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1.
The Fourier transform far infrared spectra of oxalate hydrates of whole rare-earth series except Pm and Sc are investigated in the range of 100-400 cm~(-1). The assignment of vibrational frequencies is made on the basis of normal coordinate analysis using our NORVIB program. The model used for the hghter elements of the lanthanide series (La to Eu) is based on the crystal structure of Nd_2(C_2O_4)_3. 10H_2O, in which each lanthanide ion is surrounded by nine O atoms, six from three oxalate ions and three from Water molecules.The model adopted for the heavier elements of the lanthanide series (Gd to Lu) and Ytterbium is based on the crystal structure of Yb_2(C_2O_4)_3· 6H_2O, in which each ion is surrounded by eight atoms, six from three oxalate ions and two from water molecules. The variation of the metal-ligand frequencies and force constants with the atomic numbers of lanthanides is plotted and discussed. 相似文献
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A. Coetzee M. E. Brown D. J. Eve C. A. Strydom 《Journal of Thermal Analysis and Calorimetry》1994,41(2-3):357-385
Both isothermal and programmed temperature experiments have been used to obtain kinetic parameters for the dehydrations and
the decompositions in nitrogen of the mixed metal oxalates: FeCu(ox)2·3H2O, CoCu(ox)2·3H2O and NiCu(ox)2·3.5H2O, [ox=C2O4]. Results are compared with those reported for the thermal decompositions of the individual metal oxalates, Cuox, Coox·2H2O, Niox·2H2O and Feox·2H2O. X-ray photoelectron spectroscopy (XPS) was also used to examinee the individual and the mixed oxalates.
Dehydrations of the mixed oxalates were mainly deceleratory processes with activation energies (80 to 90 kJ·mol−1), similar to those reported for the individual hydrated oxalates. Temperature ranges for dehydration were broadly similar
for all the hydrates studied here (130 to 180°C).
Decompositions of the mixed oxalates were all complex endothermic processes with no obvious resemblance to the exothermic
reaction of Cuox, or the reactions of physical mixtures of the corresponding individual oxalates.
The order of decreasing stability, as indicated by the temperature ranges giving comparable decomposition rates, was NiCu(ox)2>CoCu(ox)2>FeCu(ox)2, which also corresponds to the order of increasing covalency of the Cu−O bonds as shown by XPS.
In celebration of the 60th birthday of Dr. Andrew K. Galwey 相似文献
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On the refluxing ofM(II) oxalate (M=Mn, Co, Ni, Cu, Zn or Cd) and 2-ethanolamine in chloroform, the following complexes were obtained: MnC2O4·HOCH2CH2NH2·H2O, CoC2O4·2HOCH2CH2NH2, Ni2(C2O4)2·5HOCH2CH2NH2·3H2O, Cu2(C2O4)2·5HOCH2CH2NH2, Zn2(C2O4)2·5HOCH2CH2NH2·2H2O and Cd2(C2O4)2·HOCH2CH2NH2·2H2O. Following the reaction ofM(II) oxalate with 2-ethanolamine in the presence of ethanolammonium oxalate, a compound with the empirical formula ZnC2O4·HOCH2CH2NH2·2H2O1 was isolated. The complexes were identified by using elemental analysis, X-ray powder diffraction patterns, IR spectra, and thermogravimetric and differential thermal analysis. The IR spectra and X-ray powder diffraction patterns showed that the complexes obtained were not isostructural. Their thermal decompositions, in the temperature interval between 20 and about 900°C, also take place in different ways, mainly through the formation of different amine complexes. The DTA curves exhibit a number of thermal effects. 相似文献
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B. Chapelet-Arab G. Nowogrocki S. Grandjean 《Journal of solid state chemistry》2005,178(10):3055-3065
Two new hydrazinium lanthanide(III) oxalates, (N2H5)[Nd(C2O4)2(H2O)]·4H2O (1) and (N2H5)[Gd(C2O4)2(H2O)]·4.5H2O (2) have been prepared and their crystal structures determined by single-crystal X-ray diffraction. The crystal structures were solved by the direct methods and Fourier difference techniques, and refined by a least-squares method on the basis of F2 for all unique reflections. Crystallographic data: 1, triclinic, space group , , b=9.762(4), , α=62.378(5), β=76.681(5), γ=73.858(5), Z=2, R1=0.0335 for 172 parameters with 3430 reflections with I?2σ(I); 2, triclinic, space group , , b=9.51(3), , α=62.11(4), β=76.15(5), γ=73.73(5), Z=2, R1=0.0325 for 172 parameters with 1742 reflections with I?2σ(I). The two isotypic structures are built from a three-dimensional (3D) arrangement of lanthanide and oxalate ions. The lanthanide atom is coordinated by eight oxygen atoms from four tetradentate oxalate ions and one aqua oxygen. Alternating lanthanide and oxalate ions form six-membered rings that delimit tunnels running down three directions and occupied by hydrazinium and water molecules. Starting from these lanthanide(III) compounds two isotypic mixed Ln(III)/U(IV) oxalates, (N2H5)0.75[Nd0.75U0.25(C2O4)2(H2O)]·4.5H2O (3) and (N2H5)0.75[Gd0.75U0.25(C2O4)2(H2O)]·4H2O (4), are obtained by partial substitution of Ln(III) by U(IV) in the nine-coordinated site, the charge excess being compensated by removal of monovalent ions from the tunnels. Finally, using Na+ gel, two mixed Ln(III)/U(IV) sodium oxalates, Na0.5[Nd0.5U0.5(C2O4)2(H2O)]·3H2O (5) and Na0.65[Gd0.65U0.35(C2O4)2(H2O)]·4.5H2O (6) have been obtained without any change in the 3D framework. 相似文献
