystal X-ray diffraction. The compound 1 crystallizes in the monoclinic space group C2/c with a = 23.182(8), b = 19.527(2), c = 18.737(3) Angstrom, beta = 115.15(2)degrees, V = 7678(3) Angstrom(3), Z = 4, and R1(wR2) = 0.0611(0.1504). The compound 2 crystallizes in the monoclinic space group P21/n with a = 16.516(2), b = 22.325(6), c = 20.425(7) Angstrom, beta = 91.78(2)degrees, V = 7528(3) Angstrom(3), Z = 2, and R1(wR2) = 0.0397(0.0773). The compound 1 exhibits a novel organic-inorganic sandwich-type structure, in which the crown ether-sodium complexes are coordinated to the terminal oxygen atoms of W6O192-. In compound 2, all Na+ ions are thoroughly enveloped into the organic moieties of crown ether and DMF molecules and are connected with the 'naked' polyanions W10O324- via the electrostatic attraction.

Fabrication and electrochemical behavior of a sol-gel-derived carbon ceramic composite electrode entrapping 2 : 18-molybdodiphosphate

A new type of inorganic-organic hybrid material incorporating carbon powder and alpha -type 2:18-molybdodiphosphate (P2Mo18) in a methyltrimethoxysilane (MTMOS) based gel has been produced by a sol-gel process and used to fabricate a chemically modified electrode. The P2Mo18-doped carbon ceramic composite electrode was characterized using SEM and cyclic voltammetry. Square-wave voltammetry with an excellent sensitivity was exploited to conveniently investigate the dependence of current and half-wave potential (E-1/2) on pH. The chemically modified electrode has some advantages over the modified film electrodes constructed by the conventional methods, such as long-term stability, reproducibility, and especially repeatability of surface-renewal by simple polishing in the event of surface fouling or dopant leaching. In addition, the modified electrode shows a good catalytic activity for the electrochemical reduction of bromate in an acidic aqueous solution. (C) 2000 Elsevier Science B.V. All rights reserved.

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.

Electrochemical and in situ spectroelectrochemical behavior of 2,3,7,8,12,13,17,18-octakis(hexyl-thio) tetraazaporphyrin (H(2)OHTTAP) and (Zn(II)OHTTAP)

The characterization of free base porphyrin 2,3,7,8,12,13,17,18-octakis(hexyl-thio) tetraazaporphyrin (H(2)OHTTAP) and its zinc(II) complexes [Zn(II)OHTTAP] containing eight thioether groups at the beta -pyrrole positions of the macrocycle was reported. Results obtained by cyclic voltammetry and differential pulse voltammetry indicated a five-electron reduction in five steps for each complex. They were oxidized in two single-electron-transfer steps to yield pi -cation radicals and dications and reduced in three single-electron-transfer steps to yield pi -anion radicals, dianions and trianions, respectively. The redox property of H(2)OHTTAP was unusual as compared to porphyrins (PPs) and phthalocyanines (Pcs). Each process was monitored by in situ thin-layer spectroelectrochemistry, which indicated that only the Ligand was electroactive. The existence of the eight hexylthio groups was responsible for the intrastack interactions and enhanced intracolumnar and intercolumnar electron motions, resulting in improved conductivity. Copyright (C) 2001 John Wiley & Sons, Ltd.

16-and 18-electron Cp*Rh complexes with 1,2-dicarba-closo-dodecabofane(12)-1,2-dichalcogenolato ligands, as studied by multinuclear magnetic resonance

