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241.
A series of novel two-dimensional (2D) and three-dimensional (3D) praseodymium coordination polymers, namely, {[Pr3(PDA)4(HPDA)(H2O)8] x 8H2O}n (2), {[Pr2(PDA)3(H2O)3] x H2O}n (3), {[Pr(PDA)(H2O)4] x ClO4}n (4), and { [Pr2(PDA)2(H2O)5SO4] x 2H2O}n (5) (PDA = pyridine-2,6-dicarboxylic anion), was designed and synthesized under hydrothermal conditions. Complexes 1-3 (chainlike polymer, {[Pr(PDA)(HPDA)(H2O)2] x 4H2O}n (1) was also obtained independently by us, although it has been reported recently by Ghosh et al.) were fabricated successfully by simply tuning the Pr/PDA ratio and exhibited various and intriguing topological structures from a 1D chain to a 3D network. While the synthetic strategy of 5 was triggered and further performed only after 1 was structurally characterized. The complexes were characterized by X-ray single-crystal determination, spectroscopic, and variable-temperature magnetic susceptibility analyses. In complex 2 an unusual nanosized square motif as a building block constructed by eight Pr ions was further assembled into a highly ordered 2D grid compound. In complex 3 the decanuclear Pr metal-based structure as a repeat unit interpenetrated to form a novel 3D polymer. Complex 4 was a 3D network polymer fabricated through a hexanuclear Pr ring as a building block, and ClO4- anions as guests were trapped in the cavity. In complex 5 six Pr atoms, two SO4(2-) anions, and carboxylic oxygen bridges constructed an intriguing rectangle structure as a repeat unit in the grid to form a 2D coordination polymer in which the unique bi-bidentate coordination mode of SO4(2-) anion was observed. 相似文献
242.
三核钨钼簇合物对苯乙烯氧化反应的催化 总被引:2,自引:0,他引:2
关于烯烃的催化氧化,报道较多。Takao等研究了苯乙烯在Ir和Rh络合物存在下的氧化反应;Collman曾报道环己烯在Vaska络合物[IrX(CO)(PPh_3)_2]催化下氧化成环己酮和环已烯氧化物。本文采用Cotton合成的簇合物[W_3O_2(CH_3CO_2)_6(H_2O)_3]Br_2· 相似文献
243.
一些多羟基酚酸芳基酯具有显著的生理活性,可用于医药、饮料和食品等方面。但目前关于多羟基酚酸芳基酯的合成还研究得不多。传统的方法是(1)保护多羟基酚酸中的酚羟基,(2)活化羧基成酰氯,(3)酯化,(4)去保护基的四步方法。本文将报道多羟基酚酸——2.4——二羟基苯甲酸(1)直接与酚类成酯的反应。即将二氯磷酸芳基酯(ROPOCI_2)(3)作为缩合剂,应用于一步法合成(1)芳基酯,以较好产率得到了(1)的七个新芳基酯(2_a—2_g),并经元素分析及波谱鉴定。同时还首次研究了缩合剂 相似文献
244.
245.
Pt(PPh_3)_2Cl_2在碱性介质中,与一氧化碳直接进行还原及羰基化反应,得到五种膦取代的羰基铂配合物:Pt_5(μ_2-CO)_5(CO)(PPh_3)_4 1,Pt_3(μ_2-CO)_3(PPh_3)_3 2,Pt_3(μ_2-CO)_3(PPh_3)_4 3,Pt_4(μ_2-CO)_5(PPh_3)_4 4,以及Pt(Cl)(PPh_3)_2(COOCH_3) 5。经X-射线单晶衍射分析,确定了新的三核铂羰基簇2以及配合物5的分子结构。还讨论了1和5的生成机理。 相似文献
246.
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248.
Sorption behavior of 2,4-dichlorophenol on marine sediment 总被引:1,自引:0,他引:1
The sorption behavior of 2,4-dichlorophenol on marine sediments treated by different methods was investigated systematically. The sorption of 2,4-dichlorophenol on marine sediments was completed mainly via ion exchange and surface polar sorption. Both the Freundlich and Langmuir isotherms were fit for describing its sorption behavior. The sorption behavior of 2,4-dichlorophenol was affected by various factors including aqueous salinity and temperature. The sorption amount of 2,4-dichlorophenol on marine sediments increased with increasing ion strength, but decreased with increasing temperature. 相似文献
249.
250.
A carbon paste electrode modified with chelating resin (ammino-isopropylmercaptan-type cross-linked chelating resins) for the voltammetric determination of gold(III) was characterized by cyclic voltammetry. The gold(III) ion is accumulated on the surface of the modified electrode only by the chelating effect of the modifier in the carbon paste, without application of a potential. After exchange of the medium the accumulated amount of gold(III) is determined by voltammetry in a blank electrolyte solution. The response depends on both the concentration of gold and the accumulation time. For a 5-min preconcentration time, a linear calibration graph was obtained in the range 3 × 10?8-1 × 10?6 M and the detection limit was about 1 × 10?8 M. A combination of chemical and electrochemical renewal allows the use of a single modified electrode in multiple analytical determinations over several days. For ten preconcentration—determination—renewal cycles [2 × 10?7 M Au(III)], the response could be reproduced with 4.7% relative standard deviation. Many parameters such as the composition of the paste and pH influence the response of the measurement. Many other metal ions have no or little effect on the determination of gold. The procedure was applied to the determination of gold in minerals, copper and anode mud, with good results. 相似文献