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N. A. Sanina S. M. Aldoshin G. V. Shilov E. V. Kurganova E. A. Yurieva N. A. Voloshin V. I. Minkin V. A. Nadtochenko R. B. Morgunov 《Russian Chemical Bulletin》2008,57(7):1451-1460
Paramagnetic (tris)oxalates with the composition (SP)3M(C2O4)3·4H2O (M = Cr (2), Mn (3), Fe (4), and Co (5)) were synthesized for the first time based on the spiropyran salt SP+Br− (1) with the SP+ cation containing the pyridine ring in the aliphatic chain of the benzopyran moiety, which was also prepared in the present
study. According to X-ray diffraction data, the SP+ cations in the starting salt 1 are close-packed thus hindering photochromic transformations. The spin for paramagnet 4 is 5/2, which corresponds to the FeIII atom in the high-spin state, the spin of the system remaining unchanged under UV irradiation. In complex 3, a crossover from ferromagnetic to antiferromagnetic correlations was observed after the replacement of the inorganic cation
with the organic spiropyran cation.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1424–1432, July, 2008. 相似文献
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M. Bešter-Rogač M. Tomšič J. Barthel R. Neueder A. Apelblat 《Journal of solution chemistry》2002,31(1):1-18
Conductivity measurements of oxalic acid and neutral oxalates (disodium oxalate, dipotassium oxalate, dicesium, and diammonium oxalate) were performed on dilute aqueous solutions, c < 3 × 10–3 mol-dm–3, from 5 to 35°C. These data and those available from the literature were analyzed in terms of dissociation steps of oxalic acid, the Onsager conductivity equation for neutral oxalates, the Quint–Viallard conductivity equation for the acid, and the Debye–Hückel equation for activity coefficients, to give the limiting equivalent conductances of bioxalate anion ;(HC2O4
–) and oxalate anion (1/2C2O4
2–) and the corresponding dissociation constants K
1 and K
2. 相似文献
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Iron–Oxalato Framework with One‐Dimensional Open Channels for Electrochemical Sodium‐Ion Intercalation
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Dr. Xianfen Wang Ryosuke Kurono Dr. Shin‐ichi Nishimura Dr. Masashi Okubo Prof. Atsuo Yamada 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(3):1096-1101
Discovery of a new class of ion intercalation compounds is highly desirable due to its relevance to various electrochemical devices, such as batteries. Herein, we present a new iron–oxalato open framework, which showed reversible Na+ intercalation/extraction. The hydrothermally synthesized K4Na2[Fe(C2O4)2]3 ? 2 H2O possesses one‐dimensional open channels in the oxalato‐bridged network, providing ion accessibility up to two Na+ per the formula unit. The detailed studies on the structural and electronic states revealed that the framework exhibited a solid solution state almost entirely during Na+ intercalation/extraction associated with the reversible redox of Fe. The present work demonstrates possibilities of the oxalato frameworks as tunable and robust ion intercalation electrode materials for various device applications. 相似文献
10.
Maciej Chowaniak Marcin Niemiec Zhiqiang Zhu Naim Rashidov Zofia Grdek-Szostak Anna Szelg-Sikora Jakub Sikora Maciej Kubo Salimzoda Amonullo Fayzullo Usmon Mamur Mahmadyorzoda Agnieszka Jzefowska Andrzej Lepiarczyk Florian Gambu 《Molecules (Basel, Switzerland)》2021,26(12)
Natural products have always enjoyed great popularity among consumers. Wild tea is an interesting alternative to tea from intensive plantations. The term “wild tea” is applied to many different varieties of tea, the most desirable and valued of which are native or indigenous tea plants. Special pro-health properties of wild tea are attributed to the natural conditions in which it grows. However, there are no complex studies that describe quality and health indicators of wild tea. The aim of this research was to evaluate the quality of wild and cultivated green tea from different regions of China: Wuzhishan, Baisha, Kunlushan, and Pu’Er. The assessment was carried out by verifying the concentration of selected chemical components in tea and relating it to the health risks they may pose, as well as to the nutritional requirements of adults. Wild tea was characterized by higher micronutrient concentration. The analyzed teas can constitute a valuable source of Mn in the diet. A higher concentration of nitrates and oxalates in cultivated tea can be associated with fertilizer use. The analyzed cultivated tea was a better source of antioxidants with a higher concentration of caffeine. There were no indications of health risks for wild or cultivated teas. 相似文献