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111.
以乙二胺四乙酸(EDTA)为配位剂,采用溶胶凝胶和溶剂热法相结合的方法合成了Li2MnSiO4/C纳米复合正极材料。经过EDTA配位的锂锰硅前驱体在氩气中经过700℃煅烧后,产生为颗粒尺寸约为50nm的Li2MnSiO4/C纳米复合粉体。在0.1C=33mA·g-1进行充放电测试时,其首次充电和放电比容量分别为223和140mAh·g-1,第5次循环放电比容量仍为138mAh·g-1;电流密度升至0.2C=66mA·g-1时,在第20次循环的放电比容量仍可稳定在80mAh·g-1左右。这些结果表明,EDTA的配位作用可抑制杂相的形成,这种分散性相对较好的纳米复合粉体Li2MnSiO4正极材料表现出提高的循环稳定性。 相似文献
112.
Aparna Sil & Ashwini K. Srivastava 《Supramolecular chemistry》2013,25(5):343-351
Complexation of Cu(II), Zn(II), Ni(II), Co(II), Pb(II), Cd(II), Cr(III) and Fe(III) ions with 15-crown-5, benzo-15-crown-5, 18-crown-6, dibenzo-18-crown-6, dicyclohexano-18-crown-6, dibenzo-24-crown-8, 5,6,14,15-dibenzo-1,4-dioxa-8,12-diazacyclopentadeca-5,14-diene, 1,4,10-trioxa-7,13-diazacyclopentadecane and cyclam has been investigated in 75% (v/v) DMF+water using the silver(I) ion as an auxiliary cation at 0.05?M ionic strength adjusted with tetrabutylammonium perchlorate (TBAP) by competitive potentiometry. Stability constant values obtained for the metal ion–aza macrocyclic complexes are higher than those for the oxa crowns. Shifts in the peak potential and reduction in the peak current in the differential pulse polarography (DPP) method were also used to determine the stability constants of some of the metal ions with aza and tosylated-aza macrocycles using TBAP as supporting electrolyte in 75% (v/v) DMF+water and 90% (v/v) DMSO+water media. Stability constant values determined both by shifts in the potential and by reduction in the peak current were found to be in good agreement with each other. 相似文献
113.
Jean-Pierre Dutasta Brigitte Bibal Jean-Paul Declercq Beatrice Dubessy Jean-Christophe Mulatier Bernard Tinant 《Phosphorus, sulfur, and silicon and the related elements》2013,188(6-7):1485-1488
The recent results in the chemistry of cavitands have proved that they are very efficient molecular receptors and potential precursors of molecular devices. In this context, we have investigated the synthesis and binding properties of phosphorylated cavitands. The stereoselective synthesis and the structural studies of the new compounds showed that these bowl-shaped molecules possess a well defined aromatic cavity surrounded by four phosphoryl groups (P=O or P=S). They are very efficient ligands for metal and organic cations. They are able to encapsulate cationic species by cooperative effect of the preorganized aromatic cavity and the four phosphorylated groups. Moreover, the upper and lower rim functionalitics can lead to the formation of molecular capsules and supramolecular assemblies whose properties and structures have been investigated by X-ray diffraction and NMR studies in solution. 相似文献
114.
J.D. Glennon S. Hutchinson A. Walker S.J. Harris C.C. McSweeney 《Journal of chromatography. A》1997,770(1-2):85-91
Research to date on the supercritical fluid extraction (SFE) of metal ions has focused on the use of dithiocarbamates and β-diketones. Hydroxamic acids are well known as effective chelating agents for a broad range of transition metal ions. Much attention has centred in inorganic chemistry on the effect of N-substitution on metal chelate stability and selectivity, and in analytical chemistry on the immobilisation of the chelating agents to the chosen solid supports such as silica. In this paper, the synthesis of selected fluorinated mono hydroxamic acids and their N-substituted derivatives is reported. The new reagents are applied in the SFE of metal ions in particular Fe(III) using unmodified supercritical CO2. Metal extraction is monitored using atomic absorption spectroscopy and visible spectrophotometry. The extraction efficiencies were determined as a function of pressure and temperature. The new ligands synthesised and applied were perfluorooctanohydroxamic acid (PFOHA), heptafluorobutyrichydroxamic acid (HFBHA) and their N-methylhydroxamic acid derivatives. Of the synthesised reagents, PFOHA was the most soluble and effective extractant of Fe(III) from spiked filter paper, reaching 97% extraction of the metal ion under optimised conditions. The selectivity of this ligand for Fe(III) in the presence of Cu(II), Ni(II), Pb(II) and Zn(II) is also demonstrated. 相似文献
115.
