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931.
The luminescence of Ce3+, Sm3+, Eu3+, Gd3+, Tb3+, and Dy3+ in NaLn(SO4)2H2O (Ln = lanthanide) is reported. Only Ce3+, Gd3+, and Tb3+ show efficient emission. This is explained in terms of an energy-gap law. Energy transfer is studied in several codoped compositions. The mutual transfer between Gd3+ ions is the only one encountered with high probability. The several transfers are discussed and where possible their rates are calculated. 相似文献
932.
Jian-yun Du 《Transition Metal Chemistry》2004,29(7):699-702
Two novel complexes, [Zn(dmatrz)2]Cl2
(1) and [Zn(dmatrz)2(SCN)2] (2), have been prepared and characterized by X-ray crystallography, absorption and luminescence spectrometries (dmatrz=3,5-dimethy-4-amino-1,2,4-triazole). The coordination environment of the zinc(II) ions in (1) and (2) has a distorted tetrahedral geometry completed via two independent nitrogen atoms of two triazole ligands and two anions, respectively. Both (1) and (2) show strong blue luminescence properties. Furthermore, (1) displays stronger blue photoluminescence than (2) as the result of different anions (Cl- and SCN-) coordinated to the zinc(II) ions. 相似文献
933.
Self-association system of(R)-1,3-butanediol in dilute carbon tetrachloride(CCl4)solution is studied as a model of molecular association mixture.Analysis methods including FSMWEFA(fixed-size moving window evolving factor analysis)combined with PCA(principal component analysis),SIMPLISMA (simple-to-use interactive self-modeling mixture analysis),and ITTFA(iterative target transformation factor analysis)are adopted to resolve infrared spectra of(R)-1,3-butanediol solution.Association number and equilibrium constant are computed.(R)-1,3-butanediol in dilute inert solution is determined as a monomer-trimer equilibrium system.Theoretical investigation of trimer structures is carried out with DFT(density functional theory),and structural factors are analyzed. 相似文献
934.
Keith E. Johnson Richard M. Pagni John Bartmess 《Monatshefte für Chemie / Chemical Monthly》2007,138(11):1077-1101
Summary. A background for studying acids in various solvents is developed, emphasizing the importance of knowing to what extent a solvent
conducts electricity and is therefore ionized, the dissociation equilibria of common molecular solvents and the acidic and
basic species generated by solvent leveling. Acidity measurements in the atypical solvent water are discussed and the common
method of expressing acidity in other systems – by Hammett values – is introduced. Representative examples of reactions involving Br?nsted acids in ionic liquids are presented and attention paid to the questions of speciation and acidity values. It is found that
the gas phase proton affinity of a base is often a better guide to the acidity of its conjugate acid in an ionic liquid than
is the dissociation constant of the said acid in water. 相似文献
935.
Xinbo Zhang Danzi Sun Wenya Yin Yujun Chai Minshou Zhao 《Journal of Solid State Electrochemistry》2006,10(4):236-242
This paper presents results concerning structure and electrochemical characteristics of the La0.67Mg0.33 (Ni0.8Co0.1Mn0.1)
x
(x=2.5–5.0) alloy. It can be found from the result of the Rietveld analyses that the structures of the alloys change obviously
with increasing x from 2.5 to 5.0. The main phase of the alloys with x=2.5–3.5 is LaMg2Ni9 phase with a PuNi3-type rhombohedral structure, but the main phase of the alloys with x=4.0–5.0 is LaNi5phase with a CaCu5-type hexagonal structure. Furthermore, the phase ratio, lattice parameter and cell volume of the LaMg2Ni9phase and the LaNi5 phase change with increasing x. The electrochemical studies show that the maximum discharge capacity increases from 214.7 mAh/g
(x=2.5) to 391.1 mAh/g (x=3.5) and then decreases to 238.5 mAh/g (x=5.0). As the discharge current density is 1,200 mA/g, the high rate dischargeability (HRD) increases from 51.1% (x=2.5) to 83.7% (x=3.5) and then decreases to 71.6% (x=5.0). Moreover, the exchange current density (I
0) of the alloy electrodes first increases and then decrease with increasing x from 2.5 to 5.0, which is consistent with the variation of the HRD. The cell volume reduces with increasing x in the alloys, which is detrimental to hydrogen diffusion and accordingly decreases the low-temperature dischargeability
of the alloy electrodes. 相似文献
936.
Amphiphilic phthalocyanines with one crown ether and three alkyl chain substitutions can form stable monolayers on a water surface. This monolayer can be transferred to a substrate by a vertical dipping method. The arrangement of phthalocyanine molecules in LB films was affected by the length of alkyl chains and the coordination of alkali ions in crown ether. Davydov splitting was observed in the absorption spectra of the LB films of phthalocyanine with the shortest alkyl chain substitutions, and this splitting was affected by the alkali ions in the subphase. 相似文献
937.
Xian Zhao Daren Guan Xizhang Yi Guibao Xu Minhua Jiang 《International journal of quantum chemistry》2003,93(5):335-343
A dynamic Lie algebraic (DLA) formulation is applied to the study of nonlinear optical properties of the substituted benzenes. We have described the generation of the dynamic Lie algebra for the model Hamiltonian used in the present study. In terms of these elements of the dynamic algebra we express the evolution operator as a function of the group parameters, which can be determined by means of solving a system of coupled nonlinear differential equations. Thus, in terms of the density matrix operator formalism in statistical mechanics we obtain the statistical averages of the electric polarization and then derive readily an expression for the hyperpolarizability of the paradisubstituted benzenes. Comparisons with experimental observations and other quantum calculations of the hyperpolarizabilities for the paradisubstituted benzenes are made qualitatively and quantitatively. These results imply that the DLA method appears useful in describing the nonlinear optical phenomena in the substituted benzene molecules. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 93: 335–343, 2003 相似文献
938.
The synthesis and anion binding properties of new ruthenium(II) and cobalt(II) phenanthroline complexes, containing two amide
subunits are described. Evidence for anion binding in dimethyl sulfoxide (DMSO) solution was obtained from u.v.–vis titration
experiments. Results indicated that these receptors showed strong affinity for F− and AcO−, and showed weak affinity for OH− and H2PO
4
−
, and showed no affinity for Cl−, Br−, I−. These receptors interacted with various anions examined through hydrogen-bond formation. 相似文献
939.
M. Blaauw I. H. Degenaar J. J. M. de Goeij 《Journal of Radioanalytical and Nuclear Chemistry》2007,271(3):765-770
In order to correct for neutron self-shielding in large-sample prompt gamma NAA, a method has been developed to determine
the macroscopic scattering and absorption cross sections, i.e., Σ
a and Σ
s, using four Cu flux monitors placed around the sample. With Monte Carlo computations, the neutron densities throughout the
sample and the resulting and the corresponding self-shielding factor as calculated from the Σ
a and Σ
s as obtained through the Cu monitors were compared to the true values. The derived Σ
a and Σ
s were found to be sufficiently accurate as long as Σ
t = Σ
a + Σ
s was less than 0.6 cm−1 and Σ
s/Σ
t was greater than 0.1. 相似文献
940.
Substituted carbazoles are readily prepared in good yields by the palladium-catalyzed cross-coupling of alkynes and N-(3-iodophenyl)anilines. This process proceeds by carbopalladation of the alkyne, heteroatom-directed vinylic to aryl palladium migration, and ring closure involving two consecutive C-H activation processes. The process has also been expanded to the synthesis of an indole. [Structure: see text] 相似文献