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51.
Covington's nonstatistical distribution of solvate species theory of preferential solvation is used to analyze
205
Tl chemical shift data for 0.005M TlNO
3
in nine binary solvent systems. The theory quite adequately fits the experimental data, and equilibrium constants and free energies of preferential solvation are obtained. The effect of choosing different values for the solvation number is investigated and found to be slight except for systems involving DMSO,
3
where decreasing the solvation number from 6 to 3 improves the fit to experimental data. 相似文献
52.
Mojtaba Shamsipur Gholamhossein Rounaghi Alexander I. Popov 《Journal of solution chemistry》1980,9(9):701-714
Formation constants for complexes of dibenzo-21-crown-7, dibenzo-24-crown-8 and dibenzo-27-crown-9 with the Na+, Cs+ and Tl+ ions have been determined by multinuclear NMR measurements in several nonaqueous solvents. The measurements of the cesium complexes were carried out at different temperatures and the enthalpy and entropy of complexation were determined from the temperature dependence of the formation constants.The stabilities of these complexes in solvents of low to medium donicity, —nitromethane, acetonitrile, acetone, methanol, and propylene carbonate, vary in the order Tl+>Cs+>Na+. Depending on the relative sizes of the cation and of the ligand cavity, either a three-dimensional wrap-around complex or a two-dimensional crown complex are formed. For the cesium complexes, the values of H
c
o
and S
c
o
are definitely solvent-dependent and in all cases the complexes are enthalpy stabilized but entropy destabilized. A compensating effect is observed in the variation of the enthalpy and entropy of complexation so that the overall influence of the above solvents on the stability of the complexes is rather limited. 相似文献
53.
Jos. S. Casas Eduardo E. Castellano Javier Ellena María S. García‐Tasende Agustín Snchez Jos Sordo Ezequiel M. Vzquez‐Lpez María J. Vidarte 《无机化学与普通化学杂志》2003,629(2):261-267
The reaction of 2, 6‐diacetylpyridine bis(thiosemicarbazone) (H2DAPTSC) with dimethylthallium hydroxide yielded the complexes [(TlMe2)2(DAPTSC)] and [TlMe2(HDAPTSC)]. The structure of [TlMe2(HDAPTSC)], determined by X‐ray diffractometry, exhibits a hitherto unknown coordination mode of the HDAPTSC— anion in which its deprotonated thiosemicarbazone chain coordinates one metal atom through its sulphur and hydrazinic N atoms while a second metal atom is weakly coordinated through the S atom of the undeprotonated thiosemicarbazone chain. Each thallium atom is coordinated in both ways, with the result that the [TlMe2(HDAPTSC)] units are linked in infinite helical chains in the direction of the b axis. When reacting with diphenylthallium(III) hydroxide, H2DAPTSC induced a dephenylation process which led to the monophenylthallium(III) complex [TlPh(DAPTSC)]. Recrystallization from acetone yielded crystals of [TlPh(DAPTSC)]·C3H6O in which X‐ray diffractometry showed DAPTSC2— to be pentadentate, coordinating through its sulphur, azomethine N and pyridine N atoms. The 1H, 13C and 205Tl NMR data of [TlPh(DAPTSC)] indicate that its solid state molecular structure persists in DMSO solution, while those of [TlMe2(HDAPTSC)] indicate rapid alternation between coordination of the metal atom to one of the HDAPTSC— thiosemicarbazone chains and its coordination to the other. 相似文献
54.
Polycrystalline Si0.96Mn0.04:B films were prepared by cosputtering deposition followed by rapid thermal annealing for crystallization. The films are ferromagnetic with Curie temperatures of about 250 K. Through the approach of microwave plasma enhanced chemical vapor deposition, the films were treated by hydrogen plasma and boron plasma. After the plasma treatments, the structural properties of the films did not change, while both the saturation magnetization and hole concentration in the films changed. The correlation between the magnetic properties and the transport properties of the Si0.96Mn0.04:B films suggests that free hole carriers play an important role in Si:Mn diluted magnetic semiconductors. 相似文献
55.
H.Y. Hu 《Applied Surface Science》2008,254(24):8029-8034
The chemical structure and site location of sulfur atoms on n-GaAs (1 0 0) surface treated by bombardment of S+ ions over their energy range from 10 to 100 eV have been studied by X-ray photoelectron spectroscopy and low energy electron diffraction. The formation of Ga-S and As-S species on the S+ ion bombarded n-GaAs surface is observed. An apparent donor doping effect is observed for the n-GaAs by the 100 eV S+ ion bombardment. It is found that the S+ ions with higher energy are more effective in the formation of Ga-S species, which assists the n-GaAs (1 0 0) surface in reconstruction into an ordered (1 × 1) structure upon subsequent annealing. The treatment is further extended to repair Ar+ ion damaged n-GaAs (1 0 0) surface. It is found that after a n-GaAs (1 0 0) sample is damaged by 150 eV Ar+ ion bombardment, and followed by 50 eV S+ ion treatment and subsequent annealing process, finally an (1 × 1) ordering GaAs (1 0 0) surface with low surface states is obtained. 相似文献