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排序方式: 共有732条查询结果,搜索用时 31 毫秒
721.
铀原子自电离态能级测量 总被引:2,自引:1,他引:1
用三台可调谐脉冲染料激光器三步共振电离方法,测量了在49898-50880cm^-1能量区间的一些轴原子里堡态和自电离态能级位置。 相似文献
722.
带有致钝取代基的萘衍生物和SO3的反应研究 总被引:1,自引:0,他引:1
研究了一系列带有醛基、苯甲酮基、羧基、酯基和硝基等致钝取代基的萘衍生物与SO3的反应。1-萘甲醛的单磺化得到比例为55:9:6:30的5-、6-、7-和8-磺酸取代物。1-苯甲酮萘则以83:11:6的比例得到5-、6-和7-磺酸取代物。1-硝基萘专一地得到5位磺化产物,1-萘甲酸和1-萘甲酸甲酯得到5位和8位取代产物。所有的2位取代萘衍生物均先得到5和8位取代产物,在过量磺化中生成的主产物为5,7-二磺酸取代物,提出了生成SO3络合物及迫位磺化的历程,报道了8-磺酸-1-萘甲酸酐的物理数据。 相似文献
723.
卤代萘与三氧化硫的磺化反应林静,邹友思(厦门大学化学系,厦门,361005)关键词磺化反应,三氧化硫,卤代萘甲基和甲氧基萘用三氧化硫进行的磺化反应已有报道[1~3],而卤代萘的磺化反应迄今未见报道.本文研究了6种卤代茶在非极性溶剂二氯甲烷中用三氧化硫... 相似文献
724.
《Particuology》2023
Ultrasound-assisted synthesis of Mn/Co-MOF nanomaterial was used to capture uranium from aqueous solutions. Tests of Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Fourier transformed infrared spectra (FT-IR), Zeta potential analysis, thermogravimetric analysis (TGA), and X-ray diffraction (XRD) suggest that cobalt ions were replaced partially by manganese ions to generate MOF during the synthesis process and form manganous oxide particles loaded on the surface of Mn/Co-MOF. The optimal immobilization conditions of U(VI) were systematically studied by solution pH, kinetic, contact time and preparatory uranium concentration. XPS spectroscopy analysis indicated that the chelation of imidazole ring to uranium and Mn3O4 possibly played a certain role in the adsorption process. The results indicate that the adsorption isotherms of the Mn/Co-MOF for uranium suit Langmuir isotherm model (maximum adsorption capacity were 763.36 mg/g). Furthermore, the adsorption kinetics of Mn/Co-MOF match comfortably with the pseudo-second-order kinetic model. 相似文献
725.
Marcelo S Carvalho Maria de Lourdes F Domingues José L Mantovano Euclides Quintino S Filho 《Spectrochimica Acta Part B: Atomic Spectroscopy》1998,53(14):1945-1949
A sensitive method based on the preconcentration of uranium on powdered polyurethane foam (PUF) has been developed to determinate this element in water samples by X-ray florescence. Uranium at ppb levels was sorbed as the salicylate complex on powdered PUF at pH 4.0. The resulting PUF was filtered through a filter paper and used for X-ray fluorescence measurements. For 50 μg/l of uranium the coefficient of variation for five measurements is 5% and the detection limit is 5.5 μg/l. The interference level of various ions and ligands was studied and optimum conditions were developed to determine uranium in reference materials, waste water, mine drainage, and sea water. 相似文献
726.
采用氢氟酸-硝酸-高氯酸体系对华阳川铀多金属矿进行高温消解,并对消解条件进行优化。使用电感耦合高频等离子体原子发射光谱仪(ICP-OES),在最佳仪器条件下,对华阳川铀多金属矿中铌元素和铅元素进行检测。结果表明,方法线性相关系数为分别为0.9998和0.9999,两种元素在标准样品中的加标回收率在96.0% ~104% 之间,平行样的相对标准偏差约0.50%~3.32%。实际样品加标回收率约为96.1 % ~ 102 %。该分析测试方法可以对华阳川铀多金属矿中铌铅元素进行快速、准确的测定。 相似文献
727.