The reaction of [Cp*RhCl2](2) 1 with dilithium 1,2-dicarba-closo-dodecaborane(12)-1,2-dithiolate (a) and -diselenolate (b) afforded the 16-electron rhodium(III) half-sandwich complexes Cp*Rh[E2C2(B10H10)] [E=S (3a), Se (3b)]. The 18-electron trimethylphosphane rhodium(III) half-sandwiches Cp*Rh(PMe3)[E2C2(B10H10)] 4a-c were prepared from the reaction of Cp*RhCl2(PMe3) 2 with the same dichalcogenolates, including the ditelluride (c). The complexes 4a,b could also be obtained from the reaction of 3a,b with trimethylphosphane. The molecular geometry of 4b was determined by X-ray structural analysis. The 16-electron complexes 3 an monomeric in solution as shown by multinuclear magnetic resonance (H-1-, B-11-, C-13-, P-31- Se-77-, Rh-103-, Te-125-NMR). also in comparison with the data for the trimethylphosphane analogues 4a-c and for 6a in which the rhodium bears the eta(5)-1,3-C5H3 Bu-t(2) ligand. The Rh-103 nuclear shielding is reduced by 831 ppm (3a) and 1114 ppm (3b) with respect to the 18-electron complexes 4a,b. Similarly, the Se-77 nuclear shielding in 3b is reduced by 676.4 ppm with respect to that in 4b. (C) 1999 Elsevier Science S.A. All rights reserved.

Ce~（3＋），Tb~（3＋）在Al_4B_2O_9和Al_（18）B_4O_（33）基质中的发光

采用固相反应法在Ａｌ２Ｏ３－Ｂ２Ｏ３体系中合成了Ａｌ４Ｂ２Ｏ９和Ａｌ１８Ｂ４Ｏ３３两个相关化合物，测定了在两种基质中Ｃｅ３＋，Ｔｂ３＋和Ｃｅ３＋－Ｔｂ３＋的光谱，观察到在两种基质中Ｃｅ３＋的光谱相似，Ｃｅ３＋的发射峰位置在Ａｌ１８Ｂ４Ｏ３３中比Ａｌ４Ｂ２Ｏ９稍有红移。实验表明，Ａｌ１８Ｂ４Ｏ３３将是一种好的发光基质

水溶性聚合物和两亲聚合物18．2－丙烯酰胺基烷磺酸类两亲单体

２－丙烯酰胺基烷磺酸的溶解行为和胶体化学性质明显随烷基长短而异。由于手性碳原子的存在，与其相邻亚甲基的质子峰在~１ＨＮＭＲ谱上清楚地发生分裂。研究了２－丙烯酰胺基十六烷磺酸（ＡＭＣ１６Ｓ）在水／二氧六环混合溶剂中的聚合动力学和胶体化学性质。发现聚合速度和所得聚合物分子量均在水／二氧六环体积比为１～１／２时出现最小值，临界胶束浓度随混合溶剂中二氧六环含量的增加而增加，当水／二氧六环体积比为１／２～１／４时，观察不到胶束化现象。

三缺位杂多化合物K_8［P_2W_（18）Mo_2Co_2（H_2O）_2O_（68）］·MoO_6·15H_2O的合成、结构及催化H_2O_2分解研究

合成了杂多化合物Ｋ８［Ｐ２Ｗ（１８）Ｍｏ２Ｃｏ２（Ｈ_２Ｏ）２Ｏ（６８）］·ＭｏＯ６·１５Ｈ２Ｏ，依据ＸＲＤ、ＩＲ、ＵＶ－Ｖｉｓ及ＸＰＳ确定了其晶体结构和配位原子价态，考察了该化合物催化Ｈ２Ｏ２分解的动力学行为。

双环己基18冠6对水/硝基苯界面离子的促进传输

Li~-和H~-因较强的亲水性,较难穿越液/液界面进行传输。本文报道了冠醚双环已基18冠6对Li~+,Na~+,Rb~-和H~-在水/硝基苯界面的促进传输行为,求得了相应促进传输过程的一系列参数,并对被传输离子在传输过程中的形态变化进行了初步的探讨。

气相离子C_(18)H_(37)NH_3~+在低碰撞能下的远电荷碎裂反应

本文研究了电子轰击、化学电离条件下四碘合钴酸十八胺、四氯合钴酸十八胺加热分解产生的C_(18)H_(37)NH_3~+(m/z270)离子碰撞诱导解离谱,在低碰撞能量范围(0～10eV)、多次碰撞条件下观察到了远电荷碎裂反应,给出了反应所需内能的估计值,该离子比直接由正十八胺质子化得到的离子具有较高的内能。