116.
A procedure for the extraction of Cr(VI) from solid soil-like samples was presented in which the complexing properties of
diethylenetriaminepentaacetic acid (DTPA) were exploited to extract insoluble compounds of Cr(VI). A concentration of DTPA
in an ammonium sulphate/ammonium hydroxide buffer equal to 0.02 mol l−1 was chosen. The conditions of extraction of insoluble Cr(VI) from solid samples were optimised using soil certified reference
material spiked with known concentration of insoluble Cr(VI) added as PbCrO4. The extracts were analysed by adsorptive stripping voltammetry. Validation of the proposed procedure of extraction was carried
out by analysis of certified reference material (CRM) 545 and comparison of the results obtained using the proposed and other
methods of extraction in the course of analysis of natural soil samples. 相似文献
117.
The complexation of Eu(III), Am(III) and Cm(III) with dicarboxylate anions with O, N or S donor groups was measured in I=6.60 mol⋅kg−1 (NaClO4) at temperatures of 0–60 °C by potentiometry and solvent extraction. The complexation thermodynamics of these complexes show
that their stability is due to highly favorable complexation entropies because the complexation enthalpies are endothermic.
Luminescence studies with Eu(III) and Cm(III) were used to measure the hydration numbers of the complexes. NMR spectra of
1H and 13C were used to determine the binding modes of La(III) with the ligands. The formation of 1:1:1 ternary complexes of M(EDTA)− with the dicarboxylate ligands was studied to determine changes in coordination of the metal cation with formation of the
ternary species. The complexation of ternary complexes changes from bidentate to monodentate as the chain length between the
binding sites of the dicarboxylates increases from 1 (malonate) to 4 (adipate). DFT computations were used to confirm the
structural aspects of the interaction of these complexes. 相似文献
118.
It has been demonstrated that calcium montanate (a mixture of aliphatic hydrocarbons, fatty acid esters of C28–C32 acids, the calcium salts of these fatty acids, and the acids themselves) can be selectively extracted with supercritical fluids. By use of carbon dioxide, carbon dioxide containing 10% methanol, and carbon dioxide containing 10% methanol and citric acid (as a further additive), the various compound classes could be isolated with high selectivity. The addition of citric acid results in the complexation of Ca2+ and the simultaneous formation of the free fatty acids, which are soluble in the extractant. 相似文献
119.
Jun-Hui Xue Xiao-Hui Hua Li-Min Yang Wei-Hong Li Yi-Zhuang Xu Guo-Zhong Zhao Gao-Hui Zhang Ke-Xin Liu Jia-Er Chen Jin-Guang Wua 《中国化学快报》2014,25(6):887-891
The novel coordination structures of europium and terbium chloride-picolinamide complexes (EuCl3-(C6H6N2O)2.5H2O, Eu-pa and TbCl3.(C6H6N2O)2.5H2O, Tb-pa) are reported. The crystal structures in the solid state are characterized by X-ray single crystal diffraction, FTIR, Raman, FIR, THz and luminescence spectroscopy. In the crystal structures, the pyridyl nitrogen and carbonyl oxygen atoms in picolinamide are coordinated to the metal ions to form a five-membered ring structure. The experimental results indicate the similar coordination structures of Eu and Tb-pa complexes and the changes of hydrogen bonds and conformation provide models for the coordination structures of the ligands induced by complexation. The results of lanthanide ions with ligands having amide groups. 相似文献
120.
Feyyaz Durap Nermin Biricik Bahattin Gümgüm Saim Özkar Wee Han Ang Zhaofu Fei Rosario Scopelliti 《Polyhedron》2008
N,N-Bis(diphenylphosphino)ethylaniline compounds, [Ph2P]2N-C6H4-C2H5, with ethyl groups at the ortho- and para-positions have been synthesized. Oxidation of the aminophosphines with hydrogen peroxide, elemental sulfur and selenium gave the corresponding oxides, sulfides and selenides [Ph2P(E)]2N-C6H4-C2H5 (E = O, S, Se). Complexes [MCl2{(Ph2P)2N-C6H4-(C2H5)}] (M = Pd, Pt) and [Cu{(Ph2P)2N-C6H4-C2H5}2]PF6 were obtained by the reaction of N,N-bis(diphenylphosphino)ethylaniline with [MCl2(COD)] (M = Pd, Pt) and [Cu(MeCN)4]PF6. The new compounds were characterized by NMR, IR spectroscopy and microanalysis. In addition, representative solid-state structures of the palladium and platinum complexes were determined using single crystal X-ray diffraction analyses. 相似文献