Zuowei Xie Chaoguo Yan Qingchuan Yang Thomas C. W. Mak 《Angewandte Chemie (International ed. in English)》1999,38(12):1761-1763
The tetranion ligand η7-C2B10H124− has been observed for the first time in 1 , which was obtained from the reaction of o-C2B10H12 with excess K metal followed by treatment with UCl4. As shown in the picture (without K cations and coordinated THF molecules), 1 is a centrosymmetric dimer with a bent sandwich structure. 相似文献
728.
Julia G. Knapp Dr. Xijun Wang Dr. Andrew S. Rosen Xingjie Wang Dr. Xinyi Gong Dr. Matthew Schneider Dr. Tatyana Elkin Dr. Kent O. Kirlikovali Dr. Melissa Fairley Dr. Matthew D. Krzyaniak Prof. Michael R. Wasielewski Prof. Nathan C. Gianneschi Prof. Randall Q. Snurr Prof. Omar K. Farha 《Angewandte Chemie (International ed. in English)》2023,62(29):e202305526
The interactions between uranium and non-innocent organic species are an essential component of fundamental uranium redox chemistry. However, they have seldom been explored in the context of multidimensional, porous materials. Uranium-based metal–organic frameworks (MOFs) offer a new angle to study these interactions, as these self-assembled species stabilize uranium species through immobilization by organic linkers within a crystalline framework, while potentially providing a method for adjusting metal oxidation state through coordination of non-innocent linkers. We report the synthesis of the MOF NU-1700 , assembled from U4+-paddlewheel nodes and catecholate-based linkers. We propose this highly unusual structure, which contains two U4+ ions in a paddlewheel built from four linkers—a first among uranium materials—as a result of extensive characterization via powder X-ray diffraction (PXRD), sorption, transmission electron microscopy (TEM), and thermogravimetric analysis (TGA), in addition to density functional theory (DFT) calculations. 相似文献
729.
Jinghang Shen Thayalan Rajeshkumar Genfeng Feng Yue Zhao Shuao Wang Laurent Maron Congqing Zhu 《Angewandte Chemie (International ed. in English)》2023,62(21):e202303379
Although examples of multiple bonds between actinide elements and main-group elements are quite common, studies of the multiple bonds between actinide elements and transition metals are extremely rare owing to difficulties associated with their synthesis. Here we report the first example of molecular uranium complexes featuring a cis-[M U M] core (M=Rh, Ir), which exhibits an unprecedented arrangement of two M U double dative bond linkages to a single U center. These complexes were prepared by the reactions of chlorine-bridged heterometallic complexes [{U{N(CH3)(CH2CH2NPiPr2)2}(Cl)2[(μ-Cl)M(COD)]2}] (M=Rh, Ir) with MeMgBr or MeLi, a new method for the construction of species with U−M multiple bonds. Theoretical calculations including dispersion confirmed the presence of two U M double dative bonds in these complexes. This study not only enriches the U M multiple bond chemistry, but also provides a new opportunity to explore the bonding of actinide elements. 相似文献
730.
Tongyu Li Dongwei Wang Yi Heng Dr. Guohua Hou Prof. Guofu Zi Dr. Wanjian Ding Prof. Dr. Laurent Maron Prof. Dr. Marc D. Walter 《Angewandte Chemie (International ed. in English)》2023,62(50):e202313010
Uranium diazomethanediide complexes can be prepared and their synthesis, structure and reactivity were explored. Reaction of the uranium imido compound [η5-1,2,4-(Me3Si)3C5H2]2U=N(p-tolyl)(dmap) ( 1 ) or [η5-1,3-(Me3C)2C5H3]2U=N(p-tolyl)(dmap) ( 4 ) with Me3SiCHN2 cleanly yields the first isocyanoimido metal complexes [η5-1,2,4-(Me3Si)3C5H2]2U(=NNC)(μ-CNN=)U(dmap)[η5-1,2,4-(Me3Si)3C5H2]2 ( 2 ) and {[η5-1,3-(Me3C)2C5H3]2U[μ-(=NNC)]}6 ( 5 ), respectively. Both compounds exhibit remarkable thermal stability and were fully characterized. According to density functional theory (DFT) studies the bonding between the Cp2U2+ and [NNC]2− moieties is strongly polarized with a significant 5 f orbital contribution, which is also reflected in the reactivity of these complexes. For example, complex 5 acts as a nucleophile toward alkylsilyl halides and engages in a [2+2] cycloaddition with CS2, but no reaction occurs in the presence of internal alkynes. 相似文献