ELECTROCHEMICAL STUDY OF ISOPOLY AND HETEROPOLY OXOMETALLATE FILM MODIFIED MICROELECTRODES .5. PREPARATION AND ELECTROCHEMICAL-BEHAVIOR OF A 2/18-MOLYBDODIPHOSPHATE ANION MONOLAYER MODIFIED ELECTRODE

In this paper a carbon fibre (CF) microelectrode modified with the 2:18-molybdodiphosphate anion by simple adsorption is described and its electrochemical behaviour is reported. The 2:18-molybdodiphosphate anion (alpha-P2Mo18O626-), which is a Dawson structure, undergoes five successive multielectron reductions in acidic solution. The first three redox waves correspond to the two-electron process, and the last two waves are four-electron and six-electron processes respectively. On the basis of the experimental results it is shown that the electrode process of alpha-P2Mo18O626- on the CF electrode in acidic solution is simultaneously controlled by the diffusion and adsorption of alpha-P2Mo18O626- anions. When the concentration of the alpha-P2Mo18O626- in the solution is reduced, the electrode process mainly exhibits non-diffusion-controlled behaviour, and the diffusion-limited process takes over as the concentration of alpha-P2Mo18O626- becomes higher. The CF electrode modified with a thin film of alpha-P2Mo18O626- exhibits very good stability and redox behaviour in aqueous acidic solution. The alpha-P2Mo18O626- is reduced to heteropoly blue, with an accompanying protonation process. The addition of more than six electrons to the alpha-P2Mo18O626- anion in an aqueous solution does not result in its decomposition. The result obtained is not the same as that reported previously.

Benthic foraminifera and bottom water evolution in the middle-southern Okinawa Trough during the last 18 ka

A piston sediment core E017 from the middle-southern Okinawa Trough was investigated. A preliminary study of the deep-water evolution since 18 cal. ka BP was performed based on the quantitative census data of benthic foraminiferal fauna, together with planktonic foraminiferal oxygen and carbon isotope, AMS(14)C dating, and the previous results achieved in the southern Okinawa Trough. The result shows that the benthic fauna was dominated by Bulimina aculeata (d'Orbigny), Uvigerina peregrina (Cushman), Hispid Uvigerina and Uvigerina dirupta (Todd) during the glaciation-deglaciation before 9.2 cal. ka BP, while Epistominella exigua (Brady), Pullenia bulloides (d'Orbigny), Cibicidoides hyalina (Hofker), Sphaeroidina bulloides (d'Orbigny) and Globocassidulina subglobosa (Brady) predominated the fauna in the post-glacial period after 9.2 cal. ka BP. The benthic foraminifera accumulation rate (BFAR), paleoproductivity estimates and benthic foraminiferal assemblage conformably indicate that surface water paleoproductivity and organic matter flux during the glaciation-deglaciation were higher than those of the post-glacial period in the middle-southern Okinawa Trough, and gradually enhanced from the southern to the central Okinawa Trough during the glaciation-deglaciation, which could be caused by the discrepancy of the terrigenous nutrients supply. High abundances of E exigua, an indicator of pulsed organic matter input, after 9.2 cal. ka. BP may indicate that the intensity of seasonally riverine pulsed flux during the post-glacial period was stronger than that of the glaciation-deglaciation period, and the seasonal influx in the central trough might be stronger than in the south. The temporal distributions of the typical species indicating bottom water oxygen content and ventilation condition show that the ventilation of the bottom water during the post-glacial period is more active than the glaciation-deglaciation, which reflects that the evolution of the intermediate and deep waters of the northwestern Pacific during the last glaciation has no evident influence on the deep-water of the middle-southern Okinawa Trough. Additionally, the variations in agglutinated benthic foraminiferal abundance and other carbonate dissolution proxies indicate that carbonate dissolution gradually increased since the last 18 ka in the Okinawa Trough and rapidly enhanced at 9.2 cal. ka BP. The modern shallow carbonate lysocline could form at 3 cal. ka BP.

18.7”AX/VX型钢圈取放器——一种ROV携带的水下作业工具

目前,ROV(无人遥控潜水器)在水下工程和海洋石油工业上得到了广泛应用。ROV是通过各种水下作业工具来完成相应的作业任务。本文介绍了一种ROV携带海上石油钻井平台需要的新型水下作业工具一钢圈取放器。