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81.
Arkosi Z Szabó-Plánka T Rockenbauer A Nagy NV Lázár L Fülöp F 《Inorganic chemistry》2003,42(16):4842-4848
We have studied the complex equilibria of copper(II) with a series of beta-substituted beta-amino acids (R: H, Me, Et, iBu, iPr, cHex, 1-EtPr, and tBu) in aqueous solution by pH potentiometry and electron paramagnetic resonace (EPR) spectroscopy in the range pH = 2-8 at various metal and ligand concentrations. The basicities of the corresponding donor groups differed only slightly in the series of ligands. A purely mathematical method, the matrix rank analysis carried out on the EPR spectrum package recorded in the presence of copper(II), indicated the formation of 6 independent paramagnetic species. Accordingly, Cu(2+) (aqua complex) and the complexes [CuLH](2+), [CuL](+), [CuL(2)H(2)](2+), [CuL(2)H](+), and [CuL(2)] were considered in the subsequent analysis of series of spectra, and also two isomers of [CuL(2)] were identified. The formation constants and the EPR parameters, e.g. the isotropic g-factors and the copper and nitrogen hyperfine couplings for the above species, were determined in the same optimization procedure by the simultaneous evaluation of spectra. The ligands "LH" are suggested to bind in equatorial positions through their carboxylate groups, while the amino acids in the L protonation state are likely to occupy two equatorial sites via the amino and carboxylate groups. For the isomers of [CuL(2)], the donors of the same kind are in the cis or trans position. As far as we know, this is the first reported case in which a strong correlation has been found between the steric effects of substituents characterized by Meyer's steric parameter V(a) and the protonation constants of metal complexes. The observed trend for the preference for nonprotonated complexes [CuL](+) and [CuL(2)] to increase with the steric demand of the substituent was explained by the increasing shielding effect of the substituent hindering protonation of the nonprotonated complex. 相似文献
82.
Two-step synthesis of the novel fused heterocycles pyrazolo[4′,3′:5,6]pyrido[2,3-b][1,5]benzoxazepine ( 8 ) and pyrazolo[4′,3′:5,6]pyrido[2,3-b][1,5]benzothiazepine ( 9 ) from the pyrazolo[3,4-b]pyridine derivative 1 is described. 相似文献
83.
A solid-phase extraction sample preparation method using a molecularly imprinted polymer (MIP) selective for the triazine type pesticide terbutylazine has been developed. The method involves preconcentration from large volumes of water samples on a C18 disk coupled to selective clean-up on the MIP. The method has been optimised by studying the recovery and retention of terbutylazine and some other structurally related triazine derivates as a function of the selective washing solvent used. The effect of the water content of the selective washing solvent was also investigated on the recovery of the MIP. River water samples were analysed with the coupled technique, and efficient clean-up of the samples was observed. 相似文献
84.
Sekine T. Yoshihara K. Németh Zs. Lakosi L. Veres Á. 《Journal of Radioanalytical and Nuclear Chemistry》1989,130(2):269-278
A new nuclear excitation process,99Tc (, )99mTc reaction, was applied for the first time to radioactivation analysis of technetium. Bremsstrahlung irradiation of99Tc samples gave the reaction product99mTc which emits -ray measurable with ease by a semiconductor detector. The production rate of99mTc per g99Tc was linearly correlated with the flux of bremsstrahlung. The detection limit of99Tc was estimated to be nanogram order (0.63 Bq99Tc) under the optimum irradiation condition. Possible interference by100Ru(, p)99mTc reaction was also studied, which could be discriminated from the (, ) reaction by simultaneously occurring98Ru (, p)97Ru reaction. 相似文献
85.
The enantiomers of 1-(alpha-aminobenzyl)-2-naphthol and 2-(alpha-aminobenzyl)-1-naphthol analogs were separated isothermally on a cellulose-tris-3,5-dimethylphenyl carbamate-based chiral stationary phase (Chiralcel OD-H), at 10 degrees C increments in the range of 5-35 degrees C, using n-hexane/2-propanol/diethylamine as mobile phase. The mobile phase composition and temperature were varied to achieve baseline resolutions in a single chromatographic run. The dependence of the natural logarithms of selectivity factors, In alpha, on the inverse of temperature, 1/T, was used to determine the thermodynamic data of the enantiomers. The thermodynamic data revealed that all the compounds in this study separate via the same enthalpy-driven chiral recognition mechanism. 相似文献
86.
87.
The enthalpic relaxation of the title glasses, studied by differential scanning calorimetry, is well described by a mathematical
model based on the stretched exponential relaxation function with the relaxation time proportional to the actual viscosity.
The dependence of viscosity on temperature and the fictive temperature was expressed by Mazurin's approximation. The relaxation
parameters obtained correlated significantly with the glass composition, indicating the changes in the structural of the TiO2 role near a TiO2 content of 3–4 mol%.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
88.
É. Svingor M. Molnár L. Palcsu M. Veres T. Pintér L. Köves 《Czechoslovak Journal of Physics》2006,56(4):D133-D139
Continuous monitoring of the uncontrolled tritium emission from Paks Nuclear Power Plant (NPP) has been carried out since starting the NPP operation. In order to control the release of fission and corrosion products as well as 14C automatic samplers were designed and installed into 20 observation wells in the vicinity of the reactor units. The automatic samplers contain two columns filled with anion and cation exchanger resins and are equipped with filters for trapping the chelating agents. The samplers are placed two meters below the groundwater level. Water pumps fed by accumulator ensure the water flowing through the ion-exchange columns. After a two-month working period the trapped ions are eluted from the resins. The activity of the gamma-emitters, 14C, 90Sr and transuranium elements are measured in the dried elute, the tritium is measured in the collected water phase. The experiences of a five-year monitoring work in the surroundings of Paks NPP are given here. 相似文献
89.
A simple and efficient synthesis of amides by selective hydration of aromatic and aliphatic nitriles is described. The catalysts are prepared in situ from easily available Ru-precursors and ligands using water as the solvent. The most active catalyst, is obtained from [RuCl2(dmso)4] and benzylated 1,3,5-triaza-7-phosphaadamantane. Of the 16 substrates examined, 92–99% conversions of 14 nitriles were achieved in one hour at reflux temperature. 相似文献
90.
Denisova K. O. Ilyin A. A. Veres K. A. Ilyin A. P. 《Russian Journal of Applied Chemistry》2022,95(1):113-117
Russian Journal of Applied Chemistry - The paper defines the conditions for the synthesis of hydrogen sulfide adsorbent based on zinc oxide from basic zinc carbonate in order to produce strong,... 相